feat: add transitions, track mixing, and voiceover controls

1 files changed, 93 insertions, 0 deletions

diff --git a/apps/web/src/voiceover/devices.ts b/apps/web/src/voiceover/devices.ts
new file mode 100644
index 00000000..dd5b680c
--- /dev/null
+++ b/apps/web/src/voiceover/devices.ts
@@ -0,0 +1,93 @@
+"use client";
+
+export const DEFAULT_AUDIO_INPUT_DEVICE_ID = "default";
+
+export interface VoiceOverInputDevice {
+	deviceId: string;
+	label: string;
+	isDefault: boolean;
+}
+
+export function buildVoiceOverAudioConstraints({
+	deviceId,
+}: {
+	deviceId?: string | null;
+}): MediaStreamConstraints {
+	const audio: MediaTrackConstraints = {
+		echoCancellation: true,
+		noiseSuppression: true,
+		autoGainControl: true,
+	};
+
+	if (deviceId && deviceId !== DEFAULT_AUDIO_INPUT_DEVICE_ID) {
+		audio.deviceId = { exact: deviceId };
+	}
+
+	return { audio };
+}
+
+export function normalizeSelectedDeviceId({
+	deviceId,
+	devices,
+}: {
+	deviceId: string | null;
+	devices: VoiceOverInputDevice[];
+}): string | null {
+	if (!deviceId) {
+		return null;
+	}
+
+	if (deviceId === DEFAULT_AUDIO_INPUT_DEVICE_ID) {
+		return deviceId;
+	}
+
+	return devices.some((device) => device.deviceId === deviceId)
+		? deviceId
+		: null;
+}
+
+export async function listVoiceOverInputDevices({
+	requestPermission = false,
+}: {
+	requestPermission?: boolean;
+} = {}): Promise<VoiceOverInputDevice[]> {
+	const mediaDevices = navigator.mediaDevices;
+	if (!mediaDevices?.enumerateDevices) {
+		throw new Error("Microphone selection is not supported in this browser");
+	}
+
+	let permissionStream: MediaStream | null = null;
+	if (requestPermission) {
+		permissionStream = await mediaDevices.getUserMedia({
+			audio: {
+				echoCancellation: true,
+				noiseSuppression: true,
+				autoGainControl: true,
+			},
+		});
+	}
+
+	try {
+		const devices = await mediaDevices.enumerateDevices();
+		let inputIndex = 1;
+		return devices
+			.filter((device) => device.kind === "audioinput")
+			.map((device) => {
+				const isDefault = device.deviceId === DEFAULT_AUDIO_INPUT_DEVICE_ID;
+				const fallbackLabel = isDefault
+					? "System default microphone"
+					: `Microphone ${inputIndex++}`;
+				return {
+					deviceId: device.deviceId,
+					label: device.label || fallbackLabel,
+					isDefault,
+				};
+			});
+	} finally {
+		if (permissionStream) {
+			for (const track of permissionStream.getTracks()) {
+				track.stop();
+			}
+		}
+	}
+}