/**
 * Backend registry -- creates and caches backend instances by type.
 */
import type { BackendType, CredentialBackend, VaultConfig } from "../types.js";
import { AgeBackend } from "./age-backend.js";
import { KeychainBackend } from "./keychain-backend.js";
import { PassthroughBackend } from "./passthrough-backend.js";

const instances = new Map<string, CredentialBackend>();

export function createBackend(
	type: BackendType,
	config: VaultConfig,
): CredentialBackend {
	const cacheKey = type;
	const cached = instances.get(cacheKey);
	if (cached) {
		return cached;
	}

	let backend: CredentialBackend;
	switch (type) {
		case "age":
			backend = new AgeBackend(config.age);
			break;
		case "keychain":
			backend = new KeychainBackend(config.keychain);
			break;
		case "passthrough":
			backend = new PassthroughBackend();
			break;
		default: {
			const exhaustive: never = type;
			throw new Error(`Unknown backend type: ${String(exhaustive)}`);
		}
	}

	instances.set(cacheKey, backend);
	return backend;
}

export function getPassthroughBackend(): CredentialBackend {
	return createBackend("passthrough", {
		backend: "passthrough",
		managedProviders: "all",
	});
}

/**
 * Clear cached backend instances (used on config change or reload).
 */
export function clearBackendCache(): void {
	instances.clear();
}