"use client";

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

export type CommandBarItem = {
  label: string;
  /** Link to open when picked (if no onSelect is given). */
  href?: string;
  /** Group heading the item sits under. */
  group?: string;
  /** Small text on the right, e.g. a shortcut. */
  hint?: string;
  /** Icon (an svg works best). */
  icon?: ReactNode;
  /** Extra words that should also find this item. */
  keywords?: string[];
};

type CommandBarProps = {
  items: CommandBarItem[];
  /** Called when an item is picked. Leave out to open item.href. */
  onSelect?: (item: CommandBarItem) => void;
  /** Letter that opens it with Ctrl / Cmd. false = no shortcut. */
  hotkey?: string | false;
  placeholder?: string;
  /** Keep the dialog inside the nearest `relative` parent instead of the whole screen. */
  contained?: boolean;
  /** Text on the open button. */
  trigger?: ReactNode;
  triggerClassName?: string;
  /** Colour of the highlight bar. */
  accent?: string;
  /** Name read out by screen readers. */
  label?: string;
  /** Dialog look. */
  className?: string;
};

const noop = () => () => {};
const isMac = () => /Mac|iPhone|iPad/.test(navigator.userAgent);

/* CommandBar: a Ctrl/Cmd + K palette. Type to filter, arrows move a gliding highlight, Enter goes. */
export function CommandBar({
  items,
  onSelect,
  hotkey = "k",
  placeholder = "Search or jump to…",
  contained = false,
  trigger = "Search",
  triggerClassName = "inline-flex items-center gap-3 rounded-xl border border-white/10 bg-white/5 py-2 pr-2 pl-3 text-sm text-white/60 outline-none hover:bg-white/10 focus-visible:ring-2 focus-visible:ring-white/70",
  accent = "#a78bfa",
  label = "Command bar",
  className = "border border-white/10 bg-[#141026]/95 text-white shadow-2xl shadow-black/60 backdrop-blur-xl",
}: CommandBarProps) {
  const reduce = useReducedMotion();
  const button = useRef<HTMLButtonElement>(null);
  const [open, setOpen] = useState(false);
  const mac = useSyncExternalStore(noop, isMac, () => false);
  const pos = contained ? "absolute" : "fixed";

  // Ctrl / Cmd + hotkey toggles the bar from anywhere on the page.
  useEffect(() => {
    if (!hotkey) return;
    const onKey = (e: globalThis.KeyboardEvent) => {
      if ((e.ctrlKey || e.metaKey) && e.key.toLowerCase() === hotkey.toLowerCase()) {
        e.preventDefault();
        setOpen((o) => !o);
      }
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [hotkey]);

  // 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 close = () => {
    setOpen(false);
    button.current?.focus();
  };

  const choose = (item: CommandBarItem) => {
    close();
    if (onSelect) onSelect(item);
    else if (item.href) window.location.assign(item.href);
  };

  return (
    <>
      <button
        ref={button}
        type="button"
        aria-haspopup="dialog"
        aria-expanded={open}
        onClick={() => setOpen(true)}
        className={triggerClassName}
      >
        <SearchIcon />
        <span>{trigger}</span>
        {hotkey && (
          <kbd className="ml-4 rounded-md border border-white/10 bg-white/5 px-1.5 py-0.5 font-mono text-[11px] text-white/50">
            {mac ? "⌘" : "Ctrl"} {hotkey.toUpperCase()}
          </kbd>
        )}
      </button>

      <AnimatePresence>
        {open && (
          <motion.div
            key="layer"
            className={`${pos} inset-0 z-50 flex items-start justify-center p-4 ${contained ? "pt-[8%]" : "pt-[12vh]"}`}
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            exit={{ opacity: 0 }}
            transition={{ duration: reduce ? 0 : 0.18 }}
          >
            <div aria-hidden onClick={close} className="absolute inset-0 bg-black/55 backdrop-blur-[2px]" />
            <Palette
              items={items}
              onChoose={choose}
              onClose={close}
              placeholder={placeholder}
              accent={accent}
              label={label}
              className={className}
              reduce={!!reduce}
            />
          </motion.div>
        )}
      </AnimatePresence>
    </>
  );
}

/* The dialog itself. It mounts fresh on every open, so the search box starts empty. */
function Palette({
  items,
  onChoose,
  onClose,
  placeholder,
  accent,
  label,
  className,
  reduce,
}: {
  items: CommandBarItem[];
  onChoose: (item: CommandBarItem) => void;
  onClose: () => void;
  placeholder: string;
  accent: string;
  label: string;
  className: string;
  reduce: boolean;
}) {
  const uid = useId();
  const input = useRef<HTMLInputElement>(null);
  const list = useRef<HTMLUListElement>(null);
  const [query, setQuery] = useState("");
  const [index, setIndex] = useState(0);

  const results = useMemo(() => {
    const q = query.trim().toLowerCase();
    if (!q) return items;
    return items.filter((i) => [i.label, i.group ?? "", ...(i.keywords ?? [])].join(" ").toLowerCase().includes(q));
  }, [items, query]);
  const active = Math.min(index, results.length - 1);

  useEffect(() => input.current?.focus(), []);

  // Keep the highlighted row in view.
  useEffect(() => {
    list.current?.querySelector(`[data-index="${active}"]`)?.scrollIntoView({ block: "nearest" });
  }, [active]);

  const onKeyDown = (e: KeyboardEvent<HTMLDivElement>) => {
    if (e.key === "Escape") return onClose();
    if (e.key === "Tab") return e.preventDefault(); // focus stays in the search box
    if (!results.length) return;
    if (e.key === "ArrowDown") {
      e.preventDefault();
      setIndex((i) => (Math.min(i, results.length - 1) + 1) % results.length);
    } else if (e.key === "ArrowUp") {
      e.preventDefault();
      setIndex((i) => (Math.min(i, results.length - 1) - 1 + results.length) % results.length);
    } else if (e.key === "Enter") {
      e.preventDefault();
      onChoose(results[active]);
    }
  };

  return (
    <motion.div
      role="dialog"
      aria-modal="true"
      aria-label={label}
      onKeyDown={onKeyDown}
      initial={{ opacity: 0, scale: reduce ? 1 : 0.96, y: reduce ? 0 : -8, filter: reduce ? "none" : "blur(6px)" }}
      animate={{ opacity: 1, scale: 1, y: 0, filter: "blur(0px)" }}
      exit={{ opacity: 0, scale: reduce ? 1 : 0.97, y: reduce ? 0 : -4, filter: reduce ? "none" : "blur(4px)" }}
      transition={reduce ? { duration: 0 } : { type: "spring", stiffness: 420, damping: 32 }}
      className={`relative w-full max-w-lg overflow-hidden rounded-2xl ${className}`}
    >
      <div className="flex items-center gap-3 border-b border-white/10 px-4">
        <SearchIcon />
        <input
          ref={input}
          type="text"
          role="combobox"
          aria-expanded="true"
          aria-controls={`${uid}-list`}
          aria-activedescendant={results.length ? `${uid}-opt-${active}` : undefined}
          aria-autocomplete="list"
          aria-label={label}
          placeholder={placeholder}
          value={query}
          onChange={(e) => {
            setQuery(e.target.value);
            setIndex(0);
          }}
          className="h-12 min-w-0 flex-1 bg-transparent text-sm outline-none placeholder:text-white/35"
        />
        <kbd className="rounded-md border border-white/10 px-1.5 py-0.5 font-mono text-[10px] text-white/40">Esc</kbd>
      </div>

      <ul ref={list} id={`${uid}-list`} role="listbox" aria-label={label} className="max-h-72 overflow-y-auto p-2">
        {results.map((item, i) => {
          const on = i === active;
          const head = item.group && item.group !== results[i - 1]?.group;
          return (
            <li key={`${item.group}-${item.label}`} role="presentation">
              {head && (
                <p aria-hidden className="px-3 pt-2 pb-1 font-mono text-[10px] uppercase tracking-[0.18em] text-white/35">
                  {item.group}
                </p>
              )}
              <div
                id={`${uid}-opt-${i}`}
                data-index={i}
                role="option"
                aria-selected={on}
                onPointerMove={() => i !== active && setIndex(i)}
                onClick={() => onChoose(item)}
                className={`relative flex cursor-pointer items-center gap-3 rounded-lg px-3 py-2 text-sm transition-colors duration-150 ${on ? "text-white" : "text-white/65"}`}
              >
                {on && (
                  <motion.span
                    layoutId={`${uid}-hl`}
                    aria-hidden
                    className="absolute inset-0 rounded-lg bg-white/[0.07]"
                    transition={reduce ? { duration: 0 } : { type: "spring", stiffness: 520, damping: 40 }}
                  >
                    <span className="absolute top-2 bottom-2 left-0 w-0.5 rounded-full" style={{ background: accent }} />
                  </motion.span>
                )}
                {item.icon && (
                  <span aria-hidden className="relative grid size-4 shrink-0 place-items-center [&>svg]:size-full">
                    {item.icon}
                  </span>
                )}
                <span className="relative min-w-0 flex-1 truncate">{item.label}</span>
                {item.hint && <span className="relative font-mono text-[11px] text-white/35">{item.hint}</span>}
              </div>
            </li>
          );
        })}
        {!results.length && (
          <li role="presentation" className="px-3 py-8 text-center text-sm text-white/40">
            Nothing found for “{query}”.
          </li>
        )}
      </ul>
    </motion.div>
  );
}

function SearchIcon() {
  return (
    <svg aria-hidden viewBox="0 0 16 16" className="size-4 shrink-0 opacity-60">
      <circle cx="7" cy="7" r="4.5" fill="none" stroke="currentColor" strokeWidth="1.5" />
      <path d="m10.5 10.5 3 3" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" />
    </svg>
  );
}