import 'dart:convert';

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

import 'alpaca_env.dart';
import 'alpaca_models.dart';
import '../trading/market_history_session_slot.dart';

/// REST client for Alpaca Market Data API v2 (IEX feed on Basic plan).
class AlpacaMarketDataClient {
  AlpacaMarketDataClient({
    required AlpacaEnv env,
    http.Client? httpClient,
    Future<void> Function()? beforeHttpRequest,
  })  : _env = env,
        _client = httpClient ?? http.Client(),
        _beforeHttpRequest = beforeHttpRequest;

  final AlpacaEnv _env;
  final http.Client _client;
  final Future<void> Function()? _beforeHttpRequest;

  Future<void> _throttle() async {
    final Future<void> Function()? hook = _beforeHttpRequest;
    if (hook != null) {
      await hook();
    }
  }

  /// `GET /v2/stocks/{symbol}/trades/latest`
  Future<AlpacaLatestTradeResponse> getLatestTrade(String symbol) async {
    _env.requireCredentials();
    final Uri uri = Uri.parse(
      '${_env.dataBaseUrl}/v2/stocks/${Uri.encodeComponent(symbol)}/trades/latest',
    ).replace(queryParameters: <String, String>{'feed': _env.dataFeed});

    await _throttle();
    final http.Response response =
        await _client.get(uri, headers: _env.authHeaders);
    if (response.statusCode != 200) {
      throw AlpacaMarketDataException(
        'getLatestTrade($symbol) failed: ${response.statusCode} ${response.body}',
      );
    }
    return AlpacaLatestTradeResponse.fromJson(
      jsonDecode(response.body) as Map<String, dynamic>,
    );
  }

  /// `GET /v2/stocks/bars` — batched symbols, daily bars newest last.
  Future<AlpacaBarsResponse> getDailyBars(
    List<String> symbols, {
    int limit = 2,
  }) async {
    _env.requireCredentials();
    if (symbols.isEmpty) {
      return AlpacaBarsResponse(barsBySymbol: <String, List<AlpacaBar>>{});
    }

    final Uri uri = Uri.parse('${_env.dataBaseUrl}/v2/stocks/bars').replace(
      queryParameters: <String, String>{
        'symbols': symbols.join(','),
        'timeframe': '1Day',
        'limit': limit.toString(),
        'feed': _env.dataFeed,
      },
    );

    await _throttle();
    final http.Response response =
        await _client.get(uri, headers: _env.authHeaders);
    if (response.statusCode != 200) {
      throw AlpacaMarketDataException(
        'getDailyBars failed: ${response.statusCode} ${response.body}',
      );
    }
    return AlpacaBarsResponse.fromJson(
      jsonDecode(response.body) as Map<String, dynamic>,
    );
  }

  /// `GET /v2/stocks/bars` over a time range with pagination.
  ///
  /// Follows `next_page_token` until exhausted or [maxPages] is reached.
  /// HTTP 429 responses throw [AlpacaMarketDataException] with `rate` in
  /// the message so callers can back off.
  Future<AlpacaBarsResponse> getBarsRange({
    required List<String> symbols,
    required String timeframe,
    required DateTime start,
    required DateTime end,
    int maxPages = 20,
    int limit = 10000,
  }) async {
    _env.requireCredentials();
    if (symbols.isEmpty) {
      return AlpacaBarsResponse(barsBySymbol: <String, List<AlpacaBar>>{});
    }

    AlpacaBarsResponse merged =
        AlpacaBarsResponse(barsBySymbol: <String, List<AlpacaBar>>{});
    String? pageToken;
    int pagesFetched = 0;

    while (pagesFetched < maxPages) {
      final Map<String, String> query = <String, String>{
        'symbols': symbols.join(','),
        'timeframe': timeframe,
        'start': MarketHistorySessionSlot.wireUtc(start),
        'end': MarketHistorySessionSlot.wireUtc(end),
        'feed': _env.dataFeed,
        'limit': limit.toString(),
        if (pageToken != null && pageToken.isNotEmpty) 'page_token': pageToken,
      };

      final Uri uri = Uri.parse('${_env.dataBaseUrl}/v2/stocks/bars')
          .replace(queryParameters: query);

      await _throttle();
      final http.Response response =
          await _client.get(uri, headers: _env.authHeaders);

      if (response.statusCode == 429) {
        throw AlpacaMarketDataException.rateLimited(
          'getBarsRange rate limited: ${response.statusCode} ${response.body}',
        );
      }
      if (response.statusCode != 200) {
        throw AlpacaMarketDataException(
          'getBarsRange failed: ${response.statusCode} ${response.body}',
        );
      }

      final Map<String, dynamic> decoded =
          jsonDecode(response.body) as Map<String, dynamic>;
      final AlpacaBarsResponse page = AlpacaBarsResponse.fromJson(decoded);
      merged = merged.merge(page);
      pagesFetched++;

      pageToken = page.nextPageToken;
      if (pageToken == null || pageToken.isEmpty) {
        break;
      }
    }

    return merged;
  }

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

class AlpacaMarketDataException implements Exception {
  AlpacaMarketDataException(this.message, {this.statusCode});

  AlpacaMarketDataException.rateLimited(this.message)
      : statusCode = 429;

  final String message;
  final int? statusCode;

  bool get isRateLimited =>
      statusCode == 429 ||
      message.toLowerCase().contains('rate limited') ||
      message.contains('429');

  @override
  String toString() => message;
}