/**
 * @module tests/conformance/golden-log-fold
 * @description THE GOLDEN-LOG FOLD-CONFORMANCE ORACLE (brainy leg).
 *
 * One deterministic v2 log — fixed ids, ints, timestamps, vectors — whose
 * ENCODED BYTES and whose FOLDED STATE are both pinned by content hash.
 * The second (native) reader implementation consumes the identical fixture
 * (tests/fixtures/golden-log-v2.bin, written and verified here) and must
 * produce the identical fold digest; the pair is normative on disagreement.
 *
 * What the pins catch, loudly:
 * - Any byte drift in the encoder (envelope, msgpack layout, seals, CRC).
 * - Any semantic drift in the fold (tombstone masking, vector landing,
 *   sameAsGeneration resolution, last-writer-wins ordering).
 * - Any divergence between the two implementations, before the cut.
 *
 * The pinned hashes change ONLY with a deliberate, versioned format or
 * fold-law change — never silently. Updating them requires updating the
 * fixture AND the native side in the same train.
 */
import { describe, it, expect } from 'vitest'
import { createHash } from 'node:crypto'
import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'node:fs'
import { join, dirname } from 'node:path'
import {
  encodeFactV2,
  encodeSegmentHeaderV2,
  sealGroup,
  decodeGroupV2,
  SEGMENT_HEADER_BYTES,
  type CommitFactV2,
  type LogRecord
} from '../../src/db/factLogFormat.js'
import { recordDigest } from '../../src/db/logAuthority.js'

const FIXTURE = join(__dirname, '../fixtures/golden-log-v2.bin')

const sha256 = (b: Uint8Array): string => createHash('sha256').update(b).digest('hex')

// Fixed identities — never regenerate.
const BRAIN = '00000000-0000-4000-8000-00000000b1a1'
const A = '00000000-0000-4000-8000-0000000000a1'
const B = '00000000-0000-4000-8000-0000000000b2'
const C = '00000000-0000-4000-8000-0000000000c3'
const V = '00000000-0000-4000-8000-0000000000d4'

const vec = (seed: number): number[] => [seed + 0.25, seed + 0.5, seed + 0.75]

/** The golden fact sequence — every fold-relevant behavior in nine facts. */
function goldenFacts(): CommitFactV2[] {
  const f = (generation: number, records: LogRecord[]): CommitFactV2 => ({
    generation,
    timestamp: 1_700_000_000_000 + generation,
    records
  })
  return [
    f(1, [{ type: 'log.genesis', idSpaceWidth: 64, brainId: BRAIN, createdAt: 1_700_000_000_000 }]),
    f(2, [{ type: 'noun.afterImage', id: A, entityInt: 1n, metadata: { name: 'alpha', rank: 1 }, vectorLeg: vec(1) }]),
    f(3, [
      { type: 'noun.afterImage', id: B, entityInt: 2n, metadata: { name: 'beta' }, vectorLeg: null },
      { type: 'embed.pending', id: B, enqueuedAt: 1_700_000_000_003 }
    ]),
    // A metadata-only update: the vector rides by reference to generation 2.
    f(4, [{ type: 'noun.afterImage', id: A, entityInt: 1n, metadata: { name: 'alpha', rank: 2 }, vectorLeg: { sameAsGeneration: 2 } }]),
    // B's deferred vector lands.
    f(5, [{ type: 'embed.landed', id: B, vector: vec(9) }]),
    // A relationship.
    f(6, [{ type: 'verb.afterImage', id: V, verbInt: 3n, metadata: { w: 0.5 }, vectorLeg: null, verb: 'relatedTo', sourceId: A, sourceInt: 1n, targetId: B, targetInt: 2n }]),
    // C exists briefly…
    f(7, [{ type: 'noun.afterImage', id: C, entityInt: 4n, metadata: { name: 'gamma' }, vectorLeg: vec(7) }]),
    // …and is tombstoned (masking must hold in the fold).
    f(8, [{ type: 'noun.tombstone', id: C }]),
    // An all-deduped batch: a real generation with zero records.
    f(9, [])
  ]
}

/** Build the golden segment: v2 header + sealed frame group. */
function goldenSegment(): Uint8Array {
  // Single-hop law: generation 2 carried A's inline vector (5 carries B's
  // via embed.landed); the ref in generation 4 must verify against it.
  const inline = new Set([2, 5, 7])
  const frames = goldenFacts().map((fact) => encodeFactV2(fact, { inlineVectorGenerations: inline }))
  const sealed = sealGroup(frames, 4096)
  const out = new Uint8Array(SEGMENT_HEADER_BYTES + sealed.length)
  out.set(encodeSegmentHeaderV2(1, 4096), 0)
  out.set(sealed, SEGMENT_HEADER_BYTES)
  return out
}

/**
 * THE FOLD LAW (shared with the native implementation, normative):
 * fold facts in generation order → per-id latest state with tombstone
 * masking; embed.landed applies the vector to the id's current state;
 * {sameAsGeneration: N} resolves to the inline vector the log carried at N;
 * verbs fold like nouns under their own ids. Digest = recordDigest (key-
 * sorted JSON sha256) of the id-sorted state map.
 */
function foldGoldenLog(bytes: Uint8Array): string {
  const group = decodeGroupV2(bytes.slice(SEGMENT_HEADER_BYTES))
  const state = new Map<string, Record<string, unknown>>()
  const inlineVectorAt = new Map<number, number[]>()
  for (const fact of group.facts) {
    for (const rec of fact.records) {
      if (rec.type === 'noun.afterImage' || rec.type === 'verb.afterImage') {
        let vector: number[] | null = null
        if (Array.isArray(rec.vectorLeg)) {
          vector = rec.vectorLeg
          inlineVectorAt.set(fact.generation, vector)
        } else if (rec.vectorLeg && typeof rec.vectorLeg === 'object' && 'sameAsGeneration' in rec.vectorLeg) {
          vector = inlineVectorAt.get((rec.vectorLeg as { sameAsGeneration: number }).sameAsGeneration) ?? null
        }
        state.set(rec.id, {
          kind: rec.type === 'noun.afterImage' ? 'noun' : 'verb',
          int: (rec.type === 'noun.afterImage'
            ? (rec as { entityInt: bigint }).entityInt
            : (rec as { verbInt: bigint }).verbInt
          ).toString(),
          metadata: rec.metadata,
          vector,
          generation: fact.generation
        })
      } else if (rec.type === 'noun.tombstone' || rec.type === 'verb.tombstone') {
        state.delete(rec.id)
      } else if (rec.type === 'embed.landed') {
        const cur = state.get(rec.id)
        if (cur) state.set(rec.id, { ...cur, vector: rec.vector, generation: fact.generation })
        inlineVectorAt.set(fact.generation, rec.vector)
      }
      // embed.pending / genesis / blob / projection notes carry no fold state here.
    }
  }
  const sorted = [...state.entries()].sort(([x], [y]) => (x < y ? -1 : 1))
  return recordDigest(sorted)
}

// ── THE PINS ────────────────────────────────────────────────────────────────
// Byte-exact encode + semantics-exact fold. These literals are the contract.
const GOLDEN_BYTES_SHA256 = 'f898ed29f6f7d41135c6c85eb07725348b20cf8efec5f050ff50ad6d54a09dad'
const GOLDEN_FOLD_DIGEST = 'fad1b1d9865d6c9c84493c5481599ebd39b7ecf4cd203af4c435dfea7cd78ed4'

describe('golden-log fold conformance (brainy leg)', () => {
  it('the encoder reproduces the golden bytes exactly', () => {
    const seg = goldenSegment()
    expect(seg.length % 4096, 'sealed to the sector boundary (header excluded)').toBe(SEGMENT_HEADER_BYTES % 4096)
    expect(sha256(seg)).toBe(GOLDEN_BYTES_SHA256)
  })

  it('the fixture on disk is byte-identical (the shared artifact both readers consume)', () => {
    const seg = goldenSegment()
    if (!existsSync(FIXTURE)) {
      mkdirSync(dirname(FIXTURE), { recursive: true })
      writeFileSync(FIXTURE, seg)
    }
    const onDisk = new Uint8Array(readFileSync(FIXTURE))
    expect(sha256(onDisk), 'fixture bytes match the encoder').toBe(GOLDEN_BYTES_SHA256)
  })

  it('folding the golden log yields the pinned state digest', () => {
    expect(foldGoldenLog(goldenSegment())).toBe(GOLDEN_FOLD_DIGEST)
  })

  it('fold semantics spot-checks (human-readable guardrails beside the hash)', () => {
    const group = decodeGroupV2(goldenSegment().slice(SEGMENT_HEADER_BYTES))
    expect(group.facts.length, 'nine facts, pads invisible').toBe(9)
    const gens = group.facts.map((f) => f.generation)
    expect(gens).toEqual([1, 2, 3, 4, 5, 6, 7, 8, 9])
    expect(group.facts[8].records).toEqual([])
  })
})