import 'dart:async';
import 'dart:ffi';
import 'dart:ui';
import 'dart:typed_data';
import 'dart:math';
import 'package:flutter/material.dart';

import 'package:camera/camera.dart';
import 'package:image/image.dart' as img;

List<CameraDescription> cameras = [];

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  cameras = await availableCameras();
  runApp(CameraApp());
}

class CameraApp extends StatefulWidget {
  @override
  _CameraAppState createState() => _CameraAppState();
}

class _CameraAppState extends State<CameraApp> {
  CameraController? controller;
  var streaming = false;
  var image_width = 0;
  var image_height = 0;
  var posy = 0.0;
  var posx = 0.0;
  var count = 0;
  var frameNumber = 0;
  static const alpha = 0.90;
  static const thresh = 50;

  var previousImage = <int>[];
  var gray = <int>[];
  var diff = <int>[];
  var dst = <int>[];
  var background = <double>[];

  @override
  void initState() {
    super.initState();
    controller = CameraController(cameras[1], ResolutionPreset.low);
    controller!.initialize().then((_) {
      if (!mounted) {
        return;
      }
      setState(() {});
    });
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final CameraController cameraController = controller!;
    if (!cameraController.value.isInitialized) {
      return Container();
    }

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Home'),
        ),
        body: Stack(children: <Widget>[
          diffView(),
          Container(
            height: image_height.toDouble(),
            width: image_width.toDouble(),
            child: CustomPaint(
              painter: OpenPainter(posx, posy),
            ),
          ),
        ]),
        floatingActionButton: FloatingActionButton(
          child: const Icon(Icons.plus_one),
          onPressed: () {
            startStream();
          },
        ),
      ),
      debugShowCheckedModeBanner: false,
    );
  }

  Widget diffView() {
    return Transform.rotate(
      angle: 0.0, //pi * -0.5
      child: diff.isEmpty
          ? Container()
          : Image.memory(Uint8List.fromList(img.encodeJpg((img.Image.fromBytes(
              image_width, image_height, diff,
              format: img.Format.luminance))))),
    );
  }

  void startStream() {
    final CameraController? cameraController = controller;

    if (cameraController == null || !cameraController.value.isInitialized) {
      return;
    }

    if (streaming == false) {
      cameraController.startImageStream(handleImage);
    } else {
      cameraController.stopImageStream();
    }

    setState(() {
      streaming = !streaming;
    });
  }

  void handleImage(CameraImage src) async {
    if (previousImage.isEmpty) {
      previousImage = List.filled(src.planes[0].bytes.length, 0);
      gray = List.filled(src.planes[0].bytes.length, 0);
      diff = List.filled(src.planes[0].bytes.length, 0);
      dst = List.filled(src.planes[0].bytes.length, 0);
      background = List.filled(src.planes[0].bytes.length, 0.0);

      image_width = src.width;
      image_height = src.height;
    } else {
      if (frameNumber % 10 == 0) {
        gray = src.planes[0].bytes;

        count = 0;
        var xVal = 0.0;
        var yVal = 0.0;

        for (var i = 0; i < gray.length; i++) {
          background[i] = background[i] * alpha + gray[i] * (1.0 - alpha);
          diff[i] = (gray[i] - background[i].toInt()).abs();
          dst[i] = background[i].toInt();
          if (diff[i] < thresh) {
            diff[i] = 0;
          } else {
            //diff[i] = 255;
            xVal += diff[i] * ((i % image_width) + 1);
            yVal += diff[i] * ((i % image_height) + 1);
            count += diff[i];
          }
        }

        // End Processing
        previousImage = gray.toList();
        if (count != 0) {
          posx = xVal / count;
          posy = yVal / count;
          print("$count ${posx.toInt()} ${posy.toInt()}");
        }
        setState(() {});
      }
      frameNumber += 1;
    }
  }
}

class OpenPainter extends CustomPainter {
  double posx;
  double posy;
  OpenPainter(this.posx, this.posy);
  @override
  void paint(Canvas canvas, Size size) {
    canvas.drawCircle(Offset(posx, posy), 10,
        Paint()..color = Color.fromARGB(255, 0, 255, 0));
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}