#!/usr/bin/env node
// Protocol-level stand-in for the companion app (mobile/claude.md's real
// target — this is not a preview of it, per the run-flow plan's explicit
// scope note). Drives the companion's real cryptographic and network
// responsibilities against the real server and a real running extension,
// so the run flow can be verified end-to-end without the companion app
// existing yet — same "curl/Puppeteer instead of mocks" approach used
// throughout this project.
//
// Subcommands, in increasing order of manual effort:
//
//   node companion-harness.mjs run <signed_token> [username] [password]
//     The easy path for manual testing. Does the key exchange, prints the
//     PIN, then polls interfaces.md's PIN confirmation endpoint — the real
//     signal, not a human keypress standing in for it — before delivering
//     a credential (defaults: alice@example.com / hunter2). One paste, no
//     keypress needed.
//
//   node companion-harness.mjs key-exchange <signed_token>
//   node companion-harness.mjs deliver-credential <runId> <runKeyB64> <username> <password>
//     The two steps split apart, for scripted/automated use.
//
// This is a real two-way handshake now, not the companion proceeding on
// its own schedule: the extension posts its confirmation when the user
// clicks Confirm, and the companion (real or, here, this harness) is
// expected to wait for it before it ever selects/sends a credential —
// `run` above does exactly that via waitForPinConfirmation(). Calling
// `deliver-credential` directly, without confirmation ever having been
// posted, is still possible (nothing here stops you) but the extension
// will just discard it — the actual gate lives there, not in this script.

import { readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { webcrypto } from 'node:crypto';
import { Agent, setGlobalDispatcher } from 'undici';
import { ed25519, x25519 } from '@noble/curves/ed25519.js';
import { ml_kem768 } from '@noble/post-quantum/ml-kem.js';
import canonicalize from 'canonicalize';

const __dirname = dirname(fileURLToPath(import.meta.url));

const API_BASE = process.env.LOCQR_API_BASE ?? 'https://api.locqr.dev:3000';
// dev/keys/ed25519-public.b64 — same pinned dev constant compiled into the
// extension (crypto.md's ED25519_PUBLIC_KEY_B64); must match or every
// signature check below fails.
const ED25519_PUBLIC_KEY_B64 = 'Z9ppr33AB5gznf-mQU2F9Y3E-MEoNcGHtmlh7rzaTh4';
// interfaces.md: 30s clock-skew leeway past expires_at is the only clock
// tolerance in the protocol.
const EXPIRY_LEEWAY_SECONDS = 30;

// Trust the local mkcert CA (dev.md) for the harness's own TLS connections —
// Node doesn't consult the system/NSS trust stores the browsers use.
setGlobalDispatcher(new Agent({ connect: { ca: readFileSync(join(__dirname, '..', 'dev', 'certs', 'rootCA.pem')) } }));

function b64urlDecode(s) {
    return new Uint8Array(Buffer.from(s, 'base64url'));
}

function b64urlEncode(bytes) {
    return Buffer.from(bytes).toString('base64url');
}

function concat(...parts) {
    const total = parts.reduce((n, p) => n + p.length, 0);
    const out = new Uint8Array(total);
    let offset = 0;
    for (const p of parts) {
        out.set(p, offset);
        offset += p.length;
    }
    return out;
}

async function hkdfSha256(ikm, salt, info, lengthBytes) {
    const key = await webcrypto.subtle.importKey('raw', ikm, 'HKDF', false, ['deriveBits']);
    const bits = await webcrypto.subtle.deriveBits(
        { name: 'HKDF', hash: 'SHA-256', salt, info: new TextEncoder().encode(info) },
        key,
        lengthBytes * 8,
    );
    return new Uint8Array(bits);
}

// crypto.md: run_key = HKDF-SHA256(x25519_shared || kem_shared_secret, salt=runId_utf8, info="locqr-run-key-v1", 32).
async function deriveRunKey(x25519Shared, kemSharedSecret, runId) {
    const ikm = concat(x25519Shared, kemSharedSecret);
    const salt = new TextEncoder().encode(runId);
    return hkdfSha256(ikm, salt, 'locqr-run-key-v1', 32);
}

// mobile/claude.md: PIN = HKDF-SHA256(run_key, salt=[], info="locqr-pin-v1", 4) -> big-endian uint32 -> mod 1e6 -> zero-padded.
// Must match extension/src/background/crypto.ts's derivePin() exactly, or the two sides' PINs never agree.
async function derivePin(runKey) {
    const bits = await hkdfSha256(runKey, new Uint8Array(0), 'locqr-pin-v1', 4);
    const value = new DataView(bits.buffer, bits.byteOffset, bits.byteLength).getUint32(0, false);
    return (value % 1_000_000).toString().padStart(6, '0');
}

async function sha256(...parts) {
    const digest = await webcrypto.subtle.digest('SHA-256', concat(...parts));
    return new Uint8Array(digest);
}

function bytesEqual(a, b) {
    return a.length === b.length && a.every((v, i) => v === b[i]);
}

async function postRelay(runId, type, payloadB64) {
    const response = await fetch(`${API_BASE}/run/relay/${runId}`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ type, payload_b64: payloadB64 }),
    });
    if (!response.ok) {
        throw new Error(`POST /run/relay/${runId} (${type}) failed: ${response.status}`);
    }
}

async function keyExchange(signedToken) {
    const envelope = JSON.parse(Buffer.from(signedToken, 'base64url').toString('utf8'));
    const { v, runId, url, expires_at: expiresAt, alpha_hash: alphaHashB64, sig } = envelope;

    if (v !== 1) throw new Error(`unsupported token version: ${v}`);

    // interfaces.md: signed payload is the envelope minus `sig`, JCS-canonicalised.
    const payload = { v, runId, url, expires_at: expiresAt, alpha_hash: alphaHashB64 };
    const signatureValid = ed25519.verify(b64urlDecode(sig), Buffer.from(canonicalize(payload), 'utf8'), b64urlDecode(ED25519_PUBLIC_KEY_B64));
    if (!signatureValid) throw new Error('token_signature_invalid');

    const nowSeconds = Date.now() / 1000;
    if (nowSeconds > expiresAt + EXPIRY_LEEWAY_SECONDS) throw new Error('ttl_expired');

    const bundleResponse = await fetch(`${API_BASE}/run/bundle/${runId}`);
    if (!bundleResponse.ok) throw new Error(`bundle_consumed_or_expired (${bundleResponse.status})`);
    const { x25519_pubkey: x25519PubB64, kem_pubkey: kemPubB64 } = await bundleResponse.json();

    const extensionX25519Pub = b64urlDecode(x25519PubB64);
    const extensionKemPub = b64urlDecode(kemPubB64);

    const recomputedAlphaHash = await sha256(extensionX25519Pub, extensionKemPub);
    if (!bytesEqual(recomputedAlphaHash, b64urlDecode(alphaHashB64))) throw new Error('alpha_hash_mismatch');

    const companionX25519 = x25519.keygen();
    const x25519Shared = x25519.getSharedSecret(companionX25519.secretKey, extensionX25519Pub);

    const { cipherText: kemCiphertext, sharedSecret: kemSharedSecret } = ml_kem768.encapsulate(extensionKemPub);

    const runKey = await deriveRunKey(x25519Shared, kemSharedSecret, runId);
    const pin = await derivePin(runKey);

    await postRelay(runId, 'kem_ciphertext', b64urlEncode(concat(companionX25519.publicKey, kemCiphertext)));

    return { runId, pin, runKey: b64urlEncode(runKey) };
}

async function deliverCredential(runId, runKeyB64, username, password) {
    const runKey = b64urlDecode(runKeyB64);
    const nonce = webcrypto.getRandomValues(new Uint8Array(12));
    const plaintext = new TextEncoder().encode(JSON.stringify({ username, password }));

    const key = await webcrypto.subtle.importKey('raw', runKey, 'AES-GCM', false, ['encrypt']);
    const ciphertextAndTag = new Uint8Array(await webcrypto.subtle.encrypt({ name: 'AES-GCM', iv: nonce }, key, plaintext));

    await postRelay(runId, 'credential', b64urlEncode(concat(nonce, ciphertextAndTag)));
}

const CONFIRMATION_POLL_INTERVAL_MS = 1000;
const CONFIRMATION_POLL_TIMEOUT_MS = 180_000; // generous safety net — the extension's own pin_ttl alarm is the real, authoritative deadline

/**
 * Polls interfaces.md's PIN confirmation endpoint rather than trusting a
 * human keypress to mean "I've confirmed and the browser has processed
 * it" — those aren't the same thing (a click can be sent and still not
 * have landed yet, e.g. a slow service worker wake). This waits for the
 * real signal instead of a proxy for it.
 */
async function waitForPinConfirmation(runId) {
    const deadline = Date.now() + CONFIRMATION_POLL_TIMEOUT_MS;
    while (Date.now() < deadline) {
        const response = await fetch(`${API_BASE}/run/relay/${runId}/confirm`);
        if (response.ok) {
            const { confirmed } = await response.json();
            if (confirmed) return;
        }
        await new Promise((resolve) => setTimeout(resolve, CONFIRMATION_POLL_INTERVAL_MS));
    }
    throw new Error('timed out waiting for PIN confirmation from the browser');
}

async function runInteractive(signedToken, username, password) {
    const { runId, pin, runKey } = await keyExchange(signedToken);

    console.log(`\nPIN: ${pin}`);
    console.log('Compare that against the PIN shown in the extension popup, then click Confirm there.');
    console.log('Waiting for the browser to confirm...');

    await waitForPinConfirmation(runId);
    console.log('Confirmed by the browser.');

    await deliverCredential(runId, runKey, username, password);
    console.log(`Delivered credential (${username} / ${password}). The popup should now show "Signed in".`);
}

async function main() {
    const [command, ...args] = process.argv.slice(2);

    if (command === 'run') {
        const [signedToken, username = 'alice@example.com', password = 'hunter2'] = args;
        if (!signedToken) throw new Error('usage: companion-harness.mjs run <signed_token> [username] [password]');
        await runInteractive(signedToken, username, password);
        return;
    }

    if (command === 'key-exchange') {
        const [signedToken] = args;
        if (!signedToken) throw new Error('usage: companion-harness.mjs key-exchange <signed_token>');
        console.log(JSON.stringify(await keyExchange(signedToken)));
        return;
    }

    if (command === 'deliver-credential') {
        const [runId, runKeyB64, username, password] = args;
        if (!runId || !runKeyB64 || !username || !password) {
            throw new Error('usage: companion-harness.mjs deliver-credential <runId> <runKeyB64> <username> <password>');
        }
        await deliverCredential(runId, runKeyB64, username, password);
        console.log(JSON.stringify({ ok: true }));
        return;
    }

    throw new Error(`unknown command: ${command ?? '(none)'} — expected "run", "key-exchange", or "deliver-credential"`);
}

main().catch((err) => {
    console.error(err instanceof Error ? err.message : err);
    process.exitCode = 1;
});