"use client";

import type { CSSProperties, ReactNode } from "react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";

const SHAPES = {
  text: { grid: "grid gap-2.5", bones: ["h-3.5 w-full rounded", "h-3.5 w-11/12 rounded", "h-3.5 w-3/5 rounded"] },
  list: { grid: "grid grid-cols-[2.5rem_1fr] items-center gap-x-3 gap-y-2", bones: ["row-span-2 size-10 rounded-full", "h-3.5 w-2/5 self-end rounded", "h-3 w-4/5 self-start rounded"] },
  card: { grid: "grid gap-3", bones: ["h-28 w-full rounded-xl", "h-4 w-3/5 rounded", "h-3 w-full rounded", "h-3 w-4/5 rounded"] },
};

const WIPE = "linear-gradient(100deg, #000 calc(var(--sf-wipe) - 30%), transparent var(--sf-wipe))";

type SkeletonFlowProps = {
  /** True shows the placeholder, false shows the children. */
  loading: boolean;
  /** The real content. */
  children: ReactNode;
  /** Placeholder layout. Pick the one closest to the content. */
  shape?: keyof typeof SHAPES;
  /** How many times the shape repeats. */
  count?: number;
  /** Read by screen readers while loading. */
  label?: string;
  /** Colour of the light that runs through the blocks. */
  accent?: string;
  /** Replaces the block look. */
  className?: string;
};

/* SkeletonFlow: a light runs from one placeholder block to the next, then the real content wipes in as the placeholder folds away. */
export function SkeletonFlow({ loading, children, shape = "text", count = 1, label = "Loading", accent = "#a78bfa", className = "bg-white/10" }: SkeletonFlowProps) {
  const reduce = useReducedMotion();
  const { grid, bones } = SHAPES[shape];
  const move = reduce ? { duration: 0 } : { duration: 0.5, ease: [0.16, 1, 0.3, 1] as const };

  return (
    <div aria-busy={loading} style={{ "--sf": accent } as CSSProperties} className="w-full">
      <span role="status" className="sr-only">
        {loading ? label : ""}
      </span>
      <AnimatePresence initial={false}>
        {loading ? (
          <motion.div
            key="bones"
            aria-hidden
            className="grid gap-5 overflow-hidden"
            initial={{ height: 0, opacity: 0 }}
            animate={{ height: "auto", opacity: 1 }}
            exit={{ height: 0, opacity: 0 }}
            transition={move}
          >
            {Array.from({ length: count }, (_, row) => (
              <div key={row} className={grid}>
                {bones.map((bone, i) => (
                  <div key={bone} className={`relative overflow-hidden ${bone} ${className}`}>
                    {!reduce && (
                      <motion.span
                        className="absolute inset-0 bg-linear-to-r from-transparent via-(--sf)/30 to-transparent"
                        initial={{ x: "-100%" }}
                        animate={{ x: "100%" }}
                        transition={{ duration: 1.1, ease: "easeInOut", repeat: Infinity, repeatDelay: 0.5, delay: (row * bones.length + i) * 0.08 }}
                      />
                    )}
                  </div>
                ))}
              </div>
            ))}
          </motion.div>
        ) : (
          <motion.div
            key="content"
            style={reduce ? undefined : { maskImage: WIPE, WebkitMaskImage: WIPE }}
            initial={{ height: 0, opacity: 0, overflow: "hidden", "--sf-wipe": "-30%" }}
            animate={{ height: "auto", opacity: 1, "--sf-wipe": "130%", transitionEnd: { overflow: "visible", maskImage: "none", WebkitMaskImage: "none" } }}
            exit={{ height: 0, opacity: 0, overflow: "hidden" }}
            transition={move}
          >
            {children}
          </motion.div>
        )}
      </AnimatePresence>
    </div>
  );
}