import { useCallback, useEffect, useState } from 'react';

export type PermissionState = 'unknown' | 'granted' | 'denied';

interface UseMediaDevicesResult {
  audioInputs: MediaDeviceInfo[];
  videoInputs: MediaDeviceInfo[];
  permissionState: PermissionState;
  refresh: () => Promise<void>;
  requestLabels: () => Promise<void>;
  error: string | null;
}

/**
 * Enumerates input devices and stays subscribed to `devicechange`.
 *
 * Labels are only populated after the user has granted mic/camera
 * permission — `requestLabels` triggers a brief getUserMedia so that
 * subsequent enumerations return human-readable names, matching the
 * pattern most video-conferencing apps use.
 */
export function useMediaDevices(): UseMediaDevicesResult {
  const [devices, setDevices] = useState<MediaDeviceInfo[]>([]);
  const [permissionState, setPermissionState] =
    useState<PermissionState>('unknown');
  const [error, setError] = useState<string | null>(null);

  const refresh = useCallback(() => {
    return navigator.mediaDevices
      .enumerateDevices()
      .then((list) => {
        setDevices(list);
        // If at least one input device has a non-empty label, permission
        // has been granted at some point for that device kind.
        const hasLabels = list.some(
          (d) =>
            (d.kind === 'audioinput' || d.kind === 'videoinput') &&
            d.label.length > 0,
        );
        if (hasLabels) setPermissionState('granted');
      })
      .catch((err) => {
        setError(err instanceof Error ? err.message : 'Failed to list devices');
      });
  }, []);

  const requestLabels = useCallback(async () => {
    try {
      const stream = await navigator.mediaDevices.getUserMedia({
        audio: true,
        video: true,
      });
      // Immediately stop — we only needed the permission grant.
      stream.getTracks().forEach((t) => t.stop());
      setPermissionState('granted');
      setError(null);
      await refresh();
    } catch (err) {
      setPermissionState('denied');
      setError(
        err instanceof Error ? err.message : 'Microphone/camera access denied',
      );
    }
  }, [refresh]);

  useEffect(() => {
    refresh();
    const handle = () => {
      refresh();
    };
    navigator.mediaDevices.addEventListener('devicechange', handle);
    return () => {
      navigator.mediaDevices.removeEventListener('devicechange', handle);
    };
  }, [refresh]);

  return {
    // Before permission is granted, enumerateDevices returns placeholder
    // entries with an empty deviceId — filter them out so consumers never
    // render an empty-value <SelectItem />, which Radix rejects.
    audioInputs: devices.filter(
      (d) => d.kind === 'audioinput' && d.deviceId !== '',
    ),
    videoInputs: devices.filter(
      (d) => d.kind === 'videoinput' && d.deviceId !== '',
    ),
    permissionState,
    refresh,
    requestLabels,
    error,
  };
}