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(*
    DO NOT EDIT THIS FILE.
    This file is automatically generated from the individual
    source files in the Vext repository.
*)

(* 
    Vext

    A simple manager for third-party source code dependencies

    Copyright 2017 Chris Cannam, Particular Programs Ltd,
    and Queen Mary, University of London

    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
    files (the "Software"), to deal in the Software without
    restriction, including without limitation the rights to use, copy,
    modify, merge, publish, distribute, sublicense, and/or sell copies
    of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
    ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
    CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    Except as contained in this notice, the names of Chris Cannam,
    Particular Programs Ltd, and Queen Mary, University of London
    shall not be used in advertising or otherwise to promote the sale,
    use or other dealings in this Software without prior written
    authorization.
*)

val vext_version = "0.9.92"


datatype vcs =
         HG |
         GIT |
         SVN

datatype source =
         URL_SOURCE of string |
         SERVICE_SOURCE of {
             service : string,
             owner : string option,
             repo : string option
         }

type id_or_tag = string

datatype pin =
         UNPINNED |
         PINNED of id_or_tag

datatype libstate =
         ABSENT |
         CORRECT |
         SUPERSEDED |
         WRONG

datatype localstate =
         MODIFIED |
         LOCK_MISMATCHED |
         CLEAN

datatype branch =
         BRANCH of string |
         DEFAULT_BRANCH
             
(* If we can recover from an error, for example by reporting failure
   for this one thing and going on to the next thing, then the error
   should usually be returned through a result type rather than an
   exception. *)
             
datatype 'a result =
         OK of 'a |
         ERROR of string

type libname = string

type libspec = {
    libname : libname,
    vcs : vcs,
    source : source,
    branch : branch,
    project_pin : pin,
    lock_pin : pin
}

type lock = {
    libname : libname,
    id_or_tag : id_or_tag
}

type remote_spec = {
    anon : string option,
    auth : string option
}

type provider = {
    service : string,
    supports : vcs list,
    remote_spec : remote_spec
}

type account = {
    service : string,
    login : string
}
                    
type context = {
    rootpath : string,
    extdir : string,
    providers : provider list,
    accounts : account list
}

type userconfig = {
    providers : provider list,
    accounts : account list
}
                   
type project = {
    context : context,
    libs : libspec list
}

structure VextFilenames = struct
    val project_file = "vext-project.json"
    val project_lock_file = "vext-lock.json"
    val user_config_file = ".vext.json"
    val archive_dir = ".vext-archive"
end
                   
signature VCS_CONTROL = sig

    (** Test whether the library is present locally at all *)
    val exists : context -> libname -> bool result
                                            
    (** Return the id (hash) of the current revision for the library *)
    val id_of : context -> libname -> id_or_tag result

    (** Test whether the library is at the given id *)
    val is_at : context -> libname * id_or_tag -> bool result

    (** Test whether the library is on the given branch, i.e. is at
        the branch tip or an ancestor of it *)
    val is_on_branch : context -> libname * branch -> bool result

    (** Test whether the library is at the newest revision for the
        given branch. False may indicate that the branch has advanced
        or that the library is not on the branch at all. This function
        may use the network to check for new revisions *)
    val is_newest : context -> libname * source * branch -> bool result

    (** Test whether the library is at the newest revision available
        locally for the given branch. False may indicate that the
        branch has advanced or that the library is not on the branch
        at all. This function must not use the network *)
    val is_newest_locally : context -> libname * branch -> bool result

    (** Test whether the library has been modified in the local
        working copy *)
    val is_modified_locally : context -> libname -> bool result

    (** Check out, i.e. clone a fresh copy of, the repo for the given
        library on the given branch *)
    val checkout : context -> libname * source * branch -> unit result

    (** Update the library to the given branch tip. Assumes that a
        local copy of the library already exists *)
    val update : context -> libname * source * branch -> unit result

    (** Update the library to the given specific id or tag *)
    val update_to : context -> libname * source * id_or_tag -> unit result

    (** Return a URL from which the library can be cloned, given that
        the local copy already exists. For a DVCS this can be the
        local copy, but for a centralised VCS it will have to be the
        remote repository URL. Used for archiving *)
    val copy_url_for : context -> libname -> string result
end

signature LIB_CONTROL = sig
    val review : context -> libspec -> (libstate * localstate) result
    val status : context -> libspec -> (libstate * localstate) result
    val update : context -> libspec -> unit result
    val id_of : context -> libspec -> id_or_tag result
end

structure FileBits :> sig
    val extpath : context -> string
    val libpath : context -> libname -> string
    val subpath : context -> libname -> string -> string
    val command_output : context -> libname -> string list -> string result
    val command : context -> libname -> string list -> unit result
    val file_url : string -> string
    val file_contents : string -> string
    val mydir : unit -> string
    val homedir : unit -> string
    val mkpath : string -> unit result
    val rmpath : string -> unit result
    val nonempty_dir_exists : string -> bool
    val project_spec_path : string -> string
    val project_lock_path : string -> string
    val verbose : unit -> bool
end = struct

    fun verbose () =
        case OS.Process.getEnv "VEXT_VERBOSE" of
            SOME "0" => false
          | SOME _ => true
          | NONE => false

    fun split_relative path desc =
        case OS.Path.fromString path of
            { isAbs = true, ... } => raise Fail (desc ^ " may not be absolute")
          | { arcs, ... } => arcs
                        
    fun extpath ({ rootpath, extdir, ... } : context) =
        let val { isAbs, vol, arcs } = OS.Path.fromString rootpath
        in OS.Path.toString {
                isAbs = isAbs,
                vol = vol,
                arcs = arcs @
                       split_relative extdir "extdir"
            }
        end
    
    fun subpath ({ rootpath, extdir, ... } : context) libname remainder =
        (* NB libname is allowed to be a path fragment, e.g. foo/bar *)
        let val { isAbs, vol, arcs } = OS.Path.fromString rootpath
        in OS.Path.toString {
                isAbs = isAbs,
                vol = vol,
                arcs = arcs @
                       split_relative extdir "extdir" @
                       split_relative libname "library path" @
                       split_relative remainder "subpath"
            }
        end

    fun libpath context "" =
        extpath context
      | libpath context libname =
        subpath context libname ""

    fun project_file_path rootpath filename =
        let val { isAbs, vol, arcs } = OS.Path.fromString rootpath
        in OS.Path.toString {
                isAbs = isAbs,
                vol = vol,
                arcs = arcs @ [ filename ]
            }
        end
                
    fun project_spec_path rootpath =
        project_file_path rootpath (VextFilenames.project_file)

    fun project_lock_path rootpath =
        project_file_path rootpath (VextFilenames.project_lock_file)

    fun trim str =
        hd (String.fields (fn x => x = #"\n" orelse x = #"\r") str)
            
    fun file_url path =
        let val forward_path = 
                String.translate (fn #"\\" => "/" |
                                  c => Char.toString c)
                                 (OS.Path.mkCanonical path)
        in
            (* Path is expected to be absolute already, but if it
               starts with a drive letter, we'll need an extra slash *)
            case explode forward_path of
                #"/"::rest => "file:///" ^ implode rest
              | _ => "file:///" ^ forward_path
        end
        
    fun file_contents filename =
        let val stream = TextIO.openIn filename
            fun read_all str acc =
                case TextIO.inputLine str of
                    SOME line => read_all str (trim line :: acc)
                  | NONE => rev acc
            val contents = read_all stream []
            val _ = TextIO.closeIn stream
        in
            String.concatWith "\n" contents
        end

    fun expand_commandline cmdlist =
        (* We are quite [too] strict about what we accept here, except
           for the first element in cmdlist which is assumed to be a
           known command location rather than arbitrary user input. NB
           only ASCII accepted at this point. *)
        let open Char
            fun quote arg =
                if List.all
                       (fn c => isAlphaNum c orelse c = #"-" orelse c = #"_")
                       (explode arg)
                then arg
                else "\"" ^ arg ^ "\""
            fun check arg =
                let val valid = explode " /#:;?,._-{}@="
                in
                    app (fn c =>
                            if isAlphaNum c orelse
                               List.exists (fn v => v = c) valid
                            then ()
                            else raise Fail ("Invalid character '" ^
                                             (Char.toString c) ^
                                             "' in command list"))
                        (explode arg);
                    arg
                end
        in
            String.concatWith " "
                              (map quote
                                   (hd cmdlist :: map check (tl cmdlist)))
        end

    val tick_cycle = ref 0
    val tick_chars = Vector.fromList (map String.str (explode "|/-\\"))

    fun tick libname cmdlist =
        let val n = Vector.length tick_chars
            fun pad_to n str =
                if n <= String.size str then str
                else pad_to n (str ^ " ")
            val name = if libname <> "" then libname
                       else if cmdlist = nil then ""
                       else hd (rev cmdlist)
        in
            print ("  " ^
                   Vector.sub(tick_chars, !tick_cycle) ^ " " ^
                   pad_to 24 name ^
                   "\r");
            tick_cycle := (if !tick_cycle = n - 1 then 0 else 1 + !tick_cycle)
        end
            
    fun run_command context libname cmdlist redirect =
        let open OS
            val dir = libpath context libname
            val cmd = expand_commandline cmdlist
            val _ = if verbose ()
                    then print ("Running: " ^ cmd ^
                                " (in dir " ^ dir ^ ")...\n")
                    else tick libname cmdlist
            val _ = FileSys.chDir dir
            val status = case redirect of
                             NONE => Process.system cmd
                           | SOME file => Process.system (cmd ^ ">" ^ file)
        in
            if Process.isSuccess status
            then OK ()
            else ERROR ("Command failed: " ^ cmd ^ " (in dir " ^ dir ^ ")")
        end
        handle ex => ERROR ("Unable to run command: " ^ exnMessage ex)

    fun command context libname cmdlist =
        run_command context libname cmdlist NONE
            
    fun command_output context libname cmdlist =
        let open OS
            val tmpFile = FileSys.tmpName ()
            val result = run_command context libname cmdlist (SOME tmpFile)
            val contents = file_contents tmpFile
            val _ = if verbose ()
                    then print ("Output was:\n\"" ^ contents ^ "\"\n")
                    else ()
        in
            FileSys.remove tmpFile handle _ => ();
            case result of
                OK () => OK contents
              | ERROR e => ERROR e
        end

    fun mydir () =
        let open OS
            val { dir, file } = Path.splitDirFile (CommandLine.name ())
        in
            FileSys.realPath
                (if Path.isAbsolute dir
                 then dir
                 else Path.concat (FileSys.getDir (), dir))
        end

    fun homedir () =
        (* Failure is not routine, so we use an exception here *)
        case (OS.Process.getEnv "HOME",
              OS.Process.getEnv "HOMEPATH") of
            (SOME home, _) => home
          | (NONE, SOME home) => home
          | (NONE, NONE) =>
            raise Fail "Failed to look up home directory from environment"

    fun mkpath' path =
        if OS.FileSys.isDir path handle _ => false
        then OK ()
        else case OS.Path.fromString path of
                 { arcs = nil, ... } => OK ()
               | { isAbs = false, ... } => ERROR "mkpath requires absolute path"
               | { isAbs, vol, arcs } => 
                 case mkpath' (OS.Path.toString {      (* parent *)
                                    isAbs = isAbs,
                                    vol = vol,
                                    arcs = rev (tl (rev arcs)) }) of
                     ERROR e => ERROR e
                   | OK () => ((OS.FileSys.mkDir path; OK ())
                               handle OS.SysErr (e, _) =>
                                      ERROR ("Directory creation failed: " ^ e))

    fun mkpath path =
        mkpath' (OS.Path.mkCanonical path)

    fun dir_contents dir =
        let open OS
            fun files_from dirstream =
                case FileSys.readDir dirstream of
                    NONE => []
                  | SOME file =>
                    (* readDir is supposed to filter these, 
                       but let's be extra cautious: *)
                    if file = Path.parentArc orelse file = Path.currentArc
                    then files_from dirstream
                    else file :: files_from dirstream
            val stream = FileSys.openDir dir
            val files = map (fn f => Path.joinDirFile
                                         { dir = dir, file = f })
                            (files_from stream)
            val _ = FileSys.closeDir stream
        in
            files
        end

    fun rmpath' path =
        let open OS
            fun remove path =
                if FileSys.isLink path (* dangling links bother isDir *)
                then FileSys.remove path
                else if FileSys.isDir path
                then (app remove (dir_contents path); FileSys.rmDir path)
                else FileSys.remove path
        in
            (remove path; OK ())
            handle SysErr (e, _) => ERROR ("Path removal failed: " ^ e)
        end

    fun rmpath path =
        rmpath' (OS.Path.mkCanonical path)

    fun nonempty_dir_exists path =
        let open OS.FileSys
        in
            (not (isLink path) andalso
             isDir path andalso
             dir_contents path <> [])
            handle _ => false
        end                                        
                
end
                                         
functor LibControlFn (V: VCS_CONTROL) :> LIB_CONTROL = struct

    (* Valid states for unpinned libraries:

       - CORRECT: We are on the right branch and are up-to-date with
         it as far as we can tell. (If not using the network, this
         should be reported to user as "Present" rather than "Correct"
         as the remote repo may have advanced without us knowing.)

       - SUPERSEDED: We are on the right branch but we can see that
         there is a newer revision either locally or on the remote (in
         Git terms, we are at an ancestor of the desired branch tip).

       - WRONG: We are on the wrong branch (in Git terms, we are not
         at the desired branch tip or any ancestor of it).

       - ABSENT: Repo doesn't exist here at all.

       Valid states for pinned libraries:

       - CORRECT: We are at the pinned revision.

       - WRONG: We are at any revision other than the pinned one.

       - ABSENT: Repo doesn't exist here at all.
    *)

    fun check with_network context
              ({ libname, source, branch,
                 project_pin, lock_pin, ... } : libspec) =
        let fun check_unpinned () =
                let val newest =
                        if with_network
                        then V.is_newest context (libname, source, branch)
                        else V.is_newest_locally context (libname, branch)
                in
                    case newest of
                         ERROR e => ERROR e
                       | OK true => OK CORRECT
                       | OK false =>
                         case V.is_on_branch context (libname, branch) of
                             ERROR e => ERROR e
                           | OK true => OK SUPERSEDED
                           | OK false => OK WRONG
                end
            fun check_pinned target =
                case V.is_at context (libname, target) of
                    ERROR e => ERROR e
                  | OK true => OK CORRECT
                  | OK false => OK WRONG
            fun check_remote () =
                case project_pin of
                    UNPINNED => check_unpinned ()
                  | PINNED target => check_pinned target
            fun check_local () =
                case V.is_modified_locally context libname of
                    ERROR e => ERROR e
                  | OK true  => OK MODIFIED
                  | OK false => 
                    case lock_pin of
                        UNPINNED => OK CLEAN
                      | PINNED target =>
                        case V.is_at context (libname, target) of
                            ERROR e => ERROR e
                          | OK true => OK CLEAN
                          | OK false => OK LOCK_MISMATCHED
        in
            case V.exists context libname of
                ERROR e => ERROR e
              | OK false => OK (ABSENT, CLEAN)
              | OK true =>
                case (check_remote (), check_local ()) of
                    (ERROR e, _) => ERROR e
                  | (_, ERROR e) => ERROR e
                  | (OK r, OK l) => OK (r, l)
        end

    val review = check true
    val status = check false

    fun update context
               ({ libname, source, branch,
                  project_pin, lock_pin, ... } : libspec) =
        let fun update_unpinned () =
                case V.is_newest context (libname, source, branch) of
                    ERROR e => ERROR e
                  | OK true => OK ()
                  | OK false => V.update context (libname, source, branch)
            fun update_pinned target =
                case V.is_at context (libname, target) of
                    ERROR e => ERROR e
                  | OK true => OK ()
                  | OK false => V.update_to context (libname, source, target)
            fun update' () =
                case lock_pin of
                    PINNED target => update_pinned target
                  | UNPINNED =>
                    case project_pin of
                        PINNED target => update_pinned target
                      | UNPINNED => update_unpinned ()
        in
            case V.exists context libname of
                ERROR e => ERROR e
              | OK true => update' ()
              | OK false =>
                case V.checkout context (libname, source, branch) of
                    ERROR e => ERROR e
                  | OK () => update' ()
        end

    fun id_of context ({ libname, ... } : libspec) =
        V.id_of context libname
                
end

(* Simple Standard ML JSON parser
   ==============================

   https://bitbucket.org/cannam/sml-simplejson

   An RFC-compliant JSON parser in one SML file with no dependency 
   on anything outside the Basis library. Also includes a simple
   serialiser.

   Tested with MLton, Poly/ML, and SML/NJ compilers.

   Parser notes:

   * Complies with RFC 7159, The JavaScript Object Notation (JSON)
     Data Interchange Format

   * Passes all of the JSONTestSuite parser accept/reject tests that
     exist at the time of writing, as listed in "Parsing JSON is a
     Minefield" (http://seriot.ch/parsing_json.php)
 
   * Two-pass parser using naive exploded strings, therefore not
     particularly fast and not suitable for large input files

   * Only supports UTF-8 input, not UTF-16 or UTF-32. Doesn't check
     that JSON strings are valid UTF-8 -- the caller must do that --
     but does handle \u escapes

   * Converts all numbers to type "real". If that is a 64-bit IEEE
     float type (common but not guaranteed in SML) then we're pretty
     standard for a JSON parser

   Copyright 2017 Chris Cannam.
   Parts based on the JSON parser in the Ponyo library by Phil Eaton.

   Permission is hereby granted, free of charge, to any person
   obtaining a copy of this software and associated documentation
   files (the "Software"), to deal in the Software without
   restriction, including without limitation the rights to use, copy,
   modify, merge, publish, distribute, sublicense, and/or sell copies
   of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
   ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
   CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
   WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

   Except as contained in this notice, the names of Chris Cannam and
   Particular Programs Ltd shall not be used in advertising or
   otherwise to promote the sale, use or other dealings in this
   Software without prior written authorization.
*)

signature JSON = sig

    datatype json = OBJECT of (string * json) list
                  | ARRAY of json list
                  | NUMBER of real
                  | STRING of string
                  | BOOL of bool
                  | NULL

    datatype 'a result = OK of 'a
                       | ERROR of string

    val parse : string -> json result
    val serialise : json -> string
    val serialiseIndented : json -> string

end

structure Json :> JSON = struct

    datatype json = OBJECT of (string * json) list
                  | ARRAY of json list
                  | NUMBER of real
                  | STRING of string
                  | BOOL of bool
                  | NULL

    datatype 'a result = OK of 'a
                       | ERROR of string

    structure T = struct
        datatype token = NUMBER of char list
                       | STRING of string
                       | BOOL of bool
                       | NULL
                       | CURLY_L
                       | CURLY_R
                       | SQUARE_L
                       | SQUARE_R
                       | COLON
                       | COMMA

        fun toString t =
            case t of NUMBER digits => implode digits
                    | STRING s => s
                    | BOOL b => Bool.toString b
                    | NULL => "null"
                    | CURLY_L => "{"
                    | CURLY_R => "}"
                    | SQUARE_L => "["
                    | SQUARE_R => "]"
                    | COLON => ":"
                    | COMMA => ","
    end

    fun bmpToUtf8 cp =  (* convert a codepoint in Unicode BMP to utf8 bytes *)
        let open Word
	    infix 6 orb andb >>
        in
            map (Char.chr o toInt)
                (if cp < 0wx80 then
                     [cp]
                 else if cp < 0wx800 then
                     [0wxc0 orb (cp >> 0w6), 0wx80 orb (cp andb 0wx3f)]
                 else if cp < 0wx10000 then
                     [0wxe0 orb (cp >> 0w12),
                      0wx80 orb ((cp >> 0w6) andb 0wx3f),
		      0wx80 orb (cp andb 0wx3f)]
                 else raise Fail ("Invalid BMP point " ^ (Word.toString cp)))
        end
                      
    fun error pos text = ERROR (text ^ " at character position " ^
                                Int.toString (pos - 1))
    fun token_error pos = error pos ("Unexpected token")

    fun lexNull pos acc (#"u" :: #"l" :: #"l" :: xs) =
        lex (pos + 3) (T.NULL :: acc) xs
      | lexNull pos acc _ = token_error pos

    and lexTrue pos acc (#"r" :: #"u" :: #"e" :: xs) =
        lex (pos + 3) (T.BOOL true :: acc) xs
      | lexTrue pos acc _ = token_error pos

    and lexFalse pos acc (#"a" :: #"l" :: #"s" :: #"e" :: xs) =
        lex (pos + 4) (T.BOOL false :: acc) xs
      | lexFalse pos acc _ = token_error pos

    and lexChar tok pos acc xs =
        lex pos (tok :: acc) xs
        
    and lexString pos acc cc =
        let datatype escaped = ESCAPED | NORMAL
            fun lexString' pos text ESCAPED [] =
                error pos "End of input during escape sequence"
              | lexString' pos text NORMAL [] = 
                error pos "End of input during string"
              | lexString' pos text ESCAPED (x :: xs) =
                let fun esc c = lexString' (pos + 1) (c :: text) NORMAL xs
                in case x of
                       #"\"" => esc x
                     | #"\\" => esc x
                     | #"/"  => esc x
                     | #"b"  => esc #"\b"
                     | #"f"  => esc #"\f"
                     | #"n"  => esc #"\n"
                     | #"r"  => esc #"\r"
                     | #"t"  => esc #"\t"
                     | _     => error pos ("Invalid escape \\" ^
                                           Char.toString x)
                end
              | lexString' pos text NORMAL (#"\\" :: #"u" ::a::b::c::d:: xs) =
                if List.all Char.isHexDigit [a,b,c,d]
                then case Word.fromString ("0wx" ^ (implode [a,b,c,d])) of
                         SOME w => (let val utf = rev (bmpToUtf8 w) in
                                        lexString' (pos + 6) (utf @ text)
                                                   NORMAL xs
                                    end
                                    handle Fail err => error pos err)
                       | NONE => error pos "Invalid Unicode BMP escape sequence"
                else error pos "Invalid Unicode BMP escape sequence"
              | lexString' pos text NORMAL (x :: xs) =
                if Char.ord x < 0x20
                then error pos "Invalid unescaped control character"
                else
                    case x of
                        #"\"" => OK (rev text, xs, pos + 1)
                      | #"\\" => lexString' (pos + 1) text ESCAPED xs
                      | _     => lexString' (pos + 1) (x :: text) NORMAL xs
        in
            case lexString' pos [] NORMAL cc of
                OK (text, rest, newpos) =>
                lex newpos (T.STRING (implode text) :: acc) rest
              | ERROR e => ERROR e
        end

    and lexNumber firstChar pos acc cc =
        let val valid = explode ".+-e"
            fun lexNumber' pos digits [] = (rev digits, [], pos)
              | lexNumber' pos digits (x :: xs) =
                if x = #"E" then lexNumber' (pos + 1) (#"e" :: digits) xs
                else if Char.isDigit x orelse List.exists (fn c => x = c) valid
                then lexNumber' (pos + 1) (x :: digits) xs
                else (rev digits, x :: xs, pos)
            val (digits, rest, newpos) =
                lexNumber' (pos - 1) [] (firstChar :: cc)
        in
            case digits of
                [] => token_error pos
              | _ => lex newpos (T.NUMBER digits :: acc) rest
        end
                                           
    and lex pos acc [] = OK (rev acc)
      | lex pos acc (x::xs) = 
        (case x of
             #" "  => lex
           | #"\t" => lex
           | #"\n" => lex
           | #"\r" => lex
           | #"{"  => lexChar T.CURLY_L
           | #"}"  => lexChar T.CURLY_R
           | #"["  => lexChar T.SQUARE_L
           | #"]"  => lexChar T.SQUARE_R
           | #":"  => lexChar T.COLON
           | #","  => lexChar T.COMMA
           | #"\"" => lexString
           | #"t"  => lexTrue
           | #"f"  => lexFalse
           | #"n"  => lexNull
           | x     => lexNumber x) (pos + 1) acc xs

    fun show [] = "end of input"
      | show (tok :: _) = T.toString tok

    fun parseNumber digits =
        (* Note lexNumber already case-insensitised the E for us *)
        let open Char

            fun okExpDigits [] = false
              | okExpDigits (c :: []) = isDigit c
              | okExpDigits (c :: cs) = isDigit c andalso okExpDigits cs

            fun okExponent [] = false
              | okExponent (#"+" :: cs) = okExpDigits cs
              | okExponent (#"-" :: cs) = okExpDigits cs
              | okExponent cc = okExpDigits cc

            fun okFracTrailing [] = true
              | okFracTrailing (c :: cs) =
                (isDigit c andalso okFracTrailing cs) orelse
                (c = #"e" andalso okExponent cs)

            fun okFraction [] = false
              | okFraction (c :: cs) =
                isDigit c andalso okFracTrailing cs

            fun okPosTrailing [] = true
              | okPosTrailing (#"." :: cs) = okFraction cs
              | okPosTrailing (#"e" :: cs) = okExponent cs
              | okPosTrailing (c :: cs) =
                isDigit c andalso okPosTrailing cs
                                                      
            fun okPositive [] = false
              | okPositive (#"0" :: []) = true
              | okPositive (#"0" :: #"." :: cs) = okFraction cs
              | okPositive (#"0" :: #"e" :: cs) = okExponent cs
              | okPositive (#"0" :: cs) = false
              | okPositive (c :: cs) = isDigit c andalso okPosTrailing cs
                    
            fun okNumber (#"-" :: cs) = okPositive cs
              | okNumber cc = okPositive cc
        in
            if okNumber digits
            then case Real.fromString (implode digits) of
                     NONE => ERROR "Number out of range"
                   | SOME r => OK r
            else ERROR ("Invalid number \"" ^ (implode digits) ^ "\"")
        end
                                     
    fun parseObject (T.CURLY_R :: xs) = OK (OBJECT [], xs)
      | parseObject tokens =
        let fun parsePair (T.STRING key :: T.COLON :: xs) =
                (case parseTokens xs of
                     ERROR e => ERROR e
                   | OK (j, xs) => OK ((key, j), xs))
              | parsePair other =
                ERROR ("Object key/value pair expected around \"" ^
                       show other ^ "\"")
            fun parseObject' acc [] = ERROR "End of input during object"
              | parseObject' acc tokens =
                case parsePair tokens of
                    ERROR e => ERROR e
                  | OK (pair, T.COMMA :: xs) =>
                    parseObject' (pair :: acc) xs
                  | OK (pair, T.CURLY_R :: xs) =>
                    OK (OBJECT (rev (pair :: acc)), xs)
                  | OK (_, _) => ERROR "Expected , or } after object element"
        in
            parseObject' [] tokens
        end

    and parseArray (T.SQUARE_R :: xs) = OK (ARRAY [], xs)
      | parseArray tokens =
        let fun parseArray' acc [] = ERROR "End of input during array"
              | parseArray' acc tokens =
                case parseTokens tokens of
                    ERROR e => ERROR e
                  | OK (j, T.COMMA :: xs) => parseArray' (j :: acc) xs
                  | OK (j, T.SQUARE_R :: xs) => OK (ARRAY (rev (j :: acc)), xs)
                  | OK (_, _) => ERROR "Expected , or ] after array element"
        in
            parseArray' [] tokens
        end

    and parseTokens [] = ERROR "Value expected"
      | parseTokens (tok :: xs) =
        (case tok of
             T.NUMBER d => (case parseNumber d of
                                OK r => OK (NUMBER r, xs)
                              | ERROR e => ERROR e)
           | T.STRING s => OK (STRING s, xs)
           | T.BOOL b   => OK (BOOL b, xs)
           | T.NULL     => OK (NULL, xs)
           | T.CURLY_L  => parseObject xs
           | T.SQUARE_L => parseArray xs
           | _ => ERROR ("Unexpected token " ^ T.toString tok ^
                         " before " ^ show xs))
                                   
    fun parse str =
        case lex 1 [] (explode str) of
           ERROR e => ERROR e
         | OK tokens => case parseTokens tokens of
                            OK (value, []) => OK value
                          | OK (_, _) => ERROR "Extra data after input"
                          | ERROR e => ERROR e

    fun stringEscape s =
        let fun esc x = [x, #"\\"]
            fun escape' acc [] = rev acc
              | escape' acc (x :: xs) =
                escape' (case x of
                             #"\"" => esc x @ acc
                           | #"\\" => esc x @ acc
                           | #"\b" => esc #"b" @ acc
                           | #"\f" => esc #"f" @ acc
                           | #"\n" => esc #"n" @ acc
                           | #"\r" => esc #"r" @ acc
                           | #"\t" => esc #"t" @ acc
                           | _ =>
                             let val c = Char.ord x
                             in
                                 if c < 0x20
                                 then let val hex = Word.toString (Word.fromInt c)
                                      in (rev o explode) (if c < 0x10
                                                          then ("\\u000" ^ hex)
                                                          else ("\\u00" ^ hex))
                                      end @ acc
                                 else 
                                     x :: acc
                             end)
                        xs
        in
            implode (escape' [] (explode s))
        end
        
    fun serialise json =
        case json of
            OBJECT pp => "{" ^ String.concatWith
                                   "," (map (fn (key, value) =>
                                                serialise (STRING key) ^ ":" ^
                                                serialise value) pp) ^
                         "}"
          | ARRAY arr => "[" ^ String.concatWith "," (map serialise arr) ^ "]"
          | NUMBER n => implode (map (fn #"~" => #"-" | c => c) 
                                     (explode (Real.toString n)))
          | STRING s => "\"" ^ stringEscape s ^ "\""
          | BOOL b => Bool.toString b
          | NULL => "null"
        
    fun serialiseIndented json =
        let fun indent 0 = ""
              | indent i = "  " ^ indent (i - 1)
            fun serialiseIndented' i json =
                let val ser = serialiseIndented' (i + 1)
                in
                    case json of
                        OBJECT [] => "{}"
                      | ARRAY [] => "[]"
                      | OBJECT pp => "{\n" ^ indent (i + 1) ^
                                     String.concatWith
                                         (",\n" ^ indent (i + 1))
                                         (map (fn (key, value) =>
                                                  ser (STRING key) ^ ": " ^
                                                  ser value) pp) ^
                                     "\n" ^ indent i ^ "}"
                      | ARRAY arr => "[\n" ^ indent (i + 1) ^
                                     String.concatWith
                                         (",\n" ^ indent (i + 1))
                                         (map ser arr) ^
                                     "\n" ^ indent i ^ "]"
                      | other => serialise other
                end
        in
            serialiseIndented' 0 json ^ "\n"
        end
                                             
end


structure JsonBits :> sig
    val load_json_from : string -> Json.json (* filename -> json *)
    val save_json_to : string -> Json.json -> unit
    val lookup_optional : Json.json -> string list -> Json.json option
    val lookup_optional_string : Json.json -> string list -> string option
    val lookup_mandatory : Json.json -> string list -> Json.json
    val lookup_mandatory_string : Json.json -> string list -> string
end = struct

    fun load_json_from filename =
        case Json.parse (FileBits.file_contents filename) of
            Json.OK json => json
          | Json.ERROR e => raise Fail ("Failed to parse file: " ^ e)

    fun save_json_to filename json =
        (* using binary I/O to avoid ever writing CR/LF line endings *)
        let val jstr = Json.serialiseIndented json
            val stream = BinIO.openOut filename
        in
            BinIO.output (stream, Byte.stringToBytes jstr);
            BinIO.closeOut stream
        end
                                  
    fun lookup_optional json kk =
        let fun lookup key =
                case json of
                    Json.OBJECT kvs =>
                    (case List.find (fn (k, v) => k = key) kvs of
                         SOME (k, v) => SOME v
                       | NONE => NONE)
                  | _ => raise Fail "Object expected"
        in
            case kk of
                [] => NONE
              | key::[] => lookup key
              | key::kk => case lookup key of
                               NONE => NONE
                             | SOME j => lookup_optional j kk
        end
                       
    fun lookup_optional_string json kk =
        case lookup_optional json kk of
            SOME (Json.STRING s) => SOME s
          | SOME _ => raise Fail ("Value (if present) must be string: " ^
                                  (String.concatWith " -> " kk))
          | NONE => NONE

    fun lookup_mandatory json kk =
        case lookup_optional json kk of
            SOME v => v
          | NONE => raise Fail ("Value is mandatory: " ^
                                (String.concatWith " -> " kk) ^ " in json: " ^
                                (Json.serialise json))
                          
    fun lookup_mandatory_string json kk =
        case lookup_optional json kk of
            SOME (Json.STRING s) => s
          | _ => raise Fail ("Value must be string: " ^
                             (String.concatWith " -> " kk))
end

structure Provider :> sig
    val load_providers : Json.json -> provider list
    val load_more_providers : provider list -> Json.json -> provider list
    val remote_url : context -> vcs -> source -> libname -> string
end = struct

    val known_providers : provider list =
        [ {
            service = "bitbucket",
            supports = [HG, GIT],
            remote_spec = {
                anon = SOME "https://bitbucket.org/{owner}/{repository}",
                auth = SOME "ssh://{vcs}@bitbucket.org/{owner}/{repository}"
            }
          },
          {
            service = "github",
            supports = [GIT],
            remote_spec = {
                anon = SOME "https://github.com/{owner}/{repository}",
                auth = SOME "ssh://{vcs}@github.com/{owner}/{repository}"
            }
          }
        ]

    fun vcs_name vcs =
        case vcs of HG => "hg"
                  | GIT => "git"
                  | SVN => "svn"
                                             
    fun vcs_from_name name =
        case name of "hg" => HG
                   | "git" => GIT 
                   | "svn" => SVN
                   | other => raise Fail ("Unknown vcs name \"" ^ name ^ "\"")

    fun load_more_providers previously_loaded json =
        let open JsonBits
            fun load pjson pname : provider =
                {
                  service = pname,
                  supports =
                  case lookup_mandatory pjson ["vcs"] of
                      Json.ARRAY vv =>
                      map (fn (Json.STRING v) => vcs_from_name v
                          | _ => raise Fail "Strings expected in vcs array")
                          vv
                    | _ => raise Fail "Array expected for vcs",
                  remote_spec = {
                      anon = lookup_optional_string pjson ["anonymous"],
                      auth = lookup_optional_string pjson ["authenticated"]
                  }
                }
            val loaded = 
                case lookup_optional json ["services"] of
                    NONE => []
                  | SOME (Json.OBJECT pl) => map (fn (k, v) => load v k) pl
                  | _ => raise Fail "Object expected for services in config"
            val newly_loaded =
                List.filter (fn p => not (List.exists (fn pp => #service p =
                                                                #service pp)
                                                      previously_loaded))
                            loaded
        in
            previously_loaded @ newly_loaded
        end

    fun load_providers json =
        load_more_providers known_providers json
                                                    
    fun expand_spec spec { vcs, service, owner, repo } login =
        (* ugly *)
        let fun replace str = 
                case str of
                    "vcs" => vcs_name vcs
                  | "service" => service
                  | "owner" =>
                    (case owner of
                         SOME ostr => ostr
                       | NONE => raise Fail ("Owner not specified for service " ^
                                             service))
                  | "repository" => repo
                  | "account" =>
                    (case login of
                         SOME acc => acc
                       | NONE => raise Fail ("Account not given for service " ^
                                             service))
                  | other => raise Fail ("Unknown variable \"" ^ other ^
                                         "\" in spec for service " ^ service)
            fun expand' acc sstr =
                case Substring.splitl (fn c => c <> #"{") sstr of
                    (pfx, sfx) =>
                    if Substring.isEmpty sfx
                    then rev (pfx :: acc)
                    else 
                        case Substring.splitl (fn c => c <> #"}") sfx of
                            (tok, remainder) =>
                            if Substring.isEmpty remainder
                            then rev (tok :: pfx :: acc)
                            else let val replacement =
                                         replace
                                             (* tok begins with "{": *)
                                             (Substring.string
                                                  (Substring.triml 1 tok))
                                 in
                                     expand' (Substring.full replacement ::
                                              pfx :: acc)
                                             (* remainder begins with "}": *)
                                             (Substring.triml 1 remainder)
                                 end
        in
            Substring.concat (expand' [] (Substring.full spec))
        end
        
    fun provider_url req login providers =
        case providers of
            [] => raise Fail ("Unknown service \"" ^ (#service req) ^
                              "\" for vcs \"" ^ (vcs_name (#vcs req)) ^ "\"")
          | ({ service, supports, remote_spec : remote_spec } :: rest) =>
            if service <> (#service req) orelse
               not (List.exists (fn v => v = (#vcs req)) supports)
            then provider_url req login rest
            else
                case (login, #auth remote_spec, #anon remote_spec) of
                    (SOME _, SOME auth, _) => expand_spec auth req login
                  | (SOME _, _, SOME anon) => expand_spec anon req NONE
                  | (NONE,   _, SOME anon) => expand_spec anon req NONE
                  | _ => raise Fail ("No suitable anonymous or authenticated " ^
                                     "URL spec provided for service \"" ^
                                     service ^ "\"")

    fun login_for ({ accounts, ... } : context) service =
        case List.find (fn a => service = #service a) accounts of
            SOME { login, ... } => SOME login
          | NONE => NONE

    fun reponame_for path =
        case String.tokens (fn c => c = #"/") path of
            [] => raise Fail "Non-empty library path required"
          | toks => hd (rev toks)
                        
    fun remote_url (context : context) vcs source libname =
        case source of
            URL_SOURCE u => u
          | SERVICE_SOURCE { service, owner, repo } =>
            provider_url { vcs = vcs,
                           service = service,
                           owner = owner,
                           repo = case repo of
                                      SOME r => r
                                    | NONE => reponame_for libname }
                         (login_for context service)
                         (#providers context)
end

structure HgControl :> VCS_CONTROL = struct

    (* Pulls always use an explicit URL, never just the default
       remote, in order to ensure we update properly if the location
       given in the project file changes. *)

    type vcsstate = { id: string, modified: bool,
                      branch: string, tags: string list }

    val hg_args = [ "--config", "ui.interactive=true",
                    "--config", "ui.merge=:merge" ]
                        
    fun hg_command context libname args =
        FileBits.command context libname ("hg" :: hg_args @ args)

    fun hg_command_output context libname args =
        FileBits.command_output context libname ("hg" :: hg_args @ args)
                        
    fun exists context libname =
        OK (OS.FileSys.isDir (FileBits.subpath context libname ".hg"))
        handle _ => OK false

    fun remote_for context (libname, source) =
        Provider.remote_url context HG source libname

    fun current_state context libname : vcsstate result =
        let fun is_branch text = text <> "" andalso #"(" = hd (explode text)
            and extract_branch b =
                if is_branch b     (* need to remove enclosing parens *)
                then (implode o rev o tl o rev o tl o explode) b
                else "default"
            and is_modified id = id <> "" andalso #"+" = hd (rev (explode id))
            and extract_id id =
                if is_modified id  (* need to remove trailing "+" *)
                then (implode o rev o tl o rev o explode) id
                else id
            and split_tags tags = String.tokens (fn c => c = #"/") tags
            and state_for (id, branch, tags) =
                OK { id = extract_id id,
                     modified = is_modified id,
                     branch = extract_branch branch,
                     tags = split_tags tags }
        in        
            case hg_command_output context libname ["id"] of
                ERROR e => ERROR e
              | OK out =>
                case String.tokens (fn x => x = #" ") out of
                    [id, branch, tags] => state_for (id, branch, tags)
                  | [id, other] => if is_branch other
                                   then state_for (id, other, "")
                                   else state_for (id, "", other)
                  | [id] => state_for (id, "", "")
                  | _ => ERROR ("Unexpected output from hg id: " ^ out)
        end

    fun branch_name branch = case branch of
                                 DEFAULT_BRANCH => "default"
                               | BRANCH "" => "default"
                               | BRANCH b => b

    fun id_of context libname =
        case current_state context libname of
            ERROR e => ERROR e
          | OK { id, ... } => OK id

    fun is_at context (libname, id_or_tag) =
        case current_state context libname of
            ERROR e => ERROR e
          | OK { id, tags, ... } => 
            OK (String.isPrefix id_or_tag id orelse
                String.isPrefix id id_or_tag orelse
                List.exists (fn t => t = id_or_tag) tags)

    fun is_on_branch context (libname, b) =
        case current_state context libname of
            ERROR e => ERROR e
          | OK { branch, ... } => OK (branch = branch_name b)
               
    fun is_newest_locally context (libname, branch) =
        case hg_command_output context libname
                               ["log", "-l1",
                                "-b", branch_name branch,
                                "--template", "{node}"] of
            ERROR e => OK false (* desired branch does not exist *)
          | OK newest_in_repo => is_at context (libname, newest_in_repo)

    fun pull context (libname, source) =
        let val url = remote_for context (libname, source)
        in
            hg_command context libname
                       (if FileBits.verbose ()
                        then ["pull", url]
                        else ["pull", "-q", url])
        end

    fun is_newest context (libname, source, branch) =
        case is_newest_locally context (libname, branch) of
            ERROR e => ERROR e
          | OK false => OK false
          | OK true =>
            case pull context (libname, source) of
                ERROR e => ERROR e
              | _ => is_newest_locally context (libname, branch)

    fun is_modified_locally context libname =
        case current_state context libname of
            ERROR e => ERROR e
          | OK { modified, ... } => OK modified
                
    fun checkout context (libname, source, branch) =
        let val url = remote_for context (libname, source)
        in
            (* make the lib dir rather than just the ext dir, since
               the lib dir might be nested and hg will happily check
               out into an existing empty dir anyway *)
            case FileBits.mkpath (FileBits.libpath context libname) of
                ERROR e => ERROR e
              | _ => hg_command context ""
                                ["clone", "-u", branch_name branch,
                                 url, libname]
        end
                                                    
    fun update context (libname, source, branch) =
        let val pull_result = pull context (libname, source)
        in
            case hg_command context libname ["update", branch_name branch] of
                ERROR e => ERROR e
              | _ =>
                case pull_result of
                    ERROR e => ERROR e
                  | _ => OK ()
        end

    fun update_to context (libname, _, "") =
        ERROR "Non-empty id (tag or revision id) required for update_to"
      | update_to context (libname, source, id) = 
        let val pull_result = pull context (libname, source)
        in
            case hg_command context libname ["update", "-r", id] of
                OK _ => OK ()
              | ERROR e =>
                case pull_result of
                    ERROR e' => ERROR e' (* this was the ur-error *)
                  | _ => ERROR e
        end

    fun copy_url_for context libname =
        OK (FileBits.file_url (FileBits.libpath context libname))
            
end

structure GitControl :> VCS_CONTROL = struct

    (* With Git repos we always operate in detached HEAD state. Even
       the master branch is checked out using a remote reference
       (vext/master). The remote we use is always named vext, and we
       update it to the expected URL each time we fetch, in order to
       ensure we update properly if the location given in the project
       file changes. The origin remote is unused. *)

    fun git_command context libname args =
        FileBits.command context libname ("git" :: args)

    fun git_command_output context libname args =
        FileBits.command_output context libname ("git" :: args)
                            
    fun exists context libname =
        OK (OS.FileSys.isDir (FileBits.subpath context libname ".git"))
        handle _ => OK false

    fun remote_for context (libname, source) =
        Provider.remote_url context GIT source libname

    fun branch_name branch = case branch of
                                 DEFAULT_BRANCH => "master"
                               | BRANCH "" => "master"
                               | BRANCH b => b

    val our_remote = "vext"
                                                 
    fun remote_branch_name branch = our_remote ^ "/" ^ branch_name branch

    fun checkout context (libname, source, branch) =
        let val url = remote_for context (libname, source)
        in
            (* make the lib dir rather than just the ext dir, since
               the lib dir might be nested and git will happily check
               out into an existing empty dir anyway *)
            case FileBits.mkpath (FileBits.libpath context libname) of
                OK () => git_command context ""
                                     ["clone", "--origin", our_remote,
                                      "--branch", branch_name branch,
                                      url, libname]
              | ERROR e => ERROR e
        end

    fun add_our_remote context (libname, source) =
        (* When we do the checkout ourselves (above), we add the
           remote at the same time. But if the repo was cloned by
           someone else, we'll need to do it after the fact. Git
           doesn't seem to have a means to add a remote or change its
           url if it already exists; seems we have to do this: *)
        let val url = remote_for context (libname, source)
        in
            case git_command context libname
                             ["remote", "set-url", our_remote, url] of
                OK () => OK ()
              | ERROR e => git_command context libname
                                       ["remote", "add", "-f", our_remote, url]
        end

    (* NB git rev-parse HEAD shows revision id of current checkout;
       git rev-list -1 <tag> shows revision id of revision with that tag *)

    fun id_of context libname =
        git_command_output context libname ["rev-parse", "HEAD"]
            
    fun is_at context (libname, id_or_tag) =
        case id_of context libname of
            ERROR e => OK false (* HEAD nonexistent, expected in empty repo *)
          | OK id =>
            if String.isPrefix id_or_tag id orelse
               String.isPrefix id id_or_tag
            then OK true
            else 
                case git_command_output context libname
                                        ["show-ref",
                                         "refs/tags/" ^ id_or_tag,
                                         "--"] of
                    OK "" => OK false
                  | ERROR _ => OK false
                  | OK s => OK (id = hd (String.tokens (fn c => c = #" ") s))

    fun branch_tip context (libname, branch) =
        (* We don't have access to the source info or the network
           here, as this is used by status (e.g. via is_on_branch) as
           well as review. It's possible the remote branch won't exist,
           e.g. if the repo was checked out by something other than
           Vext, and if that's the case, we can't add it here; we'll
           just have to fail, since checking against local branches
           instead could produce the wrong result. *)
        git_command_output context libname
                           ["rev-list", "-1",
                            remote_branch_name branch, "--"]
                       
    fun is_newest_locally context (libname, branch) =
        case branch_tip context (libname, branch) of
            ERROR e => OK false
          | OK rev => is_at context (libname, rev)

    fun is_on_branch context (libname, branch) =
        case branch_tip context (libname, branch) of
            ERROR e => OK false
          | OK rev =>
            case is_at context (libname, rev) of
                ERROR e => ERROR e
              | OK true => OK true
              | OK false =>
                case git_command context libname
                                 ["merge-base", "--is-ancestor",
                                  "HEAD", remote_branch_name branch] of
                    ERROR e => OK false  (* cmd returns non-zero for no *)
                  | _ => OK true

    fun fetch context (libname, source) =
        case add_our_remote context (libname, source) of
            ERROR e => ERROR e
          | _ => git_command context libname ["fetch", our_remote]
                            
    fun is_newest context (libname, source, branch) =
        case add_our_remote context (libname, source) of
            ERROR e => ERROR e
          | OK () => 
            case is_newest_locally context (libname, branch) of
                ERROR e => ERROR e
              | OK false => OK false
              | OK true =>
                case fetch context (libname, source) of
                    ERROR e => ERROR e
                  | _ => is_newest_locally context (libname, branch)

    fun is_modified_locally context libname =
        case git_command_output context libname ["status", "--porcelain"] of
            ERROR e => ERROR e
          | OK "" => OK false
          | OK _ => OK true

    (* This function updates to the latest revision on a branch rather
       than to a specific id or tag. We can't just checkout the given
       branch, as that will succeed even if the branch isn't up to
       date. We could checkout the branch and then fetch and merge,
       but it's perhaps cleaner not to maintain a local branch at all,
       but instead checkout the remote branch as a detached head. *)

    fun update context (libname, source, branch) =
        case fetch context (libname, source) of
            ERROR e => ERROR e
          | _ =>
            case git_command context libname ["checkout", "--detach",
                                              remote_branch_name branch] of
                ERROR e => ERROR e
              | _ => OK ()

    (* This function is dealing with a specific id or tag, so if we
       can successfully check it out (detached) then that's all we
       need to do, regardless of whether fetch succeeded or not. We do
       attempt the fetch first, though, purely in order to avoid ugly
       error messages in the common case where we're being asked to
       update to a new pin (from the lock file) that hasn't been
       fetched yet. *)

    fun update_to context (libname, _, "") = 
        ERROR "Non-empty id (tag or revision id) required for update_to"
      | update_to context (libname, source, id) =
        let val fetch_result = fetch context (libname, source)
        in
            case git_command context libname ["checkout", "--detach", id] of
                OK _ => OK ()
              | ERROR e =>
                case fetch_result of
                    ERROR e' => ERROR e' (* this was the ur-error *)
                  | _ => ERROR e
        end

    fun copy_url_for context libname =
        OK (FileBits.file_url (FileBits.libpath context libname))
            
end

structure SvnControl :> VCS_CONTROL = struct

    fun svn_command context libname args =
        FileBits.command context libname ("svn" :: args)

    fun svn_command_output context libname args =
        FileBits.command_output context libname ("svn" :: args)

    fun svn_command_lines context libname args =
        case svn_command_output context libname args of
            ERROR e => ERROR e
          | OK s => OK (String.tokens (fn c => c = #"\n" orelse c = #"\r") s)

    fun split_line_pair line =
        let fun strip_leading_ws str = case explode str of
                                           #" "::rest => implode rest
                                         | _ => str
        in
            case String.tokens (fn c => c = #":") line of
                [] => ("", "")
              | first::rest =>
                (first, strip_leading_ws (String.concatWith ":" rest))
        end
            
    fun svn_info_item context libname key =
        (* SVN 1.9 has info --show-item which is what we need, but at
           this point we still have 1.8 on the CI boxes so we might as 
           well aim to support it *)
        case svn_command_lines context libname ["info"] of
            ERROR e => ERROR e
          | OK lines =>
            case List.find (fn (k, v) => k = key) (map split_line_pair lines) of
                NONE => ERROR ("Key \"" ^ key ^ "\" not found in output")
              | SOME (_, v) => OK v
            
    fun exists context libname =
        OK (OS.FileSys.isDir (FileBits.subpath context libname ".svn"))
        handle _ => OK false

    fun remote_for context (libname, source) =
        Provider.remote_url context SVN source libname

    fun id_of context libname =
        svn_info_item context libname "Revision" (*!!! check: does svn localise this? should we ensure C locale? *)

    fun is_at context (libname, id_or_tag) =
        case id_of context libname of
            ERROR e => ERROR e
          | OK id => OK (id = id_or_tag)

    fun is_on_branch context (libname, b) =
        OK (b = DEFAULT_BRANCH)
               
    fun is_newest context (libname, source, branch) =
        case svn_command_lines context libname ["status", "--show-updates"] of 
            ERROR e => ERROR e
          | OK lines =>
            case rev lines of
                [] => ERROR "No result returned for server status"
              | last_line::_ =>
                case rev (String.tokens (fn c => c = #" ") last_line) of
                    [] => ERROR "No revision field found in server status"
                  | server_id::_ => is_at context (libname, server_id)

    fun is_newest_locally context (libname, branch) =
        OK true (* no local history *)

    fun is_modified_locally context libname =
        case svn_command_output context libname ["status"] of
            ERROR e => ERROR e
          | OK "" => OK false
          | OK _ => OK true

    fun checkout context (libname, source, branch) =
        let val url = remote_for context (libname, source)
            val path = FileBits.libpath context libname
        in
            if FileBits.nonempty_dir_exists path
            then (* Surprisingly, SVN itself has no problem with
                    this. But for consistency with other VCSes we 
                    don't allow it *)
                ERROR ("Refusing checkout to nonempty dir \"" ^ path ^ "\"")
            else 
                (* make the lib dir rather than just the ext dir, since
                   the lib dir might be nested and svn will happily check
                   out into an existing empty dir anyway *)
                case FileBits.mkpath (FileBits.libpath context libname) of
                    ERROR e => ERROR e
                  | _ => svn_command context "" ["checkout", url, libname]
        end
                                                    
    fun update context (libname, source, branch) =
        case svn_command context libname
                         ["update", "--accept", "postpone"] of
            ERROR e => ERROR e
          | _ => OK ()

    fun update_to context (libname, _, "") =
        ERROR "Non-empty id (tag or revision id) required for update_to"
      | update_to context (libname, source, id) = 
        case svn_command context libname
                         ["update", "-r", id, "--accept", "postpone"] of
            ERROR e => ERROR e
          | OK _ => OK ()

    fun copy_url_for context libname =
        svn_info_item context libname "URL"

end

structure AnyLibControl :> LIB_CONTROL = struct

    structure H = LibControlFn(HgControl)
    structure G = LibControlFn(GitControl)
    structure S = LibControlFn(SvnControl)

    fun review context (spec as { vcs, ... } : libspec) =
        (fn HG => H.review | GIT => G.review | SVN => S.review) vcs context spec

    fun status context (spec as { vcs, ... } : libspec) =
        (fn HG => H.status | GIT => G.status | SVN => S.status) vcs context spec

    fun update context (spec as { vcs, ... } : libspec) =
        (fn HG => H.update | GIT => G.update | SVN => S.update) vcs context spec

    fun id_of context (spec as { vcs, ... } : libspec) =
        (fn HG => H.id_of | GIT => G.id_of | SVN => S.id_of) vcs context spec

end


type exclusions = string list
              
structure Archive :> sig

    val archive : string * exclusions -> project -> OS.Process.status
        
end = struct

    (* The idea of "archive" is to replace hg/git archive, which won't
       include files, like the Vext-introduced external libraries,
       that are not under version control with the main repo.

       The process goes like this:

       - Make sure we have a target filename from the user, and take
         its basename as our archive directory name

       - Make an "archive root" subdir of the project repo, named
         typically .vext-archive
       
       - Identify the VCS used for the project repo. Note that any
         explicit references to VCS type in this structure are to
         the VCS used for the project (something Vext doesn't 
         otherwise care about), not for an individual library

       - Synthesise a Vext project with the archive root as its
         root path, "." as its extdir, with one library whose
         name is the user-supplied basename and whose explicit
         source URL is the original project root; update that
         project -- thus cloning the original project to a subdir
         of the archive root

       - Synthesise a Vext project identical to the original one for
         this project, but with the newly-cloned copy as its root
         path; update that project -- thus checking out clean copies
         of the external library dirs

       - Call out to an archive program to archive up the new copy,
         running e.g.
         tar cvzf project-release.tar.gz \
             --exclude=.hg --exclude=.git project-release
         in the archive root dir

       - (We also omit the vext-project.json file and any trace of
         Vext. It can't properly be run in a directory where the
         external project folders already exist but their repo history
         does not. End users shouldn't get to see Vext)

       - Clean up by deleting the new copy
    *)

    fun project_vcs_id_and_url dir =
        let val context = {
                rootpath = dir,
                extdir = ".",
                providers = [],
                accounts = []
            }
            val vcs_maybe = 
                case [HgControl.exists context ".",
                      GitControl.exists context ".",
                      SvnControl.exists context "."] of
                    [OK true, OK false, OK false] => OK HG
                  | [OK false, OK true, OK false] => OK GIT
                  | [OK false, OK false, OK true] => OK SVN
                  | _ => ERROR ("Unable to identify VCS for directory " ^ dir)
        in
            case vcs_maybe of
                ERROR e => ERROR e
              | OK vcs =>
                case (fn HG => HgControl.id_of
                       | GIT => GitControl.id_of 
                       | SVN => SvnControl.id_of)
                         vcs context "." of
                    ERROR e => ERROR ("Unable to find id of project repo: " ^ e)
                  | OK id =>
                    case (fn HG => HgControl.copy_url_for
                           | GIT => GitControl.copy_url_for
                           | SVN => SvnControl.copy_url_for)
                             vcs context "." of
                        ERROR e => ERROR ("Unable to find URL of project repo: "
                                          ^ e)
                      | OK url => OK (vcs, id, url)
        end
            
    fun make_archive_root (context : context) =
        let val path = OS.Path.joinDirFile {
                    dir = #rootpath context,
                    file = VextFilenames.archive_dir
                }
        in
            case FileBits.mkpath path of
                ERROR e => raise Fail ("Failed to create archive directory \""
                                       ^ path ^ "\": " ^ e)
              | OK () => path
        end

    fun archive_path archive_dir target_name =
        OS.Path.joinDirFile {
            dir = archive_dir,
            file = target_name
        }

    fun check_nonexistent path =
        case SOME (OS.FileSys.fileSize path) handle OS.SysErr _ => NONE of
            NONE => ()
          | _ => raise Fail ("Path " ^ path ^ " exists, not overwriting")
            
    fun make_archive_copy target_name (vcs, project_id, source_url)
                          ({ context, ... } : project) =
        let val archive_root = make_archive_root context
            val synthetic_context = {
                rootpath = archive_root,
                extdir = ".",
                providers = [],
                accounts = []
            }
            val synthetic_library = {
                libname = target_name,
                vcs = vcs,
                source = URL_SOURCE source_url,
                branch = DEFAULT_BRANCH, (* overridden by pinned id below *)
                project_pin = PINNED project_id,
                lock_pin = PINNED project_id
            }
            val path = archive_path archive_root target_name
            val _ = print ("Cloning original project to " ^ path
                           ^ " at revision " ^ project_id ^ "...\n");
            val _ = check_nonexistent path
        in
            case AnyLibControl.update synthetic_context synthetic_library of
                ERROR e => ERROR ("Failed to clone original project to "
                                  ^ path ^ ": " ^ e)
              | OK _ => OK archive_root
        end

    fun update_archive archive_root target_name
                       (project as { context, ... } : project) =
        let val synthetic_context = {
                rootpath = archive_path archive_root target_name,
                extdir = #extdir context,
                providers = #providers context,
                accounts = #accounts context
            }
        in
            foldl (fn (lib, acc) =>
                      case acc of
                          ERROR e => ERROR e
                        | OK () => AnyLibControl.update synthetic_context lib)
                  (OK ())
                  (#libs project)
        end

    datatype packer = TAR
                    | TAR_GZ
                    | TAR_BZ2
                    | TAR_XZ
    (* could add other packers, e.g. zip, if we knew how to
       handle the file omissions etc properly in pack_archive *)
                          
    fun packer_and_basename path =
        let val extensions = [ (".tar", TAR),
                               (".tar.gz", TAR_GZ),
                               (".tar.bz2", TAR_BZ2),
                               (".tar.xz", TAR_XZ)]
            val filename = OS.Path.file path
        in
            foldl (fn ((ext, packer), acc) =>
                      if String.isSuffix ext filename
                      then SOME (packer,
                                 String.substring (filename, 0,
                                                   String.size filename -
                                                   String.size ext))
                      else acc)
                  NONE
                  extensions
        end
            
    fun pack_archive archive_root target_name target_path packer exclusions =
        case FileBits.command {
                rootpath = archive_root,
                extdir = ".",
                providers = [],
                accounts = []
            } "" ([
                     "tar",
                     case packer of
                         TAR => "cf"
                       | TAR_GZ => "czf"
                       | TAR_BZ2 => "cjf"
                       | TAR_XZ => "cJf",
                     target_path,
                     "--exclude=.hg",
                     "--exclude=.git",
                     "--exclude=.svn",
                     "--exclude=vext",
                     "--exclude=vext.sml",
                     "--exclude=vext.ps1",
                     "--exclude=vext.bat",
                     "--exclude=vext-project.json",
                     "--exclude=vext-lock.json"
                 ] @ (map (fn e => "--exclude=" ^ e) exclusions) @
                  [ target_name ])
         of
            ERROR e => ERROR e
          | OK _ => FileBits.rmpath (archive_path archive_root target_name)
            
    fun archive (target_path, exclusions) (project : project) =
        let val _ = check_nonexistent target_path
            val (packer, name) =
                case packer_and_basename target_path of
                    NONE => raise Fail ("Unsupported archive file extension in "
                                        ^ target_path)
                  | SOME pn => pn
            val details =
                case project_vcs_id_and_url (#rootpath (#context project)) of
                    ERROR e => raise Fail e
                  | OK details => details
            val archive_root =
                case make_archive_copy name details project of
                    ERROR e => raise Fail e
                  | OK archive_root => archive_root
            val outcome = 
                case update_archive archive_root name project of
                    ERROR e => ERROR e
                  | OK _ =>
                    case pack_archive archive_root name
                                      target_path packer exclusions of
                        ERROR e => ERROR e
                      | OK _ => OK ()
        in
            case outcome of
                ERROR e => raise Fail e
              | OK () => OS.Process.success
        end
            
end

val libobjname = "libraries"
                                             
fun load_libspec spec_json lock_json libname : libspec =
    let open JsonBits
        val libobj   = lookup_mandatory spec_json [libobjname, libname]
        val vcs      = lookup_mandatory_string libobj ["vcs"]
        val retrieve = lookup_optional_string libobj
        val service  = retrieve ["service"]
        val owner    = retrieve ["owner"]
        val repo     = retrieve ["repository"]
        val url      = retrieve ["url"]
        val branch   = retrieve ["branch"]
        val project_pin = case retrieve ["pin"] of
                              NONE => UNPINNED
                            | SOME p => PINNED p
        val lock_pin = case lookup_optional lock_json [libobjname, libname] of
                           NONE => UNPINNED
                         | SOME ll => case lookup_optional_string ll ["pin"] of
                                          SOME p => PINNED p
                                        | NONE => UNPINNED
    in
        {
          libname = libname,
          vcs = case vcs of
                    "hg" => HG
                  | "git" => GIT
                  | "svn" => SVN
                  | other => raise Fail ("Unknown version-control system \"" ^
                                         other ^ "\""),
          source = case (url, service, owner, repo) of
                       (SOME u, NONE, _, _) => URL_SOURCE u
                     | (NONE, SOME ss, owner, repo) =>
                       SERVICE_SOURCE { service = ss, owner = owner, repo = repo }
                     | _ => raise Fail ("Must have exactly one of service " ^
                                        "or url string"),
          project_pin = project_pin,
          lock_pin = lock_pin,
          branch = case branch of
                       NONE => DEFAULT_BRANCH
                     | SOME b => 
                       case vcs of
                           "svn" => raise Fail ("Branches not supported for " ^
                                                "svn repositories; change " ^
                                                "URL instead")
                         | _ => BRANCH b
        }
    end  

fun load_userconfig () : userconfig =
    let val home = FileBits.homedir ()
        val conf_json = 
            JsonBits.load_json_from
                (OS.Path.joinDirFile {
                      dir = home,
                      file = VextFilenames.user_config_file })
            handle IO.Io _ => Json.OBJECT []
    in
        {
          accounts = case JsonBits.lookup_optional conf_json ["accounts"] of
                         NONE => []
                       | SOME (Json.OBJECT aa) =>
                         map (fn (k, (Json.STRING v)) =>
                                 { service = k, login = v }
                             | _ => raise Fail
                                          "String expected for account name")
                             aa
                       | _ => raise Fail "Array expected for accounts",
          providers = Provider.load_providers conf_json
        }
    end

datatype pintype =
         NO_LOCKFILE |
         USE_LOCKFILE
        
fun load_project (userconfig : userconfig) rootpath pintype : project =
    let val spec_file = FileBits.project_spec_path rootpath
        val lock_file = FileBits.project_lock_path rootpath
        val _ = if OS.FileSys.access (spec_file, [OS.FileSys.A_READ])
                   handle OS.SysErr _ => false
                then ()
                else raise Fail ("Failed to open project spec file " ^
                                 (VextFilenames.project_file) ^ " in " ^
                                 rootpath ^
                                 ".\nPlease ensure the spec file is in the " ^
                                 "project root and run this from there.")
        val spec_json = JsonBits.load_json_from spec_file
        val lock_json = if pintype = USE_LOCKFILE
                        then JsonBits.load_json_from lock_file
                             handle IO.Io _ => Json.OBJECT []
                        else Json.OBJECT []
        val extdir = JsonBits.lookup_mandatory_string spec_json
                                                      ["config", "extdir"]
        val spec_libs = JsonBits.lookup_optional spec_json [libobjname]
        val lock_libs = JsonBits.lookup_optional lock_json [libobjname]
        val providers = Provider.load_more_providers
                            (#providers userconfig) spec_json
        val libnames = case spec_libs of
                           NONE => []
                         | SOME (Json.OBJECT ll) => map (fn (k, v) => k) ll
                         | _ => raise Fail "Object expected for libs"
    in
        {
          context = {
            rootpath = rootpath,
            extdir = extdir,
            providers = providers,
            accounts = #accounts userconfig
          },
          libs = map (load_libspec spec_json lock_json) libnames
        }
    end

fun save_lock_file rootpath locks =
    let val lock_file = FileBits.project_lock_path rootpath
        open Json
        val lock_json =
            OBJECT [
                (libobjname,
                 OBJECT (map (fn { libname, id_or_tag } =>
                                 (libname,
                                  OBJECT [ ("pin", STRING id_or_tag) ]))
                             locks))
            ]
    in
        JsonBits.save_json_to lock_file lock_json
    end
        
fun pad_to n str =
    if n <= String.size str then str
    else pad_to n (str ^ " ")

fun hline_to 0 = ""
  | hline_to n = "-" ^ hline_to (n-1)

val libname_width = 25
val libstate_width = 11
val localstate_width = 17
val notes_width = 5
val divider = " | "
val clear_line = "\r" ^ pad_to 80 "";

fun print_status_header () =
    print (clear_line ^ "\n " ^
           pad_to libname_width "Library" ^ divider ^
           pad_to libstate_width "State" ^ divider ^
           pad_to localstate_width "Local" ^ divider ^
           "Notes" ^ "\n " ^
           hline_to libname_width ^ "-+-" ^
           hline_to libstate_width ^ "-+-" ^
           hline_to localstate_width ^ "-+-" ^
           hline_to notes_width ^ "\n")

fun print_outcome_header () =
    print (clear_line ^ "\n " ^
           pad_to libname_width "Library" ^ divider ^
           pad_to libstate_width "Outcome" ^ divider ^
           "Notes" ^ "\n " ^
           hline_to libname_width ^ "-+-" ^
           hline_to libstate_width ^ "-+-" ^
           hline_to notes_width ^ "\n")
                        
fun print_status with_network (libname, status) =
    let val libstate_str =
            case status of
                OK (ABSENT, _) => "Absent"
              | OK (CORRECT, _) => if with_network then "Correct" else "Present"
              | OK (SUPERSEDED, _) => "Superseded"
              | OK (WRONG, _) => "Wrong"
              | ERROR _ => "Error"
        val localstate_str =
            case status of
                OK (_, MODIFIED) => "Modified"
              | OK (_, LOCK_MISMATCHED) => "Differs from Lock"
              | OK (_, CLEAN) => "Clean"
              | ERROR _ => ""
        val error_str =
            case status of
                ERROR e => e
              | _ => ""
    in
        print (" " ^
               pad_to libname_width libname ^ divider ^
               pad_to libstate_width libstate_str ^ divider ^
               pad_to localstate_width localstate_str ^ divider ^
               error_str ^ "\n")
    end

fun print_update_outcome (libname, outcome) =
    let val outcome_str =
            case outcome of
                OK id => "Ok"
              | ERROR e => "Failed"
        val error_str =
            case outcome of
                ERROR e => e
              | _ => ""
    in
        print (" " ^
               pad_to libname_width libname ^ divider ^
               pad_to libstate_width outcome_str ^ divider ^
               error_str ^ "\n")
    end

fun act_and_print action print_header print_line (libs : libspec list) =
    let val lines = map (fn lib => (#libname lib, action lib)) libs
        val _ = print_header ()
    in
        app print_line lines;
        lines
    end

fun return_code_for outcomes =
    foldl (fn ((_, result), acc) =>
              case result of
                  ERROR _ => OS.Process.failure
                | _ => acc)
          OS.Process.success
          outcomes
        
fun status_of_project ({ context, libs } : project) =
    return_code_for (act_and_print (AnyLibControl.status context)
                                   print_status_header (print_status false)
                                   libs)
                                             
fun review_project ({ context, libs } : project) =
    return_code_for (act_and_print (AnyLibControl.review context)
                                   print_status_header (print_status true)
                                   libs)

fun lock_project ({ context, libs } : project) =
    let val _ = if FileBits.verbose ()
                then print ("Scanning IDs for lock file...\n")
                else ()
        val outcomes = map (fn lib =>
                               (#libname lib, AnyLibControl.id_of context lib))
                           libs
        val locks =
            List.concat
                (map (fn (libname, result) =>
                         case result of
                             ERROR _ => []
                           | OK id => [{ libname = libname, id_or_tag = id }])
                     outcomes)
        val return_code = return_code_for outcomes
        val _ = print clear_line
    in
        if OS.Process.isSuccess return_code
        then save_lock_file (#rootpath context) locks
        else ();
        return_code
    end

fun update_project (project as { context, libs }) =
    let val outcomes = act_and_print
                           (AnyLibControl.update context)
                           print_outcome_header print_update_outcome libs
        val _ = if List.exists (fn (_, OK _) => true | _ => false) outcomes
                then lock_project project
                else OS.Process.success
    in
        return_code_for outcomes
    end
    
fun load_local_project pintype =
    let val userconfig = load_userconfig ()
        val rootpath = OS.FileSys.getDir ()
    in
        load_project userconfig rootpath pintype
    end    

fun with_local_project pintype f =
    let val return_code = f (load_local_project pintype)
                          handle e => (print ("Error: " ^ exnMessage e);
                                       OS.Process.failure)
        val _ = print "\n";
    in
        return_code
    end
        
fun review () = with_local_project USE_LOCKFILE review_project
fun status () = with_local_project USE_LOCKFILE status_of_project
fun update () = with_local_project NO_LOCKFILE update_project
fun lock () = with_local_project NO_LOCKFILE lock_project
fun install () = with_local_project USE_LOCKFILE update_project

fun version () =
    (print ("v" ^ vext_version ^ "\n");
     OS.Process.success)
                      
fun usage () =
    (print "\nVext ";
     version ();
     print ("\nA simple manager for third-party source code dependencies.\n\n"
            ^ "Usage:\n\n"
            ^ "  vext <command>\n\n"
            ^ "where <command> is one of:\n\n"
            ^ "  status   print quick report on local status only, without using network\n"
            ^ "  review   check configured libraries against their providers, and report\n"
            ^ "  install  update configured libraries according to project specs and lock file\n"
            ^ "  update   update configured libraries and lock file according to project specs\n"
            ^ "  lock     update lock file to match local library status\n"
            ^ "  archive  pack up project and all libraries into an archive file\n"
            ^ "           (invoke as 'vext archive target-file.tar.gz')\n"
            ^ "  version  print the Vext version number and exit\n\n");
    OS.Process.failure)

fun archive target args =
    case args of
        [] =>
        with_local_project USE_LOCKFILE (Archive.archive (target, []))
      | "--exclude"::xs =>
        with_local_project USE_LOCKFILE (Archive.archive (target, xs))
      | _ => usage ()

fun vext args =
    let val return_code = 
            case args of
                ["review"] => review ()
              | ["status"] => status ()
              | ["install"] => install ()
              | ["update"] => update ()
              | ["lock"] => lock ()
              | ["version"] => version ()
              | "archive"::target::args => archive target args
              | _ => usage ()
    in
        OS.Process.exit return_code;
        ()
    end
        
fun main () =
    vext (CommandLine.arguments ())