import 'dart:async';
import 'package:http/http.dart' as http;
import 'package:meta/meta.dart';
import '../models/stream_entry.dart';

class M3uParseException implements Exception {
  final String message;
  M3uParseException(this.message);
  @override
  String toString() => 'M3uParseException: $message';
}

class M3UService {
  final http.Client _client;
  final Duration cacheTTL;

  String? _cachedUrl;
  DateTime? _cachedAt;
  List<StreamEntry>? _cachedEntries;

  M3UService({http.Client? client, this.cacheTTL = const Duration(minutes: 5)})
      : _client = client ?? http.Client();

  /// Fetches an M3U (over HTTP) and returns parsed list of [StreamEntry].
  /// Uses a short in-memory cache to avoid repeated network calls.
  Future<List<StreamEntry>> fetch(String url,
      {bool forceRefresh = false}) async {
    if (!forceRefresh &&
        _cachedUrl == url &&
        _cachedEntries != null &&
        _cachedAt != null &&
        DateTime.now().difference(_cachedAt!) < cacheTTL) {
      return _cachedEntries!;
    }

    final resp = await _client.get(Uri.parse(url));
    if (resp.statusCode != 200) {
      throw Exception('Failed to fetch M3U: HTTP ${resp.statusCode}');
    }

    final content = resp.body;
    final entries = parse(content);

    // Update cache
    _cachedUrl = url;
    _cachedAt = DateTime.now();
    _cachedEntries = entries;

    return entries;
  }

  /// Parse raw M3U content into [StreamEntry] list.
  List<StreamEntry> parse(String content) {
    final lines = content.replaceAll('\r', '').split('\n');
    final entries = <StreamEntry>[];

    String? pendingTitle;

    for (var raw in lines) {
      final line = raw.trim();
      if (line.isEmpty) continue;
      if (line.startsWith('#EXTINF')) {
        // Format: #EXTINF:-1 tvg-id="" tvg-name="Channel" tvg-logo="" group-title="...") ,Display title
        final parts = line.split(',');
        if (parts.length >= 2) {
          pendingTitle = parts.sublist(1).join(',').trim();
        } else {
          // Fallback: try to extract text after the last space
          final idx = line.indexOf(',');
          if (idx >= 0 && idx < line.length - 1)
            pendingTitle = line.substring(idx + 1).trim();
        }
        continue;
      }

      if (line.startsWith('#')) continue;

      // At this point 'line' is a URL
      final url = line;
      final title = pendingTitle ?? url;
      entries.add(StreamEntry(title: title, url: url));
      pendingTitle = null;
    }

    if (entries.isEmpty) {
      throw M3uParseException('No entries found in M3U');
    }

    return entries;
  }
}