import 'dart:convert';

import 'package:http/http.dart' as http;

import 'alpaca_env.dart';
import 'alpaca_models.dart';

/// REST client for Alpaca Trading API v2 (paper by default).
///
/// Step 9 (`TRADING_TDD_PLAN.md`) — wraps `POST /v2/orders` and
/// `GET /v2/orders:by_client_order_id` with idempotent semantics.
class AlpacaTradingClient {
  AlpacaTradingClient({
    required AlpacaEnv env,
    http.Client? httpClient,
  })  : _env = env,
        _client = httpClient ?? http.Client();

  final AlpacaEnv _env;
  final http.Client _client;

  Map<String, String> get _headers => <String, String>{
        'APCA-API-KEY-ID': _env.apiKeyId,
        'APCA-API-SECRET-KEY': _env.apiSecretKey,
        'Content-Type': 'application/json',
        'Accept': 'application/json',
      };

  /// `POST /v2/orders` — places a market order.
  ///
  /// Throws [AlpacaTradingDuplicateClientOrderIdException] when Alpaca rejects
  /// the request because [request.clientOrderId] was already used. Callers
  /// should resolve the existing order with [getOrderByClientOrderId].
  Future<AlpacaOrderResponse> submitOrder(AlpacaOrderRequest request) async {
    _env.requireCredentials();
    _env.assertPaperOnly();
    final Uri uri = Uri.parse('${_env.tradingBaseUrl}/v2/orders');

    final http.Response response = await _client.post(
      uri,
      headers: _headers,
      body: jsonEncode(request.toJson()),
    );

    if (response.statusCode == 200 || response.statusCode == 201) {
      return AlpacaOrderResponse.fromJson(
        jsonDecode(response.body) as Map<String, dynamic>,
      );
    }

    if (response.statusCode == 422 &&
        response.body.toLowerCase().contains('client_order_id')) {
      throw AlpacaTradingDuplicateClientOrderIdException(
        clientOrderId: request.clientOrderId,
        body: response.body,
      );
    }

    throw AlpacaTradingException(
      'submitOrder failed: ${response.statusCode} ${response.body}',
    );
  }

  /// `GET /v2/orders:by_client_order_id?client_order_id=...` — returns null
  /// when Alpaca has no order under that id (404).
  Future<AlpacaOrderResponse?> getOrderByClientOrderId(
    String clientOrderId,
  ) async {
    _env.requireCredentials();
    final Uri uri =
        Uri.parse('${_env.tradingBaseUrl}/v2/orders:by_client_order_id').replace(
      queryParameters: <String, String>{'client_order_id': clientOrderId},
    );

    final http.Response response = await _client.get(uri, headers: _headers);
    if (response.statusCode == 200) {
      return AlpacaOrderResponse.fromJson(
        jsonDecode(response.body) as Map<String, dynamic>,
      );
    }
    if (response.statusCode == 404) {
      return null;
    }
    throw AlpacaTradingException(
      'getOrderByClientOrderId failed: ${response.statusCode} ${response.body}',
    );
  }

  void close() => _client.close();
}

class AlpacaTradingException implements Exception {
  AlpacaTradingException(this.message);
  final String message;
  @override
  String toString() => message;
}

class AlpacaTradingDuplicateClientOrderIdException
    extends AlpacaTradingException {
  AlpacaTradingDuplicateClientOrderIdException({
    required this.clientOrderId,
    required this.body,
  }) : super('duplicate client_order_id=$clientOrderId: $body');

  final String clientOrderId;
  final String body;
}