import fs from 'node:fs';
import path from 'node:path';
import { x25519, b64 } from './crypto.js';

export interface ChannelKeys {
  pub: string;
  priv: string;
}

/** Fresh channel x25519 keypair — generated by the channel's first user. */
export function newChannelKeypair(): ChannelKeys {
  const priv = x25519.utils.randomPrivateKey();
  return { pub: b64(x25519.getPublicKey(priv)), priv: b64(priv) };
}

/** Channels file: { "<channel>": { "pub": "<b64>", "priv": "<b64>" } }.
 *  Missing or invalid file = no channels. */
export function loadChannelKeys(file: string): Record<string, ChannelKeys> {
  try {
    const raw = JSON.parse(fs.readFileSync(file, 'utf8')) as Record<string, Partial<ChannelKeys>>;
    const out: Record<string, ChannelKeys> = {};
    for (const [name, keys] of Object.entries(raw)) {
      if (typeof keys?.pub === 'string' && typeof keys?.priv === 'string') {
        out[name] = { pub: keys.pub, priv: keys.priv };
      }
    }
    return out;
  } catch {
    return {};
  }
}

/** Read-modify-write: keeps the other channels; creates the parent dir
 *  (e.g. ~/.dap) on demand. */
export function persistChannelKeys(file: string, name: string, keys: ChannelKeys): void {
  const all = loadChannelKeys(file);
  all[name] = keys;
  fs.mkdirSync(path.dirname(file), { recursive: true });
  fs.writeFileSync(file, JSON.stringify(all, null, 2) + '\n');
}