# frozen_string_literal: true

# File Download Service allows remote file download into tmp directory.
#
# @param configuration [BulkImports::Configuration] Config object containing url and access token
# @param relative_url [String] Relative URL to download the file from
# @param tmpdir [String] Temp directory to store downloaded file to. Must be located under `Dir.tmpdir`.
# @param file_size_limit [Integer] Maximum allowed file size
# @param allowed_content_types [Array<String>] Allowed file content types
# @param filename [String] Name of the file to download, if known. Use remote filename if none given.
module BulkImports
  class FileDownloadService
    include ::BulkImports::FileDownloads::FilenameFetch
    include ::BulkImports::FileDownloads::Validations

    ServiceError = Class.new(StandardError)

    DEFAULT_FILE_SIZE_LIMIT = 5.gigabytes
    DEFAULT_ALLOWED_CONTENT_TYPES = %w(application/gzip application/octet-stream).freeze

    def initialize(
      configuration:,
      relative_url:,
      tmpdir:,
      file_size_limit: DEFAULT_FILE_SIZE_LIMIT,
      allowed_content_types: DEFAULT_ALLOWED_CONTENT_TYPES,
      filename: nil)
      @configuration = configuration
      @relative_url = relative_url
      @filename = filename
      @tmpdir = tmpdir
      @file_size_limit = file_size_limit
      @allowed_content_types = allowed_content_types
      @remote_content_validated = false
    end

    def execute
      validate_tmpdir
      validate_filepath
      validate_url

      download_file

      validate_symlink

      filepath
    end

    private

    attr_reader :configuration, :relative_url, :tmpdir, :file_size_limit, :allowed_content_types, :response_headers

    def download_file
      File.open(filepath, 'wb') do |file|
        bytes_downloaded = 0

        http_client.stream(relative_url) do |chunk|
          next if bytes_downloaded == 0 && [301, 302, 303, 307, 308].include?(chunk.code)

          @response_headers ||= Gitlab::HTTP::Response::Headers.new(chunk.http_response.to_hash)

          unless @remote_content_validated
            validate_content_type
            validate_content_length

            @remote_content_validated = true
          end

          bytes_downloaded += chunk.size

          validate_size!(bytes_downloaded)

          if chunk.code == 200
            file.write(chunk)
          else
            raise(ServiceError, "File download error #{chunk.code}")
          end
        end
      end
    rescue StandardError => e
      File.delete(filepath) if File.exist?(filepath)

      raise e
    end

    def raise_error(message)
      raise ServiceError, message
    end

    def http_client
      @http_client ||= BulkImports::Clients::HTTP.new(
        url: configuration.url,
        token: configuration.access_token
      )
    end

    def allow_local_requests?
      ::Gitlab::CurrentSettings.allow_local_requests_from_web_hooks_and_services?
    end

    def validate_tmpdir
      Gitlab::Utils.check_allowed_absolute_path!(tmpdir, [Dir.tmpdir])
    end

    def filepath
      @filepath ||= File.join(@tmpdir, filename)
    end

    def filename
      @filename.presence || remote_filename
    end

    def validate_url
      ::Gitlab::UrlBlocker.validate!(
        http_client.resource_url(relative_url),
        allow_localhost: allow_local_requests?,
        allow_local_network: allow_local_requests?,
        schemes: %w(http https)
      )
    end
  end
end