import React, { useEffect, useRef } from 'react';
import {
  View,
  StyleSheet,
  Animated,
  ViewStyle,
  Easing,
  DimensionValue,
} from 'react-native';
import { AppColors, BorderRadius, Spacing } from '@/constants/theme';

interface SkeletonProps {
  width?: DimensionValue;
  height?: DimensionValue;
  borderRadius?: number;
  style?: ViewStyle;
}

/**
 * Animated skeleton loader for placeholder content
 * Uses a shimmer effect to indicate loading state
 */
export function Skeleton({
  width = '100%',
  height = 20,
  borderRadius = BorderRadius.sm,
  style,
}: SkeletonProps) {
  const shimmerAnim = useRef(new Animated.Value(0)).current;

  useEffect(() => {
    const animation = Animated.loop(
      Animated.sequence([
        Animated.timing(shimmerAnim, {
          toValue: 1,
          duration: 1000,
          easing: Easing.ease,
          useNativeDriver: true,
        }),
        Animated.timing(shimmerAnim, {
          toValue: 0,
          duration: 1000,
          easing: Easing.ease,
          useNativeDriver: true,
        }),
      ])
    );

    animation.start();

    return () => animation.stop();
  }, [shimmerAnim]);

  const animatedOpacity = shimmerAnim.interpolate({
    inputRange: [0, 1],
    outputRange: [0.3, 0.7],
  });

  return (
    <Animated.View
      style={[
        styles.skeleton,
        {
          width,
          height,
          borderRadius,
          opacity: animatedOpacity,
        },
        style,
      ]}
    />
  );
}

/**
 * Skeleton for text lines - common use case
 */
export function SkeletonText({
  lines = 1,
  lineHeight = 16,
  spacing = Spacing.sm,
  lastLineWidth = '60%',
  style,
}: {
  lines?: number;
  lineHeight?: number;
  spacing?: number;
  lastLineWidth?: DimensionValue;
  style?: ViewStyle;
}) {
  return (
    <View style={style}>
      {Array.from({ length: lines }).map((_, index) => (
        <Skeleton
          key={index}
          height={lineHeight}
          width={index === lines - 1 && lines > 1 ? lastLineWidth : '100%'}
          style={index < lines - 1 ? { marginBottom: spacing } : undefined}
        />
      ))}
    </View>
  );
}

/**
 * Skeleton for avatar/circular elements
 */
export function SkeletonAvatar({
  size = 48,
  style,
}: {
  size?: number;
  style?: ViewStyle;
}) {
  return (
    <Skeleton
      width={size}
      height={size}
      borderRadius={size / 2}
      style={style}
    />
  );
}

/**
 * Skeleton for a card-like element
 */
export function SkeletonCard({
  height = 100,
  style,
}: {
  height?: DimensionValue;
  style?: ViewStyle;
}) {
  return (
    <View style={[styles.card, style]}>
      <Skeleton height={height} borderRadius={BorderRadius.lg} />
    </View>
  );
}

/**
 * Skeleton for list items with avatar and text
 */
export function SkeletonListItem({
  avatarSize = 48,
  lines = 2,
  style,
}: {
  avatarSize?: number;
  lines?: number;
  style?: ViewStyle;
}) {
  return (
    <View style={[styles.listItem, style]}>
      <SkeletonAvatar size={avatarSize} />
      <View style={styles.listItemContent}>
        <SkeletonText lines={lines} lastLineWidth="70%" />
      </View>
    </View>
  );
}

/**
 * Skeleton for beneficiary cards
 */
export function SkeletonBeneficiaryCard({ style }: { style?: ViewStyle }) {
  return (
    <View style={[styles.beneficiaryCard, style]}>
      <View style={styles.beneficiaryHeader}>
        <SkeletonAvatar size={56} />
        <View style={styles.beneficiaryInfo}>
          <Skeleton height={20} width="70%" style={{ marginBottom: Spacing.xs }} />
          <Skeleton height={14} width="50%" />
        </View>
      </View>
      <View style={styles.beneficiaryActions}>
        <Skeleton height={36} width={80} borderRadius={BorderRadius.md} />
        <Skeleton height={36} width={80} borderRadius={BorderRadius.md} />
      </View>
    </View>
  );
}

/**
 * Skeleton for sensor health cards
 */
export function SkeletonSensorCard({ style }: { style?: ViewStyle }) {
  return (
    <View style={[styles.sensorCard, style]}>
      <View style={styles.sensorHeader}>
        <Skeleton height={24} width={24} borderRadius={BorderRadius.sm} />
        <Skeleton height={18} width="60%" />
      </View>
      <Skeleton height={40} width="100%" style={{ marginTop: Spacing.md }} />
      <Skeleton height={12} width="80%" style={{ marginTop: Spacing.sm }} />
    </View>
  );
}

const styles = StyleSheet.create({
  skeleton: {
    backgroundColor: AppColors.surfaceSecondary,
  },
  card: {
    marginBottom: Spacing.md,
  },
  listItem: {
    flexDirection: 'row',
    alignItems: 'center',
    paddingVertical: Spacing.md,
    paddingHorizontal: Spacing.md,
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    marginBottom: Spacing.sm,
  },
  listItemContent: {
    flex: 1,
    marginLeft: Spacing.md,
  },
  beneficiaryCard: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.xl,
    padding: Spacing.lg,
    marginBottom: Spacing.md,
  },
  beneficiaryHeader: {
    flexDirection: 'row',
    alignItems: 'center',
    marginBottom: Spacing.md,
  },
  beneficiaryInfo: {
    flex: 1,
    marginLeft: Spacing.md,
  },
  beneficiaryActions: {
    flexDirection: 'row',
    gap: Spacing.sm,
  },
  sensorCard: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    padding: Spacing.md,
    marginBottom: Spacing.sm,
  },
  sensorHeader: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: Spacing.sm,
  },
});