import type { Video } from "./api";

// What the player does with its queue after the item it is PLAYING is removed from the list it was
// opened from. The player's launch queue is frozen at mount (see PlayerModal), so nothing external
// can take the item out for it: leaving it in would let prev/next step back onto a video that no
// longer exists, and unmounting the player instead would drop you out of the list you are triaging.
//
// Pure, because the decision is the whole of the behaviour: which item plays next, and when there is
// nothing left to play.
export interface AfterRemoval {
  /** The queue with the removed item gone. */
  queue: Video[];
  /** The item to play next. */
  playingId: string;
}

/** `null` means nothing is left — the caller closes the player.
 *
 * The next item is the one that FOLLOWED the removed one (that is what "delete and keep going"
 * means when you are working down a list), clamped to the end when the last item goes. */
export function afterRemoval(
  queue: Video[] | undefined,
  index: number,
  victimId: string,
): AfterRemoval | null {
  const rest = (queue ?? []).filter((v) => v.id !== victimId);
  if (rest.length === 0) return null;
  const next = rest[Math.min(Math.max(index, 0), rest.length - 1)]!;
  return { queue: rest, playingId: next.id };
}