"use client";

import { useRouter } from "next/navigation";
import * as React from "react";
import { EmptyState, Modal, cx } from "@agy/ui";
import { ADMIN_ITEMS, NAV_ITEMS, type NavItem } from "@/lib/nav";

/**
 * Command palette over the app's destinations.
 *
 * PLAN §12.3 asks for a command palette so power users can move between
 * sections without hunting through the sidebar. It is a client-side filter
 * over a fixed route list — the app has no dynamic search surface yet, so a
 * round trip would buy nothing and would break while offline.
 *
 * The platform-owner group is passed in rather than read from the session so
 * this component stays free of provider setup and is renderable in isolation.
 */

/** ``⌘K`` on macOS, ``Ctrl+K`` everywhere else. */
function isPaletteShortcut(event: KeyboardEvent): boolean {
  return (
    (event.metaKey || event.ctrlKey) &&
    !event.altKey &&
    !event.shiftKey &&
    event.key.toLowerCase() === "k"
  );
}

interface PalletGroup {
  title: string;
  items: NavItem[];
}

function buildGroups(isPlatformOwner: boolean): PalletGroup[] {
  const groups: PalletGroup[] = [{ title: "بخش‌ها", items: NAV_ITEMS }];
  if (isPlatformOwner) {
    groups.push({ title: "کنسول مالک سامانه", items: ADMIN_ITEMS });
  }
  return groups;
}

function matches(item: NavItem, needle: string): boolean {
  return (
    item.label.toLowerCase().includes(needle) ||
    item.hint.toLowerCase().includes(needle) ||
    item.href.includes(needle)
  );
}

export function CommandPalette({ isPlatformOwner = false }: { isPlatformOwner?: boolean }) {
  const router = useRouter();
  const [open, setOpen] = React.useState(false);
  const [query, setQuery] = React.useState("");
  const [active, setActive] = React.useState(0);
  const inputRef = React.useRef<HTMLInputElement>(null);

  const groups = React.useMemo(() => buildGroups(isPlatformOwner), [isPlatformOwner]);

  const filteredGroups = React.useMemo(() => {
    const needle = query.trim().toLowerCase();
    const keep = (item: NavItem) => !needle || matches(item, needle);
    return groups
      .map((group) => ({ title: group.title, items: group.items.filter(keep) }))
      .filter((group) => group.items.length > 0);
  }, [groups, query]);

  /**
   * Keyboard navigation walks the flattened, visible item list. `indexOf` is
   * safe here because both lists hold the same module-level object references.
   */
  const visible = React.useMemo(
    () => filteredGroups.flatMap((group) => group.items),
    [filteredGroups],
  );

  // Toggle the palette from anywhere on the page without stealing focus.
  React.useEffect(() => {
    const onKeyDown = (event: KeyboardEvent) => {
      if (!isPaletteShortcut(event)) return;
      event.preventDefault();
      setQuery("");
      setActive(0);
      setOpen((currentlyOpen) => !currentlyOpen);
    };
    window.addEventListener("keydown", onKeyDown);
    return () => window.removeEventListener("keydown", onKeyDown);
  }, []);

  // Focus the input once the dialog is mounted, so typing starts immediately.
  React.useEffect(() => {
    if (open) inputRef.current?.focus();
  }, [open]);

  // A narrowed list must not leave the highlight off the end.
  React.useEffect(() => {
    setActive(0);
  }, [query]);

  const close = React.useCallback(() => {
    setOpen(false);
    setQuery("");
  }, []);

  const go = React.useCallback(
    (href: string) => {
      close();
      router.push(href);
    },
    [close, router],
  );

  const onInputKeyDown = (event: React.KeyboardEvent<HTMLInputElement>) => {
    if (event.key === "Escape") {
      event.preventDefault();
      close();
      return;
    }
    if (visible.length === 0) return;
    if (event.key === "ArrowDown") {
      event.preventDefault();
      setActive((index) => (index + 1) % visible.length);
    } else if (event.key === "ArrowUp") {
      event.preventDefault();
      setActive((index) => (index - 1 + visible.length) % visible.length);
    } else if (event.key === "Enter") {
      const target = visible[active];
      if (target) {
        event.preventDefault();
        go(target.href);
      }
    }
  };

  return (
    <>
      <button
        type="button"
        onClick={() => {
          setQuery("");
          setActive(0);
          setOpen(true);
        }}
        aria-label="جست‌وجو و رفتن سریع"
        className="hidden items-center gap-2 rounded-lg border border-surface-border bg-surface-overlay px-2.5 py-1.5 text-xs text-slate-400 transition-colors hover:text-slate-200 focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 md:flex"
      >
        <span aria-hidden>⌕</span>
        <span>جست‌وجو…</span>
        <kbd className="rounded border border-surface-border px-1 text-[10px] text-slate-500">
          ⌘K
        </kbd>
      </button>

      <Modal
        open={open}
        title="جست‌وجو و رفتن سریع"
        description="با کلیدهای بالا و پایین جابه‌جایی کنید و Enter برای رفتن."
        onClose={close}
      >
        <input
          ref={inputRef}
          type="text"
          value={query}
          onChange={(event) => setQuery(event.target.value)}
          onKeyDown={onInputKeyDown}
          placeholder="نام بخش…"
          aria-label="جست‌وجوی بخش‌ها"
          className="h-10 w-full rounded-lg border border-surface-border bg-surface-overlay px-3 text-sm text-slate-100 placeholder:text-slate-500 focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/60"
        />

        <div className="mt-3 flex max-h-80 flex-col gap-3 overflow-y-auto">
          {filteredGroups.length === 0 ? (
            <EmptyState title="نتیجه‌ای پیدا نشد" description="عبارت دیگری را امتحان کنید." />
          ) : (
            filteredGroups.map((group) => (
              <div key={group.title} className="anim-stagger flex flex-col gap-1">
                <p className="px-1 text-[11px] font-medium text-slate-500">{group.title}</p>
                {group.items.map((item) => {
                  const index = visible.indexOf(item);
                  const isActive = index === active;
                  return (
                    <button
                      key={item.href}
                      type="button"
                      onMouseEnter={() => setActive(index)}
                      onClick={() => go(item.href)}
                      className={cx(
                        "flex items-center justify-between gap-2 rounded-md px-2 py-2 text-start",
                        isActive
                          ? "bg-accent-soft text-slate-100"
                          : "text-slate-300 hover:bg-surface-raised",
                      )}
                    >
                      <span className="text-sm">{item.label}</span>
                      <span className="text-xs text-slate-500">{item.hint}</span>
                    </button>
                  );
                })}
              </div>
            ))
          )}
        </div>
      </Modal>
    </>
  );
}