qr-code-scanner.js

import {i18n} from './i18n';
import {css, html, unsafeCSS} from 'lit-element';
import DBPLitElement from 'dbp-common/dbp-lit-element';
import * as commonStyles from 'dbp-common/styles';
import {ScopedElementsMixin} from '@open-wc/scoped-elements';
import {Icon, MiniSpinner} from 'dbp-common';
import {classMap} from 'lit-html/directives/class-map.js';
import jsQR from "jsqr";
import {getIconSVGURL} from 'dbp-common';
import {Mutex} from 'async-mutex';


/**
 * Returns the ID for the most important device
 *
 * @param {Map} devices
 * @returns {string|null} the ID
 */
function getPrimaryDevice(devices) {
    if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)) {
        if (devices.has('environment'))
            return 'environment';
    }
    if (devices.size) {
        return Array.from(devices)[0][0];
    }
    return null;
}

/**
 * Returns a map of device IDs and translated names.
 *
 * Moreimportant devices first.
 *
 * @returns {Map<string,string>} the map of devices
 */
async function getVideoDevices() {
    let devices_map = new Map();
    if (navigator.mediaDevices
        && navigator.mediaDevices.enumerateDevices
        && navigator.mediaDevices.getUserMedia) {

        let devices;
        try {
            devices = await navigator.mediaDevices.enumerateDevices();
        } catch (err) {
            console.log(err.name + ": " + err.message);
            return devices_map;
        }

        for (let device of devices) {
            if (device.kind === 'videoinput') {
                let id = device.deviceId;
                if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)) {
                    devices_map.set('environment', i18n.t('back-camera'));
                    devices_map.set('user', i18n.t('front-camera'));
                } else {
                    devices_map.set(id ? id : true, device.label || i18n.t('camera') + (devices_map.size + 1));
                }
            }
        }
        return devices_map;
    } else {
        return devices_map;
    }
}

/**
 * @param {string} deviceId
 * @returns {object|null} a video element or null
 */
async function createVideoElement(deviceId) {

    let videoId = deviceId;
    let constraint = { video:  { deviceId: videoId } };
    if ( (videoId === 'environment' || videoId === '') ) {
        console.log("vid:", videoId);
        constraint =  { video: { facingMode: "environment" } };
    } else if ( videoId === 'user' ) {
        console.log("vid2:", videoId);
        constraint =  { video: { facingMode: "user" } };
    }

    let stream = null;
    try {
        stream = await navigator.mediaDevices.getUserMedia(constraint);
    } catch(e) {
        console.log(e);
    }

    if (stream !== null) {
        let video = document.createElement("video");
        video.srcObject = stream;
        return video;
    }

    return null;
}


export class QrCodeScanner extends ScopedElementsMixin(DBPLitElement) {
    constructor() {
        super();
        this.lang = 'de';

        this._askPermission = false;
        this._loading = false;

        this.showOutput = false;
        this.stopScan = false;

        this._activeCamera = '';

        this._devices = new Map();
        this._requestID = null;
        this._loadingMessage = '';

        this.matchRegex = '.*';
        this._videoElement = null;
        this._outputData = null;
        this._videoRunning = false;
        this._lock = new Mutex();
    }

    static get scopedElements() {
        return {
            'dbp-icon': Icon,
            'dbp-mini-spinner': MiniSpinner,
        };
    }

    static get properties() {
        return {
            lang: { type: String },
            showOutput: { type: Boolean, attribute: 'show-output' },
            stopScan: { type: Boolean, attribute: 'stop-scan' },
            matchRegex: { type: String, attribute: 'match-regex' },
            _activeCamera: { type: String, attribute: false },
            _loading: { type: Boolean, attribute: false },
            _devices: { type: Map, attribute: false},
            _loadingMessage: { type: String, attribute: false },
            _outputData: { type: String, attribute: false },
            _askPermission: { type: Boolean, attribute: false },
            _videoRunning: { type: Boolean, attribute: false },
        };
    }

    async connectedCallback() {
        super.connectedCallback();
        i18n.changeLanguage(this.lang);

        let devices = await getVideoDevices();
        this._activeCamera = getPrimaryDevice(devices) || '';
        this._devices = devices;

        if (!this.stopScan) {
            await this.startScanning();
        }
    }

    async disconnectedCallback() {
        await this.stopScanning();
        super.disconnectedCallback();
    }

    updated(changedProperties) {
        if (changedProperties.get('stopScan') && !this.stopScan) {
            this.startScanning();
        } else if (!changedProperties.get('stopScan') && this.stopScan) {
            this.stopScanning();
        }
    }

    update(changedProperties) {
        changedProperties.forEach((oldValue, propName) => {
            switch (propName) {
                case "lang":
                    i18n.changeLanguage(this.lang);
                    break;
            }
        });

        super.update(changedProperties);
    }

    /**
     * Init and start the video and QR code scan
     */
    async startScanning() {
        await this.stopScanning();

        const release = await this._lock.acquire();
        try {
            await this._startScanning();
        } finally {
            release();
        }
    }

    async _startScanning() {
        console.assert(this._lock.isLocked());
        await this.updateComplete;

        let targetCanvas = this._("#canvas");
        let canvasElement = document.createElement("canvas");
        let firstDrawDone = false;

        this._askPermission = true;
        this._loadingMessage = i18n.t('no-camera-access');
        let video = await createVideoElement(this._activeCamera);
        this._askPermission = false;

        let lastVideoScanTime = -1;
        let lastCode = null;
        let lastSentData = null;

        const tick = () => {
            this._requestID = null;
            if (video.readyState === video.HAVE_ENOUGH_DATA) {
                this._loading = false;

                // draw into a temporary canvas first
                canvasElement.height = video.videoHeight;
                canvasElement.width = video.videoWidth;
                let canvas = canvasElement.getContext("2d");
                canvas.drawImage(video, 0, 0, canvasElement.width, canvasElement.height);

                let maskWidth = canvasElement.width;
                let maskHeight = canvasElement.height;
                let maskStartX = 0;
                let maskStartY = 0;

                let maxSize = canvasElement.width > canvasElement.height ? canvasElement.height/4 * 3 : canvasElement.width/4 * 3;
                console.assert(maxSize <= canvasElement.width && maxSize <= canvasElement.height);
                maskWidth = maxSize;
                maskHeight = maxSize;
                maskStartX = canvasElement.width/2 - maskWidth/2;
                maskStartY = canvasElement.height/2 - maskHeight/2;

                let code = null;
                // We only check for QR codes 5 times a second to improve performance
                let shouldAnalyze = Math.abs(lastVideoScanTime - video.currentTime) >= 1/3;
                if (shouldAnalyze) {
                    lastVideoScanTime = video.currentTime;
                    let imageData = canvas.getImageData(maskStartX, maskStartY, maskWidth, maskHeight);
                    code = jsQR(imageData.data, imageData.width, imageData.height, {
                        inversionAttempts: "dontInvert",
                    });
                    lastCode = code;
                } else {
                    code = lastCode;
                }

                let matched = code ? code.data.match(this.matchRegex) !== null : false;

                //draw mask
                canvas.beginPath();
                canvas.fillStyle = "#0000006e";
                canvas.moveTo(0,0);
                canvas.lineTo(0, canvasElement.height);
                canvas.lineTo( canvasElement.width, canvasElement.height);
                canvas.lineTo( canvasElement.width,0);
                canvas.rect(maskStartX, maskStartY, maskWidth, maskHeight);
                canvas.fill();

                canvas.beginPath();
                if (code) {
                    let okColor = getComputedStyle(this).getPropertyValue('--dbp-success-bg-color');
                    let notOkColor = getComputedStyle(this).getPropertyValue('--dbp-danger-bg-color');
                    canvas.fillStyle = matched ? okColor : notOkColor;
                } else {
                    canvas.fillStyle = 'white';
                }

                let borderWidth = Math.max(maskWidth, maskHeight) / 50;
                canvas.moveTo(maskStartX,maskStartY);
                canvas.rect(maskStartX, maskStartY, maskWidth/3, borderWidth);
                canvas.rect(maskStartX, maskStartY, borderWidth, maskHeight/3);
                canvas.rect(maskStartX + maskWidth/3*2, maskStartY, maskWidth/3, borderWidth);
                canvas.rect(maskStartX + maskWidth - borderWidth, maskStartY, borderWidth, maskHeight/3);
                canvas.rect(maskStartX, maskStartY + maskHeight - borderWidth, maskWidth/3, borderWidth);
                canvas.rect(maskStartX, maskStartY + maskHeight/3*2, borderWidth, maskHeight/3);
                canvas.rect(maskStartX + maskWidth/3*2, maskStartY + maskHeight - borderWidth, maskWidth/3, borderWidth);
                canvas.rect(maskStartX + maskWidth - borderWidth, maskStartY + maskHeight/3*2, borderWidth, maskHeight/3);
                canvas.fill();

                targetCanvas.height = canvasElement.height;
                targetCanvas.width = canvasElement.width;
                targetCanvas.getContext("2d").drawImage(canvasElement, 0, 0);

                if (!firstDrawDone) {
                    this.dispatchEvent(new CustomEvent("scan-started", {bubbles: true, composed: true}));
                    firstDrawDone = true;
                }

                if (code) {
                    if (lastSentData !== code.data) {
                        this._outputData = code.data;
                        this.dispatchEvent(new CustomEvent("code-detected",
                            {bubbles: true, composed: true, detail: {'code': code.data}}));
                    }
                    lastSentData = code.data;
                } else {
                    this._outputData = null;
                    lastSentData = null;
                }
            }
            console.assert(this._requestID === null);
            this._requestID = requestAnimationFrame(tick);
        };

        if (video !== null) {
            video.setAttribute("playsinline", true); // required to tell iOS safari we don't want fullscreen
            video.play();
            this._videoRunning = true;

            console.assert(this._requestID === null);
            this._videoElement = video;
            this._loading = true;
            this._loadingMessage = i18n.t('loading-video');
            this._requestID = requestAnimationFrame(tick);
        }
    }

    /**
     * Update if video source is changed
     *
     * @param e
     */
    async _onUpdateSource(e) {
        this._activeCamera = e.srcElement.value;
        await this.stopScanning();
        await this.startScanning();
        console.log("Changed Media");
    }

    /**
     * Stops the active video and scan process
     *
     */
    async stopScanning() {
        const release = await this._lock.acquire();
        try {
            if (this._videoElement !== null) {
                let video = this._videoElement;
                video.srcObject.getTracks().forEach(function(track) {
                    track.stop();
                });
                this._videoElement = null;
            }

            if (this._requestID !== null) {
                cancelAnimationFrame(this._requestID);
                this._requestID = null;
            }

            this._askPermission = false;
            this._videoRunning = false;
            this._loading = false;

            this._loadingMessage = '';
        } finally {
            release();
        }
    }

    static get styles() {
        // language=css
        return css`
            ${commonStyles.getThemeCSS()}
            ${commonStyles.getGeneralCSS()}
            ${commonStyles.getSelect2CSS()}
            ${commonStyles.getButtonCSS()}
            
            #loadingMessage {
                text-align: center;
                padding: 40px;
            }
            
            .wrapper-msg {
                width: 100%;
                display: flex;
                justify-content: center;
                align-items: baseline;
            }
        
            #canvas {
                width: 100%;
                margin-top: 2rem;
                max-height: 100%;
            }
        
            .output {
                  margin-top: 20px;
                  background: #eee;
                  padding: 10px;
                  padding-bottom: 0;
            }
        
            .output div {
                  padding-bottom: 10px;
                  word-wrap: break-word;
            }

            .spinner{
                margin-right: 10px;
                font-size: 0.7em;
            }
            
            #videoSource{
                padding-bottom: calc(0.375em - 2px);
                padding-left: 0.75em;
                padding-right: 1.75em;
                padding-top: calc(0.375em - 2px);
                background-position-x: calc(100% - 0.4rem);
                font-size: inherit;
            }
            
            #videoSource:hover {
                background: calc(100% - 0.2rem) center no-repeat url("${unsafeCSS(getIconSVGURL('chevron-down'))}");
                color: black;
                background-position-x: calc(100% - 0.4rem);
                background-size: auto 45%;
            }
            
            select:not(.select)#videoSource{
                background-size: auto 45%;
            }
            
            .border{
                margin-top: 2rem;
                padding-top: 2rem;
                border-top: 1px solid black;
            }
            
            @media only screen
            and (orientation: portrait)
            and (max-device-width: 765px) {   
                .button-wrapper{    
                    display: flex;
                   justify-content: space-between;
                }
            }
        `;
    }

    render() {
        let hasDevices = this._devices.size > 0;
        let showCanvas = this._videoRunning && !this._askPermission && !this._loading;

        return html`
            <div class="columns">
                <div class="column">
                    
                    <div class="${classMap({hidden: !hasDevices})}">
                    
                        
                        <div class="button-wrapper">
                            <button class="start button is-primary ${classMap({hidden: this._videoRunning})}" @click="${() => this.startScanning()}" title="${i18n.t('start-scan')}">${i18n.t('start-scan')}</button>
                            <button class="stop button is-primary ${classMap({hidden: !this._videoRunning})}" @click="${() => this.stopScanning()}" title="${i18n.t('stop-scan')}">${i18n.t('stop-scan')}</button>
                            
                            <select id="videoSource" class="button" @change=${this._onUpdateSource}>
                                ${Array.from(this._devices).map(item => html`<option value="${item[0]}">${item[1]}</option>`)}
                            </select>

                        </div>
                       
                        <div id="loadingMessage" class="${classMap({hidden: showCanvas})}">
                            <div class="wrapper-msg">
                                <dbp-mini-spinner class="spinner ${classMap({hidden: !this._loading})}"></dbp-mini-spinner>
                                <div class="loadingMsg">${this._loadingMessage}</div>
                            </div>
                       </div>
                       <canvas id="canvas" class="${classMap({hidden: !showCanvas})}"></canvas>
                        <div class="output ${classMap({hidden: !(this.showOutput && showCanvas)})}">
                          ${ (this._outputData !== null) ? html`
                            <div><b>${i18n.t('data')}:</b> <span>${this._outputData}</span></div>
                          ` : html`
                            <div>${i18n.t('no-qr-detected')}</div>
                          `}
                        </div>
                    </div>
                    <div class="${classMap({hidden: hasDevices})}">
                        ${i18n.t('no-support')}
                    </div>
                </div>
            </div>
        `;
    }
}