server/hostValidation.ts

import type {BrokerStore} from './store.js';

export type HostValidationFailure = {
  status: number;
  message: string;
};

export type HostReadyOptions = {
  /** When set, host must be registered with this cluster model id. */
  requiredModel?: string;
  requiredModelLabel?: string;
};

const MISSING_HOST_MESSAGE =
  "Missing required field 'host'. Open the app in a browser and register a host id.";

export function parseHostField(body: {host?: string}): string | HostValidationFailure {
  if (!body?.host?.trim()) {
    return {status: 400, message: MISSING_HOST_MESSAGE};
  }

  return body.host.trim();
}

export function validateHostRegistered(
  store: BrokerStore,
  hostId: string,
): HostValidationFailure | null {
  if (store.getHost(hostId)) {
    return null;
  }

  return {
    status: 404,
    message: `Host '${hostId}' not found. Register it in the browser host page first.`,
  };
}

export function validateHostOnline(
  store: BrokerStore,
  hostId: string,
): HostValidationFailure | null {
  if (store.isHostOnline(hostId)) {
    return null;
  }

  return {
    status: 503,
    message: `Host '${hostId}' is offline. Keep the browser host tab open with the model loaded.`,
  };
}

export function validateHostModel(
  store: BrokerStore,
  hostId: string,
  requiredModel: string,
  requiredModelLabel: string,
): HostValidationFailure | null {
  const host = store.getHost(hostId);
  if (host?.model === requiredModel) {
    return null;
  }

  return {
    status: 400,
    message: `Host '${hostId}' is registered for '${host?.model ?? 'unknown'}', not ${requiredModelLabel}. Open the host page, select "${requiredModelLabel}", and register again.`,
  };
}

/** Runs registered → online → optional model checks. Returns first failure or null. */
export function validateHostReady(
  store: BrokerStore,
  hostId: string,
  options: HostReadyOptions = {},
): HostValidationFailure | null {
  return (
    validateHostRegistered(store, hostId) ??
    validateHostOnline(store, hostId) ??
    (options.requiredModel
      ? validateHostModel(
          store,
          hostId,
          options.requiredModel,
          options.requiredModelLabel ?? options.requiredModel,
        )
      : null)
  );
}