// Crypto primitives. Mirrors client-app/lib/crypto.ts function-for-
// function (same signatures, same hex/base64 formats on the wire) so
// the two clients decrypt each other's envelopes and sign txs the node
// accepts interchangeably.
//
// The only real difference from mobile: we don't need expo-crypto — the
// Electron renderer is a Chromium browser, so window.crypto.getRandomValues
// is always available and we just let tweetnacl pick it up on its own
// (tweetnacl auto-detects window.crypto when present).

import nacl from 'tweetnacl';
import { decodeUTF8, encodeUTF8 } from 'tweetnacl-util';
import type { KeyFile } from './types';

// ─── Hex / base64 ────────────────────────────────────────────────────────

export function hexToBytes(hex: string): Uint8Array {
  if (hex.length % 2 !== 0) throw new Error('odd hex length');
  const b = new Uint8Array(hex.length / 2);
  for (let i = 0; i < b.length; i++) b[i] = parseInt(hex.slice(i * 2, i * 2 + 2), 16);
  return b;
}
export function bytesToHex(b: Uint8Array): string {
  return Array.from(b).map(x => x.toString(16).padStart(2, '0')).join('');
}
export function bytesToBase64(b: Uint8Array): string {
  let s = '';
  for (let i = 0; i < b.length; i++) s += String.fromCharCode(b[i]);
  return btoa(s);
}
export function base64ToBytes(b64: string): Uint8Array {
  const bin = atob(b64.replace(/-/g, '+').replace(/_/g, '/'));
  const out = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
  return out;
}

// ─── Key generation ──────────────────────────────────────────────────────

export function generateKeyFile(): KeyFile {
  const sign = nacl.sign.keyPair();
  const box  = nacl.box.keyPair();
  return {
    pub_key:     bytesToHex(sign.publicKey),
    priv_key:    bytesToHex(sign.secretKey),
    x25519_pub:  bytesToHex(box.publicKey),
    x25519_priv: bytesToHex(box.secretKey),
  };
}

// ─── NaCl box (E2E messaging) ────────────────────────────────────────────

export function encryptMessage(
  plaintext: string,
  senderSecretHex: string,
  recipientPubHex: string,
): { nonce: string; ciphertext: string } {
  const nonce = nacl.randomBytes(nacl.box.nonceLength);
  const msg   = decodeUTF8(plaintext);
  const box   = nacl.box(msg, nonce, hexToBytes(recipientPubHex), hexToBytes(senderSecretHex));
  return { nonce: bytesToHex(nonce), ciphertext: bytesToHex(box) };
}

export function decryptMessage(
  ciphertextHex: string,
  nonceHex: string,
  senderPubHex: string,
  recipientSecHex: string,
): string | null {
  try {
    const plain = nacl.box.open(
      hexToBytes(ciphertextHex), hexToBytes(nonceHex),
      hexToBytes(senderPubHex),  hexToBytes(recipientSecHex),
    );
    return plain ? encodeUTF8(plain) : null;
  } catch {
    return null;
  }
}

// ─── Ed25519 signing ─────────────────────────────────────────────────────

export function signBase64(data: Uint8Array, privKeyHex: string): string {
  const sig = nacl.sign.detached(data, hexToBytes(privKeyHex));
  return bytesToBase64(sig);
}

// ─── Helpers ─────────────────────────────────────────────────────────────

export function shortAddr(hex: string, chars = 8): string {
  if (hex.length <= chars * 2 + 3) return hex;
  return `${hex.slice(0, chars)}…${hex.slice(-chars)}`;
}