"use client";

import { useActionState, useEffect, useState, useTransition } from "react";
import { useRouter } from "next/navigation";
import { Check, KeyRound, Loader2, ShieldCheck, ShieldOff } from "lucide-react";
import { toast } from "sonner";

import { Badge } from "@/components/ui/badge";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import {
  disableMfaAction,
  initialMfaActionState,
  regenerateRecoveryCodesAction,
  startMfaEnrollAction,
  verifyMfaEnrollAction,
} from "@/lib/appwrite/mfa-actions";

type EnrollStage =
  | { kind: "idle" }
  | { kind: "loading" }
  | { kind: "verify"; uri: string; secret: string }
  | { kind: "done"; recoveryCodes: string[] };

export function MfaPanel({ initiallyEnabled }: { initiallyEnabled: boolean }) {
  const router = useRouter();
  const [enabled, setEnabled] = useState(initiallyEnabled);
  const [stage, setStage] = useState<EnrollStage>({ kind: "idle" });
  const [verifyState, verifyAction, verifying] = useActionState(
    verifyMfaEnrollAction,
    initialMfaActionState,
  );
  const [busy, startTransition] = useTransition();

  useEffect(() => {
    if (verifyState.ok && verifyState.recoveryCodes) {
      setEnabled(true);
      setStage({ kind: "done", recoveryCodes: verifyState.recoveryCodes });
      toast.success("2FA etkinleştirildi.");
      router.refresh();
    } else if (verifyState.error) {
      toast.error(verifyState.error);
    }
  }, [verifyState, router]);

  function beginEnroll() {
    setStage({ kind: "loading" });
    startTransition(async () => {
      const res = await startMfaEnrollAction();
      if (res.ok && res.uri && res.secret) {
        setStage({ kind: "verify", uri: res.uri, secret: res.secret });
      } else {
        toast.error(res.error ?? "Başlatılamadı.");
        setStage({ kind: "idle" });
      }
    });
  }

  function onDisable() {
    if (
      !window.confirm(
        "2FA devre dışı bırakılsın mı? Hesabınız sadece şifre ile korunacak.",
      )
    )
      return;
    startTransition(async () => {
      const res = await disableMfaAction();
      if (res.ok) {
        setEnabled(false);
        setStage({ kind: "idle" });
        toast.success("2FA devre dışı bırakıldı.");
        router.refresh();
      } else {
        toast.error(res.error ?? "Devre dışı bırakılamadı.");
      }
    });
  }

  function onRegenerateCodes() {
    startTransition(async () => {
      const res = await regenerateRecoveryCodesAction();
      if (res.ok && res.recoveryCodes) {
        setStage({ kind: "done", recoveryCodes: res.recoveryCodes });
        toast.success("Yeni yedek kodlar oluşturuldu — eskileri geçersiz.");
      } else {
        toast.error(res.error ?? "Üretilemedi.");
      }
    });
  }

  if (enabled && stage.kind !== "done") {
    return (
      <div className="grid gap-3">
        <div className="flex items-center gap-2">
          <Badge className="bg-emerald-600 text-white">
            <ShieldCheck className="size-3.5" />
            Aktif
          </Badge>
          <span className="text-muted-foreground text-sm">
            Authenticator uygulaması ile giriş yapıyorsunuz.
          </span>
        </div>
        <div className="flex flex-wrap gap-2">
          <Button variant="outline" onClick={onRegenerateCodes} disabled={busy}>
            <KeyRound className="size-4" />
            Yedek kodları yenile
          </Button>
          <Button variant="destructive" onClick={onDisable} disabled={busy}>
            {busy ? <Loader2 className="size-4 animate-spin" /> : <ShieldOff className="size-4" />}
            Devre dışı bırak
          </Button>
        </div>
      </div>
    );
  }

  if (stage.kind === "done") {
    return (
      <div className="grid gap-3">
        <div className="bg-emerald-50 dark:bg-emerald-950 rounded-md border border-emerald-200 dark:border-emerald-900 p-4">
          <p className="flex items-center gap-2 font-medium text-emerald-700 dark:text-emerald-300">
            <Check className="size-4" />
            Yedek kodlarınız
          </p>
          <p className="text-muted-foreground mt-1 text-xs">
            Telefonunuza erişiminizi kaybederseniz bu kodlardan biriyle giriş
            yapabilirsiniz. Her kod tek seferlik. <strong>Şimdi güvenli bir yere kaydedin</strong> —
            bu sayfadan çıktığınızda tekrar gösterilmez.
          </p>
          <pre className="bg-background mt-3 grid grid-cols-2 gap-2 rounded-md border p-3 text-sm font-mono">
            {stage.recoveryCodes.map((c) => (
              <span key={c}>{c}</span>
            ))}
          </pre>
        </div>
        <Button variant="outline" onClick={() => setStage({ kind: "idle" })}>
          Tamamladım
        </Button>
      </div>
    );
  }

  if (stage.kind === "verify") {
    const otpauthQrUrl = `https://api.qrserver.com/v1/create-qr-code/?size=200x200&data=${encodeURIComponent(stage.uri)}`;
    return (
      <form action={verifyAction} className="grid gap-4">
        <div className="grid gap-4 sm:grid-cols-[200px_1fr] sm:items-start">
          {/* eslint-disable-next-line @next/next/no-img-element */}
          <img
            src={otpauthQrUrl}
            alt="QR kodu"
            className="size-[200px] rounded-md border bg-white p-2"
            width={200}
            height={200}
          />
          <div className="grid gap-2 text-sm">
            <p>Authenticator uygulamanızı açın, QR kodu tarayın.</p>
            <p className="text-muted-foreground text-xs">
              Tarayamıyorsanız bu kodu manuel girin:
            </p>
            <code className="bg-muted rounded-md p-2 font-mono text-xs">{stage.secret}</code>
          </div>
        </div>
        <div className="grid gap-2">
          <Label htmlFor="otp">Uygulamadaki 6 haneli kod</Label>
          <Input
            id="otp"
            name="otp"
            inputMode="numeric"
            pattern="[0-9]*"
            maxLength={6}
            placeholder="000000"
            required
            autoComplete="one-time-code"
            className="font-mono text-lg tracking-widest"
          />
          {verifyState.error && (
            <p className="text-destructive text-xs">{verifyState.error}</p>
          )}
        </div>
        <div className="flex gap-2">
          <Button type="button" variant="outline" onClick={() => setStage({ kind: "idle" })}>
            Vazgeç
          </Button>
          <Button type="submit" disabled={verifying}>
            {verifying ? <Loader2 className="size-4 animate-spin" /> : <Check className="size-4" />}
            Doğrula ve etkinleştir
          </Button>
        </div>
      </form>
    );
  }

  return (
    <div className="grid gap-3">
      <div className="flex items-center gap-2">
        <Badge variant="outline">Pasif</Badge>
        <span className="text-muted-foreground text-sm">
          Hesabınız yalnızca şifre ile korunuyor.
        </span>
      </div>
      <Button onClick={beginEnroll} disabled={busy || stage.kind === "loading"}>
        {(busy || stage.kind === "loading") ? <Loader2 className="size-4 animate-spin" /> : <ShieldCheck className="size-4" />}
        İki adımlı doğrulamayı aç
      </Button>
    </div>
  );
}