/**
 * Browser/React Native-safe kill switch client for platform-service.
 *
 * Checks GET /api/flags/kill-switch to determine if the app is disabled.
 * Fail-open: returns { disabled: false } on any network error.
 *
 * @example
 * ```ts
 * import { createKillSwitchClient } from '@bytelyst/kill-switch-client';
 *
 * const ks = createKillSwitchClient({
 *   baseUrl: 'http://localhost:4003/api',
 *   productId: 'nomgap',
 * });
 *
 * const result = await ks.check();
 * if (result.disabled) showBlockScreen(result.message);
 * ```
 */

export interface KillSwitchClientConfig {
  /** Platform-service base URL (e.g. "http://localhost:4003/api"). */
  baseUrl: string;

  /** Product identifier sent as x-product-id header. */
  productId: string;

  /** Platform string for the query (e.g. "mobile", "web"). Default: "mobile". */
  platform?: string;
}

export interface KillSwitchResult {
  disabled: boolean;
  message: string | null;
}

export interface KillSwitchClient {
  /** Check if the app is disabled. Fail-open on any error. */
  check(): Promise<KillSwitchResult>;
}

export function createKillSwitchClient(config: KillSwitchClientConfig): KillSwitchClient {
  const { baseUrl, productId, platform = 'mobile' } = config;

  async function check(): Promise<KillSwitchResult> {
    try {
      const requestId =
        typeof globalThis.crypto?.randomUUID === 'function'
          ? globalThis.crypto.randomUUID()
          : `${Date.now()}-${Math.random().toString(36).slice(2, 10)}`;

      const res = await globalThis.fetch(
        `${baseUrl}/flags/kill-switch?platform=${encodeURIComponent(platform)}`,
        {
          headers: { 'x-product-id': productId, 'x-request-id': requestId },
        }
      );

      if (!res.ok) return { disabled: false, message: null };

      const data = (await res.json()) as KillSwitchResult;
      return {
        disabled: data.disabled ?? false,
        message: data.message ?? null,
      };
    } catch {
      // Fail-open: network errors should NOT block the user
      return { disabled: false, message: null };
    }
  }

  return { check };
}