module Gitlab
  module GitalyClient
    class ConflictsService
      include Gitlab::EncodingHelper

      MAX_MSG_SIZE = 128.kilobytes.freeze

      def initialize(repository, our_commit_oid, their_commit_oid)
        @gitaly_repo = repository.gitaly_repository
        @repository = repository
        @our_commit_oid = our_commit_oid
        @their_commit_oid = their_commit_oid
      end

      def list_conflict_files
        request = Gitaly::ListConflictFilesRequest.new(
          repository: @gitaly_repo,
          our_commit_oid: @our_commit_oid,
          their_commit_oid: @their_commit_oid
        )
        response = GitalyClient.call(@repository.storage, :conflicts_service, :list_conflict_files, request)

        GitalyClient::ConflictFilesStitcher.new(response)
      end

      def conflicts?
        list_conflict_files.any?
      rescue GRPC::FailedPrecondition
        # The server raises this exception when it encounters ConflictSideMissing, which
        # means a conflict exists but its `theirs` or `ours` data is nil due to a non-existent
        # file in one of the trees.
        true
      end

      def resolve_conflicts(target_repository, resolution, source_branch, target_branch)
        reader = binary_stringio(resolution.files.to_json)

        req_enum = Enumerator.new do |y|
          header = resolve_conflicts_request_header(target_repository, resolution, source_branch, target_branch)
          y.yield Gitaly::ResolveConflictsRequest.new(header: header)

          until reader.eof?
            chunk = reader.read(MAX_MSG_SIZE)

            y.yield Gitaly::ResolveConflictsRequest.new(files_json: chunk)
          end
        end

        response = GitalyClient.call(@repository.storage, :conflicts_service, :resolve_conflicts, req_enum, remote_storage: target_repository.storage)

        if response.resolution_error.present?
          raise Gitlab::Git::Conflict::Resolver::ResolutionError, response.resolution_error
        end
      end

      private

      def resolve_conflicts_request_header(target_repository, resolution, source_branch, target_branch)
        Gitaly::ResolveConflictsRequestHeader.new(
          repository: @gitaly_repo,
          our_commit_oid: @our_commit_oid,
          target_repository: target_repository.gitaly_repository,
          their_commit_oid: @their_commit_oid,
          source_branch: source_branch,
          target_branch: target_branch,
          commit_message: resolution.commit_message,
          user: Gitlab::Git::User.from_gitlab(resolution.user).to_gitaly
        )
      end
    end
  end
end