import 'dart:convert';

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

import '../../domain/waypoint/flat_waypoint_list.dart';
import '../../domain/wind/wind_math.dart';

/// Kombinierte Stuetzpunkte fuer die Windinterpolation an einem Ort, plus die
/// dort zugrunde liegende Bodenhoehe (ASL) - analog buildCombinedWindLevels()
/// im HTML-Demonstrator (Doku 3.8).
class WindCombinedLevels {
  const WindCombinedLevels({required this.levels, required this.elevationM});

  final List<WindLevel> levels;
  final double elevationM;
}

/// Holt und kombiniert Winddaten von Open-Meteo (Doku 3.8). Zwei getrennte,
/// fokussierte Requests (Druckflaechen + feste Nabenhoehen) statt eines
/// kombinierten - ein 35-Variablen-Request verursachte im HTML-Demonstrator
/// Modellauswahl-Fehler (Doku 4.10).
class WindService {
  WindService({http.Client? client}) : _client = client ?? http.Client();

  final http.Client _client;

  static const _pressureLevels = [1000, 975, 950, 925, 900, 850, 800, 750, 700];
  static const _fixedHeights = [10, 80, 120, 180];

  Uri _pressureUri(String lats, String lons) {
    final vars = _pressureLevels
        .map((p) =>
            'wind_speed_${p}hPa,wind_direction_${p}hPa,geopotential_height_${p}hPa')
        .join(',');
    return Uri.https('api.open-meteo.com', '/v1/forecast', {
      'latitude': lats,
      'longitude': lons,
      'hourly': vars,
      'wind_speed_unit': 'ms',
      'timezone': 'UTC',
      'forecast_days': '1',
    });
  }

  Uri _fixedUri(String lats, String lons) {
    final vars =
        '${_fixedHeights.map((h) => 'wind_speed_${h}m,wind_direction_${h}m').join(',')},wind_gusts_10m';
    return Uri.https('api.open-meteo.com', '/v1/forecast', {
      'latitude': lats,
      'longitude': lons,
      'hourly': vars,
      'wind_speed_unit': 'ms',
      'timezone': 'UTC',
      'forecast_days': '1',
    });
  }

  Future<dynamic> _fetchJson(Uri uri) async {
    try {
      final response =
          await _client.get(uri).timeout(const Duration(seconds: 8));
      if (response.statusCode != 200) return null;
      return jsonDecode(response.body);
    } catch (_) {
      return null;
    }
  }

  /// Open-Meteo liefert bei einem einzelnen Ort ein Objekt, bei mehreren
  /// kommagetrennten Koordinaten ein Array - hier auf eine einheitliche
  /// Liste fester Laenge normalisiert.
  List<Map<String, dynamic>?> _asResultList(dynamic decoded, int expectedCount) {
    if (decoded is List) {
      return List.generate(
        expectedCount,
        (i) => i < decoded.length ? decoded[i] as Map<String, dynamic>? : null,
      );
    }
    if (decoded is Map<String, dynamic>) {
      return [decoded, ...List<Map<String, dynamic>?>.filled(expectedCount - 1, null)];
    }
    return List<Map<String, dynamic>?>.filled(expectedCount, null);
  }

  int _nearestHourIndex(List<dynamic> time) {
    final now = DateTime.now().toUtc();
    var bestIdx = 0;
    var bestDiffMs = double.infinity;
    for (var i = 0; i < time.length; i++) {
      final t = DateTime.parse('${time[i]}:00Z');
      final diffMs = t.difference(now).inMilliseconds.abs().toDouble();
      if (diffMs < bestDiffMs) {
        bestDiffMs = diffMs;
        bestIdx = i;
      }
    }
    return bestIdx;
  }

  /// Vereint Druckflaechen- und feste Nabenhoehen-Daten zu einer
  /// gemeinsamen Stuetzpunktliste (AGL-Hoehen der Nabenhoehen werden dazu in
  /// ASL umgerechnet). Entweder Quelle darf fehlen (null); genutzt wird, was
  /// vorhanden ist - analog buildCombinedWindLevels() im HTML-Demonstrator.
  WindCombinedLevels buildCombinedWindLevels(
    Map<String, dynamic>? pressureRes,
    Map<String, dynamic>? fixedRes,
  ) {
    final levels = <WindLevel>[];
    var elevation = 0.0;

    final pHourly = pressureRes?['hourly'] as Map<String, dynamic>?;
    final pTime = pHourly?['time'] as List<dynamic>?;
    if (pHourly != null && pTime != null && pTime.isNotEmpty) {
      final idx = _nearestHourIndex(pTime);
      elevation = (pressureRes?['elevation'] as num?)?.toDouble() ?? 0.0;
      for (final p in _pressureLevels) {
        final h = (pHourly['geopotential_height_${p}hPa'] as List?)?[idx];
        final s = (pHourly['wind_speed_${p}hPa'] as List?)?[idx];
        final d = (pHourly['wind_direction_${p}hPa'] as List?)?[idx];
        if (h is num && s is num && d is num && h >= elevation) {
          levels.add(WindLevel(
            heightAmslM: h.toDouble(),
            speedMs: s.toDouble(),
            dirFromDeg: d.toDouble(),
          ));
        }
      }
    }

    final fHourly = fixedRes?['hourly'] as Map<String, dynamic>?;
    final fTime = fHourly?['time'] as List<dynamic>?;
    if (fHourly != null && fTime != null && fTime.isNotEmpty) {
      final idx = _nearestHourIndex(fTime);
      if (elevation == 0.0) {
        elevation = (fixedRes?['elevation'] as num?)?.toDouble() ?? 0.0;
      }
      for (final h in _fixedHeights) {
        final s = (fHourly['wind_speed_${h}m'] as List?)?[idx];
        final d = (fHourly['wind_direction_${h}m'] as List?)?[idx];
        if (s is num && d is num) {
          levels.add(WindLevel(
            heightAmslM: elevation + h,
            speedMs: s.toDouble(),
            dirFromDeg: d.toDouble(),
          ));
        }
      }
    }

    return WindCombinedLevels(levels: levels, elevationM: elevation);
  }

  /// Wind, interpoliert auf 120 m AGL ueber dem Referenzort (erster
  /// Wegpunkt, sonst Kartenzentrum) - fuer die Kopfleisten-Pille.
  Future<WindSample?> fetchHeaderWind(double lat, double lon) async {
    final results = await Future.wait([
      _fetchJson(_pressureUri(lat.toStringAsFixed(5), lon.toStringAsFixed(5))),
      _fetchJson(_fixedUri(lat.toStringAsFixed(5), lon.toStringAsFixed(5))),
    ]);
    final pressureRes = _asResultList(results[0], 1)[0];
    final fixedRes = _asResultList(results[1], 1)[0];
    final combined = buildCombinedWindLevels(pressureRes, fixedRes);
    if (combined.levels.isEmpty) return null;
    return interpolateWindAtHeight(combined.levels, combined.elevationM + 120);
  }

  /// Holt Wind fuer alle Wegpunkte in einem gebuendelten Request (Open-Meteo
  /// akzeptiert kommagetrennte Koordinatenlisten) und interpoliert jeweils
  /// auf die tatsaechliche Zielhoehe (Bodenhoehe + Soll-Altitude) - analog
  /// fetchWindForWaypoints() im HTML-Demonstrator.
  Future<List<Waypoint>> fetchWindForWaypoints(List<Waypoint> waypoints) async {
    if (waypoints.isEmpty) return waypoints;
    final lats = waypoints.map((w) => w.lat.toStringAsFixed(5)).join(',');
    final lons = waypoints.map((w) => w.lon.toStringAsFixed(5)).join(',');
    final results = await Future.wait([
      _fetchJson(_pressureUri(lats, lons)),
      _fetchJson(_fixedUri(lats, lons)),
    ]);
    final pressureResults = _asResultList(results[0], waypoints.length);
    final fixedResults = _asResultList(results[1], waypoints.length);

    return [
      for (var i = 0; i < waypoints.length; i++)
        _applyWind(waypoints[i], pressureResults[i], fixedResults[i]),
    ];
  }

  Waypoint _applyWind(
    Waypoint wp,
    Map<String, dynamic>? pressureRes,
    Map<String, dynamic>? fixedRes,
  ) {
    final combined = buildCombinedWindLevels(pressureRes, fixedRes);
    if (combined.levels.isEmpty) return wp;
    final result = interpolateWindAtHeight(
      combined.levels,
      combined.elevationM + wp.altitudeM,
    );
    if (result == null) return wp;
    return wp.copyWith(
      windSpeedMs: result.speedMs,
      windDirFromDeg: result.dirFromDeg,
      windElevationM: combined.elevationM,
    );
  }
}