import React, { useEffect, useState } from 'react';
import { Box, Text, useInput } from 'ink';
import type { CustomerType, CountryDTO } from '@effigenix/api-client';
import { useNavigation } from '../../../state/navigation-context.js';
import { useCustomers } from '../../../hooks/useCustomers.js';
import { FormInput } from '../../shared/FormInput.js';
import { CountryPicker } from '../../shared/CountryPicker.js';
import { LoadingSpinner } from '../../shared/LoadingSpinner.js';
import { ErrorDisplay } from '../../shared/ErrorDisplay.js';
import { client } from '../../../utils/api-client.js';
import { DEFAULT_COUNTRY, DACH_FALLBACK } from '../../shared/country-defaults.js';

type Field = 'name' | 'phone' | 'email' | 'street' | 'houseNumber' | 'postalCode' | 'city' | 'countryPicker' | 'paymentDueDays';
const FIELDS: Field[] = ['name', 'phone', 'email', 'street', 'houseNumber', 'postalCode', 'city', 'countryPicker', 'paymentDueDays'];

const FIELD_LABELS: Record<Field, string> = {
  name: 'Name *',
  phone: 'Telefon *',
  email: 'E-Mail',
  street: 'Straße *',
  houseNumber: 'Hausnummer *',
  postalCode: 'PLZ *',
  city: 'Stadt *',
  countryPicker: 'Land *',
  paymentDueDays: 'Zahlungsziel (Tage)',
};

const TYPES: CustomerType[] = ['B2B', 'B2C'];

export function CustomerCreateScreen() {
  const { replace, back } = useNavigation();
  const { createCustomer, loading, error, clearError } = useCustomers();

  const [values, setValues] = useState<Record<Exclude<Field, 'countryPicker'>, string>>({
    name: '', phone: '', email: '', street: '', houseNumber: '',
    postalCode: '', city: '', paymentDueDays: '',
  });
  const [typeIndex, setTypeIndex] = useState(0);
  const [activeField, setActiveField] = useState<Field | 'type'>('name');
  const [fieldErrors, setFieldErrors] = useState<Partial<Record<Field | 'type', string>>>({});
  const [countryQuery, setCountryQuery] = useState('');
  const [countryCode, setCountryCode] = useState(DEFAULT_COUNTRY.code);
  const [countryName, setCountryName] = useState(DEFAULT_COUNTRY.name);
  const [countries, setCountries] = useState<CountryDTO[]>([]);

  useEffect(() => {
    client.countries.search().then(setCountries).catch(() => setCountries(DACH_FALLBACK));
  }, []);

  const setField = (field: Exclude<Field, 'countryPicker'>) => (value: string) => {
    setValues((v) => ({ ...v, [field]: value }));
  };

  useInput((_input, key) => {
    if (loading) return;

    if (activeField === 'type') {
      if (key.leftArrow) setTypeIndex((i) => Math.max(0, i - 1));
      if (key.rightArrow) setTypeIndex((i) => Math.min(TYPES.length - 1, i + 1));
      if (key.tab || key.downArrow || key.return) setActiveField('name');
    } else {
      if (key.tab || key.downArrow) {
        setActiveField((f) => {
          if (f === 'type') return 'name';
          const idx = FIELDS.indexOf(f as Field);
          return FIELDS[(idx + 1) % FIELDS.length] ?? f;
        });
      }
      if (key.upArrow) {
        setActiveField((f) => {
          if (f === 'type') return f;
          const idx = FIELDS.indexOf(f as Field);
          if (idx === 0) return 'type';
          return FIELDS[idx - 1] ?? f;
        });
      }
    }
    if (key.escape) back();
  });

  const handleSubmit = async () => {
    const errors: Partial<Record<Field | 'type', string>> = {};
    if (!values.name.trim()) errors.name = 'Name ist erforderlich.';
    if (!values.phone.trim()) errors.phone = 'Telefon ist erforderlich.';
    if (!values.street.trim()) errors.street = 'Straße ist erforderlich.';
    if (!values.houseNumber.trim()) errors.houseNumber = 'Hausnummer ist erforderlich.';
    if (!values.postalCode.trim()) errors.postalCode = 'PLZ ist erforderlich.';
    if (!values.city.trim()) errors.city = 'Stadt ist erforderlich.';
    if (!countryCode) errors.countryPicker = 'Land ist erforderlich.';
    setFieldErrors(errors);
    if (Object.keys(errors).length > 0) return;

    const result = await createCustomer({
      name: values.name.trim(),
      type: TYPES[typeIndex] ?? 'B2B',
      phone: values.phone.trim(),
      street: values.street.trim(),
      houseNumber: values.houseNumber.trim(),
      postalCode: values.postalCode.trim(),
      city: values.city.trim(),
      country: countryCode,
      ...(values.email.trim() ? { email: values.email.trim() } : {}),
      ...(values.paymentDueDays.trim() ? { paymentDueDays: parseInt(values.paymentDueDays, 10) } : {}),
    });
    if (result) replace('customer-list');
  };

  const handleFieldSubmit = (field: Field) => (_value: string) => {
    const idx = FIELDS.indexOf(field);
    if (idx < FIELDS.length - 1) {
      setActiveField(FIELDS[idx + 1] ?? field);
    } else {
      void handleSubmit();
    }
  };

  if (loading) return <Box paddingY={2}><LoadingSpinner label="Kunde wird angelegt..." /></Box>;

  return (
    <Box flexDirection="column" gap={1}>
      <Text color="cyan" bold>Neuer Kunde</Text>
      {error && <ErrorDisplay message={error} onDismiss={clearError} />}

      <Box flexDirection="column" gap={1} width={60}>
        {/* Type Selector */}
        <Box flexDirection="column">
          <Text color={activeField === 'type' ? 'cyan' : 'gray'}>Typ *</Text>
          <Box gap={1}>
            <Text color={activeField === 'type' ? 'cyan' : 'gray'}>{'< '}</Text>
            <Text color={activeField === 'type' ? 'white' : 'gray'}>{TYPES[typeIndex]}</Text>
            <Text color={activeField === 'type' ? 'cyan' : 'gray'}>{' >'}</Text>
          </Box>
          {activeField === 'type' && <Text color="gray" dimColor>←→ Typ · Tab/Enter weiter</Text>}
        </Box>

        {FIELDS.map((field) => {
          if (field === 'countryPicker') {
            return (
              <CountryPicker
                key="countryPicker"
                countries={countries}
                query={countryQuery}
                onQueryChange={setCountryQuery}
                onSelect={(c) => {
                  setCountryCode(c.code);
                  setCountryName(c.name);
                  setCountryQuery('');
                  const idx = FIELDS.indexOf('countryPicker');
                  if (idx < FIELDS.length - 1) {
                    setActiveField(FIELDS[idx + 1] ?? 'countryPicker');
                  }
                }}
                focus={activeField === 'countryPicker'}
                selectedName={countryName}
              />
            );
          }
          const f = field as Exclude<Field, 'countryPicker'>;
          return (
            <FormInput
              key={f}
              label={FIELD_LABELS[f]}
              value={values[f]}
              onChange={setField(f)}
              onSubmit={handleFieldSubmit(f)}
              focus={activeField === f}
              {...(fieldErrors[f] ? { error: fieldErrors[f] } : {})}
            />
          );
        })}
      </Box>

      <Box marginTop={1}>
        <Text color="gray" dimColor>
          Tab/↑↓ Feld · ←→ Typ · Enter auf letztem Feld speichern · Escape Abbrechen
        </Text>
      </Box>
    </Box>
  );
}
