import 'dart:async';
import 'dart:ffi';
import 'package:camera/camera.dart';
import 'dart:typed_data';

import 'package:flutter/material.dart';

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 = 0.0;
  static const alpha = 0.99;
  static const thresh = 25;
  Uint8List? previousImage;
  Uint8List? diff;
  Uint8List? dst;
  Uint64List? diffValues;
  Float32List? background;
  Float64List? diffWeightsX;
  

  @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: Column(children: <Widget>[
          CameraPreview(cameraController),
        ]),
        floatingActionButton: FloatingActionButton(
          child: const Icon(Icons.plus_one),
          onPressed: () {
            startStream();
          },
        ),
      ),
      debugShowCheckedModeBanner: false,
    );
  }

  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) {
    diffWeightsX = Float64List(src.width);
    diffValues = Uint64List(src.width);
    
    if (previousImage == null || background == null) {
      previousImage = Uint8List(src.planes[0].bytes.length);
      dst = Uint8List(src.planes[0].bytes.length);
      diff = Uint8List(src.planes[0].bytes.length);
      background = Float32List(src.planes[0].bytes.length);
      image_width = src.width;
      image_height = src.height;
    } else {
      for (var i = 0; i < image_height; i++) {
        for (var j = 0; j < image_width; j++) {
          //Background calculation
          background![i + j] = (background![i + j] * alpha +
              src.planes[0].bytes[i + j].toDouble() * (1.0 - alpha));

          //Difference calculation
          diff![i + j] =  (background![i + j].toInt() - src.planes[0].bytes[i + j]).abs();
          if(diff![i + j] > thresh) {
            diffWeightsX![i] += diff![i + j] * j;
            diffValues![i] += diff![i + j];
          }
        }
      }
      // Processing

      //Average X Position
      posx = 0;
      posy = 0;
      var currentCount = 0;
      var weightsY = 0;
      for(var i = 0; i < diffWeightsX!.length; i++){
        if(diffValues![i] > 0){
          posx += (diffWeightsX![i]/diffValues![i])/diffWeightsX!.length;
          weightsY += diffValues![i] * i;
          currentCount += diffValues![i];
        }
      }

      if(currentCount > 0) {
        posy = weightsY/currentCount;
      }
      
      count = count * alpha +  (currentCount/(image_width * image_height * 255) * 100.0) * (1.0 - alpha);
      print(count);

      // End Processing
      previousImage = src.planes[0].bytes;
    }
  }
}