"use client";

import { signIn } from "next-auth/react";
import { useRouter, useSearchParams } from "next/navigation";
import { Suspense, useEffect, useState } from "react";
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";

const ERROR_MESSAGES: Record<string, string> = {
  CredentialsSignin: "Invalid username or password.",
  SessionRequired: "Please sign in to continue.",
  Verification: "Sign-in link is invalid or expired.",
  AccessDenied: "You don't have access.",
  Configuration: "Auth configuration error — contact the server admin.",
};

function LoginInner() {
  const router = useRouter();
  const params = useSearchParams();
  const [error, setError] = useState("");
  const [loading, setLoading] = useState(false);

  useEffect(() => {
    const qErr = params.get("error");
    if (qErr) setError(ERROR_MESSAGES[qErr] || `Sign-in failed (${qErr}).`);
  }, [params]);

  async function handleSubmit(e: React.FormEvent<HTMLFormElement>) {
    e.preventDefault();
    setLoading(true);
    setError("");

    const formData = new FormData(e.currentTarget);

    const res = await signIn("credentials", {
      username: formData.get("username"),
      password: formData.get("password"),
      redirect: false,
    });

    if (res?.error) {
      setError(ERROR_MESSAGES[res.error] || "Invalid credentials.");
      setLoading(false);
    } else {
      const callback = params.get("callbackUrl") || "/admin";
      router.push(callback);
    }
  }

  return (
    <div className="flex-1 flex items-center justify-center p-3 sm:p-6">
      <Card className="w-full max-w-sm">
        <CardHeader className="text-center">
          <CardTitle className="text-xl">Admin Login</CardTitle>
        </CardHeader>
        <CardContent>
          <form onSubmit={handleSubmit} className="space-y-4">
            <div className="space-y-2">
              <Label htmlFor="username">Username</Label>
              <Input
                id="username"
                name="username"
                type="text"
                autoComplete="username"
                required
                autoFocus
              />
            </div>

            <div className="space-y-2">
              <Label htmlFor="password">Password</Label>
              <Input
                id="password"
                name="password"
                type="password"
                autoComplete="current-password"
                required
              />
            </div>

            {error && (
              <div
                role="alert"
                className="rounded-md border border-red-500/30 bg-red-500/5 p-2.5 text-destructive text-sm text-center"
              >
                {error}
              </div>
            )}

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

          <div className="mt-4 text-center">
            <a
              href="/"
              className="text-sm text-muted-foreground hover:text-foreground transition"
            >
              Back to dashboard
            </a>
          </div>
        </CardContent>
      </Card>
    </div>
  );
}

export default function LoginPage() {
  return (
    <Suspense fallback={null}>
      <LoginInner />
    </Suspense>
  );
}
