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# Helpers to sort tables using clickable column headers.

#

# Author:  Stuart Rackham <srackham@methods.co.nz>, March 2005.

#          Jean-Philippe Lang, 2009

# License: This source code is released under the MIT license.

#

# - Consecutive clicks toggle the column's sort order.

# - Sort state is maintained by a session hash entry.

# - CSS classes identify sort column and state.

# - Typically used in conjunction with the Pagination module.

#

# Example code snippets:

#

# Controller:

#

#   helper :sort

#   include SortHelper

# 

#   def list

#     sort_init 'last_name'

#     sort_update %w(first_name last_name)

#     @items = Contact.find_all nil, sort_clause

#   end

# 

# Controller (using Pagination module):

#

#   helper :sort

#   include SortHelper

# 

#   def list

#     sort_init 'last_name'

#     sort_update %w(first_name last_name)

#     @contact_pages, @items = paginate :contacts,

#       :order_by => sort_clause,

#       :per_page => 10

#   end

# 

# View (table header in list.rhtml):

# 

#   <thead>

#     <tr>

#       <%= sort_header_tag('id', :title => 'Sort by contact ID') %>

#       <%= sort_header_tag('last_name', :caption => 'Name') %>

#       <%= sort_header_tag('phone') %>

#       <%= sort_header_tag('address', :width => 200) %>

#     </tr>

#   </thead>

#

# - Introduces instance variables: @sort_default, @sort_criteria

# - Introduces param :sort

#

module SortHelper

  class SortCriteria

    def initialize

      @criteria = []

    end

    def available_criteria=(criteria)

      unless criteria.is_a?(Hash)

        criteria = criteria.inject({}) {|h,k| h[k] = k; h}

      end

      @available_criteria = criteria

    end

    def from_param(param)

      @criteria = param.to_s.split(',').collect {|s| s.split(':')[0..1]}

      normalize!

    end

    def criteria=(arg)

      @criteria = arg

      normalize!

    end

    def to_param

      @criteria.collect {|k,o| k + (o ? '' : ':desc')}.join(',')

    end

    def to_sql

      sql = @criteria.collect do |k,o|

        if s = @available_criteria[k]

          (o ? s.to_a : s.to_a.collect {|c| append_desc(c)}).join(', ')

        end

      end.compact.join(', ')

      sql.blank? ? nil : sql

    end

    def add!(key, asc)

      @criteria.delete_if {|k,o| k == key}

      @criteria = [[key, asc]] + @criteria

      normalize!

    end

    def add(*args)

      r = self.class.new.from_param(to_param)

      r.add!(*args)

      r

    end

    def first_key

      @criteria.first && @criteria.first.first

    end

    def first_asc?

      @criteria.first && @criteria.first.last

    end

    def empty?

      @criteria.empty?

    end

    private

    def normalize!

      @criteria ||= []

      @criteria = @criteria.collect {|s| s = s.to_a; [s.first, (s.last == false || s.last == 'desc') ? false : true]}

      @criteria = @criteria.select {|k,o| @available_criteria.has_key?(k)} if @available_criteria

      @criteria.slice!(3)

      self

    end

    # Appends DESC to the sort criterion unless it has a fixed order

    def append_desc(criterion)

      if criterion =~ / (asc|desc)$/i

        criterion

      else

        "#{criterion} DESC"

      end

    end

  end

  def sort_name

    controller_name + '_' + action_name + '_sort'

  end

  # Initializes the default sort.

  # Examples:

  #   

  #   sort_init 'name'

  #   sort_init 'id', 'desc'

  #   sort_init ['name', ['id', 'desc']]

  #   sort_init [['name', 'desc'], ['id', 'desc']]

  #

  def sort_init(*args)

    case args.size

    when 1

      @sort_default = args.first.is_a?(Array) ? args.first : [[args.first]]

    when 2

      @sort_default = [[args.first, args.last]]

    else

      raise ArgumentError

    end

  end

  # Updates the sort state. Call this in the controller prior to calling

  # sort_clause.

  # - criteria can be either an array or a hash of allowed keys

  #

  def sort_update(criteria)

    @sort_criteria = SortCriteria.new

    @sort_criteria.available_criteria = criteria

    @sort_criteria.from_param(params[:sort] || session[sort_name])

    @sort_criteria.criteria = @sort_default if @sort_criteria.empty?

    session[sort_name] = @sort_criteria.to_param

  end

  # Clears the sort criteria session data

  #

  def sort_clear

    session[sort_name] = nil

  end

  # Returns an SQL sort clause corresponding to the current sort state.

  # Use this to sort the controller's table items collection.

  #

  def sort_clause()

    @sort_criteria.to_sql

  end

  # Returns a link which sorts by the named column.

  #

  # - column is the name of an attribute in the sorted record collection.

  # - the optional caption explicitly specifies the displayed link text.

  # - 2 CSS classes reflect the state of the link: sort and asc or desc

  #

  def sort_link(column, caption, default_order)

    css, order = nil, default_order

    if column.to_s == @sort_criteria.first_key

      if @sort_criteria.first_asc?

        css = 'sort asc'

        order = 'desc'

      else

        css = 'sort desc'

        order = 'asc'

      end

    end

    caption = column.to_s.humanize unless caption

    sort_options = { :sort => @sort_criteria.add(column.to_s, order).to_param }

    # don't reuse params if filters are present

    url_options = params.has_key?(:set_filter) ? sort_options : params.merge(sort_options)

     # Add project_id to url_options

    url_options = url_options.merge(:project_id => params[:project_id]) if params.has_key?(:project_id)

    link_to_remote(caption,

                  {:update => "content", :url => url_options, :method => :get},

                  {:href => url_for(url_options),

                   :class => css})

  end

  # Returns a table header <th> tag with a sort link for the named column

  # attribute.

  #

  # Options:

  #   :caption     The displayed link name (defaults to titleized column name).

  #   :title       The tag's 'title' attribute (defaults to 'Sort by :caption').

  #

  # Other options hash entries generate additional table header tag attributes.

  #

  # Example:

  #

  #   <%= sort_header_tag('id', :title => 'Sort by contact ID', :width => 40) %>

  #

  def sort_header_tag(column, options = {})

    caption = options.delete(:caption) || column.to_s.humanize

    default_order = options.delete(:default_order) || 'asc'

    options[:title] = l(:label_sort_by, "\"#{caption}\"") unless options[:title]

    content_tag('th', sort_link(column, caption, default_order), options)

  end

end