import { Outlet, Link, useNavigate, useLocation } from "react-router-dom";
import { Suspense } from "react";
import { SidebarProvider, SidebarTrigger } from "@/components/ui/sidebar";
import {
  Sidebar, SidebarContent, SidebarGroup, SidebarGroupContent,
  SidebarGroupLabel, SidebarMenu, SidebarMenuButton, SidebarMenuItem,
  SidebarHeader, SidebarFooter, SidebarSeparator, useSidebar,
} from "@/components/ui/sidebar";
import { Collapsible, CollapsibleContent, CollapsibleTrigger } from "@/components/ui/collapsible";
import { NavLink } from "@/components/NavLink";
import { useAuth } from "@/contexts/AuthContext";
import NotificationDropdown from "@/components/NotificationDropdown";
import { ThemeToggle } from "@/components/ThemeToggle";
import { LanguageToggle } from "@/components/LanguageToggle";
import AiAssistantDrawer from "@/components/ai/AiAssistantDrawer";
import AiSearchBar from "@/components/ai/AiSearchBar";
import { usePermissions } from "@/hooks/usePermissions";
import { Button } from "@/components/ui/button";
import {
  DropdownMenu, DropdownMenuContent, DropdownMenuItem,
  DropdownMenuSeparator, DropdownMenuTrigger,
} from "@/components/ui/dropdown-menu";
import {
  Breadcrumb, BreadcrumbItem, BreadcrumbLink, BreadcrumbList,
  BreadcrumbPage, BreadcrumbSeparator,
} from "@/components/ui/breadcrumb";
import {
  GraduationCap, LogOut, User, Settings, LayoutDashboard, ClipboardList,
  FileText, Layers, BookOpen, Wand2, GitBranch, Users, BarChart3,
  Building2, History, CreditCard, Ticket, BookA, PenTool,
  Calendar, ChevronDown, HelpCircle, LucideIcon, Target, FolderOpen,
  CalendarDays, Landmark, UserPlus, ScrollText, Award,
  HelpCircle as FaqIcon, Bell, Workflow,
  CalendarOff, DollarSign, BookMarked, BarChartHorizontal, TrendingUp,
  Library, Activity, Warehouse, UserCog, Sparkles, Compass,
} from "lucide-react";
import React from "react";
import { useTranslation } from "react-i18next";

// ============= Navigation Config =============
// Items store i18n keys (`titleKey`) rather than literal strings so Arabic
// language switches update the sidebar without the component having to
// re-mount.
interface NavItem { titleKey: string; url: string; icon: LucideIcon }

const overviewItems: NavItem[] = [
  { titleKey: "nav.smartWizard", url: "/admin/smart-wizard", icon: Sparkles },
  { titleKey: "nav.adminDashboard", url: "/admin/dashboard", icon: LayoutDashboard },
  { titleKey: "nav.platformDashboard", url: "/admin/platform", icon: BarChart3 },
];

const lmsItems: NavItem[] = [
  { titleKey: "nav.courses", url: "/admin/courses", icon: BookOpen },
  { titleKey: "nav.students", url: "/admin/students", icon: Users },
  { titleKey: "nav.teachers", url: "/admin/teachers", icon: GraduationCap },
  { titleKey: "nav.batches", url: "/admin/batches", icon: Layers },
  { titleKey: "nav.timetable", url: "/admin/timetable", icon: Calendar },
  { titleKey: "nav.reports", url: "/admin/reports", icon: BarChart3 },
];

const academicItems: NavItem[] = [
  { titleKey: "nav.assignments", url: "/admin/assignments", icon: ClipboardList },
  { titleKey: "nav.examsList", url: "/admin/examsList", icon: FileText },
  { titleKey: "nav.examStructures", url: "/admin/exam-structures", icon: Layers },
  { titleKey: "nav.rubrics", url: "/admin/rubrics", icon: BookOpen },
  { titleKey: "nav.generation", url: "/admin/generation", icon: Wand2 },
  { titleKey: "nav.reviewQueue", url: "/admin/exam/review-queue", icon: Sparkles },
  { titleKey: "nav.aiPrompts", url: "/admin/ai/prompts", icon: Wand2 },
  { titleKey: "nav.aiFeedback", url: "/admin/ai/feedback", icon: Sparkles },
  { titleKey: "nav.coursePlans", url: "/admin/course-plans", icon: Compass },
  { titleKey: "nav.approvalWorkflows", url: "/admin/approval-workflows", icon: GitBranch },
];

const adaptiveItems: NavItem[] = [
  { titleKey: "nav.taxonomy", url: "/admin/taxonomy", icon: Target },
  { titleKey: "nav.resources", url: "/admin/resources", icon: FolderOpen },
];

const institutionalItems: NavItem[] = [
  { titleKey: "nav.academicYears", url: "/admin/academic-years", icon: CalendarDays },
  { titleKey: "nav.departments", url: "/admin/departments", icon: Landmark },
  { titleKey: "nav.admissions", url: "/admin/admissions", icon: UserPlus },
  { titleKey: "nav.admissionRegister", url: "/admin/admission-register", icon: ScrollText },
  { titleKey: "nav.examSessions", url: "/admin/exam-sessions", icon: FileText },
  { titleKey: "nav.marksheets", url: "/admin/marksheets", icon: Award },
  { titleKey: "nav.studentLeave", url: "/admin/student-leave", icon: CalendarOff },
  { titleKey: "nav.fees", url: "/admin/fees", icon: DollarSign },
  { titleKey: "nav.lessons", url: "/admin/lessons", icon: BookMarked },
  { titleKey: "nav.gradebook", url: "/admin/gradebook", icon: BarChartHorizontal },
  { titleKey: "nav.studentProgress", url: "/admin/student-progress", icon: TrendingUp },
  { titleKey: "nav.library", url: "/admin/library", icon: Library },
  { titleKey: "nav.activities", url: "/admin/activities", icon: Activity },
  { titleKey: "nav.facilities", url: "/admin/facilities", icon: Warehouse },
];

const managementItems: NavItem[] = [
  { titleKey: "nav.users", url: "/admin/users", icon: Users },
  { titleKey: "nav.entities", url: "/admin/entities", icon: Building2 },
  { titleKey: "nav.classrooms", url: "/admin/classrooms", icon: GraduationCap },
  { titleKey: "nav.userRoles", url: "/admin/user-roles", icon: UserCog },
  { titleKey: "nav.rolesPermissions", url: "/admin/roles-permissions", icon: Settings },
  { titleKey: "nav.authorityMatrix", url: "/admin/authority-matrix", icon: Workflow },
];

const reportItems: NavItem[] = [
  { titleKey: "nav.studentPerformance", url: "/admin/student-performance", icon: BarChart3 },
  { titleKey: "nav.statsCorporate", url: "/admin/stats-corporate", icon: Building2 },
  { titleKey: "nav.record", url: "/admin/record", icon: History },
];

const trainingItems: NavItem[] = [
  { titleKey: "nav.vocabulary", url: "/admin/training/vocabulary", icon: BookA },
  { titleKey: "nav.grammar", url: "/admin/training/grammar", icon: PenTool },
];

const configItems: NavItem[] = [
  { titleKey: "nav.faqManager", url: "/admin/faq", icon: FaqIcon },
  { titleKey: "nav.notificationRules", url: "/admin/notification-rules", icon: Bell },
  { titleKey: "nav.approvalConfig", url: "/admin/approval-config", icon: Workflow },
];

const supportItems: NavItem[] = [
  { titleKey: "nav.paymentRecord", url: "/admin/payment-record", icon: CreditCard },
  { titleKey: "nav.tickets", url: "/admin/tickets", icon: Ticket },
  { titleKey: "nav.settings", url: "/admin/settings-platform", icon: Settings },
];

// ============= Reusable sidebar group =============
function SidebarNavGroup({ labelKey, items }: { labelKey: string; items: NavItem[] }) {
  const { state } = useSidebar();
  const { t } = useTranslation();
  const collapsed = state === "collapsed";

  return (
    <SidebarGroup>
      <SidebarGroupLabel>{t(labelKey)}</SidebarGroupLabel>
      <SidebarGroupContent>
        <SidebarMenu>
          {items.map((item) => {
            const label = t(item.titleKey);
            return (
              <SidebarMenuItem key={item.url}>
                <SidebarMenuButton asChild tooltip={label}>
                  <NavLink
                    to={item.url}
                    end={item.url.endsWith("/dashboard") || item.url.endsWith("/platform")}
                    className="flex items-center gap-2 px-2 py-1.5 rounded-md text-sm text-sidebar-foreground hover:bg-sidebar-accent transition-colors"
                    activeClassName="bg-sidebar-accent text-sidebar-accent-foreground font-medium"
                  >
                    <item.icon className="h-4 w-4 shrink-0" />
                    {!collapsed && <span>{label}</span>}
                  </NavLink>
                </SidebarMenuButton>
              </SidebarMenuItem>
            );
          })}
        </SidebarMenu>
      </SidebarGroupContent>
    </SidebarGroup>
  );
}

// ============= Breadcrumbs =============
// Map URL segments to i18n keys so breadcrumbs follow the active locale.
// Segments without an entry fall back to a Title-cased version of the slug.
const routeLabelKeys: Record<string, string> = {
  admin: "breadcrumb.admin", dashboard: "breadcrumb.dashboard",
  platform: "breadcrumb.platform", courses: "nav.courses",
  students: "nav.students", teachers: "nav.teachers", batches: "nav.batches",
  timetable: "nav.timetable", reports: "nav.reports",
  assignments: "nav.assignments", examsList: "nav.examsList",
  "exam-structures": "nav.examStructures", rubrics: "nav.rubrics",
  generation: "nav.generation", "review-queue": "nav.reviewQueue",
  review: "breadcrumb.review", prompts: "nav.aiPrompts", ai: "breadcrumb.ai",
  feedback: "breadcrumb.feedback",
  "approval-workflows": "nav.approvalWorkflows", users: "nav.users",
  entities: "nav.entities", classrooms: "nav.classrooms",
  "student-performance": "nav.studentPerformance",
  "stats-corporate": "nav.statsCorporate", record: "nav.record",
  training: "sidebarGroup.training", vocabulary: "nav.vocabulary",
  grammar: "nav.grammar", "payment-record": "nav.paymentRecord",
  tickets: "nav.tickets", "settings-platform": "nav.settings",
  settings: "nav.settings", profile: "nav.profile", exam: "breadcrumb.exam",
  "academic-years": "nav.academicYears", departments: "nav.departments",
  admissions: "nav.admissions", "admission-register": "nav.admissionRegister",
  "exam-sessions": "nav.examSessions", marksheets: "nav.marksheets",
  faq: "nav.faqManager", "notification-rules": "nav.notificationRules",
  "approval-config": "nav.approvalConfig",
  "student-leave": "nav.studentLeave", fees: "nav.fees",
  lessons: "nav.lessons", gradebook: "nav.gradebook",
  "student-progress": "nav.studentProgress", library: "nav.library",
  activities: "nav.activities", facilities: "nav.facilities",
};

function AppBreadcrumbs() {
  const location = useLocation();
  const { t } = useTranslation();
  const segments = location.pathname.split("/").filter(Boolean);

  return (
    <Breadcrumb>
      <BreadcrumbList>
        <BreadcrumbItem>
          <BreadcrumbLink asChild><Link to="/admin/dashboard">{t("common.home")}</Link></BreadcrumbLink>
        </BreadcrumbItem>
        {segments.map((seg, i) => {
          const path = "/" + segments.slice(0, i + 1).join("/");
          const key = routeLabelKeys[seg];
          const label = key ? t(key) : seg.charAt(0).toUpperCase() + seg.slice(1);
          const isLast = i === segments.length - 1;
          return (
            <React.Fragment key={path}>
              <BreadcrumbSeparator />
              <BreadcrumbItem>
                {isLast ? <BreadcrumbPage>{label}</BreadcrumbPage> : <BreadcrumbLink asChild><Link to={path}>{label}</Link></BreadcrumbLink>}
              </BreadcrumbItem>
            </React.Fragment>
          );
        })}
      </BreadcrumbList>
    </Breadcrumb>
  );
}

// ============= Route content fallback =============
// Shown only inside the main content area while a lazy-loaded route chunk
// is fetching. Keeping the fallback local means the sidebar and header
// stay mounted during navigation — previously the page felt like a full
// browser reload because the outer App-level Suspense replaced everything
// with a full-viewport spinner.
function RouteContentFallback() {
  return (
    <div className="flex items-center justify-center py-20">
      <div className="animate-spin rounded-full h-6 w-6 border-b-2 border-primary" />
    </div>
  );
}

// ============= Main Layout =============
export default function AdminLmsLayout() {
  const { user, logout } = useAuth();
  const navigate = useNavigate();
  const { t } = useTranslation();

  const initials = user?.name?.split(" ").map(w => w[0]).join("").slice(0, 2).toUpperCase() ?? "??";

  const handleLogout = async () => {
    await logout();
    navigate("/login");
  };

  return (
    <SidebarProvider>
      <div className="min-h-screen flex w-full">
        <AdminSidebar />
        <div className="flex-1 flex flex-col min-w-0">
          <header className="h-14 border-b bg-card flex items-center justify-between px-4 shrink-0">
            <div className="flex items-center gap-3">
              <SidebarTrigger aria-label={t("chrome.toggleSidebar")} />
              <AppBreadcrumbs />
            </div>
            <AiSearchBar />
            <div className="flex items-center gap-2">
              <LanguageToggle />
              <ThemeToggle />
              <NotificationDropdown />
              <Button variant="ghost" size="icon" aria-label={t("chrome.ticketsTooltip")} onClick={() => navigate("/admin/tickets")} className="text-muted-foreground hover:text-foreground">
                <Ticket className="h-4 w-4" />
              </Button>
              <DropdownMenu>
                <DropdownMenuTrigger asChild>
                  <Button variant="ghost" size="icon" className="rounded-full">
                    <div className="h-8 w-8 rounded-full bg-primary flex items-center justify-center">
                      <span className="text-xs font-semibold text-primary-foreground">{initials}</span>
                    </div>
                  </Button>
                </DropdownMenuTrigger>
                <DropdownMenuContent align="end" className="w-48">
                  <div className="px-3 py-2">
                    <p className="text-sm font-medium">{user?.name ?? t("userMenu.userFallback")}</p>
                    <p className="text-xs text-muted-foreground">{user?.email ?? ""}</p>
                  </div>
                  <DropdownMenuSeparator />
                  <DropdownMenuItem onClick={() => navigate("/admin/profile")}>
                    <User className="me-2 h-4 w-4" /> {t("userMenu.profile")}
                  </DropdownMenuItem>
                  <DropdownMenuItem onClick={() => navigate("/admin/settings-platform")}>
                    <Settings className="me-2 h-4 w-4" /> {t("userMenu.settings")}
                  </DropdownMenuItem>
                  <DropdownMenuSeparator />
                  <DropdownMenuItem onClick={handleLogout}>
                    <LogOut className="me-2 h-4 w-4" /> {t("userMenu.logout")}
                  </DropdownMenuItem>
                </DropdownMenuContent>
              </DropdownMenu>
            </div>
          </header>
          <main className="flex-1 overflow-auto p-6">
            <Suspense fallback={<RouteContentFallback />}>
              <Outlet />
            </Suspense>
          </main>
        </div>
      </div>
      <AiAssistantDrawer />
      <Link
        to="/admin/tickets"
        className="fixed bottom-6 end-6 z-50 flex items-center gap-2 rounded-full bg-primary px-4 py-2.5 text-primary-foreground shadow-lg hover:opacity-90 transition-opacity"
      >
        <HelpCircle className="h-4 w-4" />
        <span className="text-sm font-medium">{t("chrome.needHelp")}</span>
      </Link>
    </SidebarProvider>
  );
}

// ============= Admin Sidebar =============
function AdminSidebar() {
  const { state } = useSidebar();
  const collapsed = state === "collapsed";
  const { user } = useAuth();
  const { hasAnyPermission, isAdmin } = usePermissions();
  const { t, i18n } = useTranslation();
  const sidebarSide = i18n.dir() === "rtl" ? "right" : "left";

  const showManagement = isAdmin || hasAnyPermission(["view_entities", "view_students", "view_teachers"]);
  const showReports = isAdmin || hasAnyPermission(["view_statistics", "view_student_performance", "view_entity_statistics"]);
  const showPayments = isAdmin || hasAnyPermission(["view_payment_record", "pay_entity"]);

  return (
    <Sidebar side={sidebarSide} collapsible="icon">
      <SidebarHeader className="p-4">
        <div className="flex items-center gap-2">
          {collapsed ? (
            <img
              src="/logo.png"
              alt={t("chrome.adminAlt")}
              className="h-9 w-9 shrink-0 rounded-lg object-contain"
            />
          ) : (
            <img
              src="/logo.png"
              alt={t("chrome.adminAltLong")}
              className="h-14 w-auto shrink-0 object-contain"
            />
          )}
        </div>
      </SidebarHeader>
      <SidebarSeparator />
      <SidebarContent>
        <SidebarNavGroup labelKey="sidebarGroup.overview" items={overviewItems} />
        <SidebarNavGroup labelKey="sidebarGroup.lms" items={lmsItems} />
        <SidebarNavGroup labelKey="sidebarGroup.adaptiveLearning" items={adaptiveItems} />
        <SidebarNavGroup labelKey="sidebarGroup.institutional" items={institutionalItems} />
        <SidebarNavGroup labelKey="sidebarGroup.academic" items={academicItems} />
        {showManagement && <SidebarNavGroup labelKey="sidebarGroup.management" items={managementItems} />}
        {showReports && <SidebarNavGroup labelKey="sidebarGroup.reports" items={reportItems} />}
        <SidebarNavGroup labelKey="sidebarGroup.configuration" items={configItems} />

        <SidebarGroup>
          <Collapsible defaultOpen className="group/collapsible">
            <SidebarGroupLabel asChild>
              <CollapsibleTrigger className="flex w-full items-center justify-between">
                {t("sidebarGroup.training")}
                {!collapsed && <ChevronDown className="h-4 w-4 transition-transform group-data-[state=open]/collapsible:rotate-180" />}
              </CollapsibleTrigger>
            </SidebarGroupLabel>
            <CollapsibleContent>
              <SidebarGroupContent>
                <SidebarMenu>
                  {trainingItems.map((item) => {
                    const label = t(item.titleKey);
                    return (
                      <SidebarMenuItem key={item.url}>
                        <SidebarMenuButton asChild tooltip={label}>
                          <NavLink
                            to={item.url}
                            className="flex items-center gap-2 px-2 py-1.5 rounded-md text-sm text-sidebar-foreground hover:bg-sidebar-accent transition-colors"
                            activeClassName="bg-sidebar-accent text-sidebar-accent-foreground font-medium"
                          >
                            <item.icon className="h-4 w-4 shrink-0" />
                            {!collapsed && <span>{label}</span>}
                          </NavLink>
                        </SidebarMenuButton>
                      </SidebarMenuItem>
                    );
                  })}
                </SidebarMenu>
              </SidebarGroupContent>
            </CollapsibleContent>
          </Collapsible>
        </SidebarGroup>

        <SidebarNavGroup labelKey="sidebarGroup.support" items={showPayments ? supportItems : supportItems.filter(i => i.url !== "/admin/payment-record")} />
      </SidebarContent>
      <SidebarSeparator />
      <SidebarFooter className="p-3">
        <div className="flex items-center gap-2">
          <div className="h-8 w-8 rounded-full bg-primary/10 flex items-center justify-center shrink-0">
            <span className="text-xs font-semibold text-primary">{user?.name?.split(" ").map(w => w[0]).join("").slice(0, 2).toUpperCase() ?? "??"}</span>
          </div>
          {!collapsed && (
            <div className="flex flex-col min-w-0">
              <span className="text-sm font-medium truncate text-sidebar-foreground">{user?.name ?? t("userMenu.userFallback")}</span>
              <span className="text-xs text-muted-foreground truncate">{user?.email ?? ""}</span>
            </div>
          )}
        </div>
      </SidebarFooter>
    </Sidebar>
  );
}