import { env } from '$env/dynamic/private';
import { dev } from '$app/environment';

export interface Config {
	storage: 'local' | 'hf';
	hfToken: string;
	hfBucket: `buckets/${string}`;
	/** Directory inside the bucket that this deployment owns; '' means the bucket root. */
	hfPrefix: string;
	localDataDir: string;
	sessionSecret: string;
	currency: string;
	compactionIntervalMs: number;
}

function required(name: string, value: string | undefined): string {
	if (!value) throw new Error(`Missing required environment variable ${name}`);
	return value;
}

export function loadConfig(): Config {
	const storage = (env.STORAGE ?? (dev ? 'local' : 'hf')) as Config['storage'];
	if (storage !== 'local' && storage !== 'hf') throw new Error(`STORAGE must be 'local' or 'hf', got '${storage}'`);
	const sessionSecret = env.SESSION_SECRET ?? (dev ? 'dev-only-session-secret-do-not-use-in-prod' : undefined);
	const hfBucket = storage === 'hf' ? required('HF_BUCKET', env.HF_BUCKET) : '';
	if (storage === 'hf' && !hfBucket.startsWith('buckets/')) throw new Error('HF_BUCKET must look like buckets/<namespace>/<name>');
	const secret = required('SESSION_SECRET', sessionSecret);
	if (!dev && secret.length < 32) throw new Error('SESSION_SECRET must be at least 32 characters in production');
	const compactionIntervalMs = Number(env.COMPACTION_INTERVAL_MS ?? 3_600_000);
	if (!Number.isFinite(compactionIntervalMs) || compactionIntervalMs < 60_000)
		throw new Error('COMPACTION_INTERVAL_MS must be a number of milliseconds ≥ 60000');
	const currency = env.CURRENCY ?? 'USD';
	if (!/^[A-Z]{3}$/.test(currency)) throw new Error('CURRENCY must be a 3-letter uppercase ISO 4217 code');
	return {
		storage,
		hfToken: storage === 'hf' ? required('HF_TOKEN', env.HF_TOKEN) : '',
		hfBucket: hfBucket as `buckets/${string}`,
		hfPrefix: (env.HF_PREFIX ?? '').replace(/^\/+|\/+$/g, ''),
		localDataDir: env.LOCAL_DATA_DIR ?? '.data',
		sessionSecret: secret,
		currency,
		compactionIntervalMs
	};
}