import React, { createContext, useContext, useState, useEffect, useRef } from 'react';
import { Platform, AppState, AppStateStatus } from 'react-native';
import { storage } from '../utils/storage';
import { ApiService } from '../services/api';
import NetInfo from '@react-native-community/netinfo';
import { DebugLogger } from '../utils/logger';

interface AppConfig {
  branding: {
    app_name?: string;
    app_tagline?: string;
    app_icon_url?: string;
    logo_url?: string;
    splash_image_url?: string;
    brand_color?: string;
    theme_color_primary?: string;
    theme_color_secondary?: string;
    primary_font_family?: string;
  };
  control_center: {
    kill_switch_active?: boolean;
    kill_switch_message?: string;
    maintenance_start_at?: string;
    maintenance_end_at?: string;
    maintenance_bypass_ips?: string;
    announcement_enabled?: boolean;
    announcement_text?: string;
    announcement_type?: 'info' | 'warning' | 'danger';
  };
  app_updates: {
    app_version?: string;
    min_app_version?: string;
    onboarding_version?: string;
    store_url_android?: string;
    store_url_ios?: string;
    store_url_huawei?: string;
  };
  features: {
    enable_registration?: boolean;
    enable_guest_mode?: boolean;
    require_otp_registration?: boolean;
    enable_biometrics?: boolean;
    enable_remember_me?: boolean;
    review_prompt_enabled?: boolean;
    min_actions_before_review?: number;
    region_lock_enabled?: boolean;
    dashboard_categories?: string;
  };
  security_auth: {
    login_title?: string;
    login_subtitle?: string;
    token_ttl_minutes?: number;
    session_max_age?: number;
    login_max_attempts?: number;
    biometric_auth_type?: string;
    oauth_google_enabled?: boolean;
    oauth_apple_enabled?: boolean;
    oauth_facebook_enabled?: boolean;
  };
  connectivity: {
    api_base_url?: string;
    api_version?: string;
    api_timeout_ms?: number;
    api_retry_count?: number;
    request_cache_ttl?: number;
    sync_interval_ms?: number;
    enable_ssl_pinning?: boolean;
    ssl_pinning_hash?: string;
    environment_selector?: string;
  };
  notifications: {
    enable_push_notifications?: boolean;
    fcm_topic_default?: string;
    default_channel_id?: string;
    notification_sound_enabled?: boolean;
    badge_count_enabled?: boolean;
    priority_level?: string;
  };
  support_social: {
    support_email?: string;
    support_whatsapp?: string;
    live_chat_url?: string;
    faq_url?: string;
    privacy_policy_url?: string;
    social_instagram_url?: string;
    social_twitter_url?: string;
    social_facebook_url?: string;
    social_youtube_url?: string;
    faq_json?: any[];
    help_topics_json?: any[];
  };
  analytics_system: {
    crashlytics_enabled?: boolean;
    log_level?: string;
    event_sampling_rate?: string;
    google_analytics_id?: string;
    gdpr_compliance_enabled?: boolean;
    target_sdk_version?: string;
    system_timezone?: string;
    default_locale?: string;
  };
  localization?: {
    [lang: string]: Record<string, string>;
  };
}

interface ConfigContextType {
  config: AppConfig | null;
  isLoading: boolean;
  isSyncing: boolean;
  isConnected: boolean;
  syncConfig: () => Promise<void>;
}

const ConfigContext = createContext<ConfigContextType | undefined>(undefined);

const STORAGE_KEY = 'cached_mobile_config';
const ETAG_KEY    = 'cached_config_etag';

// Minimum sync interval: 3 seconds to feel "instant" while avoiding excessive load
const MIN_SYNC_INTERVAL_MS = 3_000;
const DEFAULT_SYNC_INTERVAL_MS = 5_000;

export function ConfigProvider({ children }: { children: React.ReactNode }) {
  const [config, setConfig] = useState<AppConfig | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [isConnected, setIsConnected] = useState(true);
  const [isSyncing, setIsSyncing] = useState(false);
  const isSyncingRef = useRef(false);
  const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null);
  const prevConnected = useRef<boolean | null>(null);

  useEffect(() => {
    // 1. Monitor network connection
    const unsubscribeNet = NetInfo.addEventListener(state => {
      const connected = !!state.isConnected;
      
      if (prevConnected.current !== null && prevConnected.current !== connected) {
        DebugLogger.log(`Network status changed: ${connected ? 'Online' : 'Offline'}`, connected ? 'success' : 'error');
        if (connected) syncConfig();
      }
      
      setIsConnected(connected);
      prevConnected.current = connected;
    });

    // 2. Monitor AppState (Sync on foreground)
    const subscription = AppState.addEventListener('change', (nextAppState) => {
      if (nextAppState === 'active') {
        syncConfig();
      }
    });

    loadInitialConfig();
    
    return () => {
      unsubscribeNet();
      subscription.remove();
      if (intervalRef.current) clearInterval(intervalRef.current);
    };
  }, []);

  // Re-setup interval when config changes (for dynamic sync_interval_ms)
  useEffect(() => {
    if (intervalRef.current) clearInterval(intervalRef.current);

    const rawInterval = config?.connectivity?.sync_interval_ms ?? DEFAULT_SYNC_INTERVAL_MS;
    // Clamp to minimum to avoid hammering server
    const safeInterval = Math.max(rawInterval, MIN_SYNC_INTERVAL_MS);

    intervalRef.current = setInterval(() => {
      syncConfig();
    }, safeInterval);

    return () => {
      if (intervalRef.current) clearInterval(intervalRef.current);
    };
  }, [config?.connectivity?.sync_interval_ms]);

  const loadInitialConfig = async () => {
    try {
      // 1. Load from cache first (offline-first approach)
      const str = await storage.get(STORAGE_KEY);
      if (str) {
        try {
          const cached = JSON.parse(str);
          setConfig(cached);
          setIsLoading(false);
        } catch {
          // Cache is corrupted, remove it
          await storage.remove(STORAGE_KEY);
        }
      }

      // 2. Fetch fresh config in background (non-blocking)
      await syncConfig();
    } catch (error) {
      console.warn('[Config] Initialization error:', error);
    } finally {
      setIsLoading(false);
    }
  };

  const syncConfig = async () => {
    if (isSyncingRef.current) return;
    isSyncingRef.current = true;
    setIsSyncing(true);

    try {
      const etag = await storage.get(ETAG_KEY);
      const response = await ApiService.syncMobileConfig(etag);

      if (response?.status === 'not_modified') {
        DebugLogger.log('Config is up to date (ETag match)', 'sync');
        return;
      }

      if (response?.status === 'success' && response?.data) {
        const freshConfig = response.data;
        setConfig(freshConfig);

        DebugLogger.log(`Config updated with ETag: ${response.etag?.substring(0, 8)}...`, 'sync');
        // Persist to cache
        await storage.save(STORAGE_KEY, JSON.stringify(freshConfig));
        if (response.etag) {
          await storage.save(ETAG_KEY, response.etag);
        }
      }
    } catch (error: any) {
      DebugLogger.log(`Sync error: ${error.message}`, 'error');
      console.warn('[Config] Sync failed (offline?):', error);
    } finally {
      isSyncingRef.current = false;
      setIsSyncing(false);
      setIsLoading(false);
    }
  };

  return (
    <ConfigContext.Provider value={{ config, isLoading, isSyncing, isConnected, syncConfig }}>
      {children}
    </ConfigContext.Provider>
  );
}

export function useAppConfig() {
  const context = useContext(ConfigContext);
  if (context === undefined) {
    return {
      config: { 
        branding: { app_name: 'biiproject' }, 
        control_center: {}, 
        app_updates: {}, 
        features: {}, 
        security_auth: {}, 
        connectivity: {}, 
        notifications: {}, 
        support_social: {}, 
        analytics_system: {} 
      },
      isLoading: false,
      isSyncing: false,
      isConnected: true,
      syncConfig: async () => {}
    } as any;
  }
  return context;
}