/**
 * @module tests/integration/open-does-not-wait-for-a-rebuilding-provider
 * @description OPEN DOES NOT WAIT FOR A PROVIDER THAT IS REBUILDING ITSELF.
 *
 * Measured on a production store: a metadata provider that had to rebuild made
 * `init()` pay the ENTIRE rebuild on the foreground — 641 seconds — with every
 * other family idle behind it, because a provider reporting `serving: false`
 * because it is BUSY BUILDING and one reporting `serving: false` because it is
 * BROKEN were indistinguishable, and both were answered the same way: call
 * `rebuild()`, and wait.
 *
 * The law: a provider that reports `rebuildInProgress()` owns its own rebuild.
 * `init()` returns; every other family serves; THAT family's doors refuse by
 * name, carrying the provider's own progress; and the doors open by themselves
 * when the provider reports serving. Nothing is ever served empty.
 */

import { describe, it, expect, afterEach } from 'vitest'
import { mkdtempSync, rmSync } 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 type { ProviderRebuildProgress } from '../../src/utils/indexReadiness.js'

/** How long the stub provider claims to be rebuilding. */
const REBUILD_MS = 6_000

describe('a provider rebuilding itself never blocks open', () => {
  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 */ }
    }
  })

  it('init() returns in milliseconds, the family refuses by name, then answers', async () => {
    const dir = mkdtempSync(join(tmpdir(), 'brainy-rebuilding-provider-'))
    dirs.push(dir)

    // Seed a store so the open has something to (not) rebuild.
    const seed = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await seed.init()
    await seed.add({ data: 'a row with a plain field', type: NounType.Concept, metadata: { kind: 'report' } })
    await seed.flush()
    await seed.close()

    const brain = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    brains.push(brain)

    // Dress the metadata index as a provider that is rebuilding ITSELF: not
    // serving, and honest about why. `init()` wires the real index first, so
    // the hooks are installed on the instance as soon as it exists — the gate
    // reads them by feature detection, exactly as it would a native provider's.
    const rebuildStartedAt = Date.now()
    const stillRebuilding = () => Date.now() - rebuildStartedAt < REBUILD_MS
    let rebuildCalls = 0

    const inner = brain as unknown as {
      metadataIndex: Record<string, unknown>
      setupIndex?: unknown
    }
    // Install on the prototype-free instance right after construction by
    // patching the property the moment init() assigns it.
    const install = (target: Record<string, unknown>) => {
      const realRebuild = target.rebuild as () => Promise<void>
      target.rebuildInProgress = (): ProviderRebuildProgress | null =>
        stillRebuilding()
          ? { phase: 'metadata shadow build', done: 4_096, total: 14_056, startedAt: rebuildStartedAt }
          : null
      target.healthReport = () => ({
        provider: 'metadata',
        healthy: !stillRebuilding(),
        serving: !stillRebuilding(),
        generation: 1,
        invariants: [],
        unledgered: []
      })
      target.rebuild = async () => {
        rebuildCalls++
        return realRebuild.call(target)
      }
    }

    // init() constructs the metadata index; patch as soon as it exists, before
    // the gate consults it. A microtask hop after the index is assigned is
    // enough because the gate runs later in the same init.
    const initPromise = (async () => {
      const originalEnsure = (brain as unknown as { setupIndex?: () => unknown }).setupIndex
      void originalEnsure
      return brain.init()
    })()
    // Patch on the first tick the index exists.
    const patcher = setInterval(() => {
      if (inner.metadataIndex && !inner.metadataIndex.rebuildInProgress) {
        install(inner.metadataIndex)
      }
    }, 1)
    const startedAt = Date.now()
    try {
      await initPromise
    } finally {
      clearInterval(patcher)
    }
    const openMs = Date.now() - startedAt

    // If the patch did not land before the gate ran, this test proves nothing —
    // say so loudly rather than passing vacuously.
    expect(
      typeof inner.metadataIndex.rebuildInProgress,
      'the stub provider was never installed — the test is vacuous'
    ).toBe('function')

    // 1. The open did not wait out the rebuild.
    expect(openMs).toBeLessThan(REBUILD_MS)
    // 2. And brainy did not start a rebuild of its own on top of the provider's.
    expect(rebuildCalls).toBe(0)

    // 3. The family's door refuses BY NAME, carrying the provider's progress.
    let refusal: Error | null = null
    try {
      await brain.find({ where: { kind: 'report' } } as never)
    } catch (err) {
      refusal = err as Error
    }
    expect(refusal, 'a not-serving metadata family must refuse, never serve empty').not.toBeNull()
    expect(refusal!.message).toMatch(/metadata shadow build/i)
    expect(refusal!.message).toMatch(/4,096\/14,056/)
    expect(refusal!.message).toMatch(/no action is needed/i)

    // 4. Other families keep serving — the brain is open.
    const all = await brain.getNouns?.({ pagination: { limit: 1 } } as never)
    expect(all ?? true).toBeTruthy()

    // 5. When the provider reports itself serving, the door opens by itself.
    await new Promise((r) => setTimeout(r, REBUILD_MS))
    ;(brain as unknown as { _metadataVerified: boolean })._metadataVerified = false
    await expect(brain.find({ where: { kind: 'report' } } as never)).resolves.toBeDefined()
  }, 180_000)

  it('a rebuilding provider reporting 0 entries is not a CRITICAL, and gets no second rebuild', async () => {
    const dir = mkdtempSync(join(tmpdir(), 'brainy-rebuilding-critical-'))
    dirs.push(dir)
    const seed = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await seed.init()
    await seed.add({ data: 'a stored entity', type: NounType.Concept })
    await seed.flush()
    await seed.close()

    const brain = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    brains.push(brain)

    let rebuildCalls = 0
    const errors: string[] = []
    const origError = console.error
    console.error = ((...a: unknown[]) => { errors.push(a.map(String).join(' ')) }) as typeof console.error

    const inner = brain as unknown as { metadataIndex: Record<string, unknown> }
    const patcher = setInterval(() => {
      if (inner.metadataIndex && !inner.metadataIndex.rebuildInProgress) {
        const target = inner.metadataIndex
        target.rebuildInProgress = () => ({ phase: 'online metadata rebuild', startedAt: Date.now() })
        target.healthReport = () => ({
          provider: 'metadata', healthy: false, serving: false,
          generation: 1, invariants: [], unledgered: []
        })
        // The shape the native engine now has: the index reports NOTHING while
        // its rebuild runs online behind refusing doors.
        target.getStats = async () => ({ totalEntries: 0 })
        target.rebuild = async () => { rebuildCalls++ }
      }
    }, 1)
    try {
      await brain.init()
    } finally {
      clearInterval(patcher)
      console.error = origError
    }

    expect(
      typeof inner.metadataIndex.rebuildInProgress,
      'the stub provider was never installed — the test is vacuous'
    ).toBe('function')
    expect(errors.filter((l) => /CRITICAL: Metadata index has 0 entries/.test(l))).toEqual([])
    expect(rebuildCalls).toBe(0)
  }, 180_000)
})