import { describe, expect, it } from 'vitest'
import type { AeadAlg, E2EEnvelope } from 'relay-contracts'
import { importAeadKey } from '../src/aead.js'
import { MAX_FRAME_BYTES, decodeEnvelope, encodeEnvelope, nonceForSeq } from '../src/envelope.js'
import { EnvelopeFormatError } from '../src/errors.js'
import { sealFrame } from '../src/session.js'
import { bytesToHex, hexToBytes } from './helpers.js'
import envVector from './vectors/envelope.json' with { type: 'json' }

function sample(seq: bigint): E2EEnvelope {
  return {
    seq,
    nonce: new Uint8Array([1, 2, 3, 4]),
    ciphertext: new Uint8Array([9, 8, 7]),
    tag: new Uint8Array(16).fill(0xbb),
  }
}

describe('T3 envelope codec (frozen relay-contracts shape, re-exported)', () => {
  it('KAT: frozen vector encodes to exact wire bytes and decodes back', () => {
    const key = importAeadKey(new Uint8Array(32).fill(5), 'aes-256-gcm', 'c2h')
    const env = sealFrame(key, BigInt(envVector.seq), new TextEncoder().encode('wire codec vector'))
    expect(bytesToHex(encodeEnvelope(env))).toBe(envVector.wire)
    const decoded = decodeEnvelope(hexToBytes(envVector.wire))
    expect(bytesToHex(decoded.nonce)).toBe(envVector.nonce)
    expect(bytesToHex(decoded.ciphertext)).toBe(envVector.ciphertext)
    expect(bytesToHex(decoded.tag)).toBe(envVector.tag)
  })

  it('round-trips and preserves seq as bigint past 2^53 (no float truncation)', () => {
    const env = sample(2n ** 63n - 1n)
    const decoded = decodeEnvelope(encodeEnvelope(env))
    expect(decoded.seq).toBe(2n ** 63n - 1n)
    expect(decoded).toEqual(env)
  })

  it('deterministic nonce = left-zero-padded big-endian seq', () => {
    const gcm = nonceForSeq(1n, 'aes-256-gcm' as AeadAlg)
    expect(gcm.length).toBe(12)
    expect(gcm[11]).toBe(1)
    expect(gcm.slice(0, 11).every((b) => b === 0)).toBe(true)
    const xchacha = nonceForSeq(258n, 'xchacha20-poly1305' as AeadAlg)
    expect(xchacha.length).toBe(24)
    expect(xchacha[23]).toBe(2)
    expect(xchacha[22]).toBe(1)
  })

  it('negative: truncated buffer / length mismatch → EnvelopeFormatError', () => {
    expect(() => decodeEnvelope(new Uint8Array(5))).toThrow(EnvelopeFormatError)
    const wire = encodeEnvelope(sample(0n))
    expect(() => decodeEnvelope(wire.slice(0, wire.length - 1))).toThrow(EnvelopeFormatError)
    const trailing = new Uint8Array(wire.length + 1)
    trailing.set(wire)
    expect(() => decodeEnvelope(trailing)).toThrow(EnvelopeFormatError)
  })

  it('security: a frame larger than the hard cap is rejected before allocation', () => {
    expect(() => decodeEnvelope(new Uint8Array(MAX_FRAME_BYTES + 1))).toThrow(EnvelopeFormatError)
  })
})
