import type { IDnsProviderClient } from './interfaces.js';
import type {
  TDnsProviderType,
  TDnsProviderCredentials,
} from '../../../ts_interfaces/data/dns-provider.js';
import { CloudflareDnsProvider } from './cloudflare.provider.js';

/**
 * Instantiate a runtime DNS provider client from a stored DnsProviderDoc.
 *
 * @throws if the provider type is not supported.
 *
 * ## Adding a new provider (e.g. Route53)
 *
 * 1. **Type union** — extend `TDnsProviderType` in
 *    `ts_interfaces/data/dns-provider.ts` (e.g. `'cloudflare' | 'route53'`).
 * 2. **Credentials interface** — add `IRoute53Credentials` and append it to
 *    the `TDnsProviderCredentials` discriminated union.
 * 3. **Descriptor** — append a new entry to `dnsProviderTypeDescriptors` so
 *    the OpsServer UI picks up the new type and renders the right credential
 *    form fields automatically.
 * 4. **Provider class** — create `ts/dns/providers/route53.provider.ts`
 *    implementing `IDnsProviderClient`.
 * 5. **Factory case** — add a new `case 'route53':` below. The
 *    `_exhaustive: never` line will fail to compile until you do.
 * 6. **Index** — re-export the new class from `ts/dns/providers/index.ts`.
 */
export function createDnsProvider(
  type: TDnsProviderType,
  credentials: TDnsProviderCredentials,
): IDnsProviderClient {
  switch (type) {
    case 'cloudflare': {
      if (credentials.type !== 'cloudflare') {
        throw new Error(
          `createDnsProvider: type mismatch — provider type is 'cloudflare' but credentials.type is '${credentials.type}'`,
        );
      }
      return new CloudflareDnsProvider(credentials.apiToken);
    }
    case 'dcrouter': {
      // The built-in DcRouter pseudo-provider has no runtime client — dcrouter
      // itself serves the records via the embedded smartdns.DnsServer. This
      // case exists only to satisfy the exhaustive switch; it should never
      // actually run because the handler layer rejects any CRUD that would
      // result in a DnsProviderDoc with type: 'dcrouter'.
      throw new Error(
        `createDnsProvider: 'dcrouter' is a built-in pseudo-provider — no runtime client exists. ` +
          `This call indicates a DnsProviderDoc with type: 'dcrouter' was persisted, which should never happen.`,
      );
    }
    default: {
      // If you see a TypeScript error here after extending TDnsProviderType,
      // add a `case` for the new type above. The `never` enforces exhaustiveness.
      const _exhaustive: never = type;
      throw new Error(`createDnsProvider: unsupported provider type: ${_exhaustive}`);
    }
  }
}