module Braid
  module Commands
    class Update < Command
      def run(path, options = {})
        with_reset_on_error do
          path ? update_one(path, options) : update_all(options)
        end
      end

      protected

      def update_all(options = {})
        options.reject! { |k, v| %w(revision head).include?(k) }
        msg "Updating all mirrors."
        config.mirrors.each do |path|
          update_one(path, options)
        end
      end

      def update_one(path, options = {})
        mirror           = config.get!(path)

        revision_message = options["revision"] ? " to #{display_revision(mirror, options["revision"])}" : ""
        msg "Updating mirror '#{mirror.path}'#{revision_message}."

        # check options for lock modification
        if mirror.locked?
          if options["head"]
            msg "Unlocking mirror '#{mirror.path}'." if verbose?
            mirror.lock = nil
          elsif !options["revision"]
            msg "Mirror '#{mirror.path}' is locked to #{display_revision(mirror, mirror.lock)}. Use --head to force."
            return
          end
        end

        setup_remote(mirror)
        msg "Fetching new commits for '#{mirror.path}'." if verbose?
        mirror.fetch

        new_revision    = validate_new_revision(mirror, options["revision"])
        target_revision = determine_target_revision(new_revision)

        if mirror.merged?(target_revision)
          msg "Mirror '#{mirror.path}' is already up to date."
          return
        end

        if mirror.squashed?
          diff          = mirror.diff
          base_revision = mirror.base_revision
        end

        mirror.revision = new_revision
        mirror.lock = new_revision if options["revision"]

        msg "Merging in mirror '#{mirror.path}'." if verbose?
        begin
          if mirror.squashed?
            local_hash = git.rev_parse("HEAD")
            if !diff.empty?
              base_hash = generate_tree_hash(mirror, base_revision)
            else
              base_hash = local_hash
            end
            remote_hash                   = generate_tree_hash(mirror, target_revision)
            ENV["GITHEAD_#{local_hash}"]  = "HEAD"
            ENV["GITHEAD_#{remote_hash}"] = target_revision
            git.merge_recursive(base_hash, local_hash, remote_hash)
          else
            git.merge_subtree(target_revision)
          end
        rescue Operations::MergeError => error
          msg "Caught merge error. Breaking."
        end

        config.update(mirror)
        add_config_file

        commit_message = "Update mirror '#{mirror.path}' to #{display_revision(mirror)}"
        if error
          File.open(".git/MERGE_MSG", 'w') { |f| f.puts(commit_message) }
          return
        end

        git.commit(commit_message)
        msg "Updated mirror to #{display_revision(mirror)}."
      end

      def generate_tree_hash(mirror, revision)
        git.rm_r(mirror.path)
        git.read_tree_prefix(revision, mirror.path)
        success = git.commit("Temporary commit for mirror '#{mirror.path}'")
        hash    = git.rev_parse("HEAD")
        git.reset_hard("HEAD^") if success
        hash
      end
    end
  end
end