"use client";

import { AnimatePresence, motion, useReducedMotion } from "framer-motion";
import { LayoutRouterContext } from "next/dist/shared/lib/app-router-context.shared-runtime";
import { usePathname } from "next/navigation";
import { useContext, useState, type ReactNode } from "react";

/**
 * Pins the layout-router context captured when this instance mounted. Each
 * keyed page gets its own FrozenRouter, so the *outgoing* page keeps rendering
 * its old route data while it animates out.
 */
function FrozenRouter({ children }: { children: ReactNode }) {
  const context = useContext(LayoutRouterContext);
  const [frozen] = useState(context);

  if (!frozen) {
    return <>{children}</>;
  }

  return <LayoutRouterContext.Provider value={frozen}>{children}</LayoutRouterContext.Provider>;
}

/**
 * One unified page transition on every navigation. Lives in the (persistent)
 * site layout — NOT in a `template.tsx`, which Next re-creates on each
 * navigation and would reset AnimatePresence so nothing animates. The old page
 * animates out (rise + blur), then the new page animates in from below.
 */
export function PageTransition({ children }: { children: ReactNode }) {
  const reducedMotion = useReducedMotion();
  const pathname = usePathname();

  return (
    <AnimatePresence mode="wait">
      <motion.div
        key={pathname}
        initial={reducedMotion ? false : { opacity: 0, y: 20, filter: "blur(10px)" }}
        animate={{ opacity: 1, y: 0, filter: "blur(0px)" }}
        exit={reducedMotion ? { opacity: 0 } : { opacity: 0, y: -20, filter: "blur(10px)" }}
        transition={reducedMotion ? { duration: 0 } : { duration: 0.45, ease: [0.22, 1, 0.36, 1] }}
      >
        <FrozenRouter>{children}</FrozenRouter>
      </motion.div>
    </AnimatePresence>
  );
}