import React, { useState, useEffect, useCallback } from 'react';
import { useNavigate } from 'react-router-dom';
import { makeStyles } from '@mui/styles';
import { 
  Typography, 
  Box,
  CircularProgress,
  IconButton
} from '@mui/material';
import { 
  Home as HomeIcon,
  ExitToApp as ExitIcon
} from '@mui/icons-material';

// Utils
import { fetchAllGroups } from '../../Utils/batchUpload';

const useStyles = makeStyles({
  fullscreenContainer: {
    position: 'fixed',
    top: 0,
    left: 0,
    width: '100%',
    height: '100%',
    backgroundColor: '#000',
    display: 'flex',
    flexDirection: 'column',
    justifyContent: 'center',
    alignItems: 'center',
    zIndex: 9999,
    overflow: 'hidden'
  },
  exitButton: {
    position: 'absolute',
    top: '20px',
    right: '20px',
    color: 'white',
    backgroundColor: 'rgba(0,0,0,0.5)',
    '&:hover': {
      backgroundColor: 'rgba(0,0,0,0.8)'
    }
  },
  homeButton: {
    position: 'absolute',
    top: '20px',
    left: '20px',
    color: 'white',
    backgroundColor: 'rgba(0,0,0,0.5)',
    '&:hover': {
      backgroundColor: 'rgba(0,0,0,0.8)'
    }
  },
  slideshowImage: {
    maxWidth: '100%',
    maxHeight: '100%',
    objectFit: 'contain',
    transition: 'opacity 0.5s ease-in-out'
  },
  descriptionContainer: {
    position: 'fixed',
    left: 40,
    bottom: 40,
    backgroundColor: 'rgba(0,0,0,0.8)',
    padding: '25px 35px',
    borderRadius: '12px',
    maxWidth: '35vw',
    minWidth: '260px',
    textAlign: 'left',
    backdropFilter: 'blur(5px)',
    zIndex: 10001,
    boxShadow: '0 4px 24px rgba(0,0,0,0.4)'
  },
  titleText: {
    color: 'white',
    fontSize: '28px',
    fontWeight: '500',
    margin: '0 0 8px 0',
    fontFamily: 'roboto'
  },
  yearAuthorText: {
    color: '#FFD700',
    fontSize: '18px',
    fontWeight: '400',
    margin: '0 0 12px 0',
    fontFamily: 'roboto'
  },
  descriptionText: {
    color: '#E0E0E0',
    fontSize: '16px',
    fontWeight: '300',
    margin: '0 0 12px 0',
    fontFamily: 'roboto',
    lineHeight: '1.4'
  },
  metaText: {
    color: '#999',
    fontSize: '12px',
    marginTop: '8px',
    fontFamily: 'roboto'
  },
  loadingContainer: {
    display: 'flex',
    flexDirection: 'column',
    alignItems: 'center',
    color: 'white'
  }
});

function SlideshowPage() {
  const classes = useStyles();
  const navigate = useNavigate();
  
  const [allGroups, setAllGroups] = useState([]);
  const [currentGroupIndex, setCurrentGroupIndex] = useState(0);
  const [currentImageIndex, setCurrentImageIndex] = useState(0);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);
  const [fadeOut, setFadeOut] = useState(false);

  // Slideshow-Timing Konstanten
  const IMAGE_DISPLAY_TIME = 4000; // 4 Sekunden pro Bild
  const TRANSITION_TIME = 500; // 0.5 Sekunden für Fade-Effekt

  // Gruppen laden
  useEffect(() => {
    const loadAllGroups = async () => {
      try {
        setLoading(true);
        const groupsData = await fetchAllGroups();
        
        if (groupsData.groups && groupsData.groups.length > 0) {
          // Mische die Gruppen zufällig
          const shuffledGroups = [...groupsData.groups].sort(() => Math.random() - 0.5);
          setAllGroups(shuffledGroups);
          setCurrentGroupIndex(0);
          setCurrentImageIndex(0);
        } else {
          setError('Keine Slideshows gefunden');
        }
      } catch (err) {
        console.error('Fehler beim Laden der Gruppen:', err);
        setError('Fehler beim Laden der Slideshows');
      } finally {
        setLoading(false);
      }
    };

    loadAllGroups();
  }, []);

  // Automatischer Slideshow-Wechsel
  const nextImage = useCallback(() => {
    if (allGroups.length === 0) return;

    const currentGroup = allGroups[currentGroupIndex];
    if (!currentGroup || !currentGroup.images) return;

    setFadeOut(true);
    
    setTimeout(() => {
      if (currentImageIndex + 1 < currentGroup.images.length) {
        // Nächstes Bild in der aktuellen Gruppe
        setCurrentImageIndex(prev => prev + 1);
      } else {
        // Zur nächsten Gruppe wechseln (zufällig)
        const nextGroupIndex = Math.floor(Math.random() * allGroups.length);
        setCurrentGroupIndex(nextGroupIndex);
        setCurrentImageIndex(0);
      }
      setFadeOut(false);
    }, TRANSITION_TIME);
  }, [allGroups, currentGroupIndex, currentImageIndex]);

  // Timer für automatischen Wechsel
  useEffect(() => {
    if (loading || error || allGroups.length === 0) return;

    const timer = setInterval(nextImage, IMAGE_DISPLAY_TIME);
    return () => clearInterval(timer);
  }, [loading, error, allGroups, nextImage]);

  // Keyboard-Navigation
  useEffect(() => {
    const handleKeyPress = (event) => {
      switch (event.key) {
        case 'Escape':
          navigate('/');
          break;
        case ' ':
        case 'ArrowRight':
          nextImage();
          break;
        default:
          break;
      }
    };

    document.addEventListener('keydown', handleKeyPress);
    return () => document.removeEventListener('keydown', handleKeyPress);
  }, [nextImage, navigate]);

  // Aktuelle Gruppe und Bild
  const currentGroup = allGroups[currentGroupIndex];
  const currentImage = currentGroup?.images?.[currentImageIndex];

  if (loading) {
    return (
      <Box className={classes.fullscreenContainer}>
        <Box className={classes.loadingContainer}>
          <CircularProgress style={{ color: 'white', marginBottom: '20px' }} />
          <Typography style={{ color: 'white' }}>Slideshow wird geladen...</Typography>
        </Box>
      </Box>
    );
  }

  if (error) {
    return (
      <Box className={classes.fullscreenContainer}>
        <Box className={classes.loadingContainer}>
          <Typography style={{ color: 'white', fontSize: '24px' }}>{error}</Typography>
          <IconButton
            className={classes.homeButton}
            onClick={() => navigate('/')}
            title="Zur Startseite"
          >
            <HomeIcon />
          </IconButton>
        </Box>
      </Box>
    );
  }

  if (!currentGroup || !currentImage) {
    return (
      <Box className={classes.fullscreenContainer}>
        <Box className={classes.loadingContainer}>
          <Typography style={{ color: 'white', fontSize: '24px' }}>
            Keine Bilder verfügbar
          </Typography>
          <IconButton
            className={classes.homeButton}
            onClick={() => navigate('/')}
            title="Zur Startseite"
          >
            <HomeIcon />
          </IconButton>
        </Box>
      </Box>
    );
  }

  return (
    <Box className={classes.fullscreenContainer}>
      {/* Navigation Buttons */}
      <IconButton
        className={classes.homeButton}
        onClick={() => navigate('/')}
        title="Zur Startseite"
      >
        <HomeIcon />
      </IconButton>
      
      <IconButton
        className={classes.exitButton}
        onClick={() => navigate('/')}
        title="Slideshow beenden"
      >
        <ExitIcon />
      </IconButton>

      {/* Hauptbild */}
      <img
        src={`/api${currentImage.filePath}`}
        alt={currentImage.originalName}
        className={classes.slideshowImage}
        style={{ 
          opacity: fadeOut ? 0 : 1,
          transition: `opacity ${TRANSITION_TIME}ms ease-in-out`
        }}
      />

      {/* Beschreibung */}
      <Box className={classes.descriptionContainer}>
        {/* Titel */}
        <Typography className={classes.titleText}>
          {currentGroup.title || 'Unbenanntes Projekt'}
        </Typography>

        {/* Jahr und Name */}
        <Typography className={classes.yearAuthorText}>
          {currentGroup.year}
          {currentGroup.name && ` • ${currentGroup.name}`}
        </Typography>

        {/* Beschreibung (wenn vorhanden) */}
        {currentGroup.description && (
          <Typography className={classes.descriptionText}>
            {currentGroup.description}
          </Typography>
        )}

        {/* Meta-Informationen */}
        <Typography className={classes.metaText}>
          Bild {currentImageIndex + 1} von {currentGroup.images.length} • 
          Slideshow {currentGroupIndex + 1} von {allGroups.length}
        </Typography>
      </Box>
    </Box>
  );
}

export default SlideshowPage;