jsonapi-transformer.dart

import 'dart:convert';
import 'package:dio/dio.dart';
import 'package:dart_jsona/dart_jsona.dart';
import 'package:flutter/foundation.dart';

/// Dio Transformer used to automatically serialize and
/// deserialize JSON-API payloads.
class JsonApiTransformer extends DefaultTransformer {
  static const kJsonApiMimeType = 'application/vnd.api+json';

  @override
  Future<String> transformRequest(RequestOptions options) async {
    var data = options.data ?? '';
    if (data is! String) {
      if (options.contentType.mimeType == kJsonApiMimeType) {
        return _serializeJsonApi(options.data);
      } else {
        // Fallback to standard JSON encoding if it's not a JSON API payload
        return super.transformRequest(options);
      }
    }
    return data.toString();
  }

  @override
  Future transformResponse(
    RequestOptions options,
    ResponseBody response,
  ) async {
    if (response.headers.contentType.mimeType == kJsonApiMimeType) {
      var responseBody = await super.transformResponse(options, response);
      return _parseJsonApi(responseBody);
    }

    return super.transformResponse(options, response);
  }
}

/// Handles parsing in the background using an isolate
_parseJsonApi(String text) {
  return compute(_parseAndDecodeJsonApi, text);
}

/// Decodes a JSON API response
_parseAndDecodeJsonApi(String response) {
  return Jsona().deserialize(
    jsonDecode(response),
  );
}

/// Serializes a JSON API payload
_serializeJsonApi(dynamic data) {
  return jsonEncode(
    Jsona().serialize(stuff: data),
  );
}