import React, { useState, useEffect } from 'react';
import { View, StatusBar, Alert, ActivityIndicator, Text, AppState, Platform } from 'react-native';
import { useCameraPermission, usePhotoOutput } from 'react-native-vision-camera';
import * as ImagePicker from 'expo-image-picker';
import * as FileSystem from 'expo-file-system/legacy';
import * as MediaLibrary from 'expo-media-library';
import * as Haptics from 'expo-haptics';
import AsyncStorage from '@react-native-async-storage/async-storage';

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

import { Recipe, ColorAdjustments, FrameId, GPSInfo } from './src/types';
import { getAllRecipes, saveCustomRecipe, deleteCustomRecipe } from './src/utils/storageUtils';
import { DEFAULT_ADJUSTMENTS } from './src/utils/defaultRecipes';
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>({ ...DEFAULT_ADJUSTMENTS });

  const [selectedFrame, setSelectedFrame] = useState<FrameId>('none');
  const [useGeotag, setUseGeotag] = useState(true);
  const [gpsInfo, setGpsInfo] = useState<GPSInfo | null>(null);
  // Progressive disclosure: a tool chip opens its panel; null = photo hero only.
  const [openTab, setOpenTab] = useState<TabId | null>(null);
  
  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();
  // Full-resolution photo output — attached to the live <Camera> in Viewfinder.
  // Photo capture is resolution-independent from the Skia preview output.
  const photoOutput = usePhotoOutput({
    qualityPrioritization: 'quality',
  });

  // 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({ ...DEFAULT_ADJUSTMENTS, ...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;

    // On Android 10+, picking without ACCESS_MEDIA_LOCATION makes the OS hand us
    // a redacted copy (EXIF GPS stripped). That silently kills Tier-1 EXIF GPS
    // and the photo's own coordinates (often a different place than where the
    // user stands now) get replaced by a device-GPS fallback. Request media
    // read + photo-location BEFORE the pick so the copy keeps its true EXIF GPS.
    let mediaOk = true;
    if (useGeotag && Platform.OS === 'android') {
      try {
        const perm = await MediaLibrary.requestPermissionsAsync(false, ['photo']);
        mediaOk = perm.granted;
        console.error(`[gps] pre-pick media+location permission granted=${perm.granted}`);
      } catch (e) {
        mediaOk = false;
        console.error('[gps] pre-pick media permission error: ' + String(e).slice(0, 120));
      }
    }

    const result = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: ImagePicker.MediaTypeOptions.Images,
      allowsEditing: false,
      quality: 1,
      exif: true,
      // Android 13+ photo picker always returns a redacted cache copy with
      // assetId=null — EXIF GPS stripped, MediaStore id lost → photo GPS is
      // unreachable and we'd stamp the device's location instead. The legacy
      // picker (ACTION_GET_CONTENT → DocumentsUI) hands back a
      // com.android.providers.media.documents uri, so the MediaStore asset id
      // survives AND (with ACCESS_MEDIA_LOCATION granted) the file is not
      // redacted → tier-1 EXIF / tier-2 MediaStore both work.
      legacy: Platform.OS === 'android' && useGeotag,
    });

    if (!result.canceled && result.assets && result.assets.length > 0) {
      const asset = result.assets[0];
      console.error(`[gps] picked uri=${asset.uri} assetId=${asset.assetId || 'null'} exifGPS=${asset.exif ? JSON.stringify(asset.exif.GPSLatitude ?? null) : 'no-exif'}`);
      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.
      // Device fallback only when media read was granted (else we cannot know
      // whether the photo carries its own GPS — stamping the device's current
      // spot over a photo from somewhere else would be wrong).
      const { gps, permissionDenied } = await resolvePhotoGPS(asset, {
        useGeotag,
        allowDeviceFallback: useGeotag && mediaOk,
      });
      setGpsInfo(gps);
      if (permissionDenied) {
        console.warn('Media library read permission denied — photo GPS unavailable.');
      }
      console.error(
        `[gps] resolved ${gps ? `src=${gps.source} lat=${gps.latitude.toFixed(5)} lon=${gps.longitude.toFixed(5)} loc=${(gps.locality || '').slice(0, 40)}` : 'none'}`
      );

      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 (!photoOutput) {
        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 tShot = Date.now();
        const { filePath } = await photoOutput.capturePhotoToFile({}, {});
        console.error(`[capture] shot-took ${Date.now() - tShot}ms`);
        const sourceUri = toUri(filePath);

        const tExp = Date.now();
        const result = await processAndExportPhoto(
          sourceUri,
          { ...activeRecipe, adjustments, frameId: selectedFrame, useGeotag },
          selectedFrame,
          useGeotag,
          captureGps,
          // 300dpi header + full-res screen sharpen. evFromCamera: the AE bias
          // already applied exposure compensation at capture — don't add 2^EV.
          { dpi: 300, sharpen: true, evFromCamera: true }
        );
        console.error(`[capture] export-took ${Date.now() - tExp}ms (pipeline total ${Date.now() - tShot}ms)`);

        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 (
    <View className="flex-1 bg-black">
      <StatusBar barStyle="light-content" translucent backgroundColor="transparent" />

      {/* Fullscreen hero: photo or live preview fills the whole screen */}
      <View className="absolute inset-0 bg-black">
        <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}
          photoOutput={photoOutput}
          onExposureChange={(ev) => handleUpdateAdjustments({ exposureCompensation: ev })}
        />
      </View>

      {/* Top overlay: mode label + recipe name (left), Save current (right) */}
      <TopBar mode={mode} recipeName={activeRecipe.name} onSaveRecipe={handleSaveRecipe} />

      {/* Bottom deck: chip panel (progressive disclosure) -> tool rail -> shutter */}
      <View className="absolute left-0 right-0 bottom-0 z-10">
        {openTab !== null && (
          <View
            style={{
              backgroundColor: 'rgba(8,8,10,0.96)',
              borderTopWidth: 1,
              borderTopColor: 'rgba(63,63,70,0.7)',
            }}
            className="rounded-t-2xl overflow-hidden border-l border-r border-zinc-800/60"
          >
            <AdjustmentPanel
              activeTab={openTab}
              recipes={recipes}
              currentRecipeId={selectedRecipe?.id || ''}
              adjustments={adjustments}
              selectedFrame={selectedFrame}
              useGeotag={useGeotag}
              onSelectRecipe={applyRecipe}
              onUpdateAdjustments={handleUpdateAdjustments}
              onUpdateFrame={handleUpdateFrame}
              onToggleGeotag={handleToggleGeotag}
              onSaveRecipe={handleSaveRecipe}
              onDeleteRecipe={handleDeleteRecipe}
            />
          </View>
        )}

        <ToolRail activeTab={openTab} onToggle={(tab) => setOpenTab(openTab === tab ? null : tab)} />

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

      {/* 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>
      )}
    </View>
  );
}