const maxAreaObstructionByIconRatio = 0.06; //!< The maximum amount of area in percentage allowed for the icon to cover the QR code
const iconPaddingRatio = 0.3; //!< The padding in percentage with respect of the circle (i.e. logo 30% smaller than the white circle)

//! Convert a QR code into an SVG string
function toSvgString(qr, logoBase64) {
    let parts = [];
    console.log("size",qr.size);
    for (let y = 0; y < qr.size; y++) {
        for (let x = 0; x < qr.size; x++) {
            if (qr.getModule(x, y))
                parts.push(`M${x},${y}h1v1h-1z`);
        }
    }
    var circleElementString = "";
    var iconSvgElementString = ""
    if (logoBase64 != undefined) {
        const circleElement = document.createElementNS("http://www.w3.org/2000/svg", "circle");
        const qrArea = qr.size * qr.size;
        const iconArea = maxAreaObstructionByIconRatio * qrArea;
        const circleRadius = Math.sqrt(iconArea / Math.PI);
        circleElement.setAttribute("cx", "50%");
        circleElement.setAttribute("cy", "50%");
        circleElement.setAttribute("r", circleRadius);
        circleElement.setAttribute("fill", "white");
        circleElementString = circleElement.outerHTML;
        // Add logo as svg
        const [imgMetadata, imgBase64Content] = logoBase64.split(',');
        const svgImage = atob(imgBase64Content);
        const parser = new DOMParser();
        const iconSvg = parser.parseFromString(svgImage, 'image/svg+xml').documentElement;
        const circleDiam = 2 * circleRadius;
        const logoSize = circleDiam * (1 - iconPaddingRatio);
        iconSvg.setAttribute("width", logoSize);
        iconSvg.setAttribute("height", logoSize);
        iconSvg.setAttribute("x",qr.size / 2 - logoSize / 2);
        iconSvg.setAttribute("y", qr.size / 2 - logoSize / 2);
        iconSvgElementString = iconSvg.outerHTML;
    }
    
    return `<?xml version="1.0" encoding="UTF-8"?>
                    <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
                    <svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 ${qr.size} ${qr.size}" stroke="none" style="max-width: 70%;width: 500px;">
                        <rect width="100%" height="100%" fill="#FFF"/>
                        <path d="${parts.join(" ")}" fill="#000"/>
                        ${circleElementString}
                        ${iconSvgElementString}
                    </svg>
        `;
    
}

//! Encode a list of bytes into an alphanumeric string
function alphanumericEncode(data) {
    const ALPHANUMERIC_CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
    let rs = "";
    for(let i = 0; i < data.length; i += 2) {
        let len, ab;
        if (i + 1 === data.length) {
            ab = data[i];
            len = 2;
        }
        else {
            ab = ((data[i] << 8) + data[i + 1]);
            len = 3;
        }
        let res = "";
        while (ab > 0) {
            let div = Math.floor(ab / ALPHANUMERIC_CHARS.length);
            let alphIdx = ab % ALPHANUMERIC_CHARS.length;
            res = ALPHANUMERIC_CHARS.charAt(alphIdx) + res;
            ab = div;
        }
        rs += res.padStart(len, "0");
    }
    return rs;
}

//! Create the CRC32 table
function makeCRCTable() {
    let c;
    let crcTable = [];
    for(let n = 0; n < 256; n++){
        c = n;
        for(let k = 0; k < 8; k++){
            c = ((c&1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
        }
        crcTable[n] = c;
    }
    return crcTable;
}


function crc32(data) {
    let crcTable = window.crcTable || (window.crcTable = makeCRCTable());
    let crc = 0 ^ (-1);

    for (let i = 0; i < data.length; i++ ) {
        crc = (crc >>> 8) ^ crcTable[(crc ^ data[i]) & 0xFF];
    }

    return (crc ^ (-1)) >>> 0;
}

//! Convert an integer into an array of bytes
function intToBytes(value, nBytes, signed) {
    const buffer = new ArrayBuffer(nBytes);
    const view = new DataView(buffer);
    if (nBytes == 1) {
        if (signed)
            view.setInt8(0, value);
        else
            view.setUint8(0, value);
    }
    else if (nBytes == 2) {
        if (signed)
            view.setInt16(0, value, false);
        else
            view.setUint16(0, value, false);
    }
    else if (nBytes == 4) {
        if (signed)
            view.setInt32(0, value, false);
        else
            view.setUint32(0, value, false);
    }
    else if (nBytes == 8)   {
        if (signed)
            view.setBigInt64(0, BigInt(value), false);
        else
            view.setBigUint64(0, BigInt(value), false);
    }
    let bytes = []
    for (let i = 0; i < nBytes; i++)
        bytes.push(view.getUint8(i));
    return bytes;
}

//! Show a Qr code into the given canvas
function toCanvas(qr, canvas, logoSrc) {
    // Scale up the QR code by an 8x factor
    const scale = 8;
    const border = 1;
    const size = (qr.size + 2 * border) * scale;
    const qrScaledSize = qr.size * scale;
    const qrArea = qrScaledSize * qrScaledSize; // Not considering border in the Qr area
    const iconArea = maxAreaObstructionByIconRatio * qrArea;
    const circleRadius = Math.sqrt(iconArea / Math.PI);
    const circleDiam = 2 * circleRadius;
    const logoSize = circleDiam * (1 - iconPaddingRatio);
    canvas.width = size;
    canvas.height = size;
    let ctx = canvas.getContext("2d");
    for (let y = -border; y < qr.size + border; y++) {
        for (let x = -border; x < qr.size + border; x++) {
            ctx.fillStyle = qr.getModule(x, y) ? "#000" : "#FFF";
            ctx.fillRect((x + border) * scale, (y + border) * scale, scale, scale);
        }
    }
    if (logoSrc != undefined) {
        var img = new Image();
        img.src = logoSrc
        img.onload = function() {
            const imgRatio = img.naturalWidth / img.naturalHeight;
            var imgWidth = logoSize;
            var imgHeight = logoSize / imgRatio;
            if (imgHeight > logoSize) {
                imgWidth = logoSize * imgRatio;
                imgHeight = logoSize;
            }
            var canvasCenterX = size / 2 - imgWidth / 2;
            var canvasCenterY = size / 2 - imgHeight / 2;
            ctx.beginPath();
            ctx.fillStyle = 'white';            
            ctx.arc(size / 2, size / 2, circleRadius, 0, 2 * Math.PI);
            ctx.fill();
            ctx.drawImage(img, canvasCenterX, canvasCenterY, imgWidth, imgHeight);
        };
    }
}