export type VideoFrameExtractionKind = "first" | "last" | "current";

const LAST_FRAME_EPSILON_SECONDS = 0.05;

function finiteNonNegative(value: unknown, fallback = 0) {
  const parsed = Number(value);
  return Number.isFinite(parsed) ? Math.max(0, parsed) : fallback;
}

export function getVideoFrameExtractionTarget(
  kind: VideoFrameExtractionKind,
  currentTimeSeconds: number,
  durationSeconds: number,
) {
  const duration = finiteNonNegative(durationSeconds);
  const lastFrameTime = Math.max(0, duration - LAST_FRAME_EPSILON_SECONDS);
  if (kind === "first") return 0;
  if (kind === "last") return lastFrameTime;
  return Math.min(lastFrameTime, finiteNonNegative(currentTimeSeconds));
}

export function getVideoFrameExtractionCopy(kind: VideoFrameExtractionKind) {
  if (kind === "first") return { alt: "视频首帧", title: "首帧" };
  if (kind === "last") return { alt: "视频尾帧", title: "尾帧" };
  return { alt: "视频截图", title: "截图" };
}