// Pure feed model: pick renderable posts out of raw feed items, normalise the
// card fields, and keep one list sorted strictly by publishedAt, newest first.

export interface CardMedia {
  kind: "image" | "video";
  /** Image source (images) or poster (videos). May be null for a bare video. */
  src: string | null;
  /** Mux HLS playlist (videos only). Null when the video is not ready yet. */
  hlsUrl?: string | null;
  /** Direct progressive MP4 on the feed CDN (videos only). Preferred for playback. */
  mp4Url?: string | null;
  /** Video length in whole seconds, when the feed reports it. */
  durationSeconds?: number | null;
}

/** "m:ss" for a duration in seconds, or null when it is missing or not positive. */
export function formatDuration(seconds: number | null | undefined): string | null {
  if (typeof seconds !== "number" || !Number.isFinite(seconds) || seconds <= 0) return null;
  const total = Math.round(seconds);
  const h = Math.floor(total / 3600);
  const m = Math.floor((total % 3600) / 60);
  const s = String(total % 60).padStart(2, "0");
  return h ? `${h}:${String(m).padStart(2, "0")}:${s}` : `${m}:${s}`;
}

export interface CardPost {
  key: string;
  id: string | null;
  /** The author's id on the feed, for matching against the signed-in feed user id. */
  authorId: string | null;
  authorName: string;
  authorPictureUrl: string | null;
  publishedAt: string | null;
  time: number;
  text: string;
  likesCount: number;
  /** Whether the signed-in person has liked the post. */
  isLiked: boolean;
  commentsCount: number;
  media: CardMedia[];
}

type Obj = Record<string, unknown>;

function isObj(v: unknown): v is Obj {
  return typeof v === "object" && v !== null && !Array.isArray(v);
}
function str(v: unknown): string | null {
  return typeof v === "string" && v.trim() ? v : null;
}
function num(v: unknown): number {
  return typeof v === "number" && Number.isFinite(v) ? v : 0;
}

export function initials(name: string): string {
  const parts = name.trim().split(/\s+/).filter(Boolean);
  if (parts.length === 0) return "?";
  const first = parts[0][0] ?? "";
  const last = parts.length > 1 ? (parts[parts.length - 1][0] ?? "") : "";
  return (first + last).toUpperCase();
}

function authorName(author: Obj): string {
  const display = str(author.displayName);
  if (display) return display.trim();
  const full = [str(author.firstName), str(author.lastName)].filter(Boolean).join(" ").trim();
  return full || "Unknown";
}

/** The HLS URL only when it is https on stream.mux.com. */
export function muxHlsUrl(v: unknown): string | null {
  const s = str(v);
  if (!s) return null;
  try {
    const u = new URL(s);
    return u.protocol === "https:" && u.hostname === "stream.mux.com" ? s : null;
  } catch {
    return null;
  }
}

/** The MP4 URL only when it is https on the feed CDN. */
export function feedMp4Url(v: unknown): string | null {
  const s = str(v);
  if (!s) return null;
  try {
    const u = new URL(s);
    return u.protocol === "https:" && u.hostname === "cdn.feed.sharedservices.vt.com" ? s : null;
  } catch {
    return null;
  }
}

function toMedia(raw: unknown): CardMedia[] {
  if (!Array.isArray(raw)) return [];
  const items = raw
    .filter(isObj)
    .map((m, i) => ({ m, i, order: typeof m.order === "number" ? m.order : i }))
    .sort((a, b) => a.order - b.order || a.i - b.i);
  const out: CardMedia[] = [];
  for (const { m } of items) {
    if (m.mediaType === "video") {
      const thumb = str(m.thumbnailUrl);
      const hls = muxHlsUrl(m.hlsUrl);
      const mp4 = feedMp4Url(m.mp4Url);
      // Keep a video even with no thumbnail or playable URL yet (just published).
      const dur = [m.videoDuration, m.durationSeconds, m.duration].find((v): v is number => typeof v === "number" && v > 0) ?? null;
      out.push({ kind: "video", src: thumb, hlsUrl: hls, mp4Url: mp4, ...(dur ? { durationSeconds: dur } : {}) });
      continue;
    }
    const src = str(m.imageMediumWebpUrl) ?? str(m.imageMediumUrl) ?? str(m.imageUrl);
    if (src) out.push({ kind: "image", src });
  }
  return out;
}

/** The card for one raw feed item, or null when it is not a post. */
export function toCardPost(item: unknown, index = 0): CardPost | null {
  if (!isObj(item) || item.type !== "post" || !isObj(item.post)) return null;
  const post = item.post;
  const author = isObj(post.author) ? post.author : {};
  const publishedAt = str(item.publishedAt);
  const t = publishedAt ? Date.parse(publishedAt) : NaN;
  const id =
    typeof post.id === "string" || typeof post.id === "number" ? String(post.id) : null;
  return {
    key: id ?? `${publishedAt ?? "unknown"}#${index}`,
    id,
    authorId:
      typeof author.id === "string" || typeof author.id === "number" ? String(author.id) : null,
    authorName: authorName(author),
    authorPictureUrl: str(author.profilePictureUrl),
    publishedAt,
    time: Number.isFinite(t) ? t : Number.NEGATIVE_INFINITY,
    text: typeof post.content === "string" ? post.content : "",
    likesCount: num(item.likesCount ?? post.likesCount),
    isLiked: post.isLiked === true || item.isLiked === true,
    commentsCount: num(item.commentsCount ?? post.commentsCount),
    media: toMedia(post.mediaItems),
  };
}

export function toCardPosts(items: unknown[]): CardPost[] {
  const out: CardPost[] = [];
  items.forEach((item, i) => {
    const p = toCardPost(item, i);
    if (p) out.push(p);
  });
  return out;
}

/** Newest first by publishedAt. Ties keep their given order. */
export function sortByPublishedDesc(posts: CardPost[]): CardPost[] {
  return posts
    .map((p, i) => ({ p, i }))
    .sort((a, b) => (a.p.time === b.p.time ? a.i - b.i : b.p.time > a.p.time ? 1 : -1))
    .map((x) => x.p);
}

/** Merge lists, drop duplicates (first wins), and sort newest first. */
export function mergePosts(...lists: CardPost[][]): CardPost[] {
  const seen = new Set<string>();
  const all: CardPost[] = [];
  for (const list of lists) {
    for (const p of list) {
      if (seen.has(p.key)) continue;
      seen.add(p.key);
      all.push(p);
    }
  }
  return sortByPublishedDesc(all);
}

/** A video is playable once it has an mp4Url or an hlsUrl. */
export const isPlayableVideo = (m: CardMedia) => m.kind === "video" && !!(m.mp4Url || m.hlsUrl);
const hasPlayable = (p: CardPost) => p.media.some(isPlayableVideo);

/**
 * Swap in the media of shown posts whose video gained an mp4Url or hlsUrl on a refresh
 * (transcoding finished), so the thumbnail upgrades to the player in place.
 * Returns the same array when nothing changed.
 */
export function upgradeVideos(current: CardPost[], fresh: CardPost[]): CardPost[] {
  const byKey = new Map(fresh.map((p) => [p.key, p]));
  let changed = false;
  const next = current.map((p) => {
    const f = byKey.get(p.key);
    if (f && !hasPlayable(p) && hasPlayable(f)) {
      changed = true;
      return { ...p, media: f.media };
    }
    return p;
  });
  return changed ? next : current;
}

/** A failed first-page load: a refresh keeps the posts and flags an inline error; an initial load shows the full error state. */
export function firstLoadFailure(refresh: boolean): { fullError: boolean; refreshFailed: boolean } {
  return { fullError: !refresh, refreshFailed: refresh };
}

/** "1 comment", "0 comments", "2 comments". */
export function commentsLabel(count: number): string {
  return count === 1 ? "1 comment" : `${count} comments`;
}

export function relativeTime(publishedAt: string | null, now: number = Date.now()): string {
  const t = publishedAt ? Date.parse(publishedAt) : NaN;
  if (!Number.isFinite(t)) return "";
  const s = Math.max(0, Math.floor((now - t) / 1000));
  if (s < 60) return "just now";
  const m = Math.floor(s / 60);
  if (m < 60) return `${m}m ago`;
  const h = Math.floor(m / 60);
  if (h < 24) return `${h}h ago`;
  const d = Math.floor(h / 24);
  if (d < 7) return `${d}d ago`;
  return new Date(t).toLocaleDateString("en-US", { month: "short", day: "numeric", year: "numeric" });
}

/** Delete is offered only on the signed-in person's own post. */
export function canDelete(post: CardPost, feedUserId: string | null | undefined): boolean {
  return !!feedUserId && !!post.id && post.authorId !== null && post.authorId === feedUserId;
}