/**
 * @module tests/integration/pending-embed-low-water
 * @description The pending-embed recovery fold is bounded and background (10.4.9).
 *
 * The fold used to scan the generation log from generation 1 at EVERY open,
 * on the open's foreground — O(whole history) per open on long-lived brains.
 * Now: an advisory low-water mark (`_system/pending_embeds_lowwater.json`)
 * records the committed generation whenever the pending set drains to empty,
 * recovery scans from `mark + 1` on the open's foreground — the crash-recovery
 * contract keeps markers re-armed when open() returns. The mark is advisory: stale-low costs a longer scan, never a
 * marker — a pending embed enqueued before a crash is still recovered.
 */
import { describe, it, expect, afterEach, vi } from 'vitest'
import { mkdtempSync, rmSync } from 'node:fs'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { Brainy } from '../../src/brainy'
import { NounType } from '../../src/types/graphTypes'

const LOWWATER_PATH = '_system/pending_embeds_lowwater.json'

describe('pending-embed recovery: bounded by the low-water mark', () => {
  const roots: string[] = []
  const dir = (): string => {
    const d = mkdtempSync(join(tmpdir(), 'brainy-lowwater-'))
    roots.push(d)
    return d
  }
  const open = async (root: string): Promise<Brainy<any>> => {
    const brain = new Brainy<any>({
      requireSubtype: false,
      storage: { type: 'filesystem', path: root }
    })
    await brain.init()
    return brain
  }

  afterEach(() => {
    for (const d of roots.splice(0)) rmSync(d, { recursive: true, force: true })
  })

  it('drain-to-empty writes the mark, and the next open scans from mark + 1', async () => {
    const root = dir()
    const brain = await open(root)
    // Hold the worker so the pending state is observable, then release it.
    const realKick = (brain as any).kickEmbedWorker.bind(brain)
    ;(brain as any).kickEmbedWorker = () => {}
    await brain.add({
      id: 'row-1',
      data: 'the first deferred row',
      type: NounType.Thing,
      deferEmbedding: true
    })
    expect(brain.pendingEmbedCount()).toBeGreaterThan(0)
    ;(brain as any).kickEmbedWorker = realKick
    await brain.awaitPendingEmbeds()
    // The drain wrote the advisory mark (fire-and-forget: settle the microtask).
    await new Promise((r) => setTimeout(r, 50))
    const mark = (await (brain as any).storage.readRawObject(LOWWATER_PATH)) as {
      generation: number
    } | null
    expect(mark).not.toBeNull()
    expect(mark!.generation).toBeGreaterThan(0)
    await brain.close()

    const brain2 = await open(root)
    const log = (brain2 as any).generationStore.getFactLog()
    const scanSpy = vi.spyOn(log, 'scanFacts')
    try {
      await (brain2 as any).recoverPendingEmbedsFromLog()
      expect(scanSpy).toHaveBeenCalledTimes(1)
      const opts = scanSpy.mock.calls[0][0] as { fromGeneration?: number }
      expect(opts.fromGeneration).toBeGreaterThanOrEqual(mark!.generation + 1)
    } finally {
      scanSpy.mockRestore()
      await brain2.close()
    }
  })

  it('a pending embed enqueued after the mark survives an unclean stop', async () => {
    const root = dir()
    const brain = await open(root)
    await brain.add({ id: 'settled', data: 'lands before the mark', type: NounType.Thing })
    await brain.awaitPendingEmbeds()
    await new Promise((r) => setTimeout(r, 50))

    // A deferred write whose embed never lands: block the worker, then drop
    // the instance without close() — the unclean-stop shape.
    ;(brain as any).kickEmbedWorker = () => {}
    await brain.add({
      id: 'orphan',
      data: 'enqueued then abandoned',
      type: NounType.Thing,
      deferEmbedding: true
    })
    expect(brain.pendingEmbedCount()).toBeGreaterThan(0)
    // No close(): simulate the crash by releasing only the writer lock so the
    // next open can proceed.
    await (brain as any).storage.releaseWriterLock()

    const brain2 = await open(root)
    expect(brain2.pendingEmbedCount()).toBeGreaterThan(0)
    await brain2.awaitPendingEmbeds()
    expect(brain2.pendingEmbedCount()).toBe(0)
    await brain2.close()
    // Reap the crashed instance: its fence is gone, so close() fails loudly —
    // swallow that here; the point is clearing its watchers and registry entry.
    await brain.close().catch(() => undefined)
  })

  it('a reopened brain has its pending set settled when open() returns', async () => {
    const root = dir()
    const brain = await open(root)
    await brain.add({ id: 'a-row', data: 'some data', type: NounType.Thing })
    await brain.awaitPendingEmbeds()
    await brain.close()

    const brain2 = await open(root)
    // The crash-recovery contract: markers are re-armed by open itself —
    // no latch, no background race. (Here the drain landed, so zero.)
    expect(brain2.pendingEmbedCount()).toBe(0)
    await brain2.close()
  })

  it('a clean close with an empty set writes the mark even if no drain happened', async () => {
    const root = dir()
    const brain = await open(root)
    await brain.add({ id: 'r1', data: 'row one', type: NounType.Thing })
    await brain.awaitPendingEmbeds()
    await brain.close()
    // Read the mark back through the storage door (the adapter owns the
    // on-disk encoding), on a fresh instance.
    const brain2 = await open(root)
    const mark = (await (brain2 as any).storage.readRawObject(LOWWATER_PATH)) as {
      generation: number
    } | null
    expect(mark).not.toBeNull()
    expect(mark!.generation).toBeGreaterThan(0)
    await brain2.close()
  })
})