'use client';

import { usePathname, useRouter } from 'next/navigation';
import {
  LayoutDashboard,
  Dumbbell,
  ListChecks,
  Calendar,
  Sparkles,
  Settings,
  LogOut,
} from 'lucide-react';
import { logoutAction } from './actions';

interface NavigationProps {
  userName: string;
  isAdmin: boolean;
}

interface NavSubItem {
  /** Either a route href or a section anchor (#…) on the parent page. */
  href: string;
  label: string;
  /** Admin-only — hidden for non-admin users. */
  adminOnly?: boolean;
}

interface NavLink {
  href: string;
  label: string;
  icon: typeof LayoutDashboard;
  /** v1.1.0:4 — sub-navigation rendered when the user is on this section.
   *  Items can either deep-link to a sibling route or scroll to an anchor
   *  on the parent page. */
  subItems?: NavSubItem[];
}

const navLinks: NavLink[] = [
  { href: '/main/dashboard', label: 'Dashboard', icon: LayoutDashboard },
  { href: '/main/workouts', label: 'Workouts', icon: Dumbbell },
  { href: '/main/programs', label: 'Programs', icon: Calendar },
  {
    href: '/main/ai',
    label: 'AI',
    icon: Sparkles,
    subItems: [
      { href: '/main/ai/generate', label: 'Generate' },
      { href: '/main/ai/history', label: 'History' },
      { href: '/main/ai/templates', label: 'Templates' },
    ],
  },
  { href: '/main/exercises', label: 'Exercises', icon: ListChecks },
  {
    href: '/main/settings',
    label: 'Settings',
    icon: Settings,
    subItems: [
      { href: '/main/settings#general', label: 'General' },
      { href: '/main/settings#password', label: 'Password' },
      { href: '/main/settings#sessions', label: 'Sessions' },
      { href: '/main/settings#ai', label: 'AI integration' },
      { href: '/main/settings#data', label: 'Export & import' },
      { href: '/main/settings#instance', label: 'Instance', adminOnly: true },
      { href: '/main/settings#danger', label: 'Danger zone' },
    ],
  },
];

export default function Navigation({ userName, isAdmin }: NavigationProps) {
  const pathname = usePathname();
  const router = useRouter();

  // A top-level item is "active" if the current pathname matches it
  // exactly OR is a subpage. We use this to decide whether to expand
  // the sub-nav under it.
  const isActive = (href: string) =>
    pathname === href || pathname.startsWith(href + '/');

  // A sub-item's active state depends on what it points to:
  //  - Route subitem (no #): exact pathname match
  //  - Anchor subitem (has #): always inactive in nav (anchor change
  //    doesn't fire pathname). The browser handles the highlight.
  const isSubActive = (subHref: string) => {
    const [path] = subHref.split('#');
    if (subHref.includes('#')) return false;
    return pathname === path;
  };

  const handleLogout = async () => {
    await logoutAction();
    router.push('/auth/login');
  };

  return (
    <>
      {/* Desktop Sidebar */}
      <aside className="hidden md:flex fixed left-0 top-0 h-screen w-[var(--sidebar-width)] border-r border-zinc-800 bg-[#0A0A0A] flex-col">
        <div className="p-6 border-b border-zinc-800">
          <h2 className="text-3xl font-display text-white tracking-wider">Proof of Work</h2>
        </div>

        <nav className="flex-1 overflow-y-auto p-4 space-y-1">
          {navLinks.map((link) => {
            const Icon = link.icon;
            const active = isActive(link.href);

            return (
              <div key={link.href}>
                <a
                  href={link.href}
                  className={`flex items-center gap-3 px-4 py-2.5 rounded transition-all duration-200 ${
                    active
                      ? 'bg-white text-black font-semibold'
                      : 'text-zinc-500 hover:text-white hover:bg-zinc-900'
                  }`}
                >
                  <Icon className="w-5 h-5 flex-shrink-0" />
                  <span className="text-sm">{link.label}</span>
                </a>

                {/* Expand sub-nav when this section is active. */}
                {active && link.subItems && link.subItems.length > 0 && (
                  <ul className="ml-4 mt-1 mb-2 border-l border-zinc-800 pl-3 space-y-0.5">
                    {link.subItems
                      .filter((s) => !s.adminOnly || isAdmin)
                      .map((sub) => {
                        const subActive = isSubActive(sub.href);
                        return (
                          <li key={sub.href}>
                            <a
                              href={sub.href}
                              className={`block px-3 py-1.5 rounded text-xs transition-colors ${
                                subActive
                                  ? 'text-white bg-zinc-800'
                                  : 'text-zinc-500 hover:text-white hover:bg-zinc-900'
                              }`}
                            >
                              {sub.label}
                            </a>
                          </li>
                        );
                      })}
                  </ul>
                )}
              </div>
            );
          })}
        </nav>

        <div className="border-t border-zinc-800 p-4 space-y-4">
          <div className="px-4 py-2">
            <p className="text-xs text-zinc-600 uppercase tracking-widest">User</p>
            <p className="font-semibold text-white truncate mt-1">{userName}</p>
          </div>

          <button
            onClick={handleLogout}
            className="flex items-center gap-3 px-4 py-2.5 rounded transition-all duration-200 w-full justify-start text-red-500 hover:text-red-400 hover:bg-red-950/30"
          >
            <LogOut className="w-5 h-5 flex-shrink-0" />
            <span className="text-sm">Logout</span>
          </button>
        </div>
      </aside>

      {/* Mobile Bottom Nav (no sub-nav — limited screen real estate) */}
      <header className="flex md:hidden fixed bottom-0 left-0 right-0 border-t border-zinc-800 bg-[#0A0A0A]">
        <nav className="flex items-center justify-around h-[var(--bottom-nav-height)] w-full">
          {navLinks.map((link) => {
            const Icon = link.icon;
            const active = isActive(link.href);

            return (
              <a
                key={link.href}
                href={link.href}
                className={`flex flex-col items-center justify-center flex-1 h-full gap-1 transition-colors duration-200 ${
                  active
                    ? 'text-white bg-zinc-900'
                    : 'text-zinc-500 hover:text-white'
                }`}
              >
                <Icon className="w-6 h-6" />
                <span className="text-xs">{link.label}</span>
              </a>
            );
          })}

          <button
            onClick={handleLogout}
            className="flex flex-col items-center justify-center flex-1 h-full gap-1 text-red-500 hover:text-red-400 transition-colors duration-200"
          >
            <LogOut className="w-6 h-6" />
            <span className="text-xs">Logout</span>
          </button>
        </nav>
      </header>
    </>
  );
}
