require 'base64'
require 'json'
require 'securerandom'
require 'uri'

module Gitlab
  class Workhorse
    SEND_DATA_HEADER = 'Gitlab-Workhorse-Send-Data'.freeze
    VERSION_FILE = 'GITLAB_WORKHORSE_VERSION'.freeze
    INTERNAL_API_CONTENT_TYPE = 'application/vnd.gitlab-workhorse+json'.freeze
    INTERNAL_API_REQUEST_HEADER = 'Gitlab-Workhorse-Api-Request'.freeze
    NOTIFICATION_CHANNEL = 'workhorse:notifications'.freeze
    ALLOWED_GIT_HTTP_ACTIONS = %w[git_receive_pack git_upload_pack info_refs].freeze

    # Supposedly the effective key size for HMAC-SHA256 is 256 bits, i.e. 32
    # bytes https://tools.ietf.org/html/rfc4868#section-2.6
    SECRET_LENGTH = 32

    class << self
      def git_http_ok(repository, is_wiki, user, action, show_all_refs: false)
        raise "Unsupported action: #{action}" unless ALLOWED_GIT_HTTP_ACTIONS.include?(action.to_s)

        project = repository.project

        {
          GL_ID: Gitlab::GlId.gl_id(user),
          GL_REPOSITORY: Gitlab::GlRepository.gl_repository(project, is_wiki),
          GL_USERNAME: user&.username,
          ShowAllRefs: show_all_refs,
          Repository: repository.gitaly_repository.to_h,
          RepoPath: 'ignored but not allowed to be empty in gitlab-workhorse',
          GitalyServer: {
            address: Gitlab::GitalyClient.address(project.repository_storage),
            token: Gitlab::GitalyClient.token(project.repository_storage)
          }
        }
      end

      def send_git_blob(repository, blob)
        params = {
          'GitalyServer' => gitaly_server_hash(repository),
          'GetBlobRequest' => {
            repository: repository.gitaly_repository.to_h,
            oid: blob.id,
            limit: -1
          }
        }

        [
          SEND_DATA_HEADER,
          "git-blob:#{encode(params)}"
        ]
      end

      def send_git_archive(repository, ref:, format:, append_sha:)
        format ||= 'tar.gz'
        format.downcase!
        params = repository.archive_metadata(ref, Gitlab.config.gitlab.repository_downloads_path, format, append_sha: append_sha)
        raise "Repository or ref not found" if params.empty?

        params['GitalyServer'] = gitaly_server_hash(repository)

        # If present DisableCache must be a Boolean. Otherwise workhorse ignores it.
        params['DisableCache'] = true if git_archive_cache_disabled?

        [
          SEND_DATA_HEADER,
          "git-archive:#{encode(params)}"
        ]
      end

      def send_git_snapshot(repository)
        params = {
          'GitalyServer' => gitaly_server_hash(repository),
          'GetSnapshotRequest' => Gitaly::GetSnapshotRequest.new(
            repository: repository.gitaly_repository
          ).to_json
        }

        [
          SEND_DATA_HEADER,
          "git-snapshot:#{encode(params)}"
        ]
      end

      def send_git_diff(repository, diff_refs)
        params = {
          'GitalyServer' => gitaly_server_hash(repository),
          'RawDiffRequest' => Gitaly::RawDiffRequest.new(
            gitaly_diff_or_patch_hash(repository, diff_refs)
          ).to_json
        }

        [
          SEND_DATA_HEADER,
          "git-diff:#{encode(params)}"
        ]
      end

      def send_git_patch(repository, diff_refs)
        params = {
          'GitalyServer' => gitaly_server_hash(repository),
          'RawPatchRequest' => Gitaly::RawPatchRequest.new(
            gitaly_diff_or_patch_hash(repository, diff_refs)
          ).to_json
        }

        [
          SEND_DATA_HEADER,
          "git-format-patch:#{encode(params)}"
        ]
      end

      def send_artifacts_entry(build, entry)
        file = build.artifacts_file
        archive = file.file_storage? ? file.path : file.url

        params = {
          'Archive' => archive,
          'Entry' => Base64.encode64(entry.to_s)
        }

        [
          SEND_DATA_HEADER,
          "artifacts-entry:#{encode(params)}"
        ]
      end

      def send_url(url, allow_redirects: false)
        params = {
          'URL' => url,
          'AllowRedirects' => allow_redirects
        }

        [
          SEND_DATA_HEADER,
          "send-url:#{encode(params)}"
        ]
      end

      def terminal_websocket(terminal)
        details = {
          'Terminal' => {
            'Subprotocols' => terminal[:subprotocols],
            'Url' => terminal[:url],
            'Header' => terminal[:headers],
            'MaxSessionTime' => terminal[:max_session_time]
          }
        }
        details['Terminal']['CAPem'] = terminal[:ca_pem] if terminal.key?(:ca_pem)

        details
      end

      def version
        path = Rails.root.join(VERSION_FILE)
        path.readable? ? path.read.chomp : 'unknown'
      end

      def secret
        @secret ||= begin
          bytes = Base64.strict_decode64(File.read(secret_path).chomp)
          raise "#{secret_path} does not contain #{SECRET_LENGTH} bytes" if bytes.length != SECRET_LENGTH

          bytes
        end
      end

      def write_secret
        bytes = SecureRandom.random_bytes(SECRET_LENGTH)
        File.open(secret_path, 'w:BINARY', 0600) do |f|
          f.chmod(0600) # If the file already existed, the '0600' passed to 'open' above was a no-op.
          f.write(Base64.strict_encode64(bytes))
        end
      end

      def verify_api_request!(request_headers)
        decode_jwt(request_headers[INTERNAL_API_REQUEST_HEADER])
      end

      def decode_jwt(encoded_message)
        JWT.decode(
          encoded_message,
          secret,
          true,
          { iss: 'gitlab-workhorse', verify_iss: true, algorithm: 'HS256' }
        )
      end

      def secret_path
        Gitlab.config.workhorse.secret_file
      end

      def set_key_and_notify(key, value, expire: nil, overwrite: true)
        Gitlab::Redis::Queues.with do |redis|
          result = redis.set(key, value, ex: expire, nx: !overwrite)
          if result
            redis.publish(NOTIFICATION_CHANNEL, "#{key}=#{value}")
            value
          else
            redis.get(key)
          end
        end
      end

      protected

      def encode(hash)
        Base64.urlsafe_encode64(JSON.dump(hash))
      end

      def gitaly_server_hash(repository)
        {
          address: Gitlab::GitalyClient.address(repository.project.repository_storage),
          token: Gitlab::GitalyClient.token(repository.project.repository_storage)
        }
      end

      def gitaly_diff_or_patch_hash(repository, diff_refs)
        {
          repository: repository.gitaly_repository,
          left_commit_id: diff_refs.base_sha,
          right_commit_id: diff_refs.head_sha
        }
      end

      def git_archive_cache_disabled?
        ENV['WORKHORSE_ARCHIVE_CACHE_DISABLED'].present? || Feature.enabled?(:workhorse_archive_cache_disabled)
      end
    end
  end
end