Facebook Messenger Audio Downloader (v12.0) - One-click download. Auto-plays/pauses to capture source, converts to real MP3 (with WAV fallback).

messenger-audio-downloader.js

// ============================================================================
// AUDIO SNIPPET DOWNLOADER v12.0 (Robust Auto-Pause)
// ============================================================================
// FIX: Uses the 'playing' event listener to ensure pause commands are respected
// by the browser's media engine.
// ============================================================================

(function() {
    console.log("Audio Downloader v12: Robust Auto-Pause Active.");

    let activeAutoDownloadBtn = null;

    // ---------------------------------------------------------
    // 1. INJECT LAMEJS (MP3 Library)
    // ---------------------------------------------------------
    let lameLoaded = false;
    const lameScript = document.createElement('script');
    lameScript.src = "https://cdn.jsdelivr.net/npm/[email protected]/lame.min.js";
    lameScript.crossOrigin = "anonymous";
    lameScript.onload = () => { lameLoaded = true; console.log("MP3 Library loaded."); };
    lameScript.onerror = () => { lameLoaded = false; console.warn("MP3 Library blocked. Fallback enabled."); };
    document.head.appendChild(lameScript);

    // ---------------------------------------------------------
    // 2. ENCODING LOGIC
    // ---------------------------------------------------------
    function floatTo16BitPCM(input) {
        const output = new Int16Array(input.length);
        for (let i = 0; i < input.length; i++) {
            const s = Math.max(-1, Math.min(1, input[i]));
            output[i] = s < 0 ? s * 0x8000 : s * 0x7FFF;
        }
        return output;
    }

    async function encodeMp3(audioBuffer) {
        if (!lameLoaded || !window.lamejs) throw new Error("LameJS missing");
        const mp3Encoder = new lamejs.Mp3Encoder(1, audioBuffer.sampleRate, 128); 
        const samples = floatTo16BitPCM(audioBuffer.getChannelData(0));
        const sampleBlockSize = 1152;
        const mp3Data = [];
        let remaining = samples.length;
        let i = 0;
        while (remaining >= sampleBlockSize) {
            const mp3buf = mp3Encoder.encodeBuffer(samples.subarray(i, i + sampleBlockSize));
            if (mp3buf.length > 0) mp3Data.push(mp3buf);
            remaining -= sampleBlockSize;
            i += sampleBlockSize;
        }
        const mp3buf = mp3Encoder.flush();
        if (mp3buf.length > 0) mp3Data.push(mp3buf);
        return new Blob(mp3Data, { type: 'audio/mp3' });
    }

    function encodeWav(audioBuffer) {
        const samples = audioBuffer.getChannelData(0);
        const buffer = new ArrayBuffer(44 + samples.length * 2);
        const view = new DataView(buffer);
        const writeString = (view, offset, string) => {
            for (let i = 0; i < string.length; i++) view.setUint8(offset + i, string.charCodeAt(i));
        };
        writeString(view, 0, 'RIFF');
        view.setUint32(4, 36 + samples.length * 2, true);
        writeString(view, 8, 'WAVE');
        writeString(view, 12, 'fmt ');
        view.setUint32(16, 16, true);
        view.setUint16(20, 1, true);
        view.setUint16(22, 1, true); 
        view.setUint32(24, audioBuffer.sampleRate, true);
        view.setUint32(28, audioBuffer.sampleRate * 2, true);
        view.setUint16(32, 2, true);
        view.setUint16(34, 16, true);
        writeString(view, 36, 'data');
        view.setUint32(40, samples.length * 2, true);
        const output = new Int16Array(buffer, 44);
        for (let i = 0; i < samples.length; i++) {
            const s = Math.max(-1, Math.min(1, samples[i]));
            output[i] = s < 0 ? s * 0x8000 : s * 0x7FFF;
        }
        return new Blob([view], { type: 'audio/wav' });
    }

    // ---------------------------------------------------------
    // 3. CORE DOWNLOAD PROCESSOR
    // ---------------------------------------------------------
    async function processAudioDownload(btn, srcUrl) {
        if (!btn) return;
        
        btn.innerText = "⏳ Downloading...";
        btn.style.backgroundColor = "#e6b800"; 
        
        try {
            const response = await fetch(srcUrl);
            const blob = await response.blob();
            const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
            const arrayBuffer = await blob.arrayBuffer();
            const audioBuffer = await audioCtx.decodeAudioData(arrayBuffer);
            
            let finalBlob = null;
            let ext = "";

            if (lameLoaded) {
                try {
                    btn.innerText = "⏳ Encoding MP3...";
                    finalBlob = await encodeMp3(audioBuffer);
                    ext = ".mp3";
                } catch (e) { console.warn("MP3 failed", e); }
            }

            if (!finalBlob) {
                btn.innerText = "⏳ Encoding WAV...";
                finalBlob = encodeWav(audioBuffer);
                ext = ".wav";
            }

            const durationTag = btn.dataset.duration ? `_${btn.dataset.duration.replace(':','m')}` : '';
            const filename = `messenger_audio${durationTag}${ext}`;
            const a = document.createElement('a');
            a.href = URL.createObjectURL(finalBlob);
            a.download = filename;
            document.body.appendChild(a);
            a.click();
            document.body.removeChild(a);

            btn.innerText = `✔ SAVED ${ext.toUpperCase()}`;
            btn.style.backgroundColor = "#31a24c";
            setTimeout(() => {
                btn.innerText = "⬇ GET AUDIO";
                btn.style.backgroundColor = "#20cef5";
            }, 3000);

        } catch (err) {
            console.error(err);
            btn.innerText = "❌ ERROR";
            alert("Download failed. See console.");
        }
    }

    // ---------------------------------------------------------
    // 4. SPY & AUTOMATION LOGIC
    // ---------------------------------------------------------
    function getTimeVariations(seconds) {
        if (!seconds) return [];
        const candidates = [Math.floor(seconds), Math.round(seconds), Math.ceil(seconds)];
        return candidates.map(sec => {
            const m = Math.floor(sec / 60);
            const s = Math.floor(sec % 60);
            return `${m}:${s.toString().padStart(2, '0')}`;
        });
    }

    const originalAudioPlay = HTMLAudioElement.prototype.play;
    
    // We attach this globally to handle paused events correctly
    function attachPauseListener(mediaElement) {
        if (mediaElement.dataset.hasPauseListener) return;
        
        mediaElement.addEventListener('playing', function() {
            if (activeAutoDownloadBtn) {
                console.log("[AutoSpy] Audio started. Pausing immediately.");
                mediaElement.pause();
                
                // Process the download
                const btn = activeAutoDownloadBtn;
                activeAutoDownloadBtn = null; 
                
                // Use currentSrc as the most reliable source
                const src = mediaElement.currentSrc || mediaElement.src;
                processAudioDownload(btn, src);
            }
        });
        mediaElement.dataset.hasPauseListener = "true";
    }

    function handlePlay(mediaElement) {
        attachPauseListener(mediaElement);
        
        // Manual play support
        const checkDuration = () => {
            const duration = mediaElement.duration;
            if (!duration || duration === Infinity) return;
            const timeStrings = getTimeVariations(duration);

            document.querySelectorAll('.custom-audio-dl-btn').forEach(btn => {
                if (timeStrings.includes(btn.dataset.duration) && btn.innerText.includes("GET AUDIO")) {
                    btn.innerText = "✔ CLICK TO DOWNLOAD";
                    btn.style.backgroundColor = "#31a24c"; 
                    btn.onclick = (e) => {
                        e.stopPropagation();
                        processAudioDownload(btn, mediaElement.src || mediaElement.currentSrc);
                    };
                }
            });
        };
        // Run check if metadata already exists, otherwise wait
        if (mediaElement.readyState >= 1) checkDuration();
        mediaElement.addEventListener('loadedmetadata', checkDuration);
    }

    HTMLAudioElement.prototype.play = function() {
        handlePlay(this);
        return originalAudioPlay.apply(this, arguments);
    };

    // ---------------------------------------------------------
    // 5. UI INJECTION
    // ---------------------------------------------------------
    const style = document.createElement('style');
    style.innerHTML = `
        .custom-audio-dl-btn {
            background-color: #20cef5;
            color: white;
            border: none;
            padding: 6px 10px;
            border-radius: 20px;
            font-size: 10px;
            font-weight: 800;
            cursor: pointer;
            margin-left: 10px;
            z-index: 10000;
            box-shadow: 0 2px 4px rgba(0,0,0,0.3);
            font-family: sans-serif;
            transition: all 0.2s;
            min-width: 80px;
        }
        .custom-audio-dl-btn:hover { opacity: 0.9; transform: scale(1.05); }
    `;
    document.head.appendChild(style);

    function addDownloadButtons() {
        const playButtons = document.querySelectorAll('[aria-label="Play"]');

        playButtons.forEach(playBtn => {
            const rowContainer = playBtn.closest('[role="gridcell"]') || playBtn.closest('.html-div');
            if (!rowContainer) return;
            if (rowContainer.querySelector('.custom-audio-dl-btn')) return;

            const timer = rowContainer.querySelector('[role="timer"]');
            let durationText = "0:00";
            if (timer) {
                durationText = timer.innerText;
            } else {
                const textNodes = rowContainer.innerText.match(/\d+:\d{2}/);
                if (textNodes) durationText = textNodes[0];
            }

            const dlBtn = document.createElement('button');
            dlBtn.innerText = "⬇ GET AUDIO";
            dlBtn.className = "custom-audio-dl-btn";
            dlBtn.dataset.duration = durationText; 
            
            // --- AUTOMATION TRIGGER ---
            dlBtn.onclick = (e) => {
                e.stopPropagation();
                
                activeAutoDownloadBtn = dlBtn;
                dlBtn.innerText = "⏳ Connecting...";
                
                playBtn.click();
                
                setTimeout(() => {
                    if (activeAutoDownloadBtn === dlBtn) {
                        dlBtn.innerText = "❌ Timeout";
                        activeAutoDownloadBtn = null;
                        alert("Could not trigger audio. Try playing it manually once.");
                    }
                }, 5000);
            };

            const insertionPoint = playBtn.parentElement.parentElement;
            if (insertionPoint) {
                insertionPoint.appendChild(dlBtn);
            } else {
                playBtn.parentNode.appendChild(dlBtn);
            }
        });
    }

    addDownloadButtons();
    setInterval(addDownloadButtons, 2000);
})();