import { promises as fs } from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { createLogger } from './logger.js';

const log = createLogger('tesla-token-store');

export interface TeslaTokens {
  accessToken: string;
  refreshToken: string;
  expiresAt: number;       // ms epoch
  scope: string;
  // Optional cached vehicle metadata so we don't have to refetch on every call.
  vehicleId?: string;       // numeric id_s used in Fleet API URLs
  vin?: string;
  carType?: string;         // e.g. modely
  trimBadging?: string;     // e.g. lrawd
  connectedAt: number;
}

interface Store {
  get(userId: string): Promise<TeslaTokens | null>;
  set(userId: string, tokens: TeslaTokens): Promise<void>;
  remove(userId: string): Promise<void>;
}

// File-backed store. Falls back to /app/data when running under Dokku (we
// will mount a Dokku storage volume on /app/data), or to ./data in dev.
const __dirname = path.dirname(fileURLToPath(import.meta.url));
const dataDir = process.env.TESLA_TOKEN_DIR
  || (process.env.NODE_ENV === 'production' ? '/app/data' : path.resolve(__dirname, '../../data'));
const tokenFile = path.join(dataDir, 'tesla-tokens.json');

let cache: Record<string, TeslaTokens> = {};
let loaded = false;
let writeLock: Promise<unknown> = Promise.resolve();

async function load(): Promise<void> {
  if (loaded) return;
  try {
    await fs.mkdir(dataDir, { recursive: true });
    const raw = await fs.readFile(tokenFile, 'utf8');
    cache = JSON.parse(raw);
    log.info({ file: tokenFile, users: Object.keys(cache).length }, 'Loaded Tesla tokens');
  } catch (err: any) {
    if (err.code !== 'ENOENT') log.warn({ err: String(err) }, 'Failed to load Tesla tokens — starting empty');
    cache = {};
  }
  loaded = true;
}

async function persist(): Promise<void> {
  // Serialise writes so concurrent set/remove calls don't race.
  writeLock = writeLock
    .then(async () => {
      await fs.mkdir(dataDir, { recursive: true });
      await fs.writeFile(tokenFile, JSON.stringify(cache, null, 2));
    })
    .catch(err => log.error({ err: String(err) }, 'Failed to persist Tesla tokens'));
  await writeLock;
}

export const teslaTokenStore: Store = {
  async get(userId) {
    await load();
    return cache[userId] || null;
  },
  async set(userId, tokens) {
    await load();
    cache[userId] = tokens;
    await persist();
  },
  async remove(userId) {
    await load();
    delete cache[userId];
    await persist();
  },
};