import React, { useState, useEffect, useRef } from 'react';
import { View, StatusBar, Alert, ActivityIndicator, Text, AppState } from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';
import { useCameraPermission, type Camera } from 'react-native-vision-camera';
import * as ImagePicker from 'expo-image-picker';
import * as FileSystem from 'expo-file-system/legacy';
import * as Haptics from 'expo-haptics';
import AsyncStorage from '@react-native-async-storage/async-storage';

import Header from './src/components/Header';
import Viewfinder from './src/components/Viewfinder';
import TabSelector, { TabId } from './src/components/TabSelector';
import AdjustmentPanel from './src/components/AdjustmentPanel';
import CameraControls from './src/components/CameraControls';
import PreviewModal from './src/components/PreviewModal';

import { Recipe, ColorAdjustments, FrameId, GPSInfo } from './src/types';
import { getAllRecipes, saveCustomRecipe, deleteCustomRecipe } from './src/utils/storageUtils';
import { getCurrentGPS, requestLocationPermissions } from './src/utils/locationUtils';
import { resolvePhotoGPS } from './src/utils/photoGps';
import { processAndExportPhoto } from './src/utils/exportEngine';

// @ts-ignore
import './global.css';

const SESSION_KEY = 'saved_session';

export default function App() {
  const [mode, setMode] = useState<'camera' | 'library'>('camera');
  const [recipes, setRecipes] = useState<Recipe[]>([]);
  const [selectedRecipe, setSelectedRecipe] = useState<Recipe | null>(null);
  
  // Custom temporary overrides for the sliders
  const [adjustments, setAdjustments] = useState<ColorAdjustments>({
    exposure: 0,
    contrast: 0,
    saturation: 0,
    temperature: 5500,
    tint: 0,
    highlight: 0,
    shadow: 0,
    denoise: 0,
    clarity: 0,
    grain: 0,
    colorChrome: 'none',
  });

  const [selectedFrame, setSelectedFrame] = useState<FrameId>('none');
  const [useGeotag, setUseGeotag] = useState(true);
  const [gpsInfo, setGpsInfo] = useState<GPSInfo | null>(null);
  const [activeTab, setActiveTab] = useState<TabId>('recipes');
  
  const [libraryImageUri, setLibraryImageUri] = useState<string | null>(null);
  const [lastPhotoUri, setLastPhotoUri] = useState<string | null>(null);
  const [lastSavedToLibrary, setLastSavedToLibrary] = useState(false);
  const [previewVisible, setPreviewVisible] = useState(false);
  const [isProcessing, setIsProcessing] = useState(false);

  // Hardware Permissions (vision-camera)
  const { hasPermission: cameraPermissionGranted, requestPermission: requestCameraPermission } = useCameraPermission();
  const cameraRef = useRef<Camera>(null);

  // vision-camera may return a raw absolute path on Android; surface a file:// URI.
  const toUri = (path: string) => (/^(file|content|ph):\/\//.test(path) ? path : `file://${path}`);

  useEffect(() => {
    // B5: run a single sequenced init — restore the session first, then fall
    // back to the first recipe only when no recipe was restored.
    initSession();
    // Do NOT auto-load device GPS here — it would override photo GPS on library mode
  }, []);

  // Save/restore session on app lifecycle changes
  useEffect(() => {
    const subscription = AppState.addEventListener('change', async (nextAppState) => {
      if (nextAppState === 'background' || nextAppState === 'inactive') {
        const session = {
          mode,
          libraryImageUri,
          adjustments,
          selectedFrame,
          useGeotag,
          selectedRecipeId: selectedRecipe?.id || null,
          gpsInfo,
        };
        try {
          await AsyncStorage.setItem(SESSION_KEY, JSON.stringify(session));
        } catch (e) {
          console.warn('Failed to save session:', e);
        }
      }
    });
    return () => subscription.remove();
  }, [mode, libraryImageUri, adjustments, selectedFrame, useGeotag, selectedRecipe, gpsInfo]);

  const initSession = async () => {
    const list = await getAllRecipes();
    setRecipes(list);

    let session: any = null;
    try {
      const raw = await AsyncStorage.getItem(SESSION_KEY);
      if (raw) session = JSON.parse(raw);
    } catch (e) {
      console.warn('Failed to read session:', e);
    }

    let restoredRecipe: Recipe | null = null;
    if (session) {
      // B12: the restored library image may no longer exist on disk
      let imageUri: string | null = session.libraryImageUri || null;
      if (imageUri) {
        try {
          const info = await FileSystem.getInfoAsync(imageUri);
          if (!info.exists) imageUri = null;
        } catch {
          imageUri = null;
        }
      }
      if (imageUri) {
        setLibraryImageUri(imageUri);
        setMode('library');
      } else {
        setMode(session.mode || 'camera');
      }
      if (session.adjustments) setAdjustments(session.adjustments);
      if (session.selectedFrame) setSelectedFrame(session.selectedFrame);
      if (session.useGeotag !== undefined) setUseGeotag(session.useGeotag);
      if (session.gpsInfo) setGpsInfo(session.gpsInfo);
      if (session.selectedRecipeId) {
        restoredRecipe = list.find((r: Recipe) => r.id === session.selectedRecipeId) || null;
      }
    }

    if (restoredRecipe) {
      applyRecipe(restoredRecipe);
    } else if (list.length > 0) {
      applyRecipe(list[0]);
    }
  };

  const loadGPS = async () => {
    const info = await getCurrentGPS();
    if (info) {
      setGpsInfo({ ...info, source: 'device' });
    }
  };

  const applyRecipe = (recipe: Recipe) => {
    setSelectedRecipe(recipe);
    setAdjustments(recipe.adjustments);
    setSelectedFrame(recipe.frameId || 'none');
    setUseGeotag(recipe.useGeotag);
  };

  const handleUpdateAdjustments = (updates: Partial<ColorAdjustments>) => {
    // B8: never call a setState inside another setState's updater.
    const next = { ...adjustments, ...updates };
    setAdjustments(next);
    if (selectedRecipe) {
      setSelectedRecipe({
        ...selectedRecipe,
        adjustments: next,
      });
    }
  };

  const handleUpdateFrame = (frameId: FrameId) => {
    setSelectedFrame(frameId);
    if (selectedRecipe) {
      setSelectedRecipe({
        ...selectedRecipe,
        frameId,
      });
    }
  };

  const handleToggleGeotag = async (enabled: boolean) => {
    setUseGeotag(enabled);
    if (selectedRecipe) {
      setSelectedRecipe({
        ...selectedRecipe,
        useGeotag: enabled,
      });
    }
    if (enabled && !gpsInfo) {
      const locationGranted = await requestLocationPermissions();
      if (locationGranted) {
        loadGPS();
      } else {
        Alert.alert('Permission Denied', 'Enable location services to use GPS Watermark.');
        setUseGeotag(false);
      }
    }
  };

  const handleSaveRecipe = async (name: string) => {
    if (!selectedRecipe) return;
    const newRecipe = await saveCustomRecipe({
      name,
      baseFilter: selectedRecipe.baseFilter,
      adjustments,
      frameId: selectedFrame,
      useGeotag,
    });
    const list = await getAllRecipes();
    setRecipes(list);
    applyRecipe(newRecipe);
    Alert.alert('Recipe Saved', `"${name}" has been created.`);
  };

  const handleDeleteRecipe = async (id: string) => {
    await deleteCustomRecipe(id);
    const list = await getAllRecipes();
    setRecipes(list);
    if (selectedRecipe?.id === id && list.length > 0) {
      applyRecipe(list[0]);
    }
  };

  const handlePickImage = async () => {
    if (isProcessing) return;
    const result = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: ImagePicker.MediaTypeOptions.Images,
      allowsEditing: false,
      quality: 1,
      exif: true,
    });

    if (!result.canceled && result.assets && result.assets.length > 0) {
      const asset = result.assets[0];
      setLibraryImageUri(asset.uri);
      setMode('library');
      // Clear old GPS — will be replaced if the photo (or device) has location data
      setGpsInfo(null);

      // Multi-tier GPS resolution: EXIF → MediaLibrary → device fallback
      const { gps, permissionDenied } = await resolvePhotoGPS(asset, {
        useGeotag,
        allowDeviceFallback: useGeotag,
      });
      setGpsInfo(gps);
      if (permissionDenied) {
        console.warn('Media library read permission denied — photo GPS unavailable.');
      }

      Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
    }
  };

  const activeRecipe: Recipe =
    selectedRecipe || {
      id: 'temp',
      name: 'Custom',
      baseFilter: 'none',
      adjustments,
      frameId: selectedFrame,
      useGeotag,
    };

  const handleCapture = async () => {
    if (isProcessing) return;

    // Camera mode (Phase 4, option A): real capture through vision-camera.
    if (mode === 'camera') {
      if (!cameraPermissionGranted) {
        Alert.alert('Permission Needed', 'Grant camera permission to take photos.');
        return;
      }
      if (!cameraRef.current) {
        Alert.alert('Camera Not Ready', 'Please wait for the camera to start, then try again.');
        return;
      }
      setIsProcessing(true);
      Haptics.impactAsync(Haptics.ImpactFeedbackStyle.Medium);
      try {
        // A photo taken now is at the device's current spot — resolve device GPS
        // fresh instead of reusing GPS left over from a previously loaded photo.
        let captureGps = gpsInfo && gpsInfo.source === 'device' ? gpsInfo : null;
        if (useGeotag && !captureGps) {
          const deviceGps = await getCurrentGPS();
          if (deviceGps) {
            captureGps = { ...deviceGps, source: 'device' as const };
            setGpsInfo(captureGps);
          }
        }

        const photo = await cameraRef.current.takePhoto({});
        const sourceUri = toUri(photo.path);

        const result = await processAndExportPhoto(
          sourceUri,
          { ...activeRecipe, adjustments, frameId: selectedFrame, useGeotag },
          selectedFrame,
          useGeotag,
          captureGps,
          { dpi: 300, sharpen: true } // 300dpi header + full-res screen sharpen
        );

        if (result) {
          setLastPhotoUri(result.uri);
          setLastSavedToLibrary(result.savedToLibrary);
          setPreviewVisible(true);
          Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
        } else {
          Alert.alert('Failed', 'Error occurred while processing the captured photo.');
        }
      } catch (error) {
        console.error('Camera capture failed:', error);
        Alert.alert('Capture Failed', 'Could not take the photo. See logs for details.');
      } finally {
        setIsProcessing(false);
      }
      return;
    }

    // Library mode capture/export: processes selected image with recipe, overlays, text
    if (!libraryImageUri || !selectedRecipe) {
      Alert.alert('Error', 'Please select an image from the library first.');
      return;
    }

    setIsProcessing(true);
    Haptics.impactAsync(Haptics.ImpactFeedbackStyle.Medium);

    const result = await processAndExportPhoto(
      libraryImageUri,
      {
        ...selectedRecipe,
        adjustments,
        frameId: selectedFrame,
        useGeotag,
      },
      selectedFrame,
      useGeotag,
      gpsInfo
    );

    setIsProcessing(false);

    if (result) {
      setLastPhotoUri(result.uri);
      setLastSavedToLibrary(result.savedToLibrary);
      setPreviewVisible(true);
      Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
    } else {
      Alert.alert('Failed', 'Error occurred while processing image.');
    }
  };

  // Switching back to camera: drop GPS that belongs to a library photo, so the
  // live view (and any capture) never stamps a stale location.
  const handleSetMode = (next: 'camera' | 'library') => {
    if (next === 'camera' && gpsInfo && gpsInfo.source !== 'device') {
      setGpsInfo(null);
    }
    setMode(next);
  };

  return (
    <SafeAreaView className="flex-1 bg-carbon">
      <StatusBar barStyle="light-content" backgroundColor="#08080a" />
      
      {/* Top Header */}
      <Header mode={mode} setMode={handleSetMode} title="CamRecipe Pro" />

      {/* Main Viewfinder Frame */}
      <View className="flex-1 justify-center items-center px-4 py-2 bg-carbon">
        <Viewfinder
          mode={mode}
          recipe={
            selectedRecipe || {
              id: 'temp',
              name: 'Custom',
              baseFilter: 'none',
              adjustments,
              frameId: selectedFrame,
              useGeotag,
            }
          }
          selectedFrame={selectedFrame}
          useGeotag={useGeotag}
          gpsInfo={gpsInfo}
          libraryImageUri={libraryImageUri}
          cameraPermissionGranted={cameraPermissionGranted}
          onRequestCameraPermission={requestCameraPermission}
          cameraRef={cameraRef}
        />
      </View>

      {/* Selector Tabs */}
      <TabSelector activeTab={activeTab} setActiveTab={setActiveTab} />

      {/* Adjustments Panel */}
      <View style={{ height: 250 }} className="bg-carbon">
        <AdjustmentPanel
          activeTab={activeTab}
          recipes={recipes}
          currentRecipeId={selectedRecipe?.id || ''}
          adjustments={adjustments}
          selectedFrame={selectedFrame}
          useGeotag={useGeotag}
          onSelectRecipe={applyRecipe}
          onUpdateAdjustments={handleUpdateAdjustments}
          onUpdateFrame={handleUpdateFrame}
          onToggleGeotag={handleToggleGeotag}
          onSaveRecipe={handleSaveRecipe}
          onDeleteRecipe={handleDeleteRecipe}
        />
      </View>

      {/* Bottom Camera Buttons */}
      <CameraControls
        lastPhotoUri={lastPhotoUri}
        onCapture={handleCapture}
        onPickImage={handlePickImage}
        onOpenPreview={() => setPreviewVisible(true)}
        isLibraryMode={mode === 'library'}
        onSwitchToCamera={() => handleSetMode('camera')}
      />

      {/* Preview Modal */}
      <PreviewModal
        visible={previewVisible}
        onClose={() => setPreviewVisible(false)}
        photoUri={lastPhotoUri}
        recipeName={selectedRecipe?.name || 'Custom'}
        savedToLibrary={lastSavedToLibrary}
      />

      {/* Global Processing Loader Overlay */}
      {isProcessing && (
        <View className="absolute inset-0 bg-black/75 flex items-center justify-center space-y-4">
          <ActivityIndicator size="large" color="#f59e0b" />
          <Text className="text-amber-500 font-mono text-sm tracking-widest font-bold">
            RENDERING PHOTO...
          </Text>
        </View>
      )}
    </SafeAreaView>
  );
}