// ============================================================
// app.crypto.js — CRYPTO module (extracted from app.js, §3.1)
// ============================================================
//
// Loaded as a classic <script> BEFORE js/app.js (after js/argon2.js).
// Classic scripts share one global lexical environment, so the consts and
// functions declared here are visible to app.js exactly as when this lived
// inline in the monofile — no import/export, no bundler. Function bodies
// reference `state` (declared in app.js) and `NobleArgon2` (js/argon2.js);
// those resolve at call time (post-DOMContentLoaded), never at load time.
//
// Split rule: this file must load before app.js and must NOT redeclare any
// of app.js's top-level consts (a duplicate `const` across classic scripts
// throws "already declared"). See CLAUDE.md build pipeline notes.
//
// CRYPTO (preserved from legacy app.js — DO NOT TOUCH)

async function deriveKey(pwd, saltHex, iterations) {
    // Iterations parameter is the per-user value returned by the server in
    // the /login response (legacy users = 100000, modern = 600000). Falling
    // back to 100000 keeps backwards compatibility with old code paths that
    // didn't pass the value, but every new caller should pass it explicitly.
    iterations = iterations || 100000;
    const enc = new TextEncoder();
    const km = await crypto.subtle.importKey('raw', enc.encode(pwd), 'PBKDF2', false, ['deriveKey']);
    // saltHex is the same string that PHP/Delphi passed to PBKDF2 — use its bytes.
    const sb = enc.encode(saltHex);
    return crypto.subtle.deriveKey(
        { name: 'PBKDF2', salt: sb, iterations: iterations, hash: 'SHA-256' },
        km,
        { name: 'AES-GCM', length: 256 },
        true, ['encrypt', 'decrypt']
    );
}

// ---- Zero-knowledge auth helpers --------------------------------
//
// Single PBKDF2 → both outputs at once:
//   - cryptoKey: the AES-GCM key used to encrypt entries (= raw PBKDF2 bytes)
//   - verifier:  the same 32 bytes in hex form, sent to the server in place
//                of the plaintext master password. Server then SHA-256-wraps
//                it (HASH_ALGO_CURRENT) or compares directly (LEGACY) without
//                ever seeing the plaintext.
//
// Doing it together avoids running PBKDF2 twice. computeVerifier() is for
// places that only need the hex (re-auth, current-pw verification on change,
// etc.) and skips the AES-GCM importKey work.

function bytesToHex(arr) {
    if (arr instanceof ArrayBuffer) arr = new Uint8Array(arr);
    let hex = '';
    for (let i = 0; i < arr.length; i++)
        hex += arr[i].toString(16).padStart(2, '0');
    return hex;
}

// Decoupled-verifier scheme markers + domain separator. When the account's
// hash_algo ends in '-v2', the verifier sent to the server is a one-way
// SHA-256 of the key hex (domain-separated), NOT the key hex itself — so
// intercepting the /login body no longer hands over the AES vault key.
// The AES key (cryptoKey) is ALWAYS the raw KDF output regardless of algo, so
// entries stay decryptable and legacy accounts are unaffected.
const HASH_ALGO_V2 = 'pbkdf2-sha256-v2';         // PBKDF2 KDF + decoupled verifier
const HASH_ALGO_ARGON2 = 'argon2id-v2';          // Argon2id KDF + decoupled verifier
const AUTH_VERIFIER_DOMAIN = 'pmserver/auth-verifier/v2';

// OWASP-recommended Argon2id baseline (m = 19 MiB, t = 2, p = 1). Stored
// per-account (like kdfIterations for PBKDF2) so it's tunable later without
// breaking existing accounts. dkLen is fixed at 32 (AES-256 key).
const ARGON2_DEFAULT_PARAMS = { m: 19456, t: 2, p: 1 };

// True for any scheme whose transmitted verifier is decoupled from the key
// (all '-v2' markers: pbkdf2-sha256-v2, argon2id-v2). endsWith keeps it
// future-proof for any later '-v2' KDF.
function isDecoupledVerifierAlgo(algo) {
    return typeof algo === 'string' && algo.endsWith('-v2');
}

async function sha256Hex(str) {
    const buf = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(str));
    return bytesToHex(new Uint8Array(buf));
}

// Map the raw KDF key hex → the verifier to transmit, per account algo.
// Decoupled ('-v2') → domain-separated SHA-256. Anything else → the key hex
// verbatim (legacy behaviour, unchanged for existing pre-v2 accounts).
async function verifierFromKeyHex(keyHex, algo) {
    if (isDecoupledVerifierAlgo(algo)) return await sha256Hex(keyHex + AUTH_VERIFIER_DOMAIN);
    return keyHex;
}

// Derive the 32 raw key bytes from the master password, per account KDF.
// Argon2id (memory-hard) for argon2id-* accounts, else PBKDF2-SHA256. Both
// feed the salt HEX STRING's UTF-8 bytes as the salt (historical quirk kept
// identical across KDFs so a given pw+salt maps to one deterministic key).
async function deriveKeyBytes(pwd, saltHex, algo, iterations, argonParams) {
    const enc = new TextEncoder();
    if (algo === HASH_ALGO_ARGON2) {
        if (typeof NobleArgon2 === 'undefined' || !NobleArgon2 || !NobleArgon2.argon2idAsync)
            throw new Error('Argon2 library not loaded (js/argon2.js missing?)');
        const p = argonParams || ARGON2_DEFAULT_PARAMS;
        // Async variant yields to the event loop periodically so the unlock
        // spinner keeps animating instead of freezing ~0.65 s. Same result as
        // the sync argon2id (both RFC-9106-verified).
        return await NobleArgon2.argon2idAsync(enc.encode(pwd), enc.encode(saltHex),
            { t: p.t, m: p.m, p: p.p, dkLen: 32, version: 0x13 });
    }
    // PBKDF2-SHA256 (default / legacy).
    iterations = iterations || 100000;
    const km = await crypto.subtle.importKey(
        'raw', enc.encode(pwd), 'PBKDF2', false, ['deriveBits']);
    const bits = await crypto.subtle.deriveBits(
        { name: 'PBKDF2', salt: enc.encode(saltHex),
          iterations: iterations, hash: 'SHA-256' },
        km, 256);   // 256 bits = 32 bytes — matches PBKDF2_SHA256_Hex output
    return new Uint8Array(bits);
}

async function deriveKeyAndVerifier(pwd, saltHex, iterations, algo, argonParams) {
    const keyBytes  = await deriveKeyBytes(pwd, saltHex, algo, iterations, argonParams);
    const cryptoKey = await crypto.subtle.importKey(
        'raw', keyBytes, { name: 'AES-GCM' }, true, ['encrypt', 'decrypt']);
    const verifier  = await verifierFromKeyHex(bytesToHex(keyBytes), algo);
    return { cryptoKey, verifier };
}

async function computeVerifier(pwd, saltHex, iterations, algo, argonParams) {
    const r = await deriveKeyAndVerifier(pwd, saltHex, iterations, algo, argonParams);
    return r.verifier;
}

async function encryptPwd(plain) {
    const iv = crypto.getRandomValues(new Uint8Array(12));
    const enc = await crypto.subtle.encrypt(
        { name: 'AES-GCM', iv }, state.cryptoKey,
        new TextEncoder().encode(plain)
    );
    return {
        encrypted: btoa(String.fromCharCode(...new Uint8Array(enc))),
        iv:        btoa(String.fromCharCode(...iv)),
    };
}

async function decryptPwd(encB64, ivB64) {
    try {
        const enc = Uint8Array.from(atob(encB64), c => c.charCodeAt(0));
        const iv  = Uint8Array.from(atob(ivB64),  c => c.charCodeAt(0));
        const dec = await crypto.subtle.decrypt({ name: 'AES-GCM', iv }, state.cryptoKey, enc);
        return new TextDecoder().decode(dec);
    } catch (e) {
        return '[ERROR]';
    }
}

async function persistCryptoKey() {
    const raw = await crypto.subtle.exportKey('raw', state.cryptoKey);
    sessionStorage.setItem('cryptoKey', btoa(String.fromCharCode(...new Uint8Array(raw))));
}

async function restoreCryptoKey() {
    const saved = sessionStorage.getItem('cryptoKey');
    if (!saved) return false;
    try {
        const raw = Uint8Array.from(atob(saved), c => c.charCodeAt(0));
        state.cryptoKey = await crypto.subtle.importKey(
            'raw', raw, { name: 'AES-GCM' }, false, ['encrypt', 'decrypt']
        );
        return true;
    } catch (e) {
        return false;
    }
}