'use client';

import { motion, AnimatePresence } from 'framer-motion';
import { usePathname } from 'next/navigation';
import { useEffect, useState } from 'react';
import { useReducedMotion } from '@/hooks/use-reduced-motion';

const pageVariants = {
  initial: {
    opacity: 0,
    y: 8,
    scale: 0.98,
  },
  animate: {
    opacity: 1,
    y: 0,
    scale: 1,
    transition: {
      duration: 0.4,
      ease: [0.25, 1, 0.5, 1] as const,
      staggerChildren: 0.05,
    },
  },
  exit: {
    opacity: 0,
    y: -8,
    scale: 0.98,
    transition: {
      duration: 0.2,
      ease: [0.22, 1, 0.36, 1] as const,
    },
  },
};

export function PageTransition({ children }: { children: React.ReactNode }) {
  const pathname = usePathname();
  const shouldReduceMotion = useReducedMotion();
  const [mounted, setMounted] = useState(false);

  useEffect(() => {
    setMounted(true);
  }, []);

  // SSR 和首次 hydration 阶段直接渲染子内容，避免 framer-motion DOM 差异导致 hydration mismatch
  if (!mounted || shouldReduceMotion) {
    return <>{children}</>;
  }

  return (
    <AnimatePresence mode="wait" initial={false}>
      <motion.div
        key={pathname}
        variants={pageVariants}
        initial="initial"
        animate="animate"
        exit="exit"
        style={{
          willChange: 'transform, opacity',
          backfaceVisibility: 'hidden',
        }}
      >
        {children}
      </motion.div>
    </AnimatePresence>
  );
}

const sectionVariants = {
  hidden: { opacity: 0, y: 20 },
  visible: (i: number) => ({
    opacity: 1,
    y: 0,
    transition: {
      delay: i * 0.08,
      duration: 0.5,
      ease: [0.25, 1, 0.5, 1] as const,
    },
  }),
};

export function StaggerChildren({ 
  children, 
  className = '',
  staggerCount = 4 
}: { 
  children: React.ReactNode;
  className?: string;
  staggerCount?: number;
}) {
  const shouldReduceMotion = useReducedMotion();

  if (shouldReduceMotion) {
    return <div className={className}>{children}</div>;
  }

  return (
    <motion.div
      className={className}
      initial="hidden"
      animate="visible"
      variants={{
        visible: {
          transition: {
            staggerChildren: 0.06,
            delayChildren: 0.05,
          },
        },
      }}
    >
      {Array.isArray(children)
        ? children.map((child, i) => (
            <motion.div key={i} custom={Math.min(i, staggerCount)} variants={sectionVariants}>
              {child}
            </motion.div>
          ))
        : children
      }
    </motion.div>
  );
}