class Thor
  module ZshCompletion
    class Generator
      SUBCOMMAND_FUNCTION_TEMPLATE = ERB.new(File.read("#{File.dirname(__FILE__)}/template/subcommand_function.erb"), trim_mode: "-")
      attr_reader :thor, :name

      def initialize(thor, name)
        @thor = thor
        @name = name
      end

      def generate
        # Format command information like below:
        #
        # { name: "__iterm",
        #   options: [],
        #   subcommands: [
        #     { name: "list-sessions",
        #       description: "List name of all sessions in current terminal",
        #       options: [],
        #       subcommands: [],
        #     },
        #     { name: "new-session",
        #       description: "Create new session in current terminal",
        #       options: [
        #         { names: ["--name", "-n"],
        #           description: nil,
        #         },
        #       ],
        #       subcommands: [],
        #     },
        #     { name: "sessions",
        #       description: "Manage sessions by .iterm-sessions",
        #       options: [],
        #       subcommands: [
        #         { name: "start",
        #           description: "Start all sessions if it's not started",
        #           options: [],
        #           subcommands: [],
        #         }
        #       ]
        #     }
        #   ]
        # }

        main = {
          name: "__#{name}",
          description: nil,
          options: [],
          subcommands: subcommand_metadata(thor),
        }

        erb = File.read("#{File.dirname(__FILE__)}/template/main.erb")
        ERB.new(erb, trim_mode: "-").result(binding)
      end

      private
      def render_subcommand_function(subcommand, options = {})
        prefix = options[:prefix] || []

        source = []

        prefix = (prefix + [subcommand[:name]])
        function_name = prefix.join("_")
        depth = prefix.size + 1

        source << SUBCOMMAND_FUNCTION_TEMPLATE.result(binding)

        subcommand[:subcommands].each do |nested|
          source << render_subcommand_function(nested, prefix: prefix)
        end
        source.join("\n").strip + "\n"
      end

      def subcommand_metadata(thor)
        result = []
        thor.tasks.each do |(name, command)|
          aliases = thor.map.select {|_, original_name|
            name == original_name
          }.map(&:first)
          result << generate_command_information(thor, name, command, aliases)
        end
        result
      end

      def generate_command_information(thor, name, command, aliases)
        subcommands = if (subcommand_class = thor.subcommand_classes[name])
          subcommand_metadata(subcommand_class)
        else
          []
        end
        {name: hyphenate(name),
         aliases: aliases.map {|a| hyphenate(a) },
         usage: command.usage,
         description: command.description,
         options: thor.class_options.map {|_, o| option_metadata(o) } +
           command.options.map {|(_, o)| option_metadata(o) },
         subcommands: subcommands,}
      end

      def option_metadata(option)
        {names: ["--#{option.name}"] + option.aliases.map {|a| "-#{a}" },
         description: option.description,}
      end

      def quote(s)
        escaped = s.gsub(/'/, "''")
        %('#{escaped}')
      end

      def bracket(s)
        %([#{s}])
      end

      def escape_option_names(names)
        if names.size == 1
          names.first
        else
          "{" + names.join(",") + "}"
        end
      end

      def hyphenate(s)
        s.gsub("_", "-")
      end
    end
  end
end