"use client";

import { cn } from "@/lib/utils";
import { signIn, verifyDevice2FA, resend2FACode } from "@/lib/actions/auth";
import { Button } from "@/components/ui/button";
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from "@/components/ui/card";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import Link from "next/link";
import { useRouter } from "next/navigation";
import { useState, useEffect, useRef, useCallback } from "react";
import { motion, AnimatePresence } from "framer-motion";
import { Ban } from "lucide-react";

function getDeviceHash(): string {
  const key = "caspos-device-id";
  let id = localStorage.getItem(key);
  if (!id) {
    id = crypto.randomUUID();
    localStorage.setItem(key, id);
  }
  return id;
}

export function LoginForm({
  className,
  ...props
}: React.ComponentPropsWithoutRef<"div">) {
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");
  const [error, setError] = useState<string | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  const [messageParam, setMessageParam] = useState<string | null>(null);
  const [errorParam, setErrorParam] = useState<string | null>(null);
  const router = useRouter();

  // 2FA state
  const [show2FA, setShow2FA] = useState(false);
  const [otpDigits, setOtpDigits] = useState<string[]>(["", "", "", "", "", ""]);
  const [userId, setUserId] = useState<string | null>(null);
  const [userRole, setUserRole] = useState<string | null>(null);
  const [resendCooldown, setResendCooldown] = useState(0);
  const inputRefs = useRef<(HTMLInputElement | null)[]>([]);

  useEffect(() => {
    const params = new URLSearchParams(window.location.search);
    setMessageParam(params.get('message'));
    setErrorParam(params.get('error'));
  }, []);

  // Resend cooldown timer
  useEffect(() => {
    if (resendCooldown <= 0) return;
    const timer = setTimeout(() => setResendCooldown(c => c - 1), 1000);
    return () => clearTimeout(timer);
  }, [resendCooldown]);

  const navigateAfterLogin = useCallback((role: string) => {
    const nextParam = typeof window !== 'undefined' ? new URLSearchParams(window.location.search).get('next') : null;
    if (nextParam) {
      router.push(nextParam);
    } else {
      router.push("/");
    }
  }, [router]);

  const handleLogin = async (e: React.FormEvent) => {
    e.preventDefault();
    setIsLoading(true);
    setError(null);

    try {
      const deviceHash = getDeviceHash();
      const res = await signIn(email, password, deviceHash);

      if (!res.success) {
        setError(res.error || "Ein Fehler ist aufgetreten.");
        return;
      }

      if (res.requires2FA) {
        setUserId(res.userId || null);
        setUserRole(res.role || null);
        setShow2FA(true);
        setResendCooldown(60);
        setOtpDigits(["", "", "", "", "", ""]);
        setTimeout(() => inputRefs.current[0]?.focus(), 300);
        return;
      }

      navigateAfterLogin(res.role || "partner");
    } catch (error: unknown) {
      setError(error instanceof Error ? error.message : "Ein Fehler ist aufgetreten.");
    } finally {
      setIsLoading(false);
    }
  };

  const handleOtpChange = (index: number, value: string) => {
    if (!/^\d*$/.test(value)) return;
    const newDigits = [...otpDigits];
    newDigits[index] = value.slice(-1);
    setOtpDigits(newDigits);

    // Auto-advance
    if (value && index < 5) {
      inputRefs.current[index + 1]?.focus();
    }

    // Auto-submit when all filled
    if (newDigits.every(d => d !== "") && newDigits.join("").length === 6) {
      handleVerify2FA(newDigits.join(""));
    }
  };

  const handleOtpKeyDown = (index: number, e: React.KeyboardEvent) => {
    if (e.key === "Backspace" && !otpDigits[index] && index > 0) {
      inputRefs.current[index - 1]?.focus();
    }
  };

  const handleOtpPaste = (e: React.ClipboardEvent) => {
    e.preventDefault();
    const paste = e.clipboardData.getData("text").replace(/\D/g, "").slice(0, 6);
    if (paste.length === 6) {
      const newDigits = paste.split("");
      setOtpDigits(newDigits);
      inputRefs.current[5]?.focus();
      handleVerify2FA(paste);
    }
  };

  const isVerifyingRef = useRef(false);

  const handleVerify2FA = async (code: string) => {
    if (!userId || isVerifyingRef.current) return;
    isVerifyingRef.current = true;
    setIsLoading(true);
    setError(null);

    try {
      const deviceHash = getDeviceHash();
      const res = await verifyDevice2FA(userId, code, deviceHash);

      if (!res.success) {
        setError(res.error || "Ungültiger Code.");
        setOtpDigits(["", "", "", "", "", ""]);
        inputRefs.current[0]?.focus();
        return;
      }

      navigateAfterLogin(res.role || userRole || "partner");
    } catch (err: unknown) {
      setError(err instanceof Error ? err.message : "Fehler bei der Verifizierung.");
      setOtpDigits(["", "", "", "", "", ""]);
      inputRefs.current[0]?.focus();
    } finally {
      setIsLoading(false);
      isVerifyingRef.current = false;
    }
  };

  const handleResend = async () => {
    if (!userId || resendCooldown > 0) return;
    setError(null);
    const deviceHash = getDeviceHash();
    const res = await resend2FACode(userId, deviceHash);
    if (res.success) {
      setResendCooldown(60);
    } else {
      setError(res.error || "Fehler beim erneuten Senden.");
    }
  };

  return (
    <div className={cn("flex flex-col gap-6", className)} {...props}>
      <Card className="overflow-hidden">
        <AnimatePresence mode="wait">
          {!show2FA ? (
            <motion.div
              key="login"
              initial={{ opacity: 1, x: 0 }}
              exit={{ opacity: 0, x: -40, filter: "blur(4px)" }}
              transition={{ duration: 0.35, ease: "easeInOut" }}
            >
              <CardHeader>
                <CardTitle className="text-2xl">Anmelden</CardTitle>
                <CardDescription>
                  Geben Sie Ihre E-Mail-Adresse und Ihr Passwort ein, um sich anzumelden.
                </CardDescription>
              </CardHeader>
              <CardContent>
                <form onSubmit={handleLogin}>
                  <div className="flex flex-col gap-6">
                    <div className="grid gap-2">
                      <Label htmlFor="email">E-Mail</Label>
                      <Input
                        id="email"
                        type="email"
                        placeholder="name@beispiel.de"
                        required
                        value={email}
                        onChange={(e) => setEmail(e.target.value)}
                      />
                    </div>
                    <div className="grid gap-2">
                      <div className="flex items-center">
                        <Label htmlFor="password">Passwort</Label>
                        <Link
                          href="/auth/forgot-password"
                          className="ml-auto inline-block text-sm underline-offset-4 hover:underline"
                        >
                          Passwort vergessen?
                        </Link>
                      </div>
                      <Input
                        id="password"
                        type="password"
                        required
                        value={password}
                        onChange={(e) => setPassword(e.target.value)}
                      />
                    </div>
                    {errorParam === "gesperrt" && (
                      <p className="text-sm text-red-500 bg-red-500/10 border border-red-500/20 p-3 rounded-lg text-center font-medium flex items-center justify-center gap-2">
                        <Ban className="w-4 h-4 shrink-0" />
                        <span>Ihr Konto wurde gesperrt. Bitte wenden Sie sich an den Administrator.</span>
                      </p>
                    )}
                    {messageParam === "concurrent" && (
                      <p className="text-sm text-amber-500 bg-amber-500/10 border border-amber-500/20 p-3 rounded-lg text-center font-medium">
                        Sie wurden abgemeldet, da Sie sich an einem anderen Gerät angemeldet haben.
                      </p>
                    )}
                    {error && <p className="text-sm text-red-500">{error}</p>}
                    <Button type="submit" className="w-full" disabled={isLoading}>
                      {isLoading ? "Wird angemeldet..." : "Anmelden"}
                    </Button>
                  </div>
                </form>
              </CardContent>
            </motion.div>
          ) : (
            <motion.div
              key="2fa"
              initial={{ opacity: 0, x: 40, filter: "blur(4px)" }}
              animate={{ opacity: 1, x: 0, filter: "blur(0px)" }}
              exit={{ opacity: 0, x: -40 }}
              transition={{ duration: 0.35, ease: "easeInOut" }}
            >
              <CardHeader className="text-center">
                <div className="mx-auto mb-3 flex h-14 w-14 items-center justify-center rounded-full bg-blue-100 dark:bg-blue-900/30">
                  <svg xmlns="http://www.w3.org/2000/svg" width="28" height="28" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" className="text-blue-600 dark:text-blue-400">
                    <rect width="18" height="11" x="3" y="11" rx="2" ry="2"/>
                    <path d="M7 11V7a5 5 0 0 1 10 0v4"/>
                  </svg>
                </div>
                <CardTitle className="text-2xl">Sicherheitscode</CardTitle>
                <CardDescription className="text-sm mt-1">
                  Wir haben einen 6-stelligen Code an<br />
                  <span className="font-semibold text-foreground">{email}</span><br />
                  gesendet.
                </CardDescription>
              </CardHeader>
              <CardContent>
                <div className="flex flex-col gap-6">
                  {/* OTP Input */}
                  <div className="flex justify-center gap-2" onPaste={handleOtpPaste}>
                    {otpDigits.map((digit, i) => (
                      <input
                        key={i}
                        ref={(el) => { inputRefs.current[i] = el; }}
                        type="text"
                        inputMode="numeric"
                        maxLength={1}
                        value={digit}
                        onChange={(e) => handleOtpChange(i, e.target.value)}
                        onKeyDown={(e) => handleOtpKeyDown(i, e)}
                        className={cn(
                          "h-14 w-11 rounded-xl border-2 bg-muted/50 text-center text-xl font-bold transition-all duration-200",
                          "focus:border-blue-500 focus:ring-2 focus:ring-blue-500/20 focus:outline-none",
                          "hover:border-muted-foreground/40",
                          digit ? "border-blue-400 bg-blue-50 dark:bg-blue-950/30" : "border-muted-foreground/20"
                        )}
                        id={`otp-${i}`}
                        autoComplete="one-time-code"
                      />
                    ))}
                  </div>

                  {error && (
                    <motion.p
                      initial={{ opacity: 0, y: -8 }}
                      animate={{ opacity: 1, y: 0 }}
                      className="text-sm text-red-500 text-center bg-red-500/10 border border-red-500/20 p-3 rounded-lg font-medium"
                    >
                      {error}
                    </motion.p>
                  )}

                  <Button
                    type="button"
                    className="w-full"
                    disabled={isLoading || otpDigits.some(d => !d)}
                    onClick={() => handleVerify2FA(otpDigits.join(""))}
                  >
                    {isLoading ? "Wird überprüft..." : "Bestätigen"}
                  </Button>

                  <div className="text-center text-sm text-muted-foreground">
                    Code nicht erhalten?{" "}
                    <button
                      type="button"
                      onClick={handleResend}
                      disabled={resendCooldown > 0}
                      className={cn(
                        "font-medium underline-offset-4 hover:underline transition-colors",
                        resendCooldown > 0
                          ? "text-muted-foreground/50 cursor-not-allowed"
                          : "text-blue-600 hover:text-blue-700 dark:text-blue-400"
                      )}
                    >
                      {resendCooldown > 0 ? `Erneut senden (${resendCooldown}s)` : "Erneut senden"}
                    </button>
                  </div>

                  <button
                    type="button"
                    onClick={() => {
                      setShow2FA(false);
                      setError(null);
                      setOtpDigits(["", "", "", "", "", ""]);
                    }}
                    className="text-sm text-muted-foreground hover:text-foreground transition-colors text-center"
                  >
                    ← Zurück zur Anmeldung
                  </button>
                </div>
              </CardContent>
            </motion.div>
          )}
        </AnimatePresence>
      </Card>
    </div>
  );
}