GitOperationService = Struct.new(:user, :repository) do
  def add_branch(branch_name, newrev)
    ref = Gitlab::Git::BRANCH_REF_PREFIX + branch_name
    oldrev = Gitlab::Git::BLANK_SHA

    with_hooks_and_update_ref(ref, oldrev, newrev)
  end

  def rm_branch(branch)
    ref = Gitlab::Git::BRANCH_REF_PREFIX + branch.name
    oldrev = branch.dereferenced_target.id
    newrev = Gitlab::Git::BLANK_SHA

    with_hooks_and_update_ref(ref, oldrev, newrev)
  end

  def add_tag(tag_name, newrev, options = {})
    ref = Gitlab::Git::TAG_REF_PREFIX + tag_name
    oldrev = Gitlab::Git::BLANK_SHA

    with_hooks(ref, oldrev, newrev) do |service|
      raw_tag = repository.rugged.tags.create(tag_name, newrev, options)
      service.newrev = raw_tag.target_id
    end
  end

  # Whenever `source_branch_name` is passed, if `branch_name` doesn't exist,
  # it would be created from `source_branch_name`.
  # If `source_project` is passed, and the branch doesn't exist,
  # it would try to find the source from it instead of current repository.
  def with_branch(
    branch_name,
    source_branch_name: nil,
    source_project: repository.project)

    check_with_branch_arguments!(
      branch_name, source_branch_name, source_project)

    update_branch_with_hooks(branch_name) do |ref|
      if repository.project == source_project
        yield(ref)
      else
        repository.with_tmp_ref(
          source_project.repository, source_branch_name) do
            yield(ref)
          end
      end
    end
  end

  private

  def update_branch_with_hooks(branch_name)
    update_autocrlf_option

    ref = Gitlab::Git::BRANCH_REF_PREFIX + branch_name
    oldrev = Gitlab::Git::BLANK_SHA
    was_empty = repository.empty?

    # Make commit
    newrev = yield(ref)

    unless newrev
      raise Repository::CommitError.new('Failed to create commit')
    end

    branch = repository.find_branch(branch_name)
    oldrev = if repository.rugged.lookup(newrev).parent_ids.empty? ||
                branch.nil?
               Gitlab::Git::BLANK_SHA
             else
               repository.rugged.merge_base(
                 newrev, branch.dereferenced_target.sha)
             end

    with_hooks_and_update_ref(ref, oldrev, newrev) do
      # If repo was empty expire cache
      repository.after_create if was_empty
      repository.after_create_branch if was_empty ||
                                        oldrev == Gitlab::Git::BLANK_SHA
    end

    newrev
  end

  def with_hooks_and_update_ref(ref, oldrev, newrev)
    with_hooks(ref, oldrev, newrev) do |service|
      update_ref!(ref, newrev, oldrev)

      yield(service) if block_given?
    end
  end

  def with_hooks(ref, oldrev, newrev)
    result = nil

    GitHooksService.new.execute(
      user,
      repository.path_to_repo,
      oldrev,
      newrev,
      ref) do |service|

      result = yield(service) if block_given?
    end

    result
  end

  def update_ref!(name, newrev, oldrev)
    # We use 'git update-ref' because libgit2/rugged currently does not
    # offer 'compare and swap' ref updates. Without compare-and-swap we can
    # (and have!) accidentally reset the ref to an earlier state, clobbering
    # commits. See also https://github.com/libgit2/libgit2/issues/1534.
    command = %W[#{Gitlab.config.git.bin_path} update-ref --stdin -z]
    _, status = Gitlab::Popen.popen(
      command,
      repository.path_to_repo) do |stdin|
      stdin.write("update #{name}\x00#{newrev}\x00#{oldrev}\x00")
    end

    unless status.zero?
      raise Repository::CommitError.new(
        "Could not update branch #{name.sub('refs/heads/', '')}." \
        " Please refresh and try again.")
    end
  end

  def update_autocrlf_option
    if repository.raw_repository.autocrlf != :input
      repository.raw_repository.autocrlf = :input
    end
  end

  def check_with_branch_arguments!(
    branch_name, source_branch_name, source_project)
    return if repository.branch_exists?(branch_name)

    if repository.project != source_project
      unless source_branch_name
        raise ArgumentError,
          'Should also pass :source_branch_name if' +
          ' :source_project is different from current project'
      end

      unless source_project.repository.commit(source_branch_name).try(:sha)
        raise Repository::CommitError.new(
          "Cannot find branch #{branch_name} nor" \
          " #{source_branch_name} from" \
          " #{source_project.path_with_namespace}")
      end
    elsif source_branch_name
      unless repository.commit(source_branch_name).try(:sha)
        raise Repository::CommitError.new(
          "Cannot find branch #{branch_name} nor" \
          " #{source_branch_name} from" \
          " #{repository.project.path_with_namespace}")
      end
    end
  end
end