# encoding: utf-8
require 'fedux_org_stdlib/require_files'
require 'fedux_org_stdlib/gem_plugins/no_plugin'
require 'fedux_org_stdlib/gem_plugins/plugin'
require 'fedux_org_stdlib/gem_plugins/exceptions'
require 'fedux_org_stdlib/list'

require_library %w( active_support/core_ext/string/inflections active_support/core_ext/object/blank hirb/console )

module FeduxOrgStdlib
  module GemPlugins
    # Plugin Manager
    #
    # To use the plugin manager you should build the plugins for your
    # application as rubygems. How you name the plugins is up to you, but it is
    # recommended to use something like `your-application-<plugin>`. For
    # the plugin to be found, it needs to include the so called plugin file
    # `your-application-extension.rb`.
    #
    # @example PluginManager-class
    #
    #    module YourApplication
    #      class PluginManager < FeduxOrgStdlib::GemPlugins::PluginManager
    #      end
    #    end
    #
    # @example Default prefix
    #
    # Please make sure you create a class for your plugin manager to make it
    # work. Otherwise give the prefix via parameter - see below.
    #
    #    # -- main.rb --
    #    # main module
    #    module YourApplication
    #      # The manager uses "#{self.name.underscore.gsub(/\//, '-')}-plugin.rb" as plugin-file
    #      @plugin_manager = PluginManager.new
    #
    #      class << self
    #        attr_reader :plugin_manager
    #
    #        def load_plugins
    #          self.plugin_manager.load_plugins
    #        end
    #      end
    #    end
    #
    #
    # @example Use different plugin file
    #    # -- main.rb --
    #    # main module
    #    module YourApplication
    #      # The manager uses 'asdf-plugin1.rb' to find plugins
    #      @plugin_manager = PluginManager.new(plugin_file: 'asdf-plugin1.rb')
    #
    #      [...]
    #    end
    #
    # At some place you need to load your plugins.
    #
    # @example Load plugins in your application
    #
    #   # -- runner.rb --
    #
    #   YourApplication.load_plugins
    #
    class PluginManager
      private

      attr_reader :plugins, :creator, :plugin_file

      public

      def initialize(creator: Plugin, plugin_file: File.join('lib', __plugin_prefix + 'plugin.rb'))
        @creator     = creator
        @plugin_file = plugin_file

        # needs variables above
        @plugins   = plugins_in_rubygems_path
      end

      # Enable a plugin
      def activate_plugin(*names)
        names.flatten.each do |n|
          plugin = plugins.find(NoPlugin.new(n)) { |p| p.name == n }

          return if plugin.blank?

          plugin.activate
        end
      end

      # String representation
      def to_s
        data = plugins.sort.reduce([]) do |a, e|
          a << {
            name: e.name,
            version: e.version,
            author: e.author,
            homepage: e.homepage,
            activated: e.active?,
            require_file: e.require_file
          }
        end

        List.new(data).to_s(
          fields: [:name, :version, :author, :homepage, :activated, :require_file]
        )
      end

      private

      # Find all installed plugins and store them in an internal array.
      def plugins_in_rubygems_path
        require 'rubygems'
        Gem.refresh

        specs = rubygems_latest_specs.select { |s| spec_has_file?(s) }

        specs.map do |s|
          creator.new(spec: s)
        end
      end

      # Where a given Gem::Specification has a specific file. Used
      # to discover plugins.
      #
      # @private
      # @param [Gem::Specification] spec
      # @param [String] path Path to look for
      # @return [Boolean] Whether the file exists
      def spec_has_file?(spec)
        File.exist? File.join(spec.full_gem_path, plugin_file)
      end

      # Backwards compatible means of finding all the latest gemspecs
      # available on the system
      #
      # @private
      # @return [Array] Array of latest Gem::Specification
      def rubygems_latest_specs
        # If newer Rubygems
        if ::Gem::Specification.respond_to? :latest_specs
          ::Gem::Specification.latest_specs(true)
        else
          ::Gem.source_index.latest_specs
        end
      end

      def __plugin_prefix
        name = if self.class.name.deconstantize.blank?
                 self.class.name
               else
                 self.class.name.deconstantize
               end

        "#{name.underscore.gsub(/\//, '-')}-"
      end
    end
  end
end