import { describe, expect, it } from "vitest";
import { createMockCronStateForJobs } from "./service.test-harness.js";
import { recomputeNextRuns, recomputeNextRunsForMaintenance } from "./service/jobs.js";
import type { CronJob } from "./types.js";

/**
 * Regression test for issue #17852: daily cron jobs skip a day (48h jump).
 *
 * Root cause: onTimer's results-processing block used the full
 * recomputeNextRuns which could silently advance a past-due nextRunAtMs
 * for a job that became due between findDueJobs and the post-execution
 * locked block — skipping that run and jumping 48h ahead.
 *
 * Fix: use recomputeNextRunsForMaintenance in the post-execution block,
 * which only fills in missing nextRunAtMs values and never overwrites
 * existing (including past-due) ones.
 */
describe("issue #17852 - daily cron jobs should not skip days", () => {
  const HOUR_MS = 3_600_000;
  const DAY_MS = 24 * HOUR_MS;

  function createDailyThreeAmJob(threeAM: number): CronJob {
    return {
      id: "daily-job",
      name: "daily 3am",
      enabled: true,
      schedule: { kind: "cron", expr: "0 3 * * *", tz: "UTC" },
      payload: { kind: "systemEvent", text: "daily task" },
      sessionTarget: "main",
      wakeMode: "next-heartbeat",
      createdAtMs: threeAM - DAY_MS,
      updatedAtMs: threeAM - DAY_MS,
      state: {
        nextRunAtMs: threeAM,
      },
    };
  }

  it("recomputeNextRunsForMaintenance should NOT advance past-due nextRunAtMs by default", () => {
    // Simulate: job scheduled for 3:00 AM, timer processing happens at 3:00:01
    // The job was NOT executed in this tick (e.g., it became due between
    // findDueJobs and the post-execution block).
    const threeAM = Date.parse("2026-02-16T03:00:00.000Z");
    const now = threeAM + 1_000; // 3:00:01

    const job = createDailyThreeAmJob(threeAM);

    const state = createMockCronStateForJobs({ jobs: [job], nowMs: now });
    recomputeNextRunsForMaintenance(state);

    // Maintenance should NOT touch existing past-due nextRunAtMs.
    // The job should still be eligible for execution on the next timer tick.
    expect(job.state.nextRunAtMs).toBe(threeAM);
  });

  it("recomputeNextRunsForMaintenance can advance expired nextRunAtMs on recovery path when slot already executed", () => {
    const threeAM = Date.parse("2026-02-16T03:00:00.000Z");
    const now = threeAM + 1_000; // 3:00:01

    const job = createDailyThreeAmJob(threeAM);
    job.state.lastRunAtMs = threeAM + 1;

    const state = createMockCronStateForJobs({ jobs: [job], nowMs: now });
    recomputeNextRunsForMaintenance(state, { recomputeExpired: true });

    const tomorrowThreeAM = threeAM + DAY_MS;
    expect(job.state.nextRunAtMs).toBe(tomorrowThreeAM);
  });

  it("full recomputeNextRuns WOULD silently advance past-due nextRunAtMs (the bug)", () => {
    // This test documents the buggy behavior that caused #17852.
    // The full recomputeNextRuns sees a past-due nextRunAtMs and advances it
    // to the next occurrence WITHOUT executing the job.
    const threeAM = Date.parse("2026-02-16T03:00:00.000Z");
    const now = threeAM + 1_000; // 3:00:01

    const job = createDailyThreeAmJob(threeAM);

    const state = createMockCronStateForJobs({ jobs: [job], nowMs: now });
    recomputeNextRuns(state);

    // The full recomputeNextRuns advances it to TOMORROW — skipping today's
    // execution entirely.  This is the 48h jump bug: from the previous run
    // (yesterday 3 AM) to the newly computed next run (tomorrow 3 AM).
    const tomorrowThreeAM = threeAM + DAY_MS;
    expect(job.state.nextRunAtMs).toBe(tomorrowThreeAM);
  });
});