import { ENV } from "./_core/env";

export type TutorialMetrics = {
  viewCount?: number;
  commentCount?: number;
  thumbnailUrl?: string;
  fetchedAt: Date;
};

export type TutorialMetricSource = {
  sourcePlatform?: string | null;
  platformVideoId?: string | null;
  metricsFetchedAt?: Date | string | null;
  viewCount?: number | null;
  commentCount?: number | null;
};

const METRIC_CACHE_MS = 12 * 60 * 60 * 1000;

function parseCount(value: unknown) {
  if (typeof value === "number" && Number.isFinite(value)) return value;
  if (typeof value === "string" && value.trim()) {
    const parsed = Number.parseInt(value, 10);
    if (Number.isFinite(parsed)) return parsed;
  }
  return undefined;
}

export function shouldRefreshTutorialMetrics(source: TutorialMetricSource) {
  if (!source.sourcePlatform || !source.platformVideoId) return false;
  if (source.sourcePlatform !== "bilibili" && source.sourcePlatform !== "youtube") return false;

  const fetchedAt =
    source.metricsFetchedAt instanceof Date
      ? source.metricsFetchedAt
      : source.metricsFetchedAt
        ? new Date(source.metricsFetchedAt)
        : null;

  if (!fetchedAt || Number.isNaN(fetchedAt.getTime())) return true;
  if (source.viewCount == null && source.commentCount == null) return true;
  return (Date.now() - fetchedAt.getTime()) > METRIC_CACHE_MS;
}

export async function fetchTutorialMetrics(sourcePlatform: string, platformVideoId: string): Promise<TutorialMetrics | null> {
  if (sourcePlatform === "bilibili") {
    return fetchBilibiliMetrics(platformVideoId);
  }
  if (sourcePlatform === "youtube") {
    return fetchYouTubeMetrics(platformVideoId);
  }
  return null;
}

async function fetchBilibiliMetrics(bvid: string): Promise<TutorialMetrics | null> {
  const response = await fetch(`https://api.bilibili.com/x/web-interface/view?bvid=${encodeURIComponent(bvid)}`, {
    headers: {
      "accept": "application/json",
      "user-agent": "tennis-training-hub/1.0",
    },
  });

  if (!response.ok) {
    throw new Error(`Bilibili metrics request failed with ${response.status}`);
  }

  const payload = await response.json();
  const stat = payload?.data?.stat;
  if (!payload?.data || !stat) return null;

  return {
    viewCount: parseCount(stat.view),
    commentCount: parseCount(stat.reply),
    thumbnailUrl: typeof payload.data.pic === "string" ? payload.data.pic.replace(/^http:\/\//, "https://") : undefined,
    fetchedAt: new Date(),
  };
}

async function fetchYouTubeMetrics(videoId: string): Promise<TutorialMetrics | null> {
  if (!ENV.youtubeApiKey) return null;

  const url = new URL("https://www.googleapis.com/youtube/v3/videos");
  url.searchParams.set("part", "statistics,snippet");
  url.searchParams.set("id", videoId);
  url.searchParams.set("key", ENV.youtubeApiKey);

  const response = await fetch(url.toString(), {
    headers: {
      "accept": "application/json",
      "user-agent": "tennis-training-hub/1.0",
    },
  });

  if (!response.ok) {
    throw new Error(`YouTube metrics request failed with ${response.status}`);
  }

  const payload = await response.json();
  const item = Array.isArray(payload?.items) ? payload.items[0] : null;
  if (!item) return null;

  return {
    viewCount: parseCount(item.statistics?.viewCount),
    commentCount: parseCount(item.statistics?.commentCount),
    thumbnailUrl:
      item.snippet?.thumbnails?.maxres?.url ||
      item.snippet?.thumbnails?.high?.url ||
      item.snippet?.thumbnails?.medium?.url ||
      item.snippet?.thumbnails?.default?.url,
    fetchedAt: new Date(),
  };
}