import 'dart:io';
import 'dart:convert';
import 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'package:latlong2/latlong.dart';
import 'package:flutter_map/flutter_map.dart' show LatLngBounds;

import '../../app_state.dart';
import '../../models/osm_node.dart';
import '../map_data_provider.dart';
import 'offline_area_models.dart';
import 'offline_tile_utils.dart';

/// Handles the actual downloading process for offline areas
class OfflineAreaDownloader {
  static const int _maxRetryPasses = 3;

  /// Download tiles and cameras for an offline area
  static Future<bool> downloadArea({
    required OfflineArea area,
    required LatLngBounds bounds,
    required int minZoom,
    required int maxZoom,
    required String directory,
    void Function(double progress)? onProgress,
    required Future<void> Function() saveAreasToDisk,
    required Future<void> Function(OfflineArea) getAreaSizeBytes,
  }) async {
    Set<List<int>> allTiles = computeTileList(bounds, minZoom, maxZoom);
    area.tilesTotal = allTiles.length;

    // Download tiles with retry logic
    final success = await downloadTilesWithRetry(
      area: area,
      allTiles: allTiles,
      directory: directory,
      onProgress: onProgress,
      saveAreasToDisk: saveAreasToDisk,
      getAreaSizeBytes: getAreaSizeBytes,
    );

    // Download nodes for all areas
    await _downloadNodes(
      area: area,
      bounds: bounds,
      minZoom: minZoom,
      directory: directory,
    );

    return success;
  }

  /// Download tiles with retry logic
  static Future<bool> downloadTilesWithRetry({
    required OfflineArea area,
    required Set<List<int>> allTiles,
    required String directory,
    void Function(double progress)? onProgress,
    required Future<void> Function() saveAreasToDisk,
    required Future<void> Function(OfflineArea) getAreaSizeBytes,
  }) async {
    int pass = 0;
    Set<List<int>> tilesToFetch = allTiles;
    int totalDone = 0;

    while (pass < _maxRetryPasses && tilesToFetch.isNotEmpty) {
      pass++;
      debugPrint('DownloadArea: pass #$pass for area ${area.id}. Need ${tilesToFetch.length} tiles.');
      
      for (final tile in tilesToFetch) {
        if (area.status == OfflineAreaStatus.cancelled) break;
        
        if (await _downloadSingleTile(tile, directory, area)) {
          totalDone++;
          area.tilesDownloaded = totalDone;
          area.progress = area.tilesTotal == 0 ? 0.0 : (totalDone / area.tilesTotal);
          onProgress?.call(area.progress);
        }
      }

      await getAreaSizeBytes(area);
      await saveAreasToDisk();
      
      // Check for missing tiles
      tilesToFetch = _findMissingTiles(allTiles, directory);
      if (tilesToFetch.isEmpty) {
        return true; // Success!
      }
    }

    return false; // Failed after max retries
  }

  /// Download a single tile using the unified MapDataProvider path
  static Future<bool> _downloadSingleTile(
    List<int> tile, 
    String directory, 
    OfflineArea area,
  ) async {
    try {
      // Use the same unified path as live tiles: always go through MapDataProvider
      // MapDataProvider will use current AppState provider for downloads
      final bytes = await MapDataProvider().getTile(
        z: tile[0], 
        x: tile[1], 
        y: tile[2], 
        source: MapSource.remote, // Force remote fetch for downloads
      );
      if (bytes.isNotEmpty) {
        await OfflineAreaDownloader.saveTileBytes(tile[0], tile[1], tile[2], directory, bytes);
        return true;
      }
    } catch (e) {
      debugPrint("Tile download failed for z=${tile[0]}, x=${tile[1]}, y=${tile[2]}: $e");
    }
    return false;
  }

  /// Find tiles that are missing from disk
  static Set<List<int>> _findMissingTiles(Set<List<int>> allTiles, String directory) {
    final missingTiles = <List<int>>{};
    for (final tile in allTiles) {
      final file = File('$directory/tiles/${tile[0]}/${tile[1]}/${tile[2]}.png');
      if (!file.existsSync()) {
        missingTiles.add(tile);
      }
    }
    return missingTiles;
  }

  /// Download nodes for the area with modest expansion (one zoom level lower)
  static Future<void> _downloadNodes({
    required OfflineArea area,
    required LatLngBounds bounds,
    required int minZoom,
    required String directory,
  }) async {
    // Modest expansion: use tiles at minZoom + 1 instead of minZoom
    // This gives a reasonable buffer without capturing entire states
    final nodeZoom = (minZoom + 1).clamp(8, 16); // Reasonable bounds for node fetching
    final expandedNodeBounds = calculateNodeBounds(bounds, nodeZoom);
    
    final nodes = await MapDataProvider().getAllNodesForDownload(
      bounds: expandedNodeBounds,
      profiles: AppState.instance.profiles, // Use ALL profiles, not just enabled ones
    );
    area.nodes = nodes;
    await OfflineAreaDownloader.saveNodes(nodes, directory);
    debugPrint('Area ${area.id}: Downloaded ${nodes.length} nodes from modestly expanded bounds (all profiles)');
  }

  /// Calculate expanded bounds that cover the entire tile area at minimum zoom
  static LatLngBounds calculateNodeBounds(LatLngBounds visibleBounds, int minZoom) {
    final tiles = computeTileList(visibleBounds, minZoom, minZoom);
    if (tiles.isEmpty) return visibleBounds;
    
    // Find the bounding box of all these tiles
    double minLat = 90.0, maxLat = -90.0;
    double minLon = 180.0, maxLon = -180.0;
    
    for (final tile in tiles) {
      final tileBounds = tileToLatLngBounds(tile[1], tile[2], tile[0]);
      
      minLat = math.min(minLat, tileBounds.south);
      maxLat = math.max(maxLat, tileBounds.north);
      minLon = math.min(minLon, tileBounds.west);
      maxLon = math.max(maxLon, tileBounds.east);
    }
    
    return LatLngBounds(
      LatLng(minLat, minLon),
      LatLng(maxLat, maxLon),
    );
  }

  /// Save tile bytes to disk
  static Future<void> saveTileBytes(int z, int x, int y, String baseDir, List<int> bytes) async {
    final dir = Directory('$baseDir/tiles/$z/$x');
    await dir.create(recursive: true);
    final file = File('${dir.path}/$y.png');
    await file.writeAsBytes(bytes);
  }

  /// Save nodes to disk as JSON
  static Future<void> saveNodes(List<OsmNode> nodes, String dir) async {
    final file = File('$dir/nodes.json');
    await file.writeAsString(jsonEncode(nodes.map((n) => n.toJson()).toList()));
  }
}