import { useCallback, useState } from 'react';
import { Redirect, router, useFocusEffect } from 'expo-router';
import {
  ActivityIndicator,
  KeyboardAvoidingView,
  Modal,
  Platform,
  Pressable,
  StyleSheet,
  Text,
  TextInput,
  View,
} from 'react-native';

import {
  getApiBaseUrlSync,
  hydrateApiBaseUrl,
  isServerSetupDone,
  markServerSetupDone,
  setApiBaseUrl as persistApiBaseUrl,
} from '@/src/lib/server-config';
import { useAuth, useTokenStorageInfo } from '@/src/providers/auth-provider';

const PRIMARY = '#69c350';

function isValidServerUrl(value: string): boolean {
  return /^https?:\/\/.+/i.test(value.trim());
}

export default function LoginScreen() {
  const { token, requiresTenantSelection, login } = useAuth();
  const storageInfo = useTokenStorageInfo();

  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [apiBaseUrl, setApiBaseUrl] = useState(getApiBaseUrlSync());
  const [serverInput, setServerInput] = useState(getApiBaseUrlSync());
  const [showServerModal, setShowServerModal] = useState(false);
  const [isServerSetupRequired, setIsServerSetupRequired] = useState(false);
  const [isServerSaving, setIsServerSaving] = useState(false);
  const [serverError, setServerError] = useState<string | null>(null);
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [error, setError] = useState<string | null>(null);

  useFocusEffect(
    useCallback(() => {
      let active = true;

      async function refreshApiBase() {
        const current = await hydrateApiBaseUrl();
        const setupDone = await isServerSetupDone();
        if (!active) return;
        setApiBaseUrl(current);
        setServerInput(current);
        setIsServerSetupRequired(!setupDone);
        setShowServerModal(!setupDone);
      }

      void refreshApiBase();
      return () => {
        active = false;
      };
    }, [])
  );

  if (token) {
    return <Redirect href={requiresTenantSelection ? '/tenant-select' : '/(tabs)'} />;
  }

  async function applyDefaultServer() {
    setIsServerSaving(true);
    setServerError(null);

    try {
      await markServerSetupDone();
      setIsServerSetupRequired(false);
      setShowServerModal(false);
      setApiBaseUrl(getApiBaseUrlSync());
    } catch (err) {
      setServerError(err instanceof Error ? err.message : 'Server-Einstellung konnte nicht gespeichert werden.');
    } finally {
      setIsServerSaving(false);
    }
  }

  async function saveCustomServer() {
    setServerError(null);
    const value = serverInput.trim();

    if (!isValidServerUrl(value)) {
      setServerError('Bitte eine gültige URL mit http:// oder https:// eingeben.');
      return;
    }

    setIsServerSaving(true);
    try {
      const normalized = await persistApiBaseUrl(value);
      setApiBaseUrl(normalized);
      setServerInput(normalized);
      setIsServerSetupRequired(false);
      setShowServerModal(false);
    } catch (err) {
      setServerError(err instanceof Error ? err.message : 'Server-Einstellung konnte nicht gespeichert werden.');
    } finally {
      setIsServerSaving(false);
    }
  }

  async function onSubmit() {
    setIsSubmitting(true);
    setError(null);

    try {
      await login(email.trim(), password);
      router.replace('/');
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Login fehlgeschlagen.');
    } finally {
      setIsSubmitting(false);
    }
  }

  return (
    <KeyboardAvoidingView
      behavior={Platform.OS === 'ios' ? 'padding' : undefined}
      style={styles.container}>
      <View style={styles.card}>
        <Text style={styles.title}>FEDEO Mobile</Text>
        <Text style={styles.subtitle}>Login mit anschliessender Tenant-Auswahl</Text>

        <Text style={styles.label}>E-Mail</Text>
        <TextInput
          autoCapitalize="none"
          autoCorrect={false}
          keyboardType="email-address"
          placeholder="name@firma.de"
          placeholderTextColor="#9ca3af"
          style={styles.input}
          value={email}
          onChangeText={setEmail}
        />

        <Text style={styles.label}>Passwort</Text>
        <TextInput
          secureTextEntry
          placeholder="••••••••"
          placeholderTextColor="#9ca3af"
          style={styles.input}
          value={password}
          onChangeText={setPassword}
        />

        {error ? <Text style={styles.error}>{error}</Text> : null}

        <Pressable
          style={[styles.button, isSubmitting ? styles.buttonDisabled : null]}
          onPress={onSubmit}
          disabled={isSubmitting || isServerSetupRequired || !email || !password}>
          {isSubmitting ? <ActivityIndicator color="#ffffff" /> : <Text style={styles.buttonText}>Anmelden</Text>}
        </Pressable>

        <Pressable style={styles.serverLink} onPress={() => setShowServerModal(true)}>
          <Text style={styles.serverLinkText}>Eigenen Server festlegen</Text>
        </Pressable>

        <View style={styles.metaBox}>
          <Text style={styles.metaText}>API: {apiBaseUrl}</Text>
          <Text style={styles.metaText}>Token Storage: {storageInfo.mode}</Text>
        </View>
      </View>

      <Modal visible={showServerModal} transparent animationType="fade" onRequestClose={() => {}}>
        <View style={styles.modalBackdrop}>
          <View style={styles.modalCard}>
            <Text style={styles.modalTitle}>Server-Instanz festlegen</Text>
            <Text style={styles.modalText}>
              Vor dem ersten Login bitte Server wählen. Standard verwenden oder eigene Instanz hinterlegen.
            </Text>

            <TextInput
              value={serverInput}
              onChangeText={setServerInput}
              autoCapitalize="none"
              autoCorrect={false}
              keyboardType="url"
              placeholder="https://dein-server.tld"
              placeholderTextColor="#9ca3af"
              style={styles.input}
            />

            {serverError ? <Text style={styles.error}>{serverError}</Text> : null}

            <Pressable
              style={[styles.modalPrimaryButton, isServerSaving ? styles.buttonDisabled : null]}
              onPress={saveCustomServer}
              disabled={isServerSaving}>
              <Text style={styles.modalPrimaryText}>{isServerSaving ? 'Speichern...' : 'Eigene Instanz speichern'}</Text>
            </Pressable>

            <Pressable
              style={[styles.modalSecondaryButton, isServerSaving ? styles.buttonDisabled : null]}
              onPress={applyDefaultServer}
              disabled={isServerSaving}>
              <Text style={styles.modalSecondaryText}>Standardserver verwenden</Text>
            </Pressable>
          </View>
        </View>
      </Modal>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    padding: 20,
    backgroundColor: '#f3f4f6',
  },
  card: {
    backgroundColor: '#ffffff',
    borderRadius: 16,
    padding: 20,
    gap: 10,
    shadowColor: '#111827',
    shadowOpacity: 0.08,
    shadowRadius: 16,
    shadowOffset: { width: 0, height: 8 },
    elevation: 3,
  },
  title: {
    fontSize: 24,
    fontWeight: '700',
    color: '#111827',
  },
  subtitle: {
    color: '#6b7280',
    marginBottom: 8,
  },
  label: {
    fontSize: 14,
    color: '#374151',
    fontWeight: '500',
  },
  input: {
    borderWidth: 1,
    borderColor: '#d1d5db',
    borderRadius: 10,
    paddingHorizontal: 12,
    paddingVertical: 10,
    fontSize: 16,
    color: '#111827',
  },
  button: {
    marginTop: 6,
    backgroundColor: PRIMARY,
    borderRadius: 10,
    minHeight: 44,
    alignItems: 'center',
    justifyContent: 'center',
  },
  buttonDisabled: {
    backgroundColor: '#86efac',
  },
  buttonText: {
    color: '#ffffff',
    fontSize: 16,
    fontWeight: '600',
  },
  error: {
    color: '#dc2626',
    fontSize: 13,
  },
  metaBox: {
    marginTop: 8,
    paddingTop: 8,
    borderTopWidth: 1,
    borderTopColor: '#e5e7eb',
    gap: 4,
  },
  serverLink: {
    marginTop: 2,
    alignSelf: 'flex-start',
    paddingVertical: 4,
  },
  serverLinkText: {
    color: PRIMARY,
    fontSize: 13,
    fontWeight: '600',
  },
  metaText: {
    fontSize: 12,
    color: '#6b7280',
  },
  modalBackdrop: {
    flex: 1,
    backgroundColor: 'rgba(17, 24, 39, 0.45)',
    justifyContent: 'center',
    padding: 20,
  },
  modalCard: {
    backgroundColor: '#ffffff',
    borderRadius: 14,
    padding: 16,
    gap: 10,
  },
  modalTitle: {
    color: '#111827',
    fontSize: 18,
    fontWeight: '700',
  },
  modalText: {
    color: '#6b7280',
    fontSize: 13,
    lineHeight: 18,
  },
  modalPrimaryButton: {
    minHeight: 42,
    borderRadius: 10,
    backgroundColor: PRIMARY,
    alignItems: 'center',
    justifyContent: 'center',
  },
  modalPrimaryText: {
    color: '#ffffff',
    fontWeight: '700',
    fontSize: 14,
  },
  modalSecondaryButton: {
    minHeight: 42,
    borderRadius: 10,
    borderWidth: 1,
    borderColor: '#d1d5db',
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: '#ffffff',
  },
  modalSecondaryText: {
    color: '#374151',
    fontWeight: '600',
    fontSize: 14,
  },
});