import { beforeEach, describe, expect, it, vi } from "vitest";
import { snapshots, type Db } from "@parking/db";
import { createTestDb } from "@parking/db/testing";
import { pruneSnapshots, type DiskUsage, type SnapshotRetention } from "./snapshot-retention.js";

// Snapshot retention: DISK-PRESSURE prune. No-op unless the DB's filesystem is over the
// high-water mark; then delete the OLDEST until ~freeTargetPct of disk is freed (estimated from
// the deleted BLOB sizes), honoring a MIN_KEEP floor, then VACUUM once. Disk usage is injected
// so the test controls the trigger without touching the real filesystem.

let db: Db;
beforeEach(() => {
  ({ db } = createTestDb());
});

/** Insert `n` snapshots, oldest first (s-0 is the oldest), each `bytes` long. */
function seed(n: number, bytes = 1000): void {
  const t0 = Date.now() - n * 1000;
  for (let i = 0; i < n; i++) {
    db.insert(snapshots)
      .values({
        id: `s-${i}`,
        direction: "entry",
        deviceId: "cam",
        identity: `s-${i}`,
        contentType: "image/jpeg",
        bytes: Buffer.alloc(bytes, 1),
        capturedAt: new Date(t0 + i * 1000).toISOString(), // s-0 oldest … s-(n-1) newest
      })
      .run();
  }
}

function count(): number {
  return db.select().from(snapshots).all().length;
}
function ids(): string[] {
  return db.select().from(snapshots).all().map((r) => r.id).sort();
}

/** A fake disk at a given used% on a 1 GB volume. */
const disk = (usedPct: number, totalBytes = 1_000_000_000): (() => Promise<DiskUsage>) =>
  () => Promise.resolve({ usedPct, totalBytes });

const ret = (o: Partial<SnapshotRetention>): SnapshotRetention => ({
  highPct: 70,
  freeTargetPct: 10,
  minKeep: 2,
  batch: 5,
  ...o,
});

describe("pruneSnapshots (disk-pressure)", () => {
  it("no-op when disk is below the high-water mark", async () => {
    seed(10);
    const res = await pruneSnapshots(db, { retention: ret({}), diskUsage: disk(50) });
    expect(res.deletedRows).toBe(0);
    expect(res.vacuumed).toBe(false);
    expect(count()).toBe(10);
  });

  it("over the mark: deletes the OLDEST until ~freeTargetPct is freed, then VACUUMs", async () => {
    // 1 GB disk, target 10% = 100 MB. Each snapshot 20 MB → ~5 deletions reach the target.
    seed(20, 20 * 1048576);
    const vacuumSpy = vi.spyOn(db.$client as { exec: (s: string) => void }, "exec");
    const res = await pruneSnapshots(db, { retention: ret({ minKeep: 2, batch: 100 }), diskUsage: disk(80) });
    expect(res.deletedRows).toBeGreaterThanOrEqual(5);
    expect(res.freedBytesEst).toBeGreaterThanOrEqual(0.1 * 1_000_000_000);
    expect(res.vacuumed).toBe(true);
    expect(vacuumSpy).toHaveBeenCalledWith("VACUUM");
    // The survivors are the NEWEST (oldest went first).
    const survivors = ids();
    expect(survivors).toContain(`s-19`); // newest kept
    expect(survivors).not.toContain(`s-0`); // oldest pruned
    vacuumSpy.mockRestore();
  });

  it("honors the MIN_KEEP floor even when still over target", async () => {
    // Target 10% of 1 GB = 100 MB, but only 3 tiny snapshots exist and minKeep=2 → at most 1 deleted.
    seed(3, 1000);
    const res = await pruneSnapshots(db, { retention: ret({ minKeep: 2, freeTargetPct: 90 }), diskUsage: disk(95) });
    expect(res.deletedRows).toBe(1); // 3 − minKeep(2)
    expect(count()).toBe(2);
    expect(res.floorHitWhileOver).toBe(true); // couldn't reach target without crossing the floor
  });

  it("skips VACUUM when nothing was deleted", async () => {
    seed(2); // == minKeep, so nothing to delete even over the mark
    const vacuumSpy = vi.spyOn(db.$client as { exec: (s: string) => void }, "exec");
    const res = await pruneSnapshots(db, { retention: ret({ minKeep: 2 }), diskUsage: disk(99) });
    expect(res.deletedRows).toBe(0);
    expect(res.vacuumed).toBe(false);
    expect(vacuumSpy).not.toHaveBeenCalled();
    vacuumSpy.mockRestore();
  });
});