/** Sequential job worker with retry and stale-job recovery. */
import { claimNextJob, updateJob } from "./db.js";
import { SkipJob } from "./review.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();
    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) {
      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;
    }
    this.timer = setTimeout(() => this.tick(), this.pollMs);
  }
}