import { useSyncExternalStore, useRef } from 'react';
import { useAviationPlayer } from '../AviationContext';
import { IDLE_POSITION, samePosition } from '../snapshots';
import type { AviationPlayer } from '../Aviation';
import type { MediaPosition } from '../specs/types.nitro';

/**
 * React hook that subscribes to a player's media position updates.
 *
 * Returns a `MediaPosition` struct with current position, duration,
 * seekable range, live edge info, and progress (0-1).
 *
 * Updates at the native time-observer frequency (~250ms for VOD,
 * ~1s for live). Uses `useSyncExternalStore` for tear-free reads.
 *
 * @example
 * ```tsx
 * function ProgressBar() {
 *   const { currentMs, durationMs, progress, isLive, isAtLiveEdge } = useMediaPosition();
 *   return <Slider value={progress} />;
 * }
 * ```
 */
export function useMediaPosition(playerArg?: AviationPlayer): MediaPosition {
  const player = useAviationPlayer(playerArg);
  const store = player.store;
  const ref = useRef<MediaPosition>(IDLE_POSITION);

  const getSnapshot = () => {
    const pos = store.mediaPosition;
    const prev = ref.current;
    if (samePosition(prev, pos)) return prev;
    ref.current = pos;
    return ref.current;
  };

  return useSyncExternalStore(store.subscribePosition, getSnapshot);
}