/**
 * Network Status Detection and Monitoring
 *
 * Provides utilities for detecting and responding to network connectivity changes.
 * Used throughout the app for graceful offline mode degradation.
 */

import NetInfo, { NetInfoState } from '@react-native-community/netinfo';
import { useEffect, useState, useCallback } from 'react';

/**
 * Network status type
 */
export type NetworkStatus = 'online' | 'offline' | 'unknown';

/**
 * Get current network status (sync)
 * Use this for one-time checks
 */
export async function getNetworkStatus(): Promise<NetworkStatus> {
  try {
    const state = await NetInfo.fetch();
    return state.isConnected ? 'online' : 'offline';
  } catch {
    return 'unknown';
  }
}

/**
 * Check if device is currently online
 * Use this before making API calls
 */
export async function isOnline(): Promise<boolean> {
  const status = await getNetworkStatus();
  return status === 'online';
}

/**
 * React hook for network status monitoring
 *
 * @example
 * function MyComponent() {
 *   const { isOnline, isOffline, status } = useNetworkStatus();
 *
 *   if (isOffline) {
 *     return <OfflineBanner />;
 *   }
 *   // ...
 * }
 */
export function useNetworkStatus() {
  const [status, setStatus] = useState<NetworkStatus>('unknown');

  useEffect(() => {
    // Get initial status
    getNetworkStatus().then(setStatus);

    // Subscribe to network changes
    const unsubscribe = NetInfo.addEventListener((state: NetInfoState) => {
      setStatus(state.isConnected ? 'online' : 'offline');
    });

    return () => {
      unsubscribe();
    };
  }, []);

  return {
    status,
    isOnline: status === 'online',
    isOffline: status === 'offline',
    isUnknown: status === 'unknown',
  };
}

/**
 * React hook for online-only callback
 * Executes callback only when online, otherwise shows error
 *
 * @example
 * function MyComponent() {
 *   const executeOnline = useOnlineOnly();
 *
 *   const handleSave = () => {
 *     executeOnline(() => {
 *       // This only runs when online
 *       api.saveBeneficiary(data);
 *     }, 'Cannot save while offline');
 *   };
 * }
 */
export function useOnlineOnly() {
  const { isOnline } = useNetworkStatus();

  return useCallback(
    async (callback: () => void | Promise<void>, offlineMessage?: string) => {
      if (!isOnline) {
        throw new Error(offlineMessage || 'This action requires an internet connection');
      }
      return await callback();
    },
    [isOnline]
  );
}

/**
 * Retry configuration for API calls
 */
export interface RetryConfig {
  maxAttempts: number;
  delayMs: number;
  backoffMultiplier: number;
}

/**
 * Default retry configuration
 */
export const DEFAULT_RETRY_CONFIG: RetryConfig = {
  maxAttempts: 3,
  delayMs: 1000,
  backoffMultiplier: 2,
};

/**
 * Retry an async operation with exponential backoff
 * Only retries if network is available
 *
 * @param operation - Async function to retry
 * @param config - Retry configuration
 * @returns Promise with operation result
 *
 * @example
 * const data = await retryWithBackoff(
 *   () => api.getBeneficiaries(),
 *   { maxAttempts: 3, delayMs: 1000, backoffMultiplier: 2 }
 * );
 */
export async function retryWithBackoff<T>(
  operation: () => Promise<T>,
  config: RetryConfig = DEFAULT_RETRY_CONFIG
): Promise<T> {
  let lastError: Error | undefined;
  let delay = config.delayMs;

  for (let attempt = 1; attempt <= config.maxAttempts; attempt++) {
    try {
      // Check network before retry (after first attempt)
      if (attempt > 1) {
        const online = await isOnline();
        if (!online) {
          throw new Error('Network unavailable');
        }
      }

      return await operation();
    } catch (error) {
      lastError = error instanceof Error ? error : new Error('Unknown error');

      // Don't retry on last attempt
      if (attempt === config.maxAttempts) {
        break;
      }

      // Wait before retry with exponential backoff
      await new Promise(resolve => setTimeout(resolve, delay));
      delay *= config.backoffMultiplier;
    }
  }

  throw lastError || new Error('Operation failed after retries');
}

/**
 * React hook for retrying async operations
 *
 * @example
 * function MyComponent() {
 *   const retry = useRetry();
 *
 *   const loadData = async () => {
 *     const data = await retry(() => api.getBeneficiaries());
 *     setData(data);
 *   };
 * }
 */
export function useRetry(config: RetryConfig = DEFAULT_RETRY_CONFIG) {
  return useCallback(
    <T>(operation: () => Promise<T>) => retryWithBackoff(operation, config),
    // eslint-disable-next-line react-hooks/exhaustive-deps
    [config.maxAttempts, config.delayMs, config.backoffMultiplier]
  );
}