/**
 * Unified Mobile Detection Composable
 * Provides consistent mobile detection across the app
 */

export interface MobileDetectionState {
  isMobile: boolean;
  isSafari: boolean;
  isMobileSafari: boolean;
  isIOS: boolean;
  isAndroid: boolean;
  safariVersion?: number;
  viewportHeight: number;
  isInitialized: boolean;
}

// Global state to ensure single source of truth
const globalState = reactive<MobileDetectionState>({
  isMobile: false,
  isSafari: false,
  isMobileSafari: false,
  isIOS: false,
  isAndroid: false,
  safariVersion: undefined,
  viewportHeight: 0,
  isInitialized: false
});

// Track if listeners are already set up
let listenersSetup = false;

export const useMobileDetection = () => {
  // Initialize detection on first use
  if (!globalState.isInitialized && typeof window !== 'undefined') {
    detectDevice();
    globalState.isInitialized = true;
    
    // Set up listeners only once globally
    if (!listenersSetup) {
      setupListeners();
      listenersSetup = true;
    }
  }

  // Return readonly state to prevent external modifications
  return readonly(globalState);
};

function detectDevice() {
  if (typeof window === 'undefined') return;

  const userAgent = navigator.userAgent;
  
  // Detect mobile
  globalState.isMobile = /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(userAgent);
  
  // Detect iOS
  globalState.isIOS = /iPad|iPhone|iPod/.test(userAgent) && !(window as any).MSStream;
  
  // Detect Android
  globalState.isAndroid = /Android/i.test(userAgent);
  
  // Detect Safari
  globalState.isSafari = /^((?!chrome|android).)*safari/i.test(userAgent);
  
  // Detect Mobile Safari specifically
  globalState.isMobileSafari = globalState.isIOS && globalState.isSafari;
  
  // Extract Safari version
  if (globalState.isSafari) {
    const match = userAgent.match(/Version\/(\d+)/);
    if (match) {
      globalState.safariVersion = parseInt(match[1]);
    }
  }
  
  // Set initial viewport height
  globalState.viewportHeight = window.innerHeight;
}

function setupListeners() {
  if (typeof window === 'undefined') return;
  
  let resizeTimeout: NodeJS.Timeout;
  let lastHeight = window.innerHeight;
  let initialHeight = window.innerHeight;
  let keyboardOpen = false;
  
  const handleResize = () => {
    // Don't handle resize if we're in the middle of a transition
    if (document.hidden) return;
    
    clearTimeout(resizeTimeout);
    
    // Debounce with longer delay for mobile
    const debounceDelay = globalState.isMobile ? 300 : 150;
    
    resizeTimeout = setTimeout(() => {
      const newHeight = window.innerHeight;
      const heightDiff = newHeight - lastHeight;
      const absoluteDiff = Math.abs(heightDiff);
      
      // Detect keyboard open/close on mobile
      if (globalState.isMobile) {
        // Keyboard likely opened (viewport got smaller)
        if (heightDiff < -100 && newHeight < initialHeight * 0.75) {
          keyboardOpen = true;
          // Don't trigger viewport updates for keyboard changes
          return;
        }
        
        // Keyboard likely closed (viewport got bigger)
        if (heightDiff > 100 && keyboardOpen) {
          keyboardOpen = false;
          // Don't trigger viewport updates for keyboard changes
          return;
        }
      }
      
      // Only update for significant non-keyboard changes (more than 50px)
      // or orientation changes (height differs significantly from initial)
      const isOrientationChange = absoluteDiff > initialHeight * 0.3;
      const isSignificantChange = absoluteDiff > 50;
      
      if (isOrientationChange || (isSignificantChange && !keyboardOpen)) {
        lastHeight = newHeight;
        globalState.viewportHeight = newHeight;
        
        // Update CSS custom property for mobile Safari
        if (globalState.isMobileSafari) {
          const vh = newHeight * 0.01;
          document.documentElement.style.setProperty('--vh', `${vh}px`);
        }
        
        // Update initial height after orientation change
        if (isOrientationChange) {
          initialHeight = newHeight;
        }
      }
    }, debounceDelay);
  };
  
  // Add resize listener with passive option for better performance
  window.addEventListener('resize', handleResize, { passive: true });
  
  // Also listen for orientation changes on mobile
  if (globalState.isMobile) {
    window.addEventListener('orientationchange', () => {
      // Reset keyboard state on orientation change
      keyboardOpen = false;
      // Wait for orientation change to complete
      setTimeout(handleResize, 200);
    });
  }
  
  // Clean up on app unmount (if needed)
  if (typeof window !== 'undefined') {
    const cleanup = () => {
      window.removeEventListener('resize', handleResize);
      if (globalState.isMobile) {
        window.removeEventListener('orientationchange', handleResize);
      }
    };
    
    // Store cleanup function for manual cleanup if needed
    (window as any).__mobileDetectionCleanup = cleanup;
  }
}

// Export helper functions
export const isMobileSafari = () => globalState.isMobileSafari;
export const isMobile = () => globalState.isMobile;
export const isIOS = () => globalState.isIOS;
export const getViewportHeight = () => globalState.viewportHeight;