import { displayScore, type ForumThread } from "@/lib/forumState";

export type ForumSortMode = "hot" | "new" | "top";

function hoursSince(ts: number): number {
  return (Date.now() - ts) / 3600000;
}

export function hotRank(t: ForumThread): number {
  const s = displayScore(t);
  const engagement = t.replies.length * 4;
  const freshness = Math.max(0, 72 - hoursSince(t.ts)) * 2;
  return s + engagement + freshness;
}

export function sortThreads(list: ForumThread[], mode: ForumSortMode): ForumThread[] {
  const copy = [...list];
  if (mode === "new") copy.sort((a, b) => b.ts - a.ts);
  else if (mode === "top") copy.sort((a, b) => displayScore(b) - displayScore(a));
  else copy.sort((a, b) => hotRank(b) - hotRank(a));
  return copy;
}