json_response.dart

import 'dart:convert';
import 'dart:io';

import 'package:shelf/shelf.dart';
// ignore: implementation_imports
import 'package:shelf/src/body.dart';

/// https://www.rfc-editor.org/rfc/rfc7231#section-6
class JsonResponse<T> extends Response {
  JsonResponse({
    required int statusCode,
    Object? body,
  }) : super(
          statusCode,
          headers: const {HttpHeaders.contentTypeHeader: 'application/json; charset=utf-8'},
          body: _JsonBody(body),
        );

  JsonResponse.ok({
    T? body,
  }) : this(
          statusCode: 200,
          body: body,
        );

  /// The server cannot or will not process the request due to something that is perceived to be a client error
  /// (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).
  JsonResponse.badRequest({
    Object? body,
  }) : this(
          statusCode: 400,
          body: body,
        );

  /// Although the HTTP standard specifies "unauthorized", semantically this response means "unauthenticated".
  /// That is, the client must authenticate itself to get the requested response.
  JsonResponse.unauthorized({
    Object? body,
  }) : this(
          statusCode: 401,
          body: body,
        );

  /// The client does not have access rights to the content; that is, it is unauthorized,
  /// so the server is refusing to give the requested resource.
  /// Unlike 401 Unauthorized, the client's identity is known to the server.
  JsonResponse.forbidden({
    Object? body,
  }) : this(
          statusCode: 403,
          body: body,
        );

  /// The server can not find the requested resource.
  /// This can also mean that the endpoint is valid but the resource itself does not exist.
  /// Servers may also send this response instead of 403 Forbidden to hide the existence of a resource
  /// from an unauthorized client.
  /// This response code is probably the most well known due to its frequent occurrence on the web.
  JsonResponse.notFound({
    Object? body,
  }) : this(
          statusCode: 404,
          body: body,
        );

  JsonResponse.conflict({
    Object? body,
  }) : this(
          statusCode: 409,
          body: body,
        );
}

class _JsonBody implements Body {
  @override
  final Encoding? encoding = null;
  @override
  final int? contentLength = null;

  final Object? data;

  _JsonBody(this.data);

  @override
  Stream<List<int>> read() async* {
    if (data == null) return;
    yield json.fuse(utf8).encode(data);
  }
}