require 'generators/actions'

module Rails
  module Generators
    DEFAULTS = {
      :actions => [],
      :fixture => true,
      :force_plural => false,
      :helper => true,
      :layout => true,
      :migration => true,
      :orm => 'active_record',
      :resource_controller => 'controller',
      :scaffold_controller => 'scaffold_controller',
      :singleton => false,
      :stylesheets => true,
      :test_framework => 'test_unit',
      :template_engine => 'erb',
      :timestamps => true
    }

    ALIASES = {
      :actions => '-a',
      :fixture_replacement => '-r',
      :orm => '-o',
      :resource_controller => '-c',
      :scaffold_controller => '-c',
      :stylesheets => '-y',
      :test_framework => '-t',
      :template_engine => '-e'
    }

    class Error < Thor::Error
    end

    class Base < Thor::Group
      include Rails::Generators::Actions
      include Thor::Actions

      # Automatically sets the source root based on the class name.
      #
      def self.source_root
        @source_root ||= File.expand_path(File.join(File.dirname(__FILE__), base_name, generator_name, 'templates'))
      end

      # Tries to get the description from a USAGE file one folder above the source
      # root otherwise uses a default description.
      #
      def self.desc(description=nil)
        return super if description
        usage = File.expand_path(File.join(source_root, "..", "USAGE"))

        @desc ||= if File.exist?(usage)
          File.read(usage)
        else
          "Description:\n    Create #{base_name.humanize.downcase} files for #{generator_name} generator."
        end
      end

      # Convenience method to get the namespace from the class name. It's the
      # same as Thor default except that the Generator at the end of the class
      # is removed.
      #
      def self.namespace(name=nil)
        return super if name
        @namespace ||= super.sub(/_generator$/, '')
      end

      # Invoke a generator based on the value supplied by the user to the
      # given option named "name". A class option is created when this method
      # is invoked and you can set a hash to customize it, although type and
      # default values cannot be given.
      #
      # ==== Examples
      #
      #   class ControllerGenerator < Rails::Generators::Base
      #     hook_for :test_framework, :aliases => "-t"
      #   end
      #
      # The example above will create a test framework option and will invoke
      # a generator based on the user supplied value.
      #
      # For example, if the user invoke the controller generator as:
      #
      #   ruby script/generate controller Account --test-framework=test_unit
      #
      # The controller generator will then try to invoke the following generators:
      #
      #   "rails:generators:test_unit", "test_unit:generators:controller", "test_unit"
      #
      # In this case, the "test_unit:generators:controller" is available and is
      # invoked. This allows any test framework to hook into Rails as long as it
      # provides any of the hooks above.
      #
      # Finally, if the user don't want to use any test framework, he can do:
      #
      #   ruby script/generate controller Account --skip-test-framework
      #
      # Or similarly:
      #
      #   ruby script/generate controller Account --no-test-framework
      #
      # ==== Custom invocations
      #
      # You can also supply a block to hook for to customize how the hook is
      # going to be invoked. The block receives two parameters, an instance
      # of the current class and the klass to be invoked.
      #
      # For example, in the resource generator, the controller should be invoked
      # with a pluralized class name. By default, it is invoked with the same
      # name as the resource generator, which is singular. To change this, we
      # can give a block to customize how the controller can be invoked.
      #
      #   hook_for :resource_controller do |instance, controller|
      #     instance.invoke controller, [ instance.name.pluralize ]
      #   end
      #
      def self.hook_for(*names, &block)
        options = names.extract_options!
        as      = options.fetch(:as, generator_name)
        verbose = options.fetch(:verbose, :blue)

        names.each do |name|
          default = { :desc => "#{name.to_s.humanize} to be invoked", :banner => "NAME" }
          class_option name, default.merge!(options)

          invocations << [ name, base_name, as ]
          invocation_blocks[name] = block if block_given?

          # hook_for :test_framework
          #
          # ==== Generates
          #
          # def invoke_for_test_framework
          #   return unless options[:test_framework]
          #
          #   klass_name = options[:test_framework]
          #   klass_name = :test_framework if TrueClass === klass_name
          #   klass = Rails::Generators.find_by_namespace(klass_name, "rails", "model")
          #
          #   if klass
          #     say_status :invoke, options[:test_framework], :blue
          #     invoke_class_with_block :test_framework, klass
          #   else
          #     say "Could not find and invoke '#{options[:test_framework]}'"
          #   end
          # end
          #
          class_eval <<-METHOD, __FILE__, __LINE__
            def invoke_for_#{name}
              return unless options[#{name.inspect}]

              klass_name = options[#{name.inspect}]
              klass_name = #{name.inspect} if TrueClass === klass_name
              klass = Rails::Generators.find_by_namespace(klass_name, #{base_name.inspect}, #{as.inspect})

              if klass
                say_status :invoke, klass_name, #{verbose.inspect}
                invoke_class_with_block #{name.inspect}, klass
              else
                say "Could not find and invoke '\#{klass_name}'."
              end
            end
          METHOD
        end
      end

      # Invoke a generator with the given name if the user requires it. The
      # difference to hook_for is that the class option here is boolean
      # and the generator invoked is not based on user input.
      #
      # A class option is created when this method is invoked and you can set
      # a hash to customize it, although type and default values cannot be
      # given.
      #
      # ==== Examples
      #
      #   class ControllerGenerator < Rails::Generators::Base
      #     invoke_if :webrat, :aliases => "-w"
      #   end
      #
      # The example above will create a helper option and will be invoked
      # when the user requires so:
      #
      #   ruby script/generate controller Account --webrat
      #
      # The controller generator will then try to invoke the following generators:
      #
      #   "rails:generators:webrat", "webrat:generators:controller", "webrat"
      #
      # ==== Custom invocations
      #
      # This method accepts custom invocations as in hook_for. Check hook_for
      # for usage and examples.
      #
      def self.invoke_if(*names, &block)
        options = names.extract_options!.merge(:type => :boolean)
        as      = options.fetch(:as, generator_name)
        verbose = options.fetch(:verbose, :blue)

        names.each do |name|
          class_option name, options

          invocations << [ name, base_name, as ]
          invocation_blocks[name] = block if block_given?

          # invoke_if :helper
          #
          # ==== Generates
          #
          # def invoke_if_helper
          #   return unless options[:helper]
          #   klass = Rails::Generators.find_by_namespace(:helper, "rails", "controller")
          #
          #   if klass
          #     say_status :invoke, :helper, :blue
          #     invoke_class_with_block :helper, klass
          #   else
          #     say "Could not find and invoke 'helper'"
          #   end
          # end
          #
          class_eval <<-METHOD, __FILE__, __LINE__
            def invoke_if_#{name}
              return unless options[#{name.inspect}]
              klass = Rails::Generators.find_by_namespace(#{name.inspect}, #{base_name.inspect}, #{as.inspect})

              if klass
                say_status :invoke, #{name.inspect}, #{verbose.inspect}
                invoke_class_with_block #{name.inspect}, klass
              else
                say "Could not find and invoke '#{name}'."
              end
            end
          METHOD
        end
      end

      # Remove a previously added hook.
      #
      # ==== Examples
      #
      #   remove_hook_for :orm
      #
      def self.remove_hook_for(*names)
        names.each do |name|
          remove_class_option name
          remove_task name
          invocations.delete_if { |i| i[0] == name }
          invocation_blocks.delete(name)
        end
      end

      # Make class option aware of DEFAULTS and ALIASES.
      #
      def self.class_option(name, options) #:nodoc:
        options[:desc]    = "Indicates when to generate #{name.to_s.humanize.downcase}" unless options.key?(:desc)
        options[:aliases] = ALIASES[name]  unless options.key?(:aliases)
        options[:default] = DEFAULTS[name] unless options.key?(:default)
        super(name, options)
      end

      protected

        # This is the common method that both hook_for and invoke_if use to
        # invoke a class. It searches for a block in the invocation blocks
        # in case the user wants to customize how the class is invoked.
        #
        def invoke_class_with_block(name, klass) #:nodoc:
          if block = self.class.invocation_blocks[name]
            block.call(self, klass)
          else
            invoke klass
          end
        end

        # Check whether the given class names are already taken by user
        # application or Ruby on Rails.
        #
        def class_collisions(*class_names)
          return unless behavior == :invoke

          class_names.flatten.each do |class_name|
            class_name = class_name.to_s
            next if class_name.strip.empty?

            # Split the class from its module nesting
            nesting = class_name.split('::')
            last_name = nesting.pop

            # Hack to limit const_defined? to non-inherited on 1.9
            extra = []
            extra << false unless Object.method(:const_defined?).arity == 1

            # Extract the last Module in the nesting
            last = nesting.inject(Object) do |last, nest|
              break unless last.const_defined?(nest, *extra)
              last.const_get(nest)
            end

            if last && last.const_defined?(last_name.camelize, *extra)
              raise Error, "The name '#{class_name}' is either already used in your application " <<
                           "or reserved by Ruby on Rails. Please choose an alternative and run "  <<
                           "this generator again."
            end
          end
        end

        # Use Rails default banner.
        #
        def self.banner
          "#{$0} #{generator_name} #{self.arguments.map(&:usage).join(' ')} [options]"
        end

        # Sets the base_name taking into account the current class namespace.
        #
        def self.base_name
          @base_name ||= self.name.split('::').first.underscore
        end

        # Removes the namespaces and get the generator name. For example,
        # Rails::Generators::MetalGenerator will return "metal" as generator name.
        #
        def self.generator_name
          @generator_name ||= begin
            klass_name = self.name.split('::').last
            klass_name.sub!(/Generator$/, '')
            klass_name.underscore
          end
        end

        # Stores invocations for this class merging with superclass values.
        #
        def self.invocations #:nodoc:
          @invocations ||= from_superclass(:invocations, [])
        end

        # Stores invocation blocks used on hook_for and invoke_if.
        #
        def self.invocation_blocks #:nodoc:
          @invocation_blocks ||= from_superclass(:invocation_blocks, {})
        end

        # Overwrite class options help to allow invoked generators options to be
        # shown recursively when invoking a generator.
        #
        def self.class_options_help(shell, ungrouped_name=nil, extra_group=nil)
          group_options = Thor::CoreExt::OrderedHash.new

          get_options_from_invocations(group_options, class_options) do |klass|
            klass.send(:get_options_from_invocations, group_options, class_options)
          end

          group_options.merge!(extra_group) if extra_group
          super(shell, ungrouped_name, group_options)
        end

        # Get invocations array and merge options from invocations. Those
        # options are added to group_options hash. Options that already exists
        # in base_options are not added twice.
        #
        def self.get_options_from_invocations(group_options, base_options)
          invocations.each do |args|
            name, base, generator = args
            option = class_options[name]

            klass_name = option.type == :boolean ? name : option.default
            next unless klass_name

            klass = Rails::Generators.find_by_namespace(klass_name, base, generator)
            next unless klass

            human_name = klass_name.to_s.classify
            group_options[human_name] ||= []

            group_options[human_name] += klass.class_options.values.select do |option|
              base_options[option.name.to_sym].nil? && option.group.nil? &&
              !group_options.values.flatten.any? { |i| i.name == option.name }
            end

            yield klass if block_given?
          end
        end

        # Small macro to add ruby as an option to the generator with proper
        # default value plus an instance helper method called shebang.
        #
        def self.add_shebang_option!
          require 'rbconfig'
          default = File.join(Config::CONFIG['bindir'], Config::CONFIG['ruby_install_name'])

          class_option :ruby, :type => :string, :aliases => "-r", :default => default,
                              :desc => "Path to the Ruby binary of your choice", :banner => "PATH"

          class_eval <<-METHOD, __FILE__, __LINE__
            protected
            def shebang
              "#!\#{options[:ruby] || "/usr/bin/env ruby"}"
            end
          METHOD
        end

    end
  end
end