require "bundler"
require "shellwords"
require "singleton"

module Shoulda
  module Matchers
    class CurrentBundle
      include Singleton

      ROOT_DIR = Pathname.new("..").expand_path(__dir__)
      APPRAISAL_GEMFILES_PATH = ROOT_DIR.join("gemfiles")

      def assert_appraisal!
        unless appraisal_in_use?
          raise AppraisalNotSpecified.new(<<~MESSAGE)
            Please run tests by specifying an appraisal, like:

                bundle exec appraisal <appraisal_name> #{current_command}

            Possible appraisals are:

            #{available_appraisals.map { |appraisal| "    - #{appraisal.name}" }.join("\n")}

            Or to simply go with the latest appraisal, use:

                bin/rspec #{shell_arguments}
          MESSAGE
        end
      end

      def appraisal_in_use?
        !current_appraisal.nil?
      end

      def current_appraisal
        if path
          available_appraisals.find do |appraisal|
            appraisal.gemfile_path.to_s == path.to_s
          end
        else
          nil
        end
      end

      def latest_appraisal
        available_appraisals.max_by(&:name)
      end

      private

      def path
        Bundler.default_gemfile
      end

      def available_appraisals
        @_available_appraisals ||= Dir.glob(
          APPRAISAL_GEMFILES_PATH.join("*.gemfile").to_s,
        ).
          map do |path|
            FakeAppraisal.new(
              name: File.basename(path).sub(/\.gemfile$/, ""),
              gemfile_path: path,
            )
          end
      end

      def current_command
        Shellwords.join([File.basename($0)] + ARGV)
      end

      def shell_arguments
        Shellwords.join(ARGV)
      end

      class FakeAppraisal
        attr_reader :name, :gemfile_path

        def initialize(name:, gemfile_path:)
          @name = name
          @gemfile_path = gemfile_path
        end
      end

      class AppraisalNotSpecified < ArgumentError; end
    end
  end
end