/** Sequential job worker with retry and stale-job recovery. */
import {
  claimNextJob, claimPendingSummary, requeueStaleSummaries,
  updateJob, updateReviewRecord,
} from "./db.js";
import { SkipJob } from "./review.js";
import { summariseReview } from "./summary.js";

const STALE_MS = 2 * 60 * 60 * 1000;

export class JobQueue {
  constructor({ db, engine, logger = console, pollMs = 3000, maxAttempts = 2 }) {
    this.db = db;
    this.engine = engine;
    this.logger = logger;
    this.pollMs = pollMs;
    this.maxAttempts = maxAttempts;
    this.running = false;
    this.busy = false;
    this.timer = null;
    this.currentJobId = null;
  }

  start() {
    if (this.running) return;
    this.running = true;
    this.recoverStale();
    const requeued = requeueStaleSummaries(this.db);
    if (requeued) this.logger.warn?.(`requeued ${requeued} interrupted summariser task(s)`);
    this.tick();
  }

  stop() {
    this.running = false;
    if (this.timer) clearTimeout(this.timer);
  }

  recoverStale() {
    const cutoff = new Date(Date.now() - STALE_MS).toISOString().replace("T", " ").slice(0, 19);
    const stale = this.db.prepare(
      "SELECT id FROM jobs WHERE status = 'running' AND started_at IS NOT NULL AND started_at < ?",
    ).all(cutoff);
    for (const row of stale) {
      updateJob(this.db, row.id, {
        status: "queued", phase: null,
        error: "requeued after worker restart or timeout",
      });
      this.logger.warn?.(`requeued stale job #${row.id}`);
    }
  }

  async tick() {
    if (!this.running) return;
    if (this.busy) {
      this.timer = setTimeout(() => this.tick(), this.pollMs);
      return;
    }
    const job = claimNextJob(this.db);
    if (!job) {
      // Nothing to review: use the idle slot for pending summaries.
      await this.runSummaryOnce();
      this.timer = setTimeout(() => this.tick(), this.pollMs);
      return;
    }
    this.busy = true;
    this.currentJobId = job.id;
    try {
      await this.engine.execute(job);
    } catch (err) {
      if (err instanceof SkipJob) {
        await this.engine.failJob(job, err);
      } else if (job.attempts < this.maxAttempts) {
        this.logger.warn?.(`job #${job.id} failed (attempt ${job.attempts}): ${err.message}; retrying`);
        updateJob(this.db, job.id, {
          status: "queued", phase: null,
          error: `${err.name || "Error"}: ${err.message}`,
        });
      } else {
        await this.engine.failJob(job, err);
      }
    } finally {
      this.busy = false;
      this.currentJobId = null;
    }
    // Summarising runs on the same worker so it never competes with a review
    // for the LLM endpoint.
    await this.runSummaryOnce();
    this.timer = setTimeout(() => this.tick(), this.pollMs);
  }

  /**
   * Summarise one finished review, if any is pending.
   * Failures are recorded on the record and never block the queue.
   */
  async runSummaryOnce() {
    const record = claimPendingSummary(this.db);
    if (!record) return false;
    try {
      const repo = this.db.prepare("SELECT * FROM repositories WHERE id = ?").get(record.repo_id);
      if (!repo) {
        updateReviewRecord(this.db, record.id, {
          summary_status: "skipped", summary_error: "repository no longer exists",
        });
        return false;
      }
      let findings = [];
      try { findings = JSON.parse(record.findings_json || "[]"); } catch { findings = []; }
      const job = this.db.prepare("SELECT result_json FROM jobs WHERE id = ?").get(record.job_id);
      let summary = null;
      try { summary = JSON.parse(job?.result_json || "{}").summary ?? null; } catch { summary = null; }

      const llm = {
        url: repo.llm_base_url || this.engine.config.llmUrl,
        token: repo.llm_token || this.engine.config.llmToken,
        model: repo.llm_model || this.engine.config.llmModel,
        protocol: repo.llm_provider || this.engine.config.llmProtocol,
        authHeader: this.engine.config.llmAuthHeader,
        extraHeaders: this.engine.config.llmExtraHeaders,
      };
      this.logger.info?.(`summarising review record #${record.id} (${repo.owner}/${repo.name} ${record.ref_name})`);
      const res = await summariseReview({
        llm, repo, record, findings, summary, requirement: record.requirement,
      });
      if (res.ok) {
        updateReviewRecord(this.db, record.id, {
          summary_status: "done",
          summary: res.text,
          summary_model: res.model,
          summary_error: res.complete ? null : "摘要缺少标准小节，已按原文保存",
        });
        this.logger.info?.(`review record #${record.id} summarised (${res.text.length} chars)`);
      } else {
        updateReviewRecord(this.db, record.id, {
          summary_status: "failed", summary_error: String(res.error).slice(0, 500),
        });
        this.logger.warn?.(`review record #${record.id} summary failed: ${res.error}`);
      }
    } catch (err) {
      updateReviewRecord(this.db, record.id, {
        summary_status: "failed", summary_error: String(err.message || err).slice(0, 500),
      });
      this.logger.warn?.(`review record #${record.id} summary error: ${err.message}`);
    }
    return true;
  }
}