User:Tar/common.js

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(function () {
    'use strict';

    function isOnFilePage() {
        const path = location.pathname;
        const params = new URLSearchParams(location.search);
        return (
            /^\/File:/.test(path) ||
            /^\/Special:Moderation/i.test(path) ||
           /^\/Special:Moderation/i.test(path) ||
            (
                params.get("title") === "Special:Moderation" &&
                params.get("modaction") === "show"
            )
        );
    }

    function extractImageData(img, callback) {
        const tmpImg = new Image();
        tmpImg.crossOrigin = 'anonymous';
        tmpImg.onload = function () {
            const canvas = document.createElement('canvas');
            canvas.width = tmpImg.width;
            canvas.height = tmpImg.height;
            const ctx = canvas.getContext('2d');
            ctx.drawImage(tmpImg, 0, 0);
            callback(ctx, canvas);
        };
        tmpImg.src = img.dataset.originalSrc;
    }

    function revealLSB(imageData, bits) {
        const data = imageData.data;
        const maskShift = 8 - bits;
        for (let i = 0; i < data.length; i += 4) {
            data[i] = (data[i] << maskShift) & 0xff;
            data[i + 1] = (data[i + 1] << maskShift) & 0xff;
            data[i + 2] = (data[i + 2] << maskShift) & 0xff;
        }
    }

    function decodeLSB(imageData, maxChars = 5000) {
        const pixels = imageData.data;
        const bits = [];
        for (let i = 0; i < pixels.length; i += 4) {
            bits.push(pixels[i] & 1, pixels[i + 1] & 1, pixels[i + 2] & 1);
        }
        let output = '';
        for (let i = 0; i + 7 < bits.length && output.length < maxChars; i += 8) {
            let c = 0;
            for (let j = 0; j < 8; j++) c = (c << 1) | bits[i + j];
            if (c === 0) break;
            output += String.fromCharCode(c);
        }
        return output;
    }

    function addStegUIForImg(img) {
        if (!img || img.dataset.stegscanInit) return;

        img.dataset.stegscanInit = '1';
        img.dataset.originalSrc = img.dataset.originalSrc || img.src;

        const container = document.createElement('div');
        Object.assign(container.style, {
            margin: '6px 0 12px',
            display: 'block',
            maxWidth: img.width ? img.width + 'px' : '422px'
        });

        const label = document.createElement('div');
        label.textContent = 'Steganography Scan:';
        Object.assign(label.style, {
            fontSize: '12px',
            fontWeight: '600',
            marginBottom: '4px'
        });

        const slider = document.createElement('input');
        Object.assign(slider, { type: 'range', min: 1, max: 8, value: 1 });
        slider.style.width = '99%';

        const buttonWrapper = document.createElement('div');
        Object.assign(buttonWrapper.style, {
            display: 'flex',
            justifyContent: 'center',
            marginTop: '6px'
        });

        const decodeBtn = document.createElement('button');
        decodeBtn.textContent = 'Decode';
        Object.assign(decodeBtn.style, {
            cursor: 'pointer',
            padding: '4px 12px',
        });

        buttonWrapper.appendChild(decodeBtn);

        container.appendChild(label);
        container.appendChild(slider);
        container.appendChild(buttonWrapper);

        const parent = img.parentNode;
        (parent.tagName.toLowerCase() === 'a' ? parent : img)
            .insertAdjacentElement('afterend', container);

        let lastBits = 1;

        slider.addEventListener('input', () => {
            const bits = Number(slider.value);
            if (bits === lastBits) return;
            lastBits = bits;
            if (bits <= 1) {
                img.src = img.dataset.originalSrc;
                return;
            }
            extractImageData(img, (ctx, canvas) => {
                const data = ctx.getImageData(0, 0, canvas.width, canvas.height);
                revealLSB(data, bits - 1);
                img.removeAttribute('srcset');
                ctx.putImageData(data, 0, 0);
                img.src = canvas.toDataURL();
            });
        });

        decodeBtn.addEventListener('click', () => {
            decodeBtn.disabled = true;
            decodeBtn.textContent = 'Decoding...';
            extractImageData(img, (ctx, canvas) => {
                const data = ctx.getImageData(0, 0, canvas.width, canvas.height);
                const message = decodeLSB(data);
                decodeBtn.textContent = 'Decode';
                decodeBtn.disabled = false;
                if (message) {
                    navigator.clipboard.writeText(message)
                        .then(() => alert('Decoded message copied to clipboard'))
                        .catch(() => prompt('Decoded message:', message));
                } else {
                    alert('No message detected.');
                }
            });
        });
    }

    function scanAllImages() {
        if (!isOnFilePage()) return; // Only run on File pages or media viewer
        const content = document.querySelector('#content');
        if (!content) return;
        content.querySelectorAll('img').forEach(img => {
            // Skip file history thumbnails
            if (img.closest('.filehistory')) return;
            addStegUIForImg(img);
        });
    }

    scanAllImages();

    const observer = new MutationObserver(() => {
        if (isOnFilePage()) scanAllImages();
        else observer.disconnect();
    });

    observer.observe(document.body, { childList: true, subtree: true });

})();