import { existsSync, mkdirSync, readFileSync, renameSync, writeFileSync } from 'node:fs';
import { homedir } from 'node:os';
import { join } from 'node:path';

const CONFIG_DIR = join(homedir(), '.qwen-s');
const CONFIG_FILE = join(CONFIG_DIR, 'config.json');

interface ScannerConfig {
	api_key?: unknown;
}

function readConfig(): ScannerConfig {
	if (!existsSync(CONFIG_FILE)) {
		return {};
	}

	try {
		const raw = readFileSync(CONFIG_FILE, 'utf8');
		const parsed = JSON.parse(raw) as ScannerConfig;
		if (parsed !== null && typeof parsed === 'object') {
			return parsed;
		}
	} catch {
		// If config is corrupted, treat as empty and allow overwriting.
	}

	return {};
}

function writeConfigAtomic(config: ScannerConfig): void {
	const payload = `${JSON.stringify(config, null, 2)}\n`;
	const tempFile = join(CONFIG_DIR, `config.${process.pid}.tmp`);
	writeFileSync(tempFile, payload, { encoding: 'utf8', mode: 0o600 });
	renameSync(tempFile, CONFIG_FILE);
}

export function saveApiKey(key: string): void {
	const normalized = key.trim();
	if (normalized.length === 0) {
		throw new Error('API key cannot be empty.');
	}

	mkdirSync(CONFIG_DIR, { recursive: true });
	const current = readConfig();
	const next: ScannerConfig = {
		...current,
		api_key: normalized,
	};

	writeConfigAtomic(next);
}

export function loadApiKey(): string | null {
	const config = readConfig();
	if (typeof config.api_key !== 'string') {
		return null;
	}

	const normalized = config.api_key.trim();
	return normalized.length > 0 ? normalized : null;
}