import type { DataSource, CollectResult } from "../types.js";
import { extractItems } from "../types.js";
import { registerCollector } from "../registry.js";
import { coveredOn, isCovered } from "@pipeline/shared/node";
import { isoDateString, formatChineseDate } from "@pipeline/shared";
import { getTimezone } from "@pipeline/shared/node";
import { fetchRepoDetail } from "./repo-detail.js";

/** Candidate from the three boards' union, with per-board gain signals. */
interface Candidate {
  owner: string;
  name: string;
  fullName: string;
  /** daily-board gain (undefined when absent from today's board). */
  todayStars?: number;
  /** weekly-board gain. */
  weekStars?: number;
  /** monthly-board gain. */
  monthStars?: number;
  /** Combined recommendation score (see scoreOf). */
  score: number;
}

/** Recommendation score — favors sustained momentum over one-day spikes:
 *  monthly gain anchors "consistently hot", weekly adds mid-term momentum,
 *  daily only tips the scale among equally-sustained candidates. A repo
 *  spiking today but absent from weekly/monthly loses to a steady climber. */
function scoreOf(c: Pick<Candidate, "todayStars" | "weekStars" | "monthStars">): number {
  return (c.monthStars ?? 0) * 0.5 + (c.weekStars ?? 0) * 0.3 + (c.todayStars ?? 0) * 0.2;
}

/**
 * github-daily-pick — the daily open-source project RECOMMENDATION's picker.
 *
 * This is NOT a trending-board recap (that's github-trending's job). A
 * recommendation should surface projects with sustained momentum, so the
 * candidate pool is the UNION of the daily / weekly / monthly boards, scored
 * by a weighted blend (monthly 0.5 + weekly 0.3 + daily 0.2) and screened
 * against the covered store's rolling window. Steady climbers beat one-day
 * spikes; a project recapped on the daily board can still be recommended
 * later once its momentum persists across boards.
 *
 *   1. Same-day idempotency: today's successful record is re-picked — a
 *      re-run (LLM/render failure retry) never changes the day's topic.
 *   2. Otherwise union + score + dedup-screen, take the top.
 *   3. Empty pool -> throw (job fails, Feishu alerts) — never silently
 *      re-feature a covered repo.
 *
 * The covered store lives outside the output dir (30-day TTL would eat it);
 * see @pipeline/shared/node's covered-store for the storage contract.
 */
class GitHubDailyPickCollector implements DataSource {
  readonly name = "github-daily-pick";
  private url: string;
  private repoUrlTemplate: string;
  private windowDays: number;
  private readmeLimit: number;

  constructor(config?: Record<string, any>) {
    this.url = config?.url ?? "";
    this.repoUrlTemplate = config?.repoUrl ?? "";
    this.windowDays = config?.windowDays ?? 90;
    this.readmeLimit = config?.readmeLimit ?? 4000;
  }

  async collect(): Promise<CollectResult> {
    if (!this.url) {
      throw new Error("github-daily-pick collector requires 'url' in config");
    }
    if (!this.repoUrlTemplate) {
      throw new Error("github-daily-pick collector requires 'repoUrl' in config");
    }

    const tz = getTimezone();
    const today = isoDateString(new Date(), tz);

    let owner: string;
    let name: string;
    let rankNote: string;

    // 1) Same-day idempotency — re-run re-picks today's already-featured repo.
    const done = coveredOn(today);
    if (done.length > 0) {
      const r = done[done.length - 1];
      owner = r.repo.owner;
      name = r.repo.name;
      rankNote = "今日已完成过一版，重新生成同一项目";
    } else {
      // 2) Union of the three boards, screened against the rolling window,
      //    ranked by the blended momentum score.
      const candidates = await this.freshCandidates();
      if (candidates.length === 0) {
        throw new Error(
          `github-daily-pick: ${this.windowDays} 天窗口内日榜、周榜与月榜候选均已讲完，无未讲项目可选。` +
            `可增大 collect.github-daily-pick.windowDays，或等待窗口滚动后重试。`,
        );
      }
      const pick = candidates[0];
      owner = pick.owner;
      name = pick.name;
      const bits = [`日 +${pick.todayStars ?? 0}`];
      if (pick.weekStars != null) bits.push(`周 +${pick.weekStars}`);
      if (pick.monthStars != null) bits.push(`月 +${pick.monthStars}`);
      rankNote = `综合热度第一的未讲项目（${bits.join("，")}）`;
    }

    // Deep detail + a longer README than the roundup collectors use.
    const detail = await fetchRepoDetail(this.repoUrlTemplate, owner, name, this.readmeLimit);
    if (!detail?.meta) {
      throw new Error(`github-daily-pick: 仓库详情获取失败 ${owner}/${name}`);
    }

    const lines = [
      `# 今日推荐选题：${detail.meta.fullName}`,
      ``,
      `选题说明：${rankNote}。讲述日：${formatChineseDate(new Date(), tz)}。`,
      ``,
      `---`,
      ``,
      detail.text,
    ];
    return { type: "text", content: lines.join("\n"), repos: [detail.meta] };
  }

  /** Union of the daily / weekly / monthly boards with per-board gains merged
   *  per repo, covered-windowed, then scored and ranked (desc). Individual
   *  board fetch failures degrade to the remaining boards. */
  private async freshCandidates(): Promise<Candidate[]> {
    const [daily, weekly, monthly] = await Promise.all([
      this.board("").catch(() => [] as any[]),
      this.board("?since=weekly").catch(() => [] as any[]),
      this.board("?since=monthly").catch(() => [] as any[]),
    ]);

    const byKey = new Map<string, Candidate>();
    const add = (repo: any, kind: "todayStars" | "weekStars" | "monthStars") => {
      const owner = repo.author ?? "";
      const name = repo.name ?? "";
      const fullName = repo.fullName || `${owner}/${name}`;
      if (!owner || !name || isCovered(fullName, this.windowDays)) return;
      const key = fullName.toLowerCase();
      const c: Candidate = byKey.get(key) ?? { owner, name, fullName, score: 0 };
      c[kind] = repo.currentPeriodStars ?? undefined;
      byKey.set(key, c);
    };
    for (const item of daily) add(item, "todayStars");
    for (const item of weekly) add(item, "weekStars");
    for (const item of monthly) add(item, "monthStars");

    return [...byKey.values()]
      .map((c) => ({ ...c, score: scoreOf(c) }))
      .sort((a, b) => b.score - a.score);
  }

  /** One board's raw items (unsorted, unscreened). */
  private async board(query: string): Promise<any[]> {
    const response = await fetch(this.url + query);
    if (!response.ok) {
      throw new Error(`GitHub trending API error: ${response.status} ${await response.text()}`);
    }
    return extractItems(await response.json()) as any[];
  }
}

registerCollector("github-daily-pick", (config) => new GitHubDailyPickCollector(config));