import { describe, expect, test } from 'bun:test'
import { readFileSync } from 'node:fs'
import { join } from 'node:path'
import { PACK_BLOB_VERSION, decodePackBlob, isV2Envelope } from './pack-blob'

/**
 * BACKWARD-COMPAT FREEZE TESTS for the memory pack-blob envelope.
 *
 * Reads FROZEN envelope bytes committed under test/fixtures/compat/ and decodes
 * them with the CURRENT code. The pack-blob is the on-chain memory partition
 * (iNFT slot 0 / slot 3, pre-encryption plaintext). A non-additive change to
 * the envelope format would brick every existing agent's memory on the next
 * reprovision/restore, and no other test catches it because they all generate
 * their input with the current encoder.
 *
 * Fixtures produced once by test/fixtures/compat/__generate.ts; bytes immutable.
 * NEW envelope versions add a NEW fixture; never edit a frozen one.
 */
const FIXTURES = join(import.meta.dir, '../../../../test/fixtures/compat')

function fixture(name: string): Uint8Array {
  return new Uint8Array(readFileSync(join(FIXTURES, name)))
}

describe('pack-blob backward-compat (frozen fixtures)', () => {
  test('FROZEN v2 envelope is sniffed as v2 and decodes to the same files', () => {
    const bytes = fixture('pack-blob-v2.json')
    expect(isV2Envelope(bytes)).toBe(true)

    const blob = decodePackBlob(bytes)
    expect(blob.v).toBe(PACK_BLOB_VERSION)
    expect(blob.root).toContain('# MEMORY.md')
    expect(blob.root).toContain('frozen compat index')
    expect(blob.files['learned-frozen.md']).toContain('frozen for compat')
    expect(blob.files['operator-preferences.md']).toContain('dark mode')
    expect(Object.keys(blob.files).sort()).toEqual(['learned-frozen.md', 'operator-preferences.md'])
  })

  test('FROZEN legacy v1 markdown blob is NOT a v2 envelope (v1 fallthrough path stays live)', () => {
    const bytes = fixture('pack-blob-v1-legacy.md')
    // Pre-v0.24.0 stored slot 0/3 as raw markdown text. isV2Envelope must keep
    // returning false so callers fall through to the legacy single-file decode
    // instead of trying (and failing) to parse it as a JSON envelope.
    expect(isV2Envelope(bytes)).toBe(false)
    // And the raw text is recoverable verbatim (the v1 "decode" is identity).
    expect(new TextDecoder().decode(bytes)).toContain('legacy single-file markdown body')
  })

  test('FROZEN legacy v1 markdown blob throws if force-decoded as v2 (no silent corruption)', () => {
    const bytes = fixture('pack-blob-v1-legacy.md')
    expect(() => decodePackBlob(bytes)).toThrow()
  })
})