/**
 * B7 · unit tests for the relay-side DPoP subprotocol decoder (`extractDpopProofFromSubprotocols`).
 * The browser (relay-web) offers the DPoP proof as an extra `term.dpop.<b64u(proofJws)>` entry on
 * the WS upgrade because native WebSocket cannot set request headers. These tests pin the wire
 * contract (valid decodes; absent → null; malformed → null, fail-closed) against the SAME isomorphic
 * base64url helper relay-web encodes with (relay-contracts), so the two sides agree byte-for-byte.
 */
import { describe, it, expect } from 'vitest'
import { encodeBase64UrlString } from 'relay-contracts'
import {
  extractDpopProofFromSubprotocols,
  DPOP_SUBPROTOCOL_PREFIX,
} from '../src/servers/dpop-subprotocol.js'
import { APP_SUBPROTOCOL, TOKEN_SUBPROTOCOL_PREFIX } from 'relay-contracts'

/** Build the wire entry exactly as relay-web `encodeDpopSubprotocol` does. */
function dpopEntry(proofJws: string): string {
  return DPOP_SUBPROTOCOL_PREFIX + encodeBase64UrlString(proofJws)
}

// A representative three-part DPoP proof JWS (header.payload.sig) — content is opaque to the decoder.
const PROOF = 'eyJhbGciOiJFZERTQSJ9.eyJodHUiOiJodHRwczovL2FsaWNlL3dzIn0.c2ln'

describe('extractDpopProofFromSubprotocols — valid', () => {
  it('decodes a term.dpop.<b64u> entry back to the exact proof JWS', () => {
    const subprotocols = [APP_SUBPROTOCOL, dpopEntry(PROOF)]
    expect(extractDpopProofFromSubprotocols(subprotocols)).toBe(PROOF)
  })

  it('finds the DPoP entry regardless of position (after app + token entries)', () => {
    const subprotocols = [
      APP_SUBPROTOCOL,
      TOKEN_SUBPROTOCOL_PREFIX + encodeBase64UrlString('v4.public.raw-token'),
      dpopEntry(PROOF),
    ]
    expect(extractDpopProofFromSubprotocols(subprotocols)).toBe(PROOF)
  })
})

describe('extractDpopProofFromSubprotocols — absent → null', () => {
  it('returns null when no term.dpop. entry is present', () => {
    expect(extractDpopProofFromSubprotocols([APP_SUBPROTOCOL])).toBeNull()
  })

  it('returns null for an empty list', () => {
    expect(extractDpopProofFromSubprotocols([])).toBeNull()
  })

  it('returns null when the prefix is present but the payload is empty', () => {
    expect(extractDpopProofFromSubprotocols([DPOP_SUBPROTOCOL_PREFIX])).toBeNull()
  })
})

describe('extractDpopProofFromSubprotocols — malformed → null (fail-closed)', () => {
  it('returns null for a non-base64url payload (illegal characters)', () => {
    expect(extractDpopProofFromSubprotocols([DPOP_SUBPROTOCOL_PREFIX + 'not*base64url!'])).toBeNull()
  })

  it('returns null for base64url bytes that are not valid UTF-8', () => {
    // 0xFF 0xFE is not a valid UTF-8 sequence; base64url of those two bytes is "__4".
    expect(extractDpopProofFromSubprotocols([DPOP_SUBPROTOCOL_PREFIX + '__4'])).toBeNull()
  })
})