Chris@909: # Generates a migration which migrates all plugins to their latest versions
Chris@909: # within the database.
Chris@909: class PluginMigrationGenerator < Rails::Generator::Base
Chris@909:   
Chris@909:   # 255 characters max for Windows NTFS (http://en.wikipedia.org/wiki/Filename)
Chris@909:   # minus 14 for timestamp, minus some extra chars for dot, underscore, file 
Chris@909:   # extension. So let's have 230.
Chris@909:   MAX_FILENAME_LENGTH = 230
Chris@909:     
Chris@909:   def initialize(runtime_args, runtime_options={})
Chris@909:     super
Chris@909:     @options = {:assigns => {}}
Chris@909:     ensure_schema_table_exists    
Chris@909:     get_plugins_to_migrate(runtime_args)
Chris@909:     
Chris@909:     if @plugins_to_migrate.empty?
Chris@909:       puts "All plugins are migrated to their latest versions"
Chris@909:       exit(0)
Chris@909:     end
Chris@909: 
Chris@909:     @options[:migration_file_name] = build_migration_name
Chris@909:     @options[:assigns][:class_name] = build_migration_name.classify
Chris@909:   end
Chris@909:   
Chris@909:   def manifest
Chris@909:     record do |m|
Chris@909:       m.migration_template 'plugin_migration.erb', 'db/migrate', @options
Chris@909:     end
Chris@909:   end
Chris@909:   
Chris@909:   protected
Chris@909: 
Chris@909:     # Create the schema table if it doesn't already exist.
Chris@909:     def ensure_schema_table_exists
Chris@909:       ActiveRecord::Base.connection.initialize_schema_migrations_table
Chris@909:     end
Chris@909: 
Chris@909:     # Determine all the plugins which have migrations that aren't present
Chris@909:     # according to the plugin schema information from the database.
Chris@909:     def get_plugins_to_migrate(plugin_names)
Chris@909: 
Chris@909:       # First, grab all the plugins which exist and have migrations
Chris@909:       @plugins_to_migrate = if plugin_names.empty?
Chris@909:         Engines.plugins
Chris@909:       else
Chris@909:         plugin_names.map do |name| 
Chris@909:           Engines.plugins[name] ? Engines.plugins[name] : raise("Cannot find the plugin '#{name}'")
Chris@909:         end
Chris@909:       end
Chris@909:       
Chris@909:       @plugins_to_migrate.reject! { |p| !p.respond_to?(:latest_migration) || p.latest_migration.nil? }
Chris@909:       
Chris@909:       # Then find the current versions from the database    
Chris@909:       @current_versions = {}
Chris@909:       @plugins_to_migrate.each do |plugin|
Chris@909:         @current_versions[plugin.name] = Engines::Plugin::Migrator.current_version(plugin)
Chris@909:       end
Chris@909: 
Chris@909:       # Then find the latest versions from their migration directories
Chris@909:       @new_versions = {}      
Chris@909:       @plugins_to_migrate.each do |plugin|
Chris@909:         @new_versions[plugin.name] = plugin.latest_migration
Chris@909:       end
Chris@909:       
Chris@909:       # Remove any plugins that don't need migration
Chris@909:       @plugins_to_migrate.map { |p| p.name }.each do |name|
Chris@909:         @plugins_to_migrate.delete(Engines.plugins[name]) if @current_versions[name] == @new_versions[name]
Chris@909:       end
Chris@909:       
Chris@909:       @options[:assigns][:plugins] = @plugins_to_migrate
Chris@909:       @options[:assigns][:new_versions] = @new_versions
Chris@909:       @options[:assigns][:current_versions] = @current_versions
Chris@909:     end
Chris@909: 
Chris@909:     # Returns a migration name. If the descriptive migration name based on the 
Chris@909:     # plugin names involved is shorter than 230 characters that one will be
Chris@909:     # used. Otherwise a shorter name will be returned.
Chris@909:     def build_migration_name
Chris@909:       descriptive_migration_name.tap do |name|        
Chris@909:         name.replace short_migration_name if name.length > MAX_FILENAME_LENGTH
Chris@909:       end
Chris@909:     end
Chris@909: 
Chris@909:     # Construct a unique migration name based on the plugins involved and the
Chris@909:     # versions they should reach after this migration is run. The name constructed
Chris@909:     # needs to be lowercase
Chris@909:     def descriptive_migration_name
Chris@909:       @plugins_to_migrate.map do |plugin| 
Chris@909:         "#{plugin.name}_to_version_#{@new_versions[plugin.name]}" 
Chris@909:       end.join("_and_").downcase
Chris@909:     end
Chris@909: 
Chris@909:     # Short migration name that will be used if the descriptive_migration_name
Chris@909:     # exceeds 230 characters
Chris@909:     def short_migration_name
Chris@909:       'plugin_migrations'
Chris@909:     end
Chris@909: end