/**
 * @module tests/integration/vfs-root-sweep-once
 * @description THE OLD-ROOT SWEEP RUNS ONCE PER STORE, NOT ONCE PER OPEN.
 *
 * The VFS bootstrap ran a filtered `find()` over the whole store on EVERY
 * open, hunting for root directories created before the fixed root id existed
 * — duplicates a store has either always had or never will. MEASURED on a
 * 14,056-noun / 72,679-verb store: the phase it dominates cost 43–53 SECONDS
 * of every open, warm reopens included.
 *
 * The law: a migration sweep is caused by the store's state, not by the clock
 * or the open count. It runs behind the doors, records that it ran, and a
 * store carrying that record never sweeps again.
 */

import { describe, it, expect, afterEach, vi } from 'vitest'
import { mkdtempSync, rmSync, existsSync } from 'node:fs'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { Brainy } from '../../src/brainy.js'
import { NounType } from '../../src/types/graphTypes.js'
import { VirtualFileSystem } from '../../src/vfs/VirtualFileSystem.js'

describe('the VFS old-root sweep', () => {
  const dirs: string[] = []
  const brains: Brainy[] = []

  afterEach(async () => {
    for (const b of brains.splice(0)) {
      try { await b.close() } catch { /* already closed */ }
    }
    for (const d of dirs.splice(0)) {
      try { rmSync(d, { recursive: true, force: true }) } catch { /* ignore */ }
    }
    vi.restoreAllMocks()
  })

  async function open(dir: string): Promise<Brainy> {
    const brain = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    brains.push(brain)
    await brain.init()
    return brain
  }

  it('sweeps on the first open, records it, and never sweeps again', async () => {
    const dir = mkdtempSync(join(tmpdir(), 'brainy-root-sweep-'))
    dirs.push(dir)

    const sweepSpy = vi.spyOn(
      VirtualFileSystem.prototype as unknown as { cleanupOldRoots: () => Promise<void> },
      'cleanupOldRoots'
    )

    const first = await open(dir)
    await (first.vfs as unknown as { whenRootSweepSettled: () => Promise<void> }).whenRootSweepSettled()
    expect(sweepSpy).toHaveBeenCalledTimes(1)
    // The record is durable engine plumbing under _system/, like every other marker.
    expect(
      existsSync(join(dir, '_system', 'vfs-root-sweep.json')) ||
        existsSync(join(dir, '_system', 'vfs-root-sweep.json.gz'))
    ).toBe(true)

    await first.add({ data: 'a row so the store is not trivially empty', type: NounType.Concept })
    await first.flush()
    await first.close()
    brains.splice(brains.indexOf(first), 1)

    sweepSpy.mockClear()
    const second = await open(dir)
    await (second.vfs as unknown as { whenRootSweepSettled: () => Promise<void> }).whenRootSweepSettled()
    expect(sweepSpy).not.toHaveBeenCalled()

    await second.close()
    brains.splice(brains.indexOf(second), 1)

    // ...and a third open, to prove it is the record and not a one-off.
    sweepSpy.mockClear()
    const third = await open(dir)
    await (third.vfs as unknown as { whenRootSweepSettled: () => Promise<void> }).whenRootSweepSettled()
    expect(sweepSpy).not.toHaveBeenCalled()
  }, 180_000)

  it('the open does not wait for the sweep', async () => {
    const dir = mkdtempSync(join(tmpdir(), 'brainy-root-sweep-async-'))
    dirs.push(dir)

    const proto = VirtualFileSystem.prototype as unknown as Record<
      string,
      (...args: unknown[]) => Promise<unknown>
    >
    const real = proto.cleanupOldRoots
    proto.cleanupOldRoots = async function slow(this: unknown, ...args: unknown[]) {
      await new Promise((r) => setTimeout(r, 4_000))
      return real.apply(this, args)
    }
    try {
      const startedAt = Date.now()
      const brain = await open(dir)
      const openMs = Date.now() - startedAt
      expect(openMs).toBeLessThan(3_000)
      await (brain.vfs as unknown as { whenRootSweepSettled: () => Promise<void> }).whenRootSweepSettled()
    } finally {
      proto.cleanupOldRoots = real
    }
  }, 180_000)
})