let gainNode = null;
let audioCtx  = null;
let sourceMap = new WeakMap();

function setVolume(percent) {
    const factor = percent / 100;
    document.querySelectorAll('video, audio').forEach(el => {
        if (!sourceMap.has(el)) {
            if (!audioCtx) {
                audioCtx = new AudioContext();
            }
            try {
                const src  = audioCtx.createMediaElementSource(el);
                const gain = audioCtx.createGain();
                src.connect(gain);
                gain.connect(audioCtx.destination);
                sourceMap.set(el, gain);
            } catch (e) {
                // Element bereits in einem anderen Context
                return;
            }
        }
        sourceMap.get(el).gain.value = factor;
    });
}

// Beim Laden: gespeicherten Wert anwenden
chrome.storage.local.get('volume', ({ volume }) => {
    if (volume !== undefined) setVolume(volume);
});

// Auf Nachrichten vom Popup hören
chrome.runtime.onMessage.addListener(({ volume }) => {
    if (volume !== undefined) setVolume(volume);
});

// Neue Media-Elemente automatisch erfassen
const observer = new MutationObserver(() => {
    chrome.storage.local.get('volume', ({ volume }) => {
        if (volume !== undefined && volume !== 100) {
            setVolume(volume);
        }
    });
});
observer.observe(document.body, {
    childList: true, subtree: true
});