import { useState } from 'react';
import { useQuery, useMutation } from '@tanstack/react-query';
import { useParams, Link } from '@tanstack/react-router';
import {
  CalendarClock,
  CheckCircle2,
  Clock,
  GraduationCap,
  Loader2,
  Moon,
  Sun,
  Users,
} from 'lucide-react';
import { Badge, Button, Input, Label } from '../components/ui';
import { Logo } from '../components/brand';
import { useTheme } from '../context/ThemeProvider';
import { getInviteInfo, joinViaInvite, ApiError } from '../lib/api';
import { BILLING_LABELS, formatPrice, formatSchedule } from '../lib/format';

export function JoinGroupView() {
  const { token } = useParams({ strict: false }) as { token: string };
  const { theme, setTheme, isDark } = useTheme();

  const [firstName, setFirstName] = useState('');
  const [lastName, setLastName] = useState('');
  const [phone, setPhone] = useState('');
  const [email, setEmail] = useState('');
  const [errorMessage, setErrorMessage] = useState<string | null>(null);

  // Success state
  const [registeredAttendee, setRegisteredAttendee] = useState<{
    fullName: string;
    phone: string | null;
  } | null>(null);

  // Waitlist state (group is full)
  const [waitlistInfo, setWaitlistInfo] = useState<{ message: string } | null>(null);

  const inviteQuery = useQuery({
    queryKey: ['public-invite', token],
    queryFn: () => getInviteInfo(token),
    enabled: Boolean(token),
    retry: 1,
  });

  const joinMutation = useMutation({
    mutationFn: () =>
      joinViaInvite(token, {
        firstName: firstName.trim(),
        lastName: lastName.trim(),
        phone: phone.trim(),
        email: email.trim() || undefined,
      }),
    onSuccess: (data) => {
      setErrorMessage(null);
      if (data.status === 'waitlisted') {
        setRegisteredAttendee(null);
        setWaitlistInfo({ message: data.message });
        return;
      }
      setWaitlistInfo(null);
      setRegisteredAttendee({
        fullName: data.attendee!.fullName,
        phone: data.attendee!.phone,
      });
    },
    onError: (error: unknown) => {
      if (error instanceof ApiError) {
        if (error.problem?.code === 'attendee_already_registered') {
          setErrorMessage(
            'Ya te encuentras registrado en este grupo con ese número de teléfono. El profesor ya tiene tus datos.',
          );
          return;
        }
        setErrorMessage(error.message || 'Error al procesar la inscripción.');
      } else if (error instanceof Error) {
        setErrorMessage(error.message);
      } else {
        setErrorMessage('Ocurrió un error inesperado. Por favor, intenta de nuevo.');
      }
    },
  });

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();
    setErrorMessage(null);

    if (!firstName.trim() || !lastName.trim() || !phone.trim()) {
      setErrorMessage('Por favor completa los campos requeridos (Nombre, Apellido y Teléfono).');
      return;
    }

    joinMutation.mutate();
  };

  const group = inviteQuery.data;

  return (
    <div className="min-h-screen bg-background text-primary flex flex-col justify-between selection:bg-accent selection:text-white">
      {/* Public Header */}
      <header className="border-b border-border bg-surface/80 backdrop-blur-md sticky top-0 z-10 px-4 py-3 sm:px-8 flex items-center justify-between">
        <Link to="/" className="flex items-center gap-2">
          <Logo className="h-7 w-auto" />
        </Link>

        <button
          type="button"
          onClick={() => setTheme(isDark ? 'light' : 'dark')}
          className="p-2 rounded-xl text-foreground/70 hover:text-primary hover:bg-primary-soft transition-colors"
          title={isDark ? 'Cambiar a tema claro' : 'Cambiar a tema oscuro'}
        >
          {isDark ? <Sun className="size-4" /> : <Moon className="size-4" />}
        </button>
      </header>

      {/* Main Content */}
      <main className="flex-1 flex items-center justify-center p-4 sm:p-6 md:p-10">
        <div className="w-full max-w-lg space-y-6">
          {inviteQuery.isPending ? (
            <div className="flex flex-col items-center justify-center py-20 gap-3">
              <Loader2 className="size-8 animate-spin text-accent" />
              <p className="text-sm text-foreground/60">Cargando información del grupo...</p>
            </div>
          ) : null}

          {inviteQuery.isError || !group ? (
            <div className="rounded-2xl border border-danger/20 bg-danger-soft p-6 sm:p-8 text-center space-y-3">
              <h2 className="text-xl font-bold text-danger">Enlace no válido o expirado</h2>
              <p className="text-sm text-foreground/70 max-w-sm mx-auto">
                No pudimos encontrar este grupo. Por favor consulta con tu profesor para solicitar un nuevo enlace de invitación.
              </p>
            </div>
          ) : null}

          {/* Registration Success Confirmation */}
          {registeredAttendee && group ? (
            <div className="rounded-2xl border border-success/30 bg-surface p-6 sm:p-8 text-center shadow-xl space-y-5 animate-step-enter">
              <div className="size-16 rounded-full bg-success-soft text-success flex items-center justify-center mx-auto">
                <CheckCircle2 className="size-10" />
              </div>

              <div>
                <Badge variant="success" className="mb-2">
                  Registro Confirmado
                </Badge>
                <h1 className="text-2xl font-bold text-primary">¡Inscripción Exitosa!</h1>
                <p className="mt-2 text-sm text-foreground/70 leading-relaxed">
                  Tus datos han sido registrados con éxito en el grupo{' '}
                  <strong className="text-primary font-semibold">{group.name}</strong>.
                </p>
              </div>

              <div className="rounded-xl border border-border bg-primary-soft/50 p-4 text-left text-xs space-y-2">
                <div className="flex justify-between">
                  <span className="text-foreground/60">Profesor:</span>
                  <span className="font-semibold text-primary">{group.teacherName}</span>
                </div>
                <div className="flex justify-between">
                  <span className="text-foreground/60">Alumno:</span>
                  <span className="font-semibold text-primary">{registeredAttendee.fullName}</span>
                </div>
                {registeredAttendee.phone ? (
                  <div className="flex justify-between">
                    <span className="text-foreground/60">Teléfono registrado:</span>
                    <span className="font-semibold text-primary">{registeredAttendee.phone}</span>
                  </div>
                ) : null}
              </div>

              <p className="text-xs text-foreground/60">
                El profesor se pondrá en contacto contigo a la brevedad por WhatsApp para darte la bienvenida y coordinar los detalles de la clase.
              </p>
            </div>
          ) : null}

          {/* Waitlist Confirmation (group full) */}
          {waitlistInfo && group ? (
            <div className="rounded-2xl border border-accent/30 bg-surface p-6 sm:p-8 text-center shadow-xl space-y-5 animate-step-enter">
              <div className="size-16 rounded-full bg-accent-soft text-accent flex items-center justify-center mx-auto">
                <Clock className="size-10" />
              </div>

              <div>
                <Badge variant="neutral" className="mb-2">
                  Lista de Espera
                </Badge>
                <h1 className="text-2xl font-bold text-primary">Cupo completo</h1>
                <p className="mt-2 text-sm text-foreground/70 leading-relaxed">
                  {waitlistInfo.message}
                </p>
              </div>

              <p className="text-xs text-foreground/60">
                El profesor se pondrá en contacto contigo cuando haya un lugar disponible en{' '}
                <strong className="text-primary font-semibold">{group.name}</strong>.
              </p>
            </div>
          ) : null}

          {/* Inscription Form */}
          {!registeredAttendee && !waitlistInfo && group ? (
            <div className="rounded-2xl border border-border bg-surface p-6 sm:p-8 shadow-xl space-y-6">
              {/* Group Info Header */}
              <div className="border-b border-border pb-5">
                <div className="flex items-center gap-2 mb-2">
                  <Badge variant="neutral" className="gap-1 text-[11px]">
                    <GraduationCap className="size-3.5 text-accent" />
                    <span>Invitación Oficial</span>
                  </Badge>
                </div>
                <h1 className="text-2xl font-bold text-primary">{group.name}</h1>
                <p className="mt-1 text-sm font-medium text-foreground/80">
                  Profesor: <span className="text-primary font-semibold">{group.teacherName}</span>
                </p>
                {group.description ? (
                  <p className="mt-2 text-sm text-foreground/60">{group.description}</p>
                ) : null}

                {/* Schedule & Price Details */}
                <div className="mt-4 flex flex-wrap gap-2 text-xs">
                  {(group.days?.length ?? 0) > 0 ? (
                    <div className="inline-flex items-center gap-1.5 rounded-lg bg-primary-soft px-2.5 py-1 text-foreground/80">
                      <CalendarClock className="size-3.5 text-accent" />
                      <span>{formatSchedule(group.days ?? [], group.time)}</span>
                    </div>
                  ) : null}

                  {group.price != null ? (
                    <div className="inline-flex items-center gap-1.5 rounded-lg bg-primary-soft px-2.5 py-1 text-foreground/80 font-medium">
                      <span>{formatPrice(group.price)}</span>
                      {group.billingType ? <span>· {BILLING_LABELS[group.billingType]}</span> : ''}
                    </div>
                  ) : null}

                  {group.capacity ? (
                    <div className="inline-flex items-center gap-1.5 rounded-lg bg-primary-soft px-2.5 py-1 text-foreground/80">
                      <Users className="size-3.5 text-accent" />
                      <span>Cupo {group.capacity}</span>
                    </div>
                  ) : null}
                </div>
              </div>

              {/* Form Header */}
              <div>
                <h2 className="text-lg font-bold text-primary">Completa tus datos</h2>
                <p className="text-xs text-foreground/60 mt-0.5">
                  Ingresa tus datos para registrarte en la lista de alumnos de este grupo.
                </p>
              </div>

              {/* Error banner */}
              {errorMessage ? (
                <div className="rounded-xl border border-danger/30 bg-danger-soft p-3 text-xs text-danger font-medium animate-fade-in">
                  {errorMessage}
                </div>
              ) : null}

              {/* Form */}
              <form onSubmit={handleSubmit} className="space-y-4">
                <div className="grid grid-cols-1 sm:grid-cols-2 gap-3">
                  <div>
                    <Label htmlFor="student-first-name" className="mb-1 block text-xs">
                      Nombre <span className="text-danger">*</span>
                    </Label>
                    <Input
                      id="student-first-name"
                      placeholder="Ej. Sofía"
                      value={firstName}
                      onChange={(e) => setFirstName(e.target.value)}
                      required
                    />
                  </div>

                  <div>
                    <Label htmlFor="student-last-name" className="mb-1 block text-xs">
                      Apellido <span className="text-danger">*</span>
                    </Label>
                    <Input
                      id="student-last-name"
                      placeholder="Ej. Fernández"
                      value={lastName}
                      onChange={(e) => setLastName(e.target.value)}
                      required
                    />
                  </div>
                </div>

                <div>
                  <Label htmlFor="student-phone" className="mb-1 block text-xs">
                    Teléfono / WhatsApp <span className="text-danger">*</span>
                  </Label>
                  <Input
                    id="student-phone"
                    placeholder="Ej. +54 9 11 2345-6789"
                    value={phone}
                    onChange={(e) => setPhone(e.target.value)}
                    required
                  />
                  <p className="mt-1 text-[11px] text-foreground/50">
                    El profesor se comunicará contigo por WhatsApp a este número.
                  </p>
                </div>

                <div>
                  <Label htmlFor="student-email" className="mb-1 block text-xs">
                    Email (opcional)
                  </Label>
                  <Input
                    id="student-email"
                    type="email"
                    placeholder="alumno@ejemplo.com"
                    value={email}
                    onChange={(e) => setEmail(e.target.value)}
                  />
                </div>

                <div className="pt-2">
                  <Button
                    type="submit"
                    variant="primary"
                    disabled={joinMutation.isPending}
                    className="w-full py-2.5 text-sm font-semibold gap-2"
                  >
                    {joinMutation.isPending ? (
                      <Loader2 className="size-4 animate-spin" />
                    ) : null}
                    <span>Completar Inscripción</span>
                  </Button>
                </div>
              </form>
            </div>
          ) : null}
        </div>
      </main>

      {/* Footer */}
      <footer className="border-t border-border py-4 px-4 text-center text-xs text-foreground/40">
        Gruperly — Gestión sencilla de cobros y grupos
      </footer>
    </div>
  );
}