src/components/organisms/Sidebar/index.tsx

"use client";

import * as React from "react";
import Link from "next/link";
import { usePathname, useRouter } from "next/navigation";
import { 
  LayoutDashboard, 
  Search, 
  Library, 
  FileEdit, 
  Settings, 
  ChevronLeft, 
  ChevronRight,
  LogOut,
  Microscope,
  User as UserIcon
} from "lucide-react";
import { Avatar, AvatarFallback } from "@/components/atoms/Avatar";
import { Icon } from "@/components/atoms/Icon";
import { Spinner } from "@/components/atoms/Spinner";
import { cn } from "@/lib/utils";

const navItems = [
  { label: "Dashboard", href: "/dashboard", icon: LayoutDashboard },
  { label: "Explore", href: "/explore", icon: Search },
  { label: "Library", href: "/library", icon: Library },
  { label: "WriteSage", href: "/editor", icon: FileEdit },
];

/**
 * Utility: Decodes JWT payload without a heavy library.
 * Backend still handles actual verification.
 */
function decodeToken(token: string) {
  try {
    const base64Url = token.split(".")[1];
    const base64 = base64Url.replace(/-/g, "+").replace(/_/g, "/");
    const jsonPayload = decodeURIComponent(
      window
        .atob(base64)
        .split("")
        .map((c) => "%" + ("00" + c.charCodeAt(0).toString(16)).slice(-2))
        .join("")
    );
    return JSON.parse(jsonPayload);
  } catch (error) {
    return null;
  }
}

export function Sidebar() {
  const pathname = usePathname();
  const router = useRouter();
  
  const [isCollapsed, setIsCollapsed] = React.useState(false);
  const [isLoggingOut, setIsLoggingOut] = React.useState(false);
  const [userData, setUserData] = React.useState<{ sub: string; is_premium?: boolean } | null>(null);

  // 1. Sync User State with Token
  React.useEffect(() => {
    const token = localStorage.getItem("token");
    if (token) {
      const decoded = decodeToken(token);
      if (decoded) setUserData(decoded);
    }
  }, []);

  const handleLogout = () => {
    setIsLoggingOut(true);
    localStorage.removeItem("token");
    router.push("/login");
    // State reset is handled by the redirect/refresh
  };

  // Get user initials for avatar fallback
  const getUserInitials = () => {
    if (userData?.sub) {
      return userData.sub.slice(0, 2).toUpperCase();
    }
    return "RA";
  };

  return (
    <aside 
      className={cn(
        "relative flex flex-col border-r bg-card transition-all duration-300 ease-in-out z-40",
        isCollapsed ? "w-20" : "w-64"
      )}
    >
      {/* Branding */}
      <div className="flex h-16 items-center border-b px-6">
        <Link href="/dashboard" className="flex items-center gap-3">
          <div className="flex h-8 w-8 items-center justify-center rounded-lg bg-primary text-primary-foreground shadow-sm">
            <Icon icon={Microscope} size={20} />
          </div>
          {!isCollapsed && (
            <span className="text-lg font-bold tracking-tight text-foreground animate-in fade-in duration-300">
              Romeo AI
            </span>
          )}
        </Link>
      </div>

      {/* Navigation */}
      <nav className="flex-1 space-y-1 p-4 overflow-y-auto">
        {navItems.map((item) => {
          const isActive = pathname.startsWith(item.href);
          return (
            <Link
              key={item.href}
              href={item.href}
              className={cn(
                "group flex items-center rounded-md px-3 py-2.5 text-sm font-medium transition-all",
                isActive 
                  ? "bg-primary text-primary-foreground shadow-sm" 
                  : "text-muted-foreground hover:bg-muted hover:text-foreground"
              )}
            >
              <Icon 
                icon={item.icon} 
                className={cn("shrink-0", isCollapsed ? "mx-auto" : "mr-3")} 
              />
              {!isCollapsed && <span className="truncate">{item.label}</span>}
            </Link>
          );
        })}
      </nav>

      {/* Bottom Context Section */}
      <div className="border-t p-4 space-y-2">
        <Link
          href="/settings"
          className={cn(
            "flex items-center rounded-md px-3 py-2 text-sm font-medium text-muted-foreground hover:bg-muted transition-colors",
            pathname === "/settings" && "bg-muted text-foreground"
          )}
        >
          <Icon icon={Settings} className={cn("shrink-0", isCollapsed ? "mx-auto" : "mr-3")} />
          {!isCollapsed && <span>Settings</span>}
        </Link>

        {/* User Badge */}
        <div className={cn(
          "flex items-center gap-3 rounded-lg border bg-muted/30 p-2",
          isCollapsed ? "justify-center" : "px-3"
        )}>
          <Avatar className="h-8 w-8 border">
            <AvatarFallback alt={getUserInitials()} className="bg-primary/5 text-primary text-xs font-semibold" />
          </Avatar>
          {!isCollapsed && (
            <div className="flex flex-col min-w-0 flex-1">
              <span className="truncate text-[11px] font-semibold leading-tight">
                {userData?.sub || "Researcher"}
              </span>
              <span className="truncate text-[9px] text-muted-foreground font-medium uppercase tracking-wider">
                {userData?.is_premium ? "Pro Plan" : "Free Plan"}
              </span>
            </div>
          )}
        </div>

        <button
          onClick={handleLogout}
          disabled={isLoggingOut}
          className={cn(
            "flex w-full items-center rounded-md px-3 py-2 text-sm font-medium text-destructive hover:bg-destructive/10 transition-colors",
            isCollapsed && "justify-center"
          )}
        >
          {isLoggingOut ? (
            <Spinner size={16} className={isCollapsed ? "" : "mr-3"} />
          ) : (
            <Icon icon={LogOut} className={cn("shrink-0", isCollapsed ? "mx-auto" : "mr-3")} />
          )}
          {!isCollapsed && <span>{isLoggingOut ? "Exiting..." : "Logout"}</span>}
        </button>
      </div>

      {/* Collapse Toggle */}
      <button
        onClick={() => setIsCollapsed(!isCollapsed)}
        className="absolute -right-3 top-20 hidden md:flex h-6 w-6 items-center justify-center rounded-full border bg-background shadow-sm hover:bg-muted transition-colors"
      >
        <Icon icon={isCollapsed ? ChevronRight : ChevronLeft} size={12} />
      </button>
    </aside>
  );
}