/**
 * Billing Admin Page
 * 
 * Admin-Seite für Billing-Verwaltung (SysAdmin only).
 * - Settings verwalten
 * - Guthaben aufladen
 * - Konten übersicht
 */

import React, { useState, useEffect, useCallback, useMemo } from 'react';
import { useBillingAdmin, type BillingSettings, type AccountSummary, type MandateUserSummary } from '../../hooks/useBilling';
import { useAdminMandates } from '../../hooks/useMandates';
import styles from './Billing.module.css';

const _formatCurrency = (amount: number) => {
  return new Intl.NumberFormat('de-CH', {
    style: 'currency',
    currency: 'CHF'
  }).format(amount);
};

// ============================================================================
// MANDATE SELECTOR
// ============================================================================

interface MandateSelectorProps {
  selectedMandateId: string | null;
  onSelect: (mandateId: string) => void;
}

const MandateSelector: React.FC<MandateSelectorProps> = ({ selectedMandateId, onSelect }) => {
  const { mandates, loading } = useAdminMandates();
  
  return (
    <div className={styles.formGroup}>
      <label>Mandant auswählen</label>
      <select 
        className={styles.select}
        value={selectedMandateId || ''}
        onChange={(e) => onSelect(e.target.value)}
        disabled={loading}
      >
        <option value="">-- Mandant wählen --</option>
        {mandates.map((mandate) => (
          <option key={mandate.id} value={mandate.id}>
            {mandate.label || mandate.name || mandate.id}
          </option>
        ))}
      </select>
    </div>
  );
};

// ============================================================================
// SETTINGS EDITOR
// ============================================================================

interface SettingsEditorProps {
  settings: BillingSettings | null;
  onSave: (settings: Partial<BillingSettings>) => Promise<void>;
  loading: boolean;
}

const SettingsEditor: React.FC<SettingsEditorProps> = ({ settings, onSave, loading }) => {
  const [formData, setFormData] = useState({
    billingModel: settings?.billingModel || 'UNLIMITED',
    defaultUserCredit: settings?.defaultUserCredit || 10,
    warningThresholdPercent: settings?.warningThresholdPercent || 10,
    blockOnZeroBalance: settings?.blockOnZeroBalance ?? true,
    notifyOnWarning: settings?.notifyOnWarning ?? true,
  });
  const [saving, setSaving] = useState(false);
  const [message, setMessage] = useState<{ type: 'success' | 'error'; text: string } | null>(null);
  
  useEffect(() => {
    if (settings) {
      setFormData({
        billingModel: settings.billingModel,
        defaultUserCredit: settings.defaultUserCredit,
        warningThresholdPercent: settings.warningThresholdPercent,
        blockOnZeroBalance: settings.blockOnZeroBalance,
        notifyOnWarning: settings.notifyOnWarning,
      });
    }
  }, [settings]);
  
  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    setSaving(true);
    setMessage(null);
    
    try {
      await onSave(formData);
      setMessage({ type: 'success', text: 'Einstellungen gespeichert!' });
    } catch (err: any) {
      setMessage({ type: 'error', text: err.message || 'Fehler beim Speichern' });
    } finally {
      setSaving(false);
    }
  };
  
  return (
    <div className={styles.adminSection}>
      <h3>Billing-Einstellungen</h3>
      
      {message && (
        <div className={message.type === 'success' ? styles.successMessage : styles.errorMessage}>
          {message.text}
        </div>
      )}
      
      <form onSubmit={handleSubmit}>
        <div className={styles.formRow}>
          <div className={styles.formGroup}>
            <label>Abrechnungsmodell</label>
            <select 
              className={styles.select}
              value={formData.billingModel}
              onChange={(e) => setFormData(prev => ({ ...prev, billingModel: e.target.value as any }))}
            >
              <option value="UNLIMITED">Unlimited</option>
              <option value="PREPAY_MANDATE">Prepaid (Mandant)</option>
              <option value="PREPAY_USER">Prepaid (Benutzer)</option>
              <option value="CREDIT_POSTPAY">Kredit (Postpay)</option>
            </select>
          </div>
          
          <div className={styles.formGroup}>
            <label>Standard-Guthaben (CHF)</label>
            <input 
              type="number"
              className={styles.input}
              value={formData.defaultUserCredit}
              onChange={(e) => setFormData(prev => ({ ...prev, defaultUserCredit: Number(e.target.value) }))}
              min="0"
              step="0.01"
            />
          </div>
        </div>
        
        <div className={styles.formRow}>
          <div className={styles.formGroup}>
            <label>Warnschwelle (%)</label>
            <input 
              type="number"
              className={styles.input}
              value={formData.warningThresholdPercent}
              onChange={(e) => setFormData(prev => ({ ...prev, warningThresholdPercent: Number(e.target.value) }))}
              min="0"
              max="100"
              step="1"
            />
          </div>
          
          <div className={styles.formGroup}>
            <label>&nbsp;</label>
            <label style={{ display: 'flex', alignItems: 'center', gap: '8px', cursor: 'pointer' }}>
              <input 
                type="checkbox"
                checked={formData.blockOnZeroBalance}
                onChange={(e) => setFormData(prev => ({ ...prev, blockOnZeroBalance: e.target.checked }))}
              />
              Bei Guthaben 0 blockieren
            </label>
          </div>
        </div>
        
        <div className={styles.formRow}>
          <div className={styles.formGroup}>
            <label>&nbsp;</label>
            <label style={{ display: 'flex', alignItems: 'center', gap: '8px', cursor: 'pointer' }}>
              <input 
                type="checkbox"
                checked={formData.notifyOnWarning}
                onChange={(e) => setFormData(prev => ({ ...prev, notifyOnWarning: e.target.checked }))}
              />
              Bei Warnung benachrichtigen
            </label>
          </div>
        </div>
        
        <button 
          type="submit" 
          className={`${styles.button} ${styles.buttonPrimary}`}
          disabled={saving || loading}
        >
          {saving ? 'Speichern...' : 'Einstellungen speichern'}
        </button>
      </form>
    </div>
  );
};

// ============================================================================
// CREDIT ADDER
// ============================================================================

interface CreditAdderProps {
  settings: BillingSettings | null;
  accounts: AccountSummary[];
  users: MandateUserSummary[];
  onAddCredit: (userId: string | undefined, amount: number, description: string) => Promise<any>;
}

const CreditAdder: React.FC<CreditAdderProps> = ({ settings, accounts, users, onAddCredit }) => {
  const [selectedUserId, setSelectedUserId] = useState<string>('');
  const [amount, setAmount] = useState<string>('');
  const [description, setDescription] = useState<string>('Manuelles Aufladen durch Admin');
  const [saving, setSaving] = useState(false);
  const [message, setMessage] = useState<{ type: 'success' | 'error'; text: string } | null>(null);
  
  const isPrepayUser = settings?.billingModel === 'PREPAY_USER';
  
  const accountsByUserId = accounts
    .filter(acc => acc.accountType === 'USER')
    .reduce((map, acc) => {
      if (acc.userId) map[acc.userId] = acc;
      return map;
    }, {} as Record<string, AccountSummary>);
  
  const _handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    const numAmount = parseFloat(amount);
    if (!numAmount || numAmount <= 0) {
      setMessage({ type: 'error', text: 'Betrag muss positiv sein' });
      return;
    }
    
    setSaving(true);
    setMessage(null);
    
    try {
      await onAddCredit(isPrepayUser ? selectedUserId : undefined, numAmount, description);
      setMessage({ type: 'success', text: `${_formatCurrency(numAmount)} erfolgreich gutgeschrieben.` });
      setAmount('');
    } catch (err: any) {
      setMessage({ type: 'error', text: err.message || 'Fehler beim Aufladen' });
    } finally {
      setSaving(false);
    }
  };
  
  return (
    <div className={styles.adminSection}>
      <h3>Guthaben manuell aufladen</h3>
      
      {message && (
        <div className={message.type === 'success' ? styles.successMessage : styles.errorMessage}>
          {message.text}
        </div>
      )}
      
      <form onSubmit={_handleSubmit}>
        {isPrepayUser && (
          <div className={styles.formRow}>
            <div className={styles.formGroup}>
              <label>Benutzer</label>
              <select 
                className={styles.select}
                value={selectedUserId}
                onChange={(e) => setSelectedUserId(e.target.value)}
                required
              >
                <option value="">-- Benutzer wählen --</option>
                {users.map((user) => {
                  const account = accountsByUserId[user.id];
                  const balanceInfo = account ? ` (${_formatCurrency(account.balance)})` : ' (kein Konto)';
                  return (
                    <option key={user.id} value={user.id}>
                      {user.displayName || user.username || user.id}{balanceInfo}
                    </option>
                  );
                })}
              </select>
            </div>
          </div>
        )}
        
        <div className={styles.formRow}>
          <div className={styles.formGroup}>
            <label>Betrag (CHF)</label>
            <input
              type="number"
              className={styles.input}
              value={amount}
              onChange={(e) => setAmount(e.target.value)}
              placeholder="z.B. 50"
              min="0.01"
              step="0.01"
              required
            />
          </div>
          <div className={styles.formGroup}>
            <label>Beschreibung</label>
            <input
              type="text"
              className={styles.input}
              value={description}
              onChange={(e) => setDescription(e.target.value)}
              placeholder="Beschreibung der Gutschrift"
            />
          </div>
        </div>
        
        <button 
          type="submit" 
          className={`${styles.button} ${styles.buttonPrimary}`}
          disabled={saving || (isPrepayUser && !selectedUserId) || !amount}
        >
          {saving ? 'Wird gutgeschrieben...' : 'Manuell aufladen'}
        </button>
      </form>
    </div>
  );
};

// ============================================================================
// ACCOUNTS OVERVIEW
// ============================================================================

interface AccountsOverviewProps {
  accounts: AccountSummary[];
  users: MandateUserSummary[];
  loading: boolean;
}

const AccountsOverview: React.FC<AccountsOverviewProps> = ({ accounts, users, loading }) => {
  const formatCurrency = (amount: number) => {
    return new Intl.NumberFormat('de-CH', {
      style: 'currency',
      currency: 'CHF'
    }).format(amount);
  };

  // Build a lookup map: userId -> display name
  const _userNameMap = useMemo(() => {
    const map = new Map<string, string>();
    for (const user of users) {
      const displayName = user.displayName
        || [user.firstName, user.lastName].filter(Boolean).join(' ')
        || user.username
        || user.id;
      map.set(user.id, displayName);
    }
    return map;
  }, [users]);
  
  if (loading) {
    return <div className={styles.loadingPlaceholder}>Lade Konten...</div>;
  }
  
  if (accounts.length === 0) {
    return <div className={styles.noData}>Keine Konten vorhanden</div>;
  }
  
  return (
    <div className={styles.adminSection}>
      <h3>Konten</h3>
      <div className={styles.accountsGrid}>
        {accounts.map((account) => (
          <div key={account.id} className={styles.accountCard}>
            <h4>{account.accountType === 'MANDATE' ? 'Mandanten-Konto' : 'Benutzer-Konto'}</h4>
            <div className={styles.accountInfo}>
              {account.userId && <span>User: {_userNameMap.get(account.userId) || account.userId}</span>}
              <span>Guthaben: <strong>{formatCurrency(account.balance)}</strong></span>
              {account.creditLimit && <span>Limit: {formatCurrency(account.creditLimit)}</span>}
              <span>Status: {account.enabled ? 'Aktiv' : 'Deaktiviert'}</span>
            </div>
          </div>
        ))}
      </div>
    </div>
  );
};

// ============================================================================
// MAIN COMPONENT
// ============================================================================

export const BillingAdmin: React.FC = () => {
  const [selectedMandateId, setSelectedMandateId] = useState<string | null>(null);
  const { settings, accounts, users, loading, saveSettings, addCredit, loadAccounts } = useBillingAdmin(selectedMandateId || undefined);
  
  const handleMandateSelect = (mandateId: string) => {
    setSelectedMandateId(mandateId || null);
  };
  
  const handleSaveSettings = useCallback(async (settingsUpdate: Partial<BillingSettings>) => {
    if (!selectedMandateId) return;
    await saveSettings(settingsUpdate);
  }, [selectedMandateId, saveSettings]);
  
  const _handleAddCredit = useCallback(async (userId: string | undefined, amount: number, description: string) => {
    if (!selectedMandateId) throw new Error('Mandant nicht ausgewählt');
    const result = await addCredit({ userId, amount, description });
    if (!result) throw new Error('Gutschrift konnte nicht erstellt werden');
    await loadAccounts();
    return result;
  }, [selectedMandateId, addCredit, loadAccounts]);

  return (
    <div className={styles.billingDashboard}>
      <header className={styles.pageHeader}>
        <h1>Billing Administration</h1>
        <p className={styles.subtitle}>Verwaltung von Abrechnungseinstellungen und Guthaben</p>
      </header>
      
      <section className={styles.section}>
        <MandateSelector 
          selectedMandateId={selectedMandateId} 
          onSelect={handleMandateSelect} 
        />
      </section>
      
      {selectedMandateId && (
        <>
          <SettingsEditor 
            settings={settings} 
            onSave={handleSaveSettings}
            loading={loading}
          />
          
          <CreditAdder 
            settings={settings}
            accounts={accounts}
            users={users}
            onAddCredit={_handleAddCredit}
          />
          
          <AccountsOverview 
            accounts={accounts}
            users={users}
            loading={loading}
          />
        </>
      )}
      
      {!selectedMandateId && (
        <div className={styles.noData}>
          Bitte wählen Sie einen Mandanten aus.
        </div>
      )}
    </div>
  );
};

export default BillingAdmin;