/**
 * OpusCapability - runtime detection of WebCodecs Ogg-Opus decode support.
 *
 * The Opus decode path is a WebCodecs `AudioDecoder` streaming pipeline (OpusStreamDecoder), NOT
 * `decodeAudioData`. So the capability gate must test the path actually used: whether the browser has
 * `AudioDecoder` AND supports the `codec: 'opus'` config. `AudioDecoder` is available on Chrome/Edge,
 * Firefox 130+, and Safari 16.4+; older Safari and older Firefox lack it, and those listeners fall back
 * to the universal lossless WAV path (§3.4 / OQ2 / AC7 — no listener ever gets silence over a codec gap).
 *
 * This module is the detection *seam* only — it answers "can this browser stream-decode Opus via
 * WebCodecs?". The player (StreamingAudioPlayerService.ResolveStreamFormatAsync) consumes the answer to
 * choose the delivery format; this module never touches the player or the stream request. The result is
 * cached after the first probe (capability does not change within a session).
 */

let cachedSupport: Promise<boolean> | null = null;

/**
 * Resolve whether this browser can stream-decode Ogg Opus via WebCodecs. Cached after the first call.
 * Never rejects — any failure (no AudioDecoder, unsupported config, thrown probe) resolves to `false`
 * (treat as unsupported, fall back to lossless) so an interop error can never silence playback.
 */
export function canDecodeOggOpus(): Promise<boolean> {
    if (cachedSupport === null) {
        cachedSupport = probe();
    }
    return cachedSupport;
}

async function probe(): Promise<boolean> {
    try {
        if (typeof AudioDecoder === 'undefined' || typeof AudioDecoder.isConfigSupported !== 'function') {
            return false;
        }
        // 48 kHz stereo is the canonical fullband Opus shape this site produces. isConfigSupported does
        // not need the OpusHead `description` to report codec support, so we probe without it.
        const result = await AudioDecoder.isConfigSupported({
            codec: 'opus',
            sampleRate: 48000,
            numberOfChannels: 2
        });
        return result.supported === true;
    } catch {
        return false;
    }
}