import { Ionicons } from '@expo/vector-icons';
import { BlurView } from 'expo-blur';
import * as ImagePicker from 'expo-image-picker';
import { useRouter } from 'expo-router';
import React, { useEffect, useMemo, useState } from 'react';
import {
  Alert,
  Image,
  Linking,
  Platform,
  ScrollView,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
} from 'react-native';
import { useSafeAreaInsets } from 'react-native-safe-area-context';

import { Colors } from '@/constants/Colors';

type PoseView = 'front' | 'side' | 'back';

type UploadState = {
  front?: string | null;
  side?: string | null;
  back?: string | null;
};

type Sample = { uri: string; correct: boolean };

const SAMPLES: Record<PoseView, Sample[]> = {
  front: [
    { uri: 'https://images.unsplash.com/photo-1594737625785-c6683fc87c73?w=400&q=80&auto=format', correct: true },
    { uri: 'https://images.unsplash.com/photo-1544716278-ca5e3f4abd8c?w=400&q=80&auto=format', correct: false },
    { uri: 'https://images.unsplash.com/photo-1571019614242-c5c5dee9f50b?w=400&q=80&auto=format', correct: false },
  ],
  side: [
    { uri: 'https://images.unsplash.com/photo-1554463529-e27854014799?w=400&q=80&auto=format', correct: true },
    { uri: 'https://images.unsplash.com/photo-1596357395104-5bcae0b1a5eb?w=400&q=80&auto=format', correct: false },
    { uri: 'https://images.unsplash.com/photo-1526506118085-60ce8714f8c5?w=400&q=80&auto=format', correct: false },
  ],
  back: [
    { uri: 'https://images.unsplash.com/photo-1517836357463-d25dfeac3438?w=400&q=80&auto=format', correct: true },
    { uri: 'https://images.unsplash.com/photo-1571721797421-f4c9f2b13107?w=400&q=80&auto=format', correct: false },
    { uri: 'https://images.unsplash.com/photo-1518611012118-696072aa579a?w=400&q=80&auto=format', correct: false },
  ],
};

export default function AIPostureAssessmentScreen() {
  const router = useRouter();
  const insets = useSafeAreaInsets();
  const theme = Colors.dark;

  const [uploadState, setUploadState] = useState<UploadState>({});
  const canStart = useMemo(
    () => Boolean(uploadState.front && uploadState.side && uploadState.back),
    [uploadState]
  );

  const [cameraPerm, setCameraPerm] = useState<ImagePicker.PermissionStatus | null>(null);
  const [libraryPerm, setLibraryPerm] = useState<ImagePicker.PermissionStatus | null>(null);
  const [libraryAccess, setLibraryAccess] = useState<'all' | 'limited' | 'none' | null>(null);
  const [cameraCanAsk, setCameraCanAsk] = useState<boolean | null>(null);
  const [libraryCanAsk, setLibraryCanAsk] = useState<boolean | null>(null);

  useEffect(() => {
    (async () => {
      const cam = await ImagePicker.getCameraPermissionsAsync();
      const lib = await ImagePicker.getMediaLibraryPermissionsAsync();
      setCameraPerm(cam.status);
      setLibraryPerm(lib.status);
      setLibraryAccess(
        (lib as any).accessPrivileges ?? (lib.status === 'granted' ? 'all' : 'none')
      );
      setCameraCanAsk(cam.canAskAgain);
      setLibraryCanAsk(lib.canAskAgain);
    })();
  }, []);

  async function requestAllPermissions() {
    try {
      const cam = await ImagePicker.requestCameraPermissionsAsync();
      const lib = await ImagePicker.requestMediaLibraryPermissionsAsync();
      setCameraPerm(cam.status);
      setLibraryPerm(lib.status);
      setLibraryAccess(
        (lib as any).accessPrivileges ?? (lib.status === 'granted' ? 'all' : 'none')
      );
      setCameraCanAsk(cam.canAskAgain);
      setLibraryCanAsk(lib.canAskAgain);
      const libGranted = lib.status === 'granted' || (lib as any).accessPrivileges === 'limited';
      if (cam.status !== 'granted' || !libGranted) {
        Alert.alert(
          '权限未完全授予',
          '请在系统设置中授予相机与相册权限以完成上传',
          [
            { text: '取消', style: 'cancel' },
            { text: '去设置', onPress: () => Linking.openSettings() },
          ]
        );
      }
    } catch { }
  }

  async function requestPermissionAndPick(source: 'camera' | 'library', key: PoseView) {
    try {
      if (source === 'camera') {
        const resp = await ImagePicker.requestCameraPermissionsAsync();
        setCameraPerm(resp.status);
        setCameraCanAsk(resp.canAskAgain);
        if (resp.status !== 'granted') {
          Alert.alert(
            '权限不足',
            '需要相机权限以拍摄照片',
            resp.canAskAgain
              ? [{ text: '好的' }]
              : [
                { text: '取消', style: 'cancel' },
                { text: '去设置', onPress: () => Linking.openSettings() },
              ]
          );
          return;
        }
        const result = await ImagePicker.launchCameraAsync({
          allowsEditing: true,
          quality: 0.8,
          aspect: [3, 4],
        });
        if (!result.canceled) {
          setUploadState((s) => ({ ...s, [key]: result.assets[0]?.uri ?? null }));
        }
      } else {
        const resp = await ImagePicker.requestMediaLibraryPermissionsAsync();
        setLibraryPerm(resp.status);
        setLibraryAccess(
          (resp as any).accessPrivileges ?? (resp.status === 'granted' ? 'all' : 'none')
        );
        setLibraryCanAsk(resp.canAskAgain);
        const libGranted = resp.status === 'granted' || (resp as any).accessPrivileges === 'limited';
        if (!libGranted) {
          Alert.alert(
            '权限不足',
            '需要相册权限以选择照片',
            resp.canAskAgain
              ? [{ text: '好的' }]
              : [
                { text: '取消', style: 'cancel' },
                { text: '去设置', onPress: () => Linking.openSettings() },
              ]
          );
          return;
        }
        const result = await ImagePicker.launchImageLibraryAsync({
          allowsEditing: true,
          quality: 0.8,
          aspect: [3, 4],
        });
        if (!result.canceled) {
          setUploadState((s) => ({ ...s, [key]: result.assets[0]?.uri ?? null }));
        }
      }
    } catch (e) {
      Alert.alert('发生错误', '选择图片失败，请重试');
    }
  }

  function handleStart() {
    if (!canStart) return;
    // TODO: 调用后端或进入分析页面
    Alert.alert('开始测评', '已收集三视角照片，准备开始AI体态分析');
  }

  return (
    <View style={[styles.screen, { backgroundColor: theme.background }]}>
      {/* Header */}
      <View style={[styles.header, { paddingTop: insets.top + 8 }]}>
        <TouchableOpacity
          accessibilityRole="button"
          onPress={() => router.back()}
          style={styles.backButton}
        >
          <Ionicons name="chevron-back" size={24} color="#ECEDEE" />
        </TouchableOpacity>
        <Text style={styles.headerTitle}>AI体态测评</Text>
        <View style={{ width: 32 }} />
      </View>

      <ScrollView
        contentContainerStyle={{ paddingBottom: insets.bottom + 120 }}
        showsVerticalScrollIndicator={false}
      >
        {/* Permissions Banner (iOS 优先提示) */}
        {Platform.OS === 'ios' && (
          (cameraPerm !== 'granted' || !(libraryPerm === 'granted' || libraryAccess === 'limited')) && (
            <BlurView intensity={18} tint="dark" style={styles.permBanner}>
              <Text style={styles.permTitle}>需要相机与相册权限</Text>
              <Text style={styles.permDesc}>
                授权后可拍摄或选择三视角全身照片用于AI体态测评。
              </Text>
              <View style={styles.permActions}>
                {((cameraCanAsk ?? true) || (libraryCanAsk ?? true)) ? (
                  <TouchableOpacity style={styles.permPrimary} onPress={requestAllPermissions}>
                    <Text style={styles.permPrimaryText}>一键授权</Text>
                  </TouchableOpacity>
                ) : (
                  <TouchableOpacity style={styles.permPrimary} onPress={() => Linking.openSettings()}>
                    <Text style={styles.permPrimaryText}>去设置开启</Text>
                  </TouchableOpacity>
                )}
                <TouchableOpacity style={styles.permSecondary} onPress={() => requestPermissionAndPick('library', 'front')}>
                  <Text style={styles.permSecondaryText}>稍后再说</Text>
                </TouchableOpacity>
              </View>
            </BlurView>
          )
        )}

        {/* Intro */}
        <View style={styles.introBox}>
          <Text style={styles.title}>上传标准姿势照片</Text>
          <Text style={styles.description}>
            请依次上传正面、侧面与背面全身照。保持光线均匀、背景简洁，身体立正自然放松。
          </Text>
        </View>

        {/* Upload sections */}
        <UploadTile
          label="正面"
          value={uploadState.front}
          onPickCamera={() => requestPermissionAndPick('camera', 'front')}
          onPickLibrary={() => requestPermissionAndPick('library', 'front')}
          samples={SAMPLES.front}
        />

        <UploadTile
          label="侧面"
          value={uploadState.side}
          onPickCamera={() => requestPermissionAndPick('camera', 'side')}
          onPickLibrary={() => requestPermissionAndPick('library', 'side')}
          samples={SAMPLES.side}
        />

        <UploadTile
          label="背面"
          value={uploadState.back}
          onPickCamera={() => requestPermissionAndPick('camera', 'back')}
          onPickLibrary={() => requestPermissionAndPick('library', 'back')}
          samples={SAMPLES.back}
        />
      </ScrollView>

      {/* Bottom CTA */}
      <View style={[styles.bottomCtaWrap, { paddingBottom: insets.bottom + 10 }]}>
        <TouchableOpacity
          disabled={!canStart}
          activeOpacity={1}
          onPress={handleStart}
          style={[
            styles.bottomCta,
            { backgroundColor: canStart ? theme.primary : theme.neutral300 },
          ]}
        >
          <Text style={[styles.bottomCtaText, { color: canStart ? theme.onPrimary : theme.textMuted }]}>
            {canStart ? '开始测评' : '请先完成三视角上传'}
          </Text>
        </TouchableOpacity>
      </View>
    </View>
  );
}

function UploadTile({
  label,
  value,
  onPickCamera,
  onPickLibrary,
  samples,
}: {
  label: string;
  value?: string | null;
  onPickCamera: () => void;
  onPickLibrary: () => void;
  samples: Sample[];
}) {
  return (
    <View style={styles.section}>
      <View style={styles.sectionHeader}>
        <Text style={styles.sectionTitle}>{label}</Text>
        {value ? (
          <Text style={styles.retakeHint}>可长按替换</Text>
        ) : (
          <Text style={styles.retakeHint}>需上传此视角</Text>
        )}
      </View>

      <TouchableOpacity
        activeOpacity={0.95}
        onLongPress={onPickLibrary}
        onPress={onPickCamera}
        style={styles.uploader}
      >
        {value ? (
          <Image source={{ uri: value }} style={styles.preview} />
        ) : (
          <View style={styles.placeholder}>
            <View style={styles.plusBadge}>
              <Ionicons name="camera" size={16} color="#192126" />
            </View>
            <Text style={styles.placeholderTitle}>拍摄或选择照片</Text>
            <Text style={styles.placeholderDesc}>点击拍摄，长按从相册选择</Text>
          </View>
        )}
      </TouchableOpacity>

      <BlurView intensity={18} tint="dark" style={styles.sampleBox}>
        <Text style={styles.sampleTitle}>示例</Text>
        <View style={styles.sampleRow}>
          {samples.map((s, idx) => (
            <View key={idx} style={styles.sampleItem}>
              <Image source={{ uri: s.uri }} style={styles.sampleImg} />
              <View style={[styles.sampleTag, { backgroundColor: s.correct ? '#2BCC7F' : '#E24D4D' }]}>
                <Text style={styles.sampleTagText}>{s.correct ? '正确示范' : '错误示范'}</Text>
              </View>
            </View>
          ))}
        </View>
      </BlurView>
    </View>
  );
}

const styles = StyleSheet.create({
  screen: {
    flex: 1,
  },
  permBanner: {
    marginTop: 12,
    marginHorizontal: 16,
    padding: 14,
    borderRadius: 16,
    backgroundColor: 'rgba(255,255,255,0.04)'
  },
  permTitle: {
    color: '#ECEDEE',
    fontSize: 16,
    fontWeight: '700',
  },
  permDesc: {
    color: 'rgba(255,255,255,0.75)',
    marginTop: 6,
    fontSize: 13,
  },
  permActions: {
    flexDirection: 'row',
    gap: 10,
    marginTop: 10,
  },
  permPrimary: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    paddingHorizontal: 14,
    height: 40,
    borderRadius: 12,
    backgroundColor: '#BBF246',
  },
  permPrimaryText: {
    color: '#192126',
    fontSize: 14,
    fontWeight: '800',
  },
  permSecondary: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    paddingHorizontal: 14,
    height: 40,
    borderRadius: 12,
    borderWidth: 1,
    borderColor: 'rgba(255,255,255,0.18)',
  },
  permSecondaryText: {
    color: 'rgba(255,255,255,0.85)',
    fontSize: 14,
    fontWeight: '700',
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: 16,
  },
  backButton: {
    width: 32,
    height: 32,
    borderRadius: 16,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: 'rgba(255,255,255,0.06)',
  },
  headerTitle: {
    fontSize: 22,
    color: '#ECEDEE',
    fontWeight: '700',
  },
  introBox: {
    marginTop: 12,
    paddingHorizontal: 20,
    gap: 10,
  },
  title: {
    fontSize: 26,
    color: '#ECEDEE',
    fontWeight: '800',
  },
  description: {
    fontSize: 15,
    lineHeight: 22,
    color: 'rgba(255,255,255,0.75)',
  },
  section: {
    marginTop: 16,
    paddingHorizontal: 16,
    gap: 12,
  },
  sectionHeader: {
    paddingHorizontal: 4,
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
  },
  sectionTitle: {
    color: '#ECEDEE',
    fontSize: 18,
    fontWeight: '700',
  },
  retakeHint: {
    color: 'rgba(255,255,255,0.55)',
    fontSize: 13,
  },
  uploader: {
    height: 220,
    borderRadius: 18,
    borderWidth: 1,
    borderStyle: 'dashed',
    borderColor: 'rgba(255,255,255,0.18)',
    backgroundColor: '#1E262C',
    overflow: 'hidden',
  },
  preview: {
    width: '100%',
    height: '100%',
  },
  placeholder: {
    flex: 1,
    alignItems: 'center',
    justifyContent: 'center',
    gap: 8,
  },
  plusBadge: {
    width: 36,
    height: 36,
    borderRadius: 18,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: '#BBF246',
  },
  placeholderTitle: {
    color: '#ECEDEE',
    fontSize: 16,
    fontWeight: '700',
  },
  placeholderDesc: {
    color: 'rgba(255,255,255,0.65)',
    fontSize: 12,
  },
  sampleBox: {
    marginTop: 8,
    borderRadius: 16,
    padding: 12,
    backgroundColor: 'rgba(255,255,255,0.04)',
  },
  sampleTitle: {
    color: 'rgba(255,255,255,0.8)',
    fontSize: 14,
    marginBottom: 8,
    fontWeight: '600',
  },
  sampleRow: {
    flexDirection: 'row',
    gap: 10,
  },
  sampleItem: {
    flex: 1,
  },
  sampleImg: {
    width: '100%',
    height: 90,
    borderRadius: 12,
    backgroundColor: '#111',
  },
  sampleTag: {
    alignSelf: 'flex-start',
    paddingHorizontal: 8,
    paddingVertical: 4,
    borderRadius: 8,
    marginTop: 6,
  },
  sampleTagText: {
    color: '#192126',
    fontSize: 12,
    fontWeight: '700',
  },
  bottomCtaWrap: {
    position: 'absolute',
    left: 16,
    right: 16,
    bottom: 0,
  },
  bottomCta: {
    height: 64,
    borderRadius: 32,
    alignItems: 'center',
    justifyContent: 'center',
  },
  bottomCtaText: {
    fontSize: 18,
    fontWeight: '800',
  },
});