using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

using ZXing;
using UnityEngine;
using UnityEngine.UI;

public class QRCodeReader : MonoBehaviour
{
    public static QRCodeReader Instance { get; private set; }

    public event Action<string> OnQRCodeRead;

    [SerializeField] AspectRatioFitter aspectRatioFitter;
    public RawImage rawImage;
    public GameObject scanFrame;

    public WebCamTexture camTexture;
    private Coroutine c_QRScanningRoutine;

    void Start()
    {
        Instance = this;

        int backCameraId = 0;
        bool backCameraEnabled = false;
        List<int> backCameraIDs = new List<int>();

        WebCamDevice[] devices = WebCamTexture.devices;
        if(devices.Length != 0)
        {
            for(int i = 0; i < devices.Length; i++)
            {
                if(Application.platform == RuntimePlatform.WindowsEditor)
                {
                    backCameraEnabled = true;
                    backCameraId = 0;
                }
                else
                {
                    if(devices[i].isFrontFacing) continue;

                    backCameraEnabled = true;
                    backCameraIDs.Add(i);
                }
            }

            if(backCameraIDs.Count != 0)
                backCameraId = backCameraIDs.First();
        }

        if(!backCameraEnabled) return;

        camTexture = new WebCamTexture(devices[backCameraId].name);
        rawImage.texture = camTexture;
        camTexture.Play();

        int orientation = -camTexture.videoRotationAngle;
        rawImage.rectTransform.localEulerAngles = Vector3.forward * orientation;

        var ratio = (float)camTexture.width / (float)camTexture.height;
        aspectRatioFitter.aspectRatio = ratio;

        float scaleY = camTexture.videoVerticallyMirrored ? -1f : 1f;
        rawImage.rectTransform.localScale = new Vector3(1f, scaleY, 1f);

        ScanningQRCode();
    }

    public void ScanningQRCode()
    {
        if(c_QRScanningRoutine != null)
        {
            StopCoroutine(c_QRScanningRoutine);
            c_QRScanningRoutine = null;
        }

        c_QRScanningRoutine = StartCoroutine(ScanQRCode());
    }

    IEnumerator ScanQRCode()
    {
        Result result;

        while(true)
        {
            try
            {
                IBarcodeReader barcodeReader = new BarcodeReader();
                result = barcodeReader.Decode
                (
                    camTexture.GetPixels32(),
                    camTexture.width,
                    camTexture.height
                );

                if(result != null) break;
            }
            catch { }

            yield return new WaitForSeconds(.5f);
        }

        yield return new WaitForSeconds(1);

        OnQRCodeRead?.Invoke(result.Text);
    }
}