import React, { useCallback, useEffect, useState } from 'react';
import { Modal, ConfirmDialog } from '../ui/Modal';
import { AvatarPicker } from '../ui/AvatarPicker';
import { UserAvatar } from '../ui/UserAvatar';
import { ColorPicker } from './ColorPicker';
import { inputClass, labelClass } from '../leads/leadUi';
import { useToast } from '../Toast';
import { useAuth } from '../../lib/auth';
import { usersApi, type UserInput } from '../../lib/api';
import { userColor, type AppUser, type Role } from '../../types';

interface UserFormState {
  username: string;
  name: string;
  email: string;
  role: Role;
  is_active: boolean;
  password: string;
  /** null = Farbe automatisch aus der Palette */
  color: string | null;
  /** '' = kein Foto, dann wird die Initiale angezeigt */
  avatar: string;
}

const emptyForm: UserFormState = {
  username: '',
  name: '',
  email: '',
  role: 'user',
  is_active: true,
  password: '',
  color: null,
  avatar: '',
};

const RoleBadge: React.FC<{ role: Role }> = ({ role }) =>
  role === 'admin' ? (
    <span className="rounded-md border border-brand-200 bg-brand-50 px-2 py-0.5 text-[10px] font-extrabold uppercase tracking-wider text-brand-700">
      Admin
    </span>
  ) : (
    <span className="rounded-md border border-ink-200 bg-ink-100 px-2 py-0.5 text-[10px] font-extrabold uppercase tracking-wider text-ink-500">
      User
    </span>
  );

export const UserManagement: React.FC = () => {
  const { addToast } = useToast();
  const { user: currentUser, updateUser } = useAuth();

  const [users, setUsers] = useState<AppUser[]>([]);
  const [isLoading, setIsLoading] = useState(true);
  const [editingUser, setEditingUser] = useState<AppUser | null>(null);
  const [isModalOpen, setIsModalOpen] = useState(false);
  const [form, setForm] = useState<UserFormState>(emptyForm);
  const [isSaving, setIsSaving] = useState(false);
  const [userToDelete, setUserToDelete] = useState<AppUser | null>(null);

  const load = useCallback(async () => {
    setIsLoading(true);
    try {
      setUsers(await usersApi.list());
    } catch (err) {
      addToast(err instanceof Error ? err.message : 'Benutzer konnten nicht geladen werden.', 'error');
    } finally {
      setIsLoading(false);
    }
  }, [addToast]);

  useEffect(() => {
    load();
  }, [load]);

  const openCreate = () => {
    setEditingUser(null);
    setForm(emptyForm);
    setIsModalOpen(true);
  };

  const openEdit = (user: AppUser) => {
    setEditingUser(user);
    setForm({
      username: user.username,
      name: user.name,
      email: user.email ?? '',
      role: user.role,
      is_active: user.is_active,
      password: '',
      color: user.color ?? null,
      avatar: user.avatar ?? '',
    });
    setIsModalOpen(true);
  };

  const set = <K extends keyof UserFormState>(key: K, value: UserFormState[K]) =>
    setForm((prev) => ({ ...prev, [key]: value }));

  const handleSubmit = async (event: React.FormEvent) => {
    event.preventDefault();
    if (!form.username.trim() || !form.name.trim()) {
      addToast('Benutzername und Name sind erforderlich.', 'error');
      return;
    }
    if (!editingUser && form.password.length < 8) {
      addToast('Das Passwort muss mindestens 8 Zeichen haben.', 'error');
      return;
    }
    if (editingUser && form.password && form.password.length < 8) {
      addToast('Das neue Passwort muss mindestens 8 Zeichen haben.', 'error');
      return;
    }

    setIsSaving(true);
    try {
      const payload: UserInput = {
        username: form.username.trim(),
        name: form.name.trim(),
        email: form.email.trim() || null,
        role: form.role,
        is_active: form.is_active,
        color: form.color,
        avatar: form.avatar || null,
      };
      if (form.password) payload.password = form.password;

      if (editingUser) {
        const updated = await usersApi.update(editingUser.id, payload);
        addToast(`Benutzer "${updated.name}" wurde aktualisiert.`, 'success');
        // Eigene Daten sofort in der laufenden Sitzung uebernehmen.
        if (currentUser && updated.id === currentUser.id) updateUser(updated);
      } else {
        const created = await usersApi.create(payload);
        addToast(`Benutzer "${created.name}" wurde angelegt.`, 'success');
      }
      setIsModalOpen(false);
      await load();
    } catch (err) {
      addToast(err instanceof Error ? err.message : 'Speichern fehlgeschlagen.', 'error');
    } finally {
      setIsSaving(false);
    }
  };

  const confirmDelete = async () => {
    if (!userToDelete) return;
    try {
      await usersApi.remove(userToDelete.id);
      addToast(`Benutzer "${userToDelete.name}" wurde gelöscht.`, 'success');
      await load();
    } catch (err) {
      addToast(err instanceof Error ? err.message : 'Löschen fehlgeschlagen.', 'error');
    } finally {
      setUserToDelete(null);
    }
  };

  return (
    <div>
      <div className="mb-4 flex items-center justify-between gap-3">
        <div>
          <h3 className="text-base text-ink-900">Benutzer ({users.length})</h3>
          <p className="text-xs text-ink-400">
            Rolle Admin sieht die Einstellungen, Rolle User nicht.
          </p>
        </div>
        <button
          onClick={openCreate}
          className="flex shrink-0 items-center gap-2 rounded-xl bg-brand-500 px-4 py-2.5 text-sm font-bold text-white shadow-card transition hover:bg-brand-600"
        >
          <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
          </svg>
          Benutzer anlegen
        </button>
      </div>

      {isLoading ? (
        <div className="flex justify-center py-14">
          <span className="h-6 w-6 animate-spin rounded-full border-2 border-brand-200 border-t-brand-500" />
        </div>
      ) : (
        <ul className="space-y-2">
          {users.map((user) => (
            <li
              key={user.id}
              className="flex items-center gap-3 rounded-xl border border-ink-200 bg-surface px-4 py-3"
            >
              <UserAvatar
                user={user}
                size={40}
                color={user.is_active ? undefined : '#c2c2c2'}
                className={user.is_active ? undefined : 'grayscale'}
              />

              <div className="min-w-0 flex-1">
                <div className="flex flex-wrap items-center gap-2">
                  <span className="truncate text-sm font-bold text-ink-900">{user.name}</span>
                  <span className="text-xs text-ink-400">@{user.username}</span>
                  <RoleBadge role={user.role} />
                  {user.id === currentUser?.id && (
                    <span className="rounded-md border border-sky-200 bg-sky-50 px-2 py-0.5 text-[10px] font-extrabold uppercase tracking-wider text-sky-700">
                      Ich
                    </span>
                  )}
                  {!user.is_active && (
                    <span className="rounded-md border border-amber-200 bg-amber-50 px-2 py-0.5 text-[10px] font-extrabold uppercase tracking-wider text-amber-700">
                      Deaktiviert
                    </span>
                  )}
                </div>
                {user.email && <p className="truncate text-xs text-ink-400">{user.email}</p>}
              </div>

              <div className="flex shrink-0 items-center gap-2">
                <button
                  onClick={() => openEdit(user)}
                  className="rounded-lg border border-ink-200 px-3 py-1.5 text-xs font-bold text-ink-600 transition hover:border-brand-300 hover:text-brand-700"
                >
                  Bearbeiten
                </button>
                {user.id !== currentUser?.id && (
                  <button
                    onClick={() => setUserToDelete(user)}
                    className="rounded-lg p-2 text-ink-400 transition hover:bg-red-50 hover:text-red-600"
                    aria-label={`${user.name} löschen`}
                  >
                    <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                      <path
                        strokeLinecap="round"
                        strokeLinejoin="round"
                        strokeWidth={2}
                        d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
                      />
                    </svg>
                  </button>
                )}
              </div>
            </li>
          ))}
        </ul>
      )}

      {isModalOpen && (
        <Modal
          title={editingUser ? `${editingUser.name} bearbeiten` : 'Neuer Benutzer'}
          subtitle={editingUser ? `@${editingUser.username}` : 'Zugang für das perinco CRM anlegen'}
          onClose={() => setIsModalOpen(false)}
          size="md"
          footer={
            <div className="flex gap-3">
              <button
                type="button"
                onClick={() => setIsModalOpen(false)}
                className="flex-1 rounded-xl border border-ink-200 py-3 text-sm font-bold text-ink-600 transition hover:bg-ink-100"
              >
                Abbrechen
              </button>
              <button
                type="submit"
                form="user-form"
                disabled={isSaving}
                className="flex-[2] rounded-xl bg-brand-500 py-3 text-sm font-bold text-white transition hover:bg-brand-600 disabled:opacity-60"
              >
                {isSaving ? 'Speichere...' : 'Speichern'}
              </button>
            </div>
          }
        >
          <form id="user-form" onSubmit={handleSubmit} className="space-y-4">
            <div>
              <label className={labelClass}>Foto</label>
              <AvatarPicker
                value={form.avatar}
                onChange={(value) => set('avatar', value)}
                initials={form.name.charAt(0).toUpperCase() || '?'}
              />
            </div>
            <div>
              <label className={labelClass}>Benutzername *</label>
              <input
                required
                value={form.username}
                onChange={(event) => set('username', event.target.value)}
                className={inputClass}
                autoComplete="off"
              />
            </div>
            <div>
              <label className={labelClass}>Anzeigename *</label>
              <input
                required
                value={form.name}
                onChange={(event) => set('name', event.target.value)}
                className={inputClass}
              />
            </div>
            <div>
              <label className={labelClass}>E-Mail</label>
              <input
                type="email"
                value={form.email}
                onChange={(event) => set('email', event.target.value)}
                className={inputClass}
                autoComplete="off"
              />
            </div>
            <div>
              <label className={labelClass}>Rolle</label>
              <select
                value={form.role}
                onChange={(event) => set('role', event.target.value as Role)}
                className={inputClass}
              >
                <option value="user">User &ndash; ohne Einstellungen</option>
                <option value="admin">Admin &ndash; mit Einstellungen</option>
              </select>
            </div>
            <div>
              <label className={labelClass}>
                {editingUser ? 'Neues Passwort (optional)' : 'Passwort *'}
              </label>
              <input
                type="password"
                required={!editingUser}
                value={form.password}
                onChange={(event) => set('password', event.target.value)}
                placeholder={editingUser ? 'Leer lassen, um es nicht zu ändern' : 'Mindestens 8 Zeichen'}
                className={inputClass}
                autoComplete="new-password"
              />
            </div>
            <div>
              <label className={labelClass}>Kalenderfarbe</label>
              <ColorPicker
                value={form.color}
                fallback={userColor(editingUser ? { id: editingUser.id, color: null } : { id: 0 })}
                onChange={(color) => set('color', color)}
              />
            </div>
            <label className="flex cursor-pointer items-center gap-3 rounded-xl border border-ink-200 px-4 py-3">
              <input
                type="checkbox"
                checked={form.is_active}
                onChange={(event) => set('is_active', event.target.checked)}
                className="h-4 w-4 accent-brand-500"
              />
              <span className="text-sm font-semibold text-ink-700">Konto aktiv</span>
            </label>
          </form>
        </Modal>
      )}

      {userToDelete && (
        <ConfirmDialog
          title="Benutzer löschen?"
          message={`"${userToDelete.name}" verliert den Zugang. Angelegte Kontakte bleiben erhalten, verlieren aber die Zuordnung.`}
          onConfirm={confirmDelete}
          onCancel={() => setUserToDelete(null)}
        />
      )}
    </div>
  );
};