"use client";

import { usePathname } from "next/navigation";
import Link from "next/link";
import { INVENTORY_ENABLED } from "@/lib/feature-flags";
import { cn } from "@/lib/utils";
import {
  LayoutDashboard,
  FileText,
  Plus,
  CheckSquare,
  CreditCard,
  History,
  Receipt,
  Users,
  Ship,
  Building2,
  Briefcase,
  Store,
  Anchor,
  Package,
  Upload,
  MapPin,
  ShoppingCart,
  UserCircle,
  ShieldCheck,
} from "lucide-react";
import type { Role } from "@prisma/client";

interface NavItem {
  href: string;
  label: string;
  icon: React.ElementType;
  roles?: Role[];
}

const NAV_ITEMS: NavItem[] = [
  { href: "/dashboard",        label: "Dashboard",              icon: LayoutDashboard },
  { href: "/po/new",           label: "New PO",                 icon: Plus,        roles: ["TECHNICAL", "MANNING", "MANAGER", "SUPERUSER"] },
  { href: "/my-orders",        label: "Closed Purchase Orders", icon: FileText,    roles: ["TECHNICAL", "MANNING", "MANAGER", "SUPERUSER"] },
  { href: "/po/import",        label: "Import PO",              icon: Upload,      roles: ["MANAGER", "SUPERUSER"] },
  { href: "/approvals",        label: "Approvals",              icon: CheckSquare, roles: ["MANAGER", "SUPERUSER"] },
  { href: "/payments",         label: "Payments",               icon: CreditCard,  roles: ["ACCOUNTS"] },
  { href: "/payments/history", label: "Payment History",        icon: Receipt,     roles: ["ACCOUNTS", "SUPERUSER"] },
  { href: "/history",          label: "History",                icon: History,     roles: ["MANAGER", "SUPERUSER", "AUDITOR", "ADMIN"] },
  { href: "/profile",          label: "My Profile",             icon: UserCircle },
];

// ── Purchasing section ────────────────────────────────────────────────────────
// Staff browsing items (product catalogue + cart for PO creation)
const PURCHASING_STAFF: NavItem[] = [
  { href: "/inventory/items",   label: "Items",         icon: Package,      roles: ["TECHNICAL", "MANNING", "SUPERUSER"] },
  { href: "/inventory/vendors", label: "Vendors",       icon: Store,        roles: ["TECHNICAL", "MANNING", "SUPERUSER"] },
  { href: "/inventory/cart",    label: "Cart",          icon: ShoppingCart, roles: ["TECHNICAL", "MANNING", "SUPERUSER", "MANAGER"] },
];

// Manager catalogue management — Sites conditionally shown
// Admin does not use Purchasing; their links live under Administration
const PURCHASING_MGMT: NavItem[] = [
  { href: "/inventory/vendors", label: "Vendors",      icon: Store,   roles: ["MANAGER"] },
  { href: "/inventory/items",   label: "Items",        icon: Package, roles: ["MANAGER"] },
  { href: "/admin/vessels",     label: "Cost Centres", icon: Ship,    roles: ["MANAGER"] },
  ...(INVENTORY_ENABLED
    ? [{ href: "/admin/sites", label: "Sites", icon: MapPin, roles: ["MANAGER"] as Role[] }]
    : []),
];

const PURCHASING_ITEMS: NavItem[] = [...PURCHASING_STAFF, ...PURCHASING_MGMT];

// ── Administration section ────────────────────────────────────────────────────
// Vendors shown to MANAGER / ACCOUNTS under their own Administration header
const MANAGER_ADMIN_ITEMS: NavItem[] = [
  { href: "/admin/vendors",   label: "Vendors", icon: Store,   roles: ["MANAGER", "ACCOUNTS", "ADMIN"] },
  { href: "/admin/products",  label: "Items",   icon: Package, roles: ["MANAGER", "ADMIN"] },
];

// Full Administration section (ADMIN only)
const ADMIN_ITEMS: NavItem[] = [
  { href: "/admin/vessels",            label: "Cost Centres",      icon: Ship       },
  { href: "/admin/sites",              label: "Sites",             icon: MapPin     },
  { href: "/admin/users",              label: "Users",             icon: Users      },
  { href: "/admin/superuser-requests", label: "SuperUser Requests",icon: ShieldCheck },
  { href: "/admin/accounts",           label: "Accounting Codes",  icon: Building2  },
  { href: "/admin/companies",          label: "Companies",         icon: Briefcase  },
];

export function Sidebar({ userRole }: { userRole: Role }) {
  const pathname = usePathname();
  const isAdmin  = userRole === "ADMIN";

  const visibleMain       = NAV_ITEMS.filter((i) => !i.roles || i.roles.includes(userRole));
  const visiblePurchasing = PURCHASING_ITEMS.filter((i) => !i.roles || i.roles.includes(userRole));
  const visibleMgrAdmin   = MANAGER_ADMIN_ITEMS.filter((i) => !i.roles || i.roles.includes(userRole));

  return (
    <aside className="flex h-screen w-60 shrink-0 flex-col border-r border-neutral-200 bg-white">
      <div className="flex h-16 items-center gap-2.5 border-b border-neutral-200 px-4">
        <div className="flex h-8 w-8 items-center justify-center rounded-lg bg-primary-600">
          <Anchor className="h-4 w-4 text-white" />
        </div>
        <span className="text-sm font-semibold text-neutral-900">PPMS</span>
      </div>

      <nav className="flex-1 overflow-y-auto px-3 py-4 space-y-0.5">
        {visibleMain.map((item) => (
          <NavLink key={item.href} item={item} pathname={pathname} />
        ))}

        {visiblePurchasing.length > 0 && (
          <>
            <SectionHeader label="Purchasing" />
            {visiblePurchasing.map((item) => (
              <NavLink key={item.href} item={item} pathname={pathname} />
            ))}
          </>
        )}

        {/* Vendors under Administration for MANAGER / ACCOUNTS */}
        {!isAdmin && visibleMgrAdmin.length > 0 && (
          <>
            <SectionHeader label="Administration" />
            {visibleMgrAdmin.map((item) => (
              <NavLink key={item.href} item={item} pathname={pathname} />
            ))}
          </>
        )}

        {/* Full Administration section for ADMIN */}
        {isAdmin && (
          <>
            <SectionHeader label="Administration" />
            {[...MANAGER_ADMIN_ITEMS, ...ADMIN_ITEMS].map((item) => (
              <NavLink key={item.href} item={item} pathname={pathname} />
            ))}
          </>
        )}
      </nav>
    </aside>
  );
}

function SectionHeader({ label }: { label: string }) {
  return (
    <div className="pt-4 pb-1 px-3">
      <p className="text-xs font-semibold text-neutral-400 uppercase tracking-wider">{label}</p>
    </div>
  );
}

function NavLink({ item, pathname }: { item: NavItem; pathname: string }) {
  const isActive = pathname === item.href || pathname.startsWith(item.href + "/");
  const Icon = item.icon;
  return (
    <Link
      href={item.href}
      className={cn(
        "flex items-center gap-3 rounded-md px-3 py-2 text-sm font-medium transition-colors",
        isActive
          ? "bg-primary-50 text-primary-700"
          : "text-neutral-600 hover:bg-neutral-100 hover:text-neutral-900"
      )}
    >
      <Icon className="h-4 w-4 shrink-0" />
      {item.label}
    </Link>
  );
}
