import 'dart:async';
import 'dart:convert';

import 'package:ac_web/Api/ApiConfig.dart';
import 'package:ac_web/Api/ApiException.dart';
import 'package:http/http.dart' as http;

/// Thin, transport only wrapper around `package:http`.
///
/// It knows nothing about the concrete controllers of the backend, it only
/// performs requests, maps failures onto [ApiException]s and decodes json.
/// Everything endpoint specific lives in the services under `Api/Services`.
class ApiClient {
  ApiClient({ApiConfig config = ApiConfig.development, http.Client? httpClient})
      : mConfig = config,
        mHttpClient = httpClient ?? http.Client(),
        mOwnsHttpClient = httpClient == null;

  final ApiConfig mConfig;
  final http.Client mHttpClient;
  final bool mOwnsHttpClient;

  ApiConfig get config => mConfig;

  /// Performs a GET request and returns the decoded json body.
  Future<dynamic> getJson(String path, {Map<String, dynamic>? query, Map<String, String>? headers}) {
    return _send('GET', path, query: query, headers: headers);
  }

  /// Performs a GET request and maps a json array onto a list of models.
  Future<List<T>> getList<T>(
    String path,
    T Function(Map<String, dynamic> json) fromJson, {
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) async {
    final uri = mConfig.buildUri(path, query);
    final body = await _send('GET', path, query: query, headers: headers);

    if (body == null) {
      return <T>[];
    }
    if (body is! List) {
      throw ApiParsingException('Expected a json array but got ${body.runtimeType}.', uri: uri);
    }

    try {
      return body
          .whereType<Map>()
          .map((entry) => fromJson(Map<String, dynamic>.from(entry)))
          .toList(growable: false);
    } on ApiException {
      rethrow;
    } catch (error) {
      throw ApiParsingException('Failed to parse list of $T: $error', uri: uri);
    }
  }

  /// Performs a GET request and maps a json object onto a single model.
  Future<T> getObject<T>(
    String path,
    T Function(Map<String, dynamic> json) fromJson, {
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) async {
    final uri = mConfig.buildUri(path, query);
    final body = await _send('GET', path, query: query, headers: headers);

    if (body is! Map) {
      throw ApiParsingException('Expected a json object but got ${body.runtimeType}.', uri: uri);
    }

    try {
      return fromJson(Map<String, dynamic>.from(body));
    } on ApiException {
      rethrow;
    } catch (error) {
      throw ApiParsingException('Failed to parse $T: $error', uri: uri);
    }
  }

  Future<dynamic> postJson(
    String path, {
    Object? body,
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) {
    return _send('POST', path, body: body, query: query, headers: headers);
  }

  Future<dynamic> putJson(
    String path, {
    Object? body,
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) {
    return _send('PUT', path, body: body, query: query, headers: headers);
  }

  Future<dynamic> deleteJson(
    String path, {
    Object? body,
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) {
    return _send('DELETE', path, body: body, query: query, headers: headers);
  }

  void dispose() {
    if (mOwnsHttpClient) {
      mHttpClient.close();
    }
  }

  Future<dynamic> _send(
    String method,
    String path, {
    Object? body,
    Map<String, dynamic>? query,
    Map<String, String>? headers,
  }) async {
    final uri = mConfig.buildUri(path, query);

    final request = http.Request(method, uri);
    request.headers.addAll({
      'Accept': 'application/json',
      ...mConfig.defaultHeaders,
      ...?headers,
    });
    if (body != null) {
      request.headers['Content-Type'] = 'application/json; charset=utf-8';
      request.body = jsonEncode(body);
    }

    http.Response response;
    try {
      final streamed = await mHttpClient.send(request).timeout(mConfig.timeout);
      response = await http.Response.fromStream(streamed);
    } on TimeoutException {
      throw ApiTimeoutException('Request timed out after ${mConfig.timeout.inSeconds}s.', uri: uri);
    } catch (error) {
      throw ApiNetworkException('Could not reach the api: $error', uri: uri);
    }

    if (response.statusCode < 200 || response.statusCode >= 300) {
      throw ApiHttpException(
        statusCode: response.statusCode,
        message: response.reasonPhrase ?? 'Request failed.',
        body: response.body,
        uri: uri,
      );
    }

    if (response.statusCode == 204 || response.body.isEmpty) {
      return null;
    }

    try {
      return jsonDecode(utf8.decode(response.bodyBytes));
    } catch (error) {
      throw ApiParsingException('Response was no valid json: $error', uri: uri, body: response.body);
    }
  }
}