"use client";

import { useState, useEffect } from "react";
import { createPortal } from "react-dom";
import Link from "next/link";
import { usePathname } from "next/navigation";
import { ChevronDown, Menu, X } from "lucide-react";
import { cn } from "@/lib/utils";

export type NavLeaf = { href: string; label: string };
export type NavItem =
  | { kind: "link"; href: string; label: string; icon: React.ReactNode }
  | { kind: "group"; label: string; icon: React.ReactNode; children: NavLeaf[] };

// A group is active when the current path is one of its children, or sits under one
// of them. A child of "/" only matches exactly — otherwise every route would count as
// "under" the dashboard.
function isGroupActive(item: Extract<NavItem, { kind: "group" }>, pathname: string): boolean {
  return item.children.some((c) =>
    c.href === "/" ? pathname === "/" : pathname === c.href || pathname.startsWith(`${c.href}/`),
  );
}

// The desktop rail and the mobile drawer render the same list from this one
// component, so the two navs can never drift apart.
function NavList({ items, onNavigate }: { items: NavItem[]; onNavigate?: () => void }) {
  const pathname = usePathname();
  return (
    <nav className="p-3 space-y-0.5 text-sm">
      {items.map((item, i) =>
        item.kind === "link" ? (
          <LeafLink
            key={i}
            href={item.href}
            label={item.label}
            icon={item.icon}
            active={pathname === item.href || (item.href !== "/" && pathname.startsWith(item.href))}
            onClick={onNavigate}
          />
        ) : (
          <Group key={i} item={item} active={isGroupActive(item, pathname)} />
        )
      )}
    </nav>
  );
}

/**
 * Desktop rail only. It is `hidden lg:block`, so it contributes ZERO width below
 * `lg` and must stay a pure sibling of `<main>` — anything visible on mobile
 * rendered in this flex row steals width from the page. The mobile trigger lives
 * in the header instead; see `MobileNav`.
 */
export function Sidebar({ items }: { items: NavItem[] }) {
  return (
    <aside className="hidden lg:block w-64 shrink-0 bg-white dark:bg-surface-muted border-r border-gray-200 dark:border-border min-h-[calc(100vh-4rem)]">
      <NavList items={items} />
    </aside>
  );
}

/**
 * Mobile nav: the hamburger plus the drawer it opens. Rendered INSIDE the header,
 * which is the whole point — the old version put the button in the content flex
 * row, where its 36px was subtracted from every page below `lg` and indented the
 * entire site on phones and tablets.
 *
 * The header is full-bleed, so a 44px trigger there costs no content width.
 * `-ml-3` pulls the hit area into the header's own `px-4`, which lands the icon's
 * left edge exactly on the logo's (16px) without changing the logo's position.
 */
export function MobileNav({ items }: { items: NavItem[] }) {
  const pathname = usePathname();
  const [open, setOpen] = useState(false);
  const [mounted, setMounted] = useState(false);

  // Close drawer on navigation
  useEffect(() => {
    setOpen(false);
  }, [pathname]);

  // Scroll lock, plus the SSR gate for the portal below — `document` does not
  // exist while this component is server-rendered.
  useEffect(() => {
    setMounted(true);
    document.body.style.overflow = open ? "hidden" : "";
    return () => {
      document.body.style.overflow = "";
    };
  }, [open]);

  return (
    <>
      <button
        type="button"
        onClick={() => setOpen(true)}
        aria-label="Open navigation"
        aria-expanded={open}
        className="lg:hidden -ml-3 w-11 h-11 shrink-0 grid place-items-center rounded-lg hover:bg-gray-100 dark:hover:bg-white/5 text-gray-500 dark:text-gray-400"
      >
        <Menu className="w-5 h-5" />
      </button>

      {/* ⚠️ THE PORTAL IS LOAD-BEARING — do not "simplify" it back to inline JSX.
          The header carries `backdrop-blur`, and a filter/backdrop-filter makes an
          element the containing block for its `position: fixed` descendants. Inline,
          this drawer would size and position itself against the 64px header box
          instead of the viewport — a 64px-tall sliver pinned under the header.
          Portalling to <body> returns it to the root stacking context.

          This is the same trap class as MachineCombobox: a portal is NOT a DOM
          descendant of the component that made it, so any hit-testing that reaches
          across this boundary (click-away, focus traps) will read as "outside". */}
      {mounted &&
        createPortal(
          <>
            {open && (
              <div
                className="lg:hidden fixed inset-0 z-[1200] bg-black/40"
                onClick={() => setOpen(false)}
              />
            )}
            <aside
              className={cn(
                "lg:hidden fixed top-0 left-0 bottom-0 z-[1300] w-72 bg-white dark:bg-surface-muted shadow-2xl transition-transform",
                open ? "translate-x-0" : "-translate-x-full"
              )}
            >
              <div className="flex items-center justify-between px-4 h-16 border-b border-gray-200 dark:border-border">
                <div className="flex items-center gap-2">
                  <img
                    src="/brand/logo.png"
                    alt="Mega Plant"
                    className="w-8 h-8 rounded-xl object-contain bg-white dark:bg-bg shadow-sm"
                  />
                  <span className="text-sm font-semibold text-[#003D5B] dark:text-white">Mega Plant</span>
                </div>
                <button
                  type="button"
                  onClick={() => setOpen(false)}
                  aria-label="Close navigation"
                  className="w-11 h-11 grid place-items-center rounded-lg hover:bg-gray-100 dark:hover:bg-white/5 text-gray-500 dark:text-gray-400"
                >
                  <X className="w-5 h-5" />
                </button>
              </div>
              <NavList items={items} onNavigate={() => setOpen(false)} />
            </aside>
          </>,
          document.body,
        )}
    </>
  );
}

function LeafLink({
  href, label, icon, active, onClick,
}: {
  href: string; label: string; icon: React.ReactNode; active: boolean; onClick?: () => void;
}) {
  return (
    <Link
      href={href}
      onClick={onClick}
      className={cn(
        "min-h-11 flex items-center gap-3 px-3 py-2 rounded-lg font-medium transition",
        active
          ? "bg-gradient-to-r from-[#30638E]/10 to-[#00798C]/5 text-[#003D5B] dark:from-[#30638E]/20 dark:to-[#00798C]/10 dark:text-white"
          : "text-gray-600 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-white/5 hover:text-gray-900 dark:hover:text-white"
      )}
    >
      <span className={cn(active ? "text-accent-ink" : "text-gray-400")}>{icon}</span>
      <span>{label}</span>
    </Link>
  );
}

function Group({ item, active }: { item: Extract<NavItem, { kind: "group" }>; active: boolean }) {
  const [open, setOpen] = useState(active);
  const pathname = usePathname();
  return (
    <div>
      <button
        onClick={() => setOpen((o) => !o)}
        className={cn(
          "w-full min-h-11 flex items-center gap-3 px-3 py-2 rounded-lg font-medium transition",
          active
            ? "text-[#003D5B] dark:text-white"
            : "text-gray-600 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-white/5 hover:text-gray-900 dark:hover:text-white"
        )}
      >
        <span className={cn(active ? "text-accent-ink" : "text-gray-400")}>{item.icon}</span>
        <span className="flex-1 text-left">{item.label}</span>
        <ChevronDown className={cn("w-4 h-4 text-gray-400 transition-transform", open && "rotate-180")} />
      </button>
      {open && (
        <div className="ml-7 mt-0.5 space-y-0.5 border-l-2 border-gray-100 dark:border-border pl-2">
          {item.children.map((child) => {
            const childActive = pathname === child.href;
            return (
              <Link
                key={child.href}
                href={child.href}
                className={cn(
                  "flex items-center min-h-11 px-3 py-1.5 rounded-lg text-xs font-medium transition",
                  childActive
                    ? "bg-[#30638E]/10 text-[#30638E] dark:bg-[#00798C]/15 dark:text-[#00798C]"
                    : "text-gray-500 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-white/5 hover:text-gray-900 dark:hover:text-white"
                )}
              >
                {child.label}
              </Link>
            );
          })}
        </div>
      )}
    </div>
  );
}