deepvoice_client/lib/modules/chat/views/chat_navigation_card.dart

import 'dart:convert';
import 'dart:math';
import 'dart:math' as math;

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

class ChatNavigationCard extends StatefulWidget {
  final Map? data;
  final bool isDarkMode;

  const ChatNavigationCard(this.data, this.isDarkMode, {super.key});

  @override
  State<ChatNavigationCard> createState() => _ChatNavigationCardState();
}

class _ChatNavigationCardState extends State<ChatNavigationCard> {
  final String apiKey = '8bde023b7e5e00f321ea17929f10fbae';
  LatLng startPoint = LatLng(116.397428, 39.90923); // 起点坐标
  LatLng endPoint = LatLng(116.397026, 39.903303); // 终点坐标

  @override
  void initState() {
    super.initState();
    _getMapUrl();
  }

  Future<String> _getMapUrl() async {
    // 1. 获取路径数据
    final route = await _fetchRouteData();

    // 2. 解析并简化路径
    List<LatLng> simplified = _simplifyPath(route, epsilon: 0.0001);

    // 3. 计算地图参数
    final zoom = _calculateAutoZoom(simplified);

    // 4. 生成静态地图URL
    return _buildStaticMapUrl(simplified, zoom);
  }

  Future<List<LatLng>> _fetchRouteData() async {
    final url = 'https://restapi.amap.com/v3/direction/driving?'
        'origin=${startPoint.lng},${startPoint.lat}&'
        'destination=${endPoint.lng},${endPoint.lat}&'
        'key=$apiKey';

    final response = await http.get(Uri.parse(url));
    if (response.statusCode == 200) {
      final data = json.decode(response.body);
      return _parsePolyline(data['route']['paths'][0]['steps']);
    }
    throw Exception('Failed to load route');
  }

  List<LatLng> _parsePolyline(List<dynamic> steps) {
    final List<LatLng> path = [];
    for (final step in steps) {
      final points = (step['polyline'] as String).split(';');
      for (final point in points) {
        final coords = point.split(',').map(double.parse).toList();
        path.add(LatLng(coords[0], coords[1]));
      }
    }
    return path;
  }

  List<LatLng> _simplifyPath(List<LatLng> points, {double epsilon = 0.0001}) {
    return douglasPeucker(points, epsilon);
  }

  int _calculateAutoZoom(List<LatLng> points,
      {int mapWidth = 1024, int mapHeight = 512}) {
    if (points.isEmpty) return 15; // 默认缩放级别

    // 1. 计算坐标范围
    double minLng = double.infinity;
    double maxLng = -double.infinity;
    double minLat = double.infinity;
    double maxLat = -double.infinity;

    for (final p in points) {
      final lng = p.lng;
      final lat = p.lat;

      minLng = math.min(minLng, lng);
      maxLng = math.max(maxLng, lng);
      minLat = math.min(minLat, lat);
      maxLat = math.max(maxLat, lat);
    }

    // 3. 计算缩放级别（基于Leaflet算法改进）
    const worldWidth = 256; // 高德瓦片尺寸
    const worldHeight = 256;
    const zoomMax = 18; // 高德最大缩放级别

    double latRad(double lat) {
      final sin = math.sin(lat * math.pi / 180);
      return math.log((1 + sin) / (1 - sin)) / 2;
    }

    final latFraction = (latRad(maxLat) - latRad(minLat)) / math.pi;
    final lngDiff = maxLng - minLng;
    final lngFraction = ((lngDiff < 0) ? (lngDiff + 360) : lngDiff) / 360;

    final latZoom =
        math.log((mapHeight / worldHeight) / latFraction) / math.ln2;
    final lngZoom = math.log((mapWidth / worldWidth) / lngFraction) / math.ln2;

    return math.min(math.min(latZoom, lngZoom).floor(), zoomMax);
  }

  String _buildStaticMapUrl(List<LatLng> path, int zoom) {
    final pathParam = path.map((p) => '${p.lng},${p.lat}').join(';');
    return 'https://restapi.amap.com/v3/staticmap?'
        'zoom=$zoom&'
        'size=1024*512&'
        'paths=10,0x0000ff,1,,:$pathParam&'
        'markers=mid,,A:${startPoint.lng},${startPoint.lat}|'
        'mid,,B:${endPoint.lng},${endPoint.lat}&'
        'key=$apiKey';
  }

  List<LatLng> douglasPeucker(List<LatLng> points, double epsilon) {
    if (points.length < 3) return points;

    double maxDistance = 0;
    int index = 0;

    for (int i = 1; i < points.length - 1; i++) {
      double d = _perpendicularDistance(points[i], points.first, points.last);
      if (d > maxDistance) {
        index = i;
        maxDistance = d;
      }
    }

    if (maxDistance > epsilon) {
      return [
        ...douglasPeucker(points.sublist(0, index + 1), epsilon),
        ...douglasPeucker(points.sublist(index), epsilon).skip(1)
      ];
    }
    return [points.first, points.last];
  }

  double _perpendicularDistance(LatLng point, LatLng start, LatLng end) {
    final area = (end.lng - start.lng) * (point.lat - start.lat) -
        (end.lat - start.lat) * (point.lng - start.lng);
    final length =
        sqrt(pow(end.lng - start.lng, 2) + pow(end.lat - start.lat, 2));
    return area.abs() / length;
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        FutureBuilder(
          future: _getMapUrl(),
          builder: (BuildContext context, AsyncSnapshot snapshot) {
            if (snapshot.hasData) {
              return Image.network(snapshot.data);
            }
            return const CircularProgressIndicator();
          },
        ),
      ],
    );
  }
}

class LatLng {
  final double lat;
  final double lng;

  LatLng(this.lng, this.lat); // 高德使用经度在前纬度在后的格式
}