"use client";

import { useEffect, useId, useRef, useState, type KeyboardEvent, type ReactNode } from "react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";

type DialogMorphProps = {
  /** Button label. */
  trigger: ReactNode;
  /** Dialog heading. Also its name for screen readers. */
  title: string;
  /** Small text under the heading. */
  description?: string;
  /** Dialog body. Pass a function to get a close() for your own buttons. */
  children?: ReactNode | ((close: () => void) => ReactNode);
  /** Keep the dialog inside the nearest positioned parent instead of the screen. */
  contained?: boolean;
  /** Replaces the default button look. */
  triggerClassName?: string;
  /** Replaces the default dialog look. */
  className?: string;
};

const FOCUSABLE = 'a[href], button:not([disabled]), input:not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"])';
const MORPH = { type: "spring" as const, stiffness: 380, damping: 34 };

/* DialogMorph: the button itself grows into the dialog and shrinks back into place on close. Focus stays trapped inside while open and returns to the button after. */
export function DialogMorph({
  trigger,
  title,
  description,
  children,
  contained = false,
  triggerClassName = "inline-flex items-center gap-2 bg-[#a78bfa] px-5 py-2.5 text-sm font-medium text-[#1a1530] outline-none focus-visible:ring-2 focus-visible:ring-white/70 focus-visible:ring-offset-2 focus-visible:ring-offset-[#0b0a14]",
  className = "border border-white/10 bg-[#141026] p-6 text-white shadow-2xl shadow-black/60",
}: DialogMorphProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const button = useRef<HTMLButtonElement>(null);
  const panel = useRef<HTMLDivElement>(null);
  const wasOpen = useRef(false);
  const [open, setOpen] = useState(false);
  const close = () => setOpen(false);
  const shared = reduce ? { initial: { opacity: 0 }, animate: { opacity: 1 }, exit: { opacity: 0 } } : { layoutId: `morph-${id}` };

  // Focus moves in on open and back to the button on close.
  useEffect(() => {
    if (open) (panel.current?.querySelector<HTMLElement>(FOCUSABLE) ?? panel.current)?.focus({ preventScroll: true });
    else if (wasOpen.current) button.current?.focus({ preventScroll: true });
    wasOpen.current = open;
  }, [open]);

  // Lock page scroll while open.
  useEffect(() => {
    if (!open || contained) return;
    const prev = document.body.style.overflow;
    document.body.style.overflow = "hidden";
    return () => {
      document.body.style.overflow = prev;
    };
  }, [open, contained]);

  const onKeyDown = (e: KeyboardEvent) => {
    if (e.key === "Escape") return close();
    if (e.key !== "Tab" || !panel.current) return;
    const items = [...panel.current.querySelectorAll<HTMLElement>(FOCUSABLE)];
    const edge = e.shiftKey ? items[0] : items[items.length - 1];
    if (document.activeElement === edge || document.activeElement === panel.current) {
      e.preventDefault();
      (e.shiftKey ? items[items.length - 1] : items[0])?.focus();
    }
  };

  return (
    <>
      {open ? (
        <span aria-hidden style={{ borderRadius: 14 }} className={`invisible ${triggerClassName}`}>
          {trigger}
        </span>
      ) : (
        <motion.button
          ref={button}
          type="button"
          aria-haspopup="dialog"
          layoutId={reduce ? undefined : `morph-${id}`}
          transition={MORPH}
          style={{ borderRadius: 14 }}
          onClick={() => setOpen(true)}
          className={triggerClassName}
        >
          {trigger}
        </motion.button>
      )}

      <AnimatePresence>
        {open && (
          <div key="layer" className={`${contained ? "absolute" : "fixed"} inset-0 z-50 grid place-items-center p-4`}>
            <motion.div
              aria-hidden
              onClick={close}
              className="absolute inset-0 bg-black/60"
              initial={{ opacity: 0 }}
              animate={{ opacity: 1 }}
              exit={{ opacity: 0 }}
              transition={{ duration: 0.2 }}
            />
            <motion.div
              ref={panel}
              role="dialog"
              aria-modal="true"
              aria-labelledby={`${id}-title`}
              aria-describedby={description ? `${id}-text` : undefined}
              tabIndex={-1}
              onKeyDown={onKeyDown}
              {...shared}
              transition={reduce ? { duration: 0.15 } : MORPH}
              style={{ borderRadius: 20 }}
              className={`relative max-h-full w-full max-w-md overflow-y-auto outline-none ${className}`}
            >
              <motion.div
                initial={{ opacity: 0 }}
                animate={{ opacity: 1, transition: { delay: reduce ? 0 : 0.16 } }}
                exit={{ opacity: 0, transition: { duration: 0.08 } }}
              >
                <h2 id={`${id}-title`} className="pr-8 text-lg font-semibold">
                  {title}
                </h2>
                {description && (
                  <p id={`${id}-text`} className="mt-1.5 text-sm text-white/60">
                    {description}
                  </p>
                )}
                {children && <div className="mt-4">{typeof children === "function" ? children(close) : children}</div>}
                <button
                  type="button"
                  aria-label="Close"
                  onClick={close}
                  className="absolute top-3.5 right-3.5 grid h-8 w-8 place-items-center rounded-lg text-white/50 outline-none hover:bg-white/10 hover:text-white focus-visible:ring-2 focus-visible:ring-white/70"
                >
                  <svg aria-hidden viewBox="0 0 12 12" className="h-3 w-3" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round">
                    <path d="M2 2l8 8M10 2l-8 8" />
                  </svg>
                </button>
              </motion.div>
            </motion.div>
          </div>
        )}
      </AnimatePresence>
    </>
  );
}