"use client";
import { fetchData } from "@/lib/data-service";
import { clientFetch } from "@/lib/client-utils";

import { useState, useEffect } from "react";
import { useRouter } from "next/navigation";
import Image from "next/image";
import Link from "next/link";
import { Button } from "@/components/ui/button";
import { Checkbox } from "@/components/ui/checkbox";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { toast } from "sonner";

export default function LoginPage() {
  const [username, setUsername] = useState("");
  const [password, setPassword] = useState("");
  const [isLoading, setIsLoading] = useState(false);
  const [isRedirecting, setIsRedirecting] = useState(false);
  const [authStatus, setAuthStatus] = useState<{
    loading: boolean;
    progress: number;
    message: string;
  }>({
    loading: false,
    progress: 0,
    message: "Preparing your session..."
  });
  const [error, setError] = useState("");
  const router = useRouter();

  // Check if already logged in
  useEffect(() => {
    const authToken = document.cookie
      .split("; ")
      .find((row) => row.startsWith("Authorization="))
      ?.split("=")[1];
      
    if (authToken) {
      router.push("/dashboard");
    }
  }, [router]);

  // Function to verify authentication and prepare navigation
  const prepareNavigation = async (token: string) => {
    try {
      setAuthStatus(prev => ({ 
        ...prev, 
        loading: true, 
        message: "Verifying your credentials..."
      }));

      // Step 1: Verify token is valid by making a simple auth check
      // This ensures we don't redirect with an invalid token
      await clientFetch("/auth/me", {
        headers: { Authorization: `Bearer ${token}` }
      });
      
      setAuthStatus(prev => ({ 
        ...prev, 
        progress: 50, 
        message: "Authentication successful!"
      }));

      // Slight delay to show success message
      await new Promise(resolve => setTimeout(resolve, 300));
      
      setAuthStatus(prev => ({ 
        ...prev, 
        progress: 100, 
        message: "Redirecting to dashboard..."
      }));

      // Tell Next.js to prefetch the dashboard page
      // This helps with faster page load but doesn't affect server data fetching
      router.prefetch('/dashboard');
      
      // Short delay to show completion
      await new Promise(resolve => setTimeout(resolve, 500));
      
      // Redirect to dashboard
      router.push("/dashboard");
      
      // Fallback redirect if router.push fails
      setTimeout(() => {
        window.location.href = "/dashboard";
      }, 1000);
      
    } catch (error) {
      console.error("Authentication verification error:", error);
      
      // Even if verification fails, still try to redirect
      // The dashboard will handle invalid auth
      setAuthStatus(prev => ({ 
        ...prev, 
        progress: 100, 
        message: "Authentication issue, redirecting anyway..."
      }));
      
      toast.warning("Authentication issue detected", {
        description: "You may need to log in again if the dashboard doesn't load."
      });
      
      // Still redirect
      setTimeout(() => {
        router.push("/dashboard");
        // Ultimate fallback
        setTimeout(() => {
          window.location.href = "/dashboard";
        }, 1000);
      }, 500);
    }
  };

  async function handleLogin(e: React.FormEvent) {
    e.preventDefault();
    
    if (isLoading || isRedirecting) return;
    
    setIsLoading(true);

    try {
      const response = await fetch(`/api/auth/login`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ username, password }),
        credentials: "include",
      });
      
      const data = await response.json();
      
      if (response.ok && data.token) {
        // Set redirecting state to prevent multiple redirect attempts
        setIsRedirecting(true);
        
        // Store the token in both cookie and localStorage for redundancy
        document.cookie = `Authorization=${data.token}; path=/; Secure; SameSite=Strict; max-age=604800`;
        localStorage.setItem("Authorization", data.token);
        
        // Show toast before redirect
        toast.success("Login successful");
        
        // Now verify auth and handle redirect
        await prepareNavigation(data.token);
      } else {
        // Handle HTTP error responses (including 401)
        const errorMessage = data.error || "Invalid credentials";
        toast.error("Login Failed", {
          description: errorMessage,
        });
      }
    } catch (error) {
      // This will now only catch network errors or JSON parsing errors
      toast.error("Connection Error", {
        description: "Unable to connect to the server. Please check your internet connection and try again.",
      });
      console.error("Login error:", error);
    } finally {
      setIsLoading(false);
    }
  }

  // If already redirecting, show loading state with progress
  if (isRedirecting) {
    return (
      <div className="flex items-center justify-center min-h-screen bg-gray-100 dark:bg-[#0F0F12]">
        <div className="w-full max-w-md p-8 space-y-8 bg-white dark:bg-[#1F1F23] rounded-xl shadow-lg text-center">
          <h2 className="mt-6 text-3xl font-bold text-gray-900 dark:text-white">Logging in</h2>
          <p className="mt-2 text-sm text-gray-600 dark:text-gray-400">{authStatus.message}</p>
          
          {/* Progress bar */}
          <div className="w-full bg-gray-200 rounded-full h-2.5 dark:bg-gray-700 mt-6">
            <div 
              className="bg-primary h-2.5 rounded-full transition-all duration-300 ease-in-out" 
              style={{ width: `${authStatus.progress}%` }}
            ></div>
          </div>
          
          <div className="mt-6 flex justify-center">
            <div className="animate-spin rounded-full h-12 w-12 border-b-2 border-primary"></div>
          </div>
        </div>
      </div>
    );
  }

  return (
    <div className="flex items-center justify-center min-h-screen bg-gray-100 dark:bg-[#0F0F12]">
      <div className="w-full max-w-md p-8 space-y-8 bg-white dark:bg-[#1F1F23] rounded-xl shadow-lg">
        <div className="text-center">
          <h2 className="mt-6 text-3xl font-bold text-gray-900 dark:text-white">Welcome back</h2>
          <p className="mt-2 text-sm text-gray-600 dark:text-gray-400">Please sign in to your account</p>
        </div>

        <form className="mt-8 space-y-6" onSubmit={handleLogin}>
          <div className="space-y-4">
            <div>
              <Label htmlFor="username">Username</Label>
              <Input
                id="username"
                name="username"
                type="text"
                autoComplete="username"
                required
                value={username}
                onChange={(e) => setUsername(e.target.value)}
                className="mt-1"
              />
            </div>
            <div>
              <Label htmlFor="password">Password</Label>
              <Input
                id="password"
                name="password"
                type="password"
                autoComplete="current-password"
                required
                value={password}
                onChange={(e) => setPassword(e.target.value)}
                className="mt-1"
              />
            </div>
          </div>

          <Button type="submit" className="w-full" disabled={isLoading || isRedirecting}>
            {isLoading ? "Signing in..." : "Sign in"}
          </Button>
        </form>

        <p className="mt-10 text-sm text-center text-gray-600 dark:text-gray-400">
          Don't have an account?{" "}
          <Link href="/auth/register" className="text-blue-600 hover:underline dark:text-blue-400">
            Sign up
          </Link>
        </p>
      </div>
    </div>
  );
}