require 'pathname/common_prefix'

module Licensed
  module Source
    class Manifest
      def initialize(config)
        @config = config
      end

      def enabled?
        @config.enabled?(type) && File.exist?(manifest_path)
      end

      def type
        'manifest'
      end

      def dependencies
        @dependencies ||= packages.map do |package_name, sources|
          Dependency.new(common_dir(sources), {
            'type'     => type,
            'name'     => package_name,
            'version'  => package_version(sources)
          })
        end
      end

      def common_dir(sources)
        common_prefix = Pathname.common_prefix(*sources)

        # if there's no common prefix, use the directory of the first source
        common_prefix = Pathname.new(sources[0]).dirname unless common_prefix

        Pathname.new(@config.path).join(common_prefix).expand_path.to_path
      end

      def package_version(sources)
        return if sources.nil? || sources.empty?

        # return the latest version from the sources
        sources.map { |s| source_version_command(s) }
               .max_by { |sha| commit_date_command(sha) }
      end

      def commit_date_command(sha)
        `git show -s -1 --format=%ct #{sha}`.strip
      end

      def source_version_command(source)
        `git rev-list -1 HEAD -- #{source}`.strip
      end

      def packages
        manifest.each_with_object({}) do |(src, package_name), hsh|
          next if src.nil? || src.empty?
          hsh[package_name] ||= []
          hsh[package_name] << src
        end
      end

      def manifest
        JSON.parse(File.read(manifest_path))
      end

      def manifest_path
        @config.path.join('manifest.json')
      end
    end
  end
end