import 'dart:math';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:flutter_map/flutter_map.dart';
import 'package:flutter_map/plugin_api.dart';

import 'scalebar_utils.dart' as util;

class ScaleLayerOptions extends LayerOptions {
  TextStyle textStyle;
  Color lineColor;
  double lineWidth;
  final EdgeInsets padding;

  ScaleLayerOptions({
    Key key,
    this.textStyle,
    this.lineColor = Colors.white,
    this.lineWidth = 2,
    this.padding,
    rebuild,
  }) : super(key: key, rebuild: rebuild);
}

class ScaleLayerWidget extends StatelessWidget {
  final ScaleLayerOptions options;

  ScaleLayerWidget({@required this.options}) : super(key: options.key);

  @override
  Widget build(BuildContext context) {
    final mapState = MapState.of(context);
    return ScaleLayer(options, mapState, mapState.onMoved);
  }
}

class ScaleLayer extends StatelessWidget {
  final ScaleLayerOptions scaleLayerOpts;
  final MapState map;
  final Stream<Null> stream;
  final scale = [
    25000000,
    15000000,
    8000000,
    4000000,
    2000000,
    1000000,
    500000,
    250000,
    100000,
    50000,
    25000,
    15000,
    8000,
    4000,
    2000,
    1000,
    500,
    250,
    100,
    50,
    25,
    10,
    5,
  ];

  ScaleLayer(this.scaleLayerOpts, this.map, this.stream) : super(key: scaleLayerOpts.key);

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<Null>(
      stream: stream,
      builder: (context, snapshot) {
        var zoom = map.zoom;
        var distance = scale[max(0, min(20, zoom.round() + 2))].toDouble();
        var center = map.center;
        var start = map.project(center);
        var targetPoint = util.calculateEndingGlobalCoordinates(center, 90, distance);
        var end = map.project(targetPoint);
        var displayDistance = distance > 999 ? '${(distance / 1000).toStringAsFixed(0)} km' : '${distance.toStringAsFixed(0)} m';
        double width = (end.x - start.x);

        return CustomPaint(
          painter: ScalePainter(
            width,
            displayDistance,
            lineColor: scaleLayerOpts.lineColor,
            lineWidth: scaleLayerOpts.lineWidth,
            padding: scaleLayerOpts.padding,
            textStyle: scaleLayerOpts.textStyle,
          ),
        );
      },
    );
  }
}

class ScalePainter extends CustomPainter {
  ScalePainter(this.width, this.text, {this.padding, this.textStyle, this.lineWidth, this.lineColor});

  final double width;
  final EdgeInsets padding;
  final String text;
  TextStyle textStyle;
  double lineWidth;
  Color lineColor;

  @override
  void paint(ui.Canvas canvas, ui.Size size) {
    final paint = Paint()
      ..color = lineColor
      ..strokeCap = StrokeCap.square
      ..strokeWidth = lineWidth;

    var sizeForStartEnd = 4;
    var paddingLeft = padding == null ? 0 : padding.left + sizeForStartEnd / 2;
    var paddingTop = padding == null ? 0 : padding.top;

    var textSpan = TextSpan(style: textStyle, text: text);
    var textPainter = TextPainter(text: textSpan, textDirection: TextDirection.ltr)..layout();
    textPainter.paint(canvas, Offset(width / 2 - textPainter.width / 2 + paddingLeft, paddingTop));
    paddingTop += textPainter.height;
    var p1 = Offset(paddingLeft, sizeForStartEnd + paddingTop);
    var p2 = Offset(paddingLeft + width, sizeForStartEnd + paddingTop);
    // draw start line
    canvas.drawLine(Offset(paddingLeft, paddingTop), Offset(paddingLeft, sizeForStartEnd + paddingTop), paint);
    // draw middle line
    var middleX = width / 2 + paddingLeft - lineWidth / 2;
    canvas.drawLine(Offset(middleX, paddingTop + sizeForStartEnd / 2), Offset(middleX, sizeForStartEnd + paddingTop), paint);
    // draw end line
    canvas.drawLine(Offset(width + paddingLeft, paddingTop), Offset(width + paddingLeft, sizeForStartEnd + paddingTop), paint);
    // draw bottom line
    canvas.drawLine(p1, p2, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}