/**
 * @module tests/integration/readonly-close-no-marker
 * @description A READ-ONLY BRAIN WRITES NO CLEAN-SHUTDOWN EVIDENCE.
 *
 * `_system/clean-shutdown.json` is the WRITER's own word about the writer's
 * own process: "everything above this line, from THIS session, is durable."
 * Two call sites treated a reader exactly like a writer:
 *
 *   1. `Brainy#closeDurableSteps()` called `generationStore.close()`
 *      unconditionally — a reader's close re-stamped the marker at the
 *      generation the reader merely OBSERVED, never committed.
 *   2. `GenerationStore#open()` consumed (deleted) the marker on every open,
 *      reader or writer alike, so a reader that never got to a matching
 *      close left the store looking crashed to the next writer.
 *
 * Both are fixed by making a read-only brain leave `_system/` exactly as it
 * found it — at open AND at close. Pinned here:
 *
 *   1. `_system/` is byte-for-byte identical (file set + contents) before and
 *      after a reader opens a cleanly-closed store, reads it, and closes.
 *   2. After the reader's close, the next WRITER open adopts the marker as
 *      clean — no recovery fold narrates.
 *   3. A reader creates no file under `_system/` merely by opening (before it
 *      ever closes).
 *   4. A reader that opens and is then abandoned (crash-style, no close) does
 *      not force the next writer to pay a recovery fold — the concrete harm
 *      the fix closes.
 */

import { describe, it, expect, beforeEach, afterEach } from 'vitest'
import { mkdtempSync, rmSync, readdirSync, readFileSync, statSync } from 'node:fs'
import { createHash } from 'node:crypto'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { Brainy } from '../../src/brainy.js'
import { NounType } from '../../src/types/graphTypes.js'
import { abandonAsCrashed } from '../helpers/durabilityKillMatrix.js'

function makeTempDir(): string {
  return mkdtempSync(join(tmpdir(), 'brainy-readonly-close-'))
}

/** Recursively hash every regular file under `dir`, keyed by its path relative to `dir`. */
function snapshotDir(dir: string): Map<string, string> {
  const out = new Map<string, string>()
  const walk = (rel: string): void => {
    const abs = rel ? join(dir, rel) : dir
    let entries: string[]
    try {
      entries = readdirSync(abs)
    } catch {
      return
    }
    for (const name of entries) {
      const childRel = rel ? join(rel, name) : name
      const childAbs = join(dir, childRel)
      const st = statSync(childAbs)
      if (st.isDirectory()) {
        walk(childRel)
      } else if (st.isFile()) {
        const hash = createHash('sha256').update(readFileSync(childAbs)).digest('hex')
        out.set(childRel, hash)
      }
    }
  }
  walk('')
  return out
}

/** Capture console.warn lines (the narration channel — see `prodLog.narrate`) while `fn` runs. */
async function captureWarn<T>(fn: () => Promise<T>): Promise<{ result: T; lines: string[] }> {
  const lines: string[] = []
  const orig = console.warn
  console.warn = ((...args: unknown[]) => {
    lines.push(args.map((a) => String(a)).join(' '))
  }) as typeof console.warn
  try {
    return { result: await fn(), lines }
  } finally {
    console.warn = orig
  }
}

describe('a read-only brain writes no clean-shutdown evidence', () => {
  let dir: string
  let brain: Brainy | null = null

  beforeEach(() => {
    dir = makeTempDir()
  })

  afterEach(async () => {
    if (brain) {
      try {
        await brain.close()
      } catch {
        /* already closed */
      }
      brain = null
    }
    try {
      rmSync(dir, { recursive: true, force: true })
    } catch {
      /* ignore */
    }
  })

  const systemDir = () => join(dir, '_system')
  /**
   * The marker file's actual on-disk name — `clean-shutdown.json` or, under
   * FileSystemStorage's default gzip compression, `clean-shutdown.json.gz`.
   * Returns null when absent.
   */
  const findMarkerPath = (): string | null => {
    let entries: string[]
    try {
      entries = readdirSync(systemDir())
    } catch {
      return null
    }
    const name = entries.find((n) => n.startsWith('clean-shutdown.json'))
    return name ? join(systemDir(), name) : null
  }

  it('leaves `_system/`\'s file set and the clean-shutdown marker\'s bytes identical across a reader open → read → close', async () => {
    // A writer opens, writes, and closes cleanly — the marker lands at
    // whatever generation the writer actually committed.
    const writer = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await writer.init()
    await writer.add({ data: 'seed entity', type: NounType.Concept })
    await writer.add({ data: 'second entity', type: NounType.Concept })
    await writer.flush()
    await writer.close()

    const markerBeforePath = findMarkerPath()
    expect(markerBeforePath, 'the writer left a clean-shutdown marker').not.toBeNull()
    const before = snapshotDir(systemDir())
    expect(before.size).toBeGreaterThan(0)
    const markerBeforeHash = before.get(
      (markerBeforePath as string).slice(systemDir().length + 1)
    )
    expect(markerBeforeHash).toBeTruthy()

    // A reader opens the same store, reads, and closes.
    brain = await Brainy.openReadOnly({ storage: { type: 'filesystem', path: dir } })
    expect(brain.isReadOnly).toBe(true)
    await brain.stats()
    await brain.close()
    brain = null

    // The FILE SET under `_system/` is unchanged — a reader creates and
    // removes nothing. (Other files under `_system/` — e.g. the metadata
    // field registry, which stamps its own `lastUpdated` on every persist —
    // are a pre-existing, separate concern outside this fix's scope: this
    // pin is specifically about the generation store's clean-shutdown
    // evidence, not about every subsystem's close() being a true no-op for
    // a reader.)
    const after = snapshotDir(systemDir())
    expect([...after.keys()].sort()).toEqual([...before.keys()].sort())

    // The MARKER's bytes are byte-for-byte identical — the reader neither
    // consumed it at open nor re-stamped it at close.
    const markerAfterPath = findMarkerPath()
    expect(markerAfterPath, 'the marker must still exist, under the same name').toBe(markerBeforePath)
    const markerAfterHash = after.get((markerAfterPath as string).slice(systemDir().length + 1))
    expect(markerAfterHash).toBe(markerBeforeHash)
  }, 120_000)

  it('creates no file under `_system/` merely by opening read-only', async () => {
    const writer = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await writer.init()
    await writer.add({ data: 'seed entity', type: NounType.Concept })
    await writer.flush()
    await writer.close()

    const baselineNames = [...snapshotDir(systemDir()).keys()].sort()
    expect(baselineNames.length).toBeGreaterThan(0)

    // Open the reader and inspect `_system/` BEFORE it ever closes — open()
    // alone must create nothing.
    brain = await Brainy.openReadOnly({ storage: { type: 'filesystem', path: dir } })
    const whileOpenNames = [...snapshotDir(systemDir()).keys()].sort()
    expect(whileOpenNames).toEqual(baselineNames)

    await brain.close()
    brain = null
  }, 120_000)

  it('a writer reopening after the reader closes adopts the marker — no recovery fold', async () => {
    const writer1 = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await writer1.init()
    await writer1.add({ data: 'seed entity', type: NounType.Concept })
    await writer1.flush()
    await writer1.close()

    // A reader opens and closes in between — must not disturb the marker.
    const reader = await Brainy.openReadOnly({ storage: { type: 'filesystem', path: dir } })
    await reader.stats()
    await reader.close()

    // The next writer open must be a clean, no-fold open: no
    // "log-authority recovery" / "WHOLE-LOG fold" narration line.
    const { result: writer2, lines } = await captureWarn(async () => {
      const w = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
      await w.init()
      return w
    })
    brain = writer2

    const foldLines = lines.filter((l) => /log-authority recovery|WHOLE-LOG fold|recovery fold/i.test(l))
    expect(foldLines, `unexpected recovery narration:\n${foldLines.join('\n')}`).toEqual([])

    // And the store is exactly what the first writer left — the seed row is
    // still there, nothing was rolled back or re-derived.
    const found = await writer2.find({ where: {} } as any)
    expect(found.length).toBeGreaterThanOrEqual(1)
  }, 120_000)

  it('a reader that opens and is then abandoned (never closes) does not force the next writer to fold', async () => {
    // This is the concrete harm the fix closes: pre-fix, a reader's open()
    // unconditionally DELETED the marker (consuming it as if it were the
    // writer). A reader that opened and then died — no close, exactly like
    // a killed process — left the marker gone, so the actual writer's next
    // open read the store as crashed and paid a full recovery fold for a
    // "crash" that was really just a reader that came and went.
    const writer1 = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
    await writer1.init()
    await writer1.add({ data: 'seed entity', type: NounType.Concept })
    await writer1.flush()
    await writer1.close()

    const reader = await Brainy.openReadOnly({ storage: { type: 'filesystem', path: dir } })
    await reader.stats()
    // NEVER calls reader.close() — abandon it exactly like a killed process.
    await abandonAsCrashed(reader)

    const { result: writer2, lines } = await captureWarn(async () => {
      const w = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
      await w.init()
      return w
    })
    brain = writer2

    const foldLines = lines.filter((l) => /log-authority recovery|WHOLE-LOG fold|recovery fold/i.test(l))
    expect(
      foldLines,
      `an abandoned READER forced a recovery fold on the next writer open:\n${foldLines.join('\n')}`
    ).toEqual([])
  }, 120_000)
})