import React, { useEffect, useState } from 'react';
import { StyleSheet, Switch, Text, View } from 'react-native';
import type { NativeStackScreenProps } from '@react-navigation/native-stack';
import Ionicons from '@react-native-vector-icons/ionicons';

import { Button, Card, ScreenShell } from '../../../components';
import { useAppDispatch, useAppSelector } from '../../../app/hooks';
import { useTheme, fontFamily } from '../../../theme';
import { useApiErrorToast } from '../../../hooks/useApiErrorToast';
import { biometrics } from '../../../services/security/biometrics';
import { authActions } from '../store/authSlice';
import { selectRegistration } from '../store/authSelectors';
import { completeMpinSetup, rememberRegisteredProfile } from '../store/authThunk';
import { MPIN_LENGTH, describeMpinProblem, isValidMpin } from '../utils/authValidation';
import { CodeInput } from '../components/CodeInput';
import type { AuthStackParamList } from '../../../navigation/types';

type Props = Readonly<NativeStackScreenProps<AuthStackParamList, 'CreateMpin'>>;

export default function CreateMpinScreen({ navigation }: Props) {
  const dispatch = useAppDispatch();
  const theme = useTheme();
  const showApiError = useApiErrorToast();
  const registration = useAppSelector(selectRegistration);

  const [mpin, setMpin] = useState('');
  const [confirmMpin, setConfirmMpin] = useState('');
  const [rememberForBiometrics, setRememberForBiometrics] = useState(false);
  const [biometricsAvailable, setBiometricsAvailable] = useState(false);
  const [submitted, setSubmitted] = useState(false);

  const isLoading = registration.status === 'loading';

  useEffect(() => {
    void biometrics.isAvailable().then(setBiometricsAvailable);
  }, []);

  // A setup token this screen never received cannot be recovered from here —
  // the five-minute window has to be reopened from the start.
  useEffect(() => {
    if (!registration.setupToken && !isLoading && !submitted) {
      dispatch(authActions.resetRegistration());
      navigation.navigate('Register');
    }
  }, [dispatch, isLoading, navigation, registration.setupToken, submitted]);

  useEffect(() => {
    if (!submitted || registration.status !== 'failed' || !registration.error) {
      return;
    }

    setSubmitted(false);
    showApiError(registration.error);

    const { code } = registration.error;

    if (code === 'OTP_NOT_VERIFIED') {
      dispatch(authActions.resetRegistration());
      navigation.navigate('Register');
      return;
    }

    if (code === 'MPIN_ALREADY_SET') {
      // verify-otp said this profile still owed an MPIN and the server now says
      // otherwise, so the profile has to be recorded here — nothing earlier in
      // this path stored one, and sign-in would read that as a device that has
      // never registered and send them back for another OTP.
      void dispatch(
        rememberRegisteredProfile({
          orgId: registration.orgId,
          mobileNumber: registration.mobileNumber,
        }),
      );
      dispatch(authActions.resetRegistration());
      navigation.navigate('Login');
      return;
    }

    setMpin('');
    setConfirmMpin('');
  }, [
    dispatch,
    navigation,
    registration.error,
    registration.mobileNumber,
    registration.orgId,
    registration.status,
    showApiError,
    submitted,
  ]);

  const mpinProblem = describeMpinProblem(mpin);
  const confirmProblem =
    confirmMpin.length === MPIN_LENGTH && confirmMpin !== mpin
      ? 'Both entries must match'
      : undefined;

  const canSubmit =
    isValidMpin(mpin) && confirmMpin === mpin && !isLoading;

  const handleSubmit = () => {
    if (!canSubmit) {
      return;
    }

    setSubmitted(true);
    void dispatch(
      completeMpinSetup({
        mpin,
        rememberForBiometrics: rememberForBiometrics && biometricsAvailable,
      }),
    );
  };

  return (
    <ScreenShell
      title="Create your MPIN"
      subtitle="You will use this to sign in from now on"
      withTabBar={false}
      contentContainerStyle={styles.container}
    >
      <Card style={styles.formCard}>
        <Text style={[styles.sectionLabel, { color: theme.colors.textSecondary }]}>
          {`CHOOSE A ${MPIN_LENGTH}-DIGIT MPIN`}
        </Text>

        <CodeInput
          value={mpin}
          onChangeText={setMpin}
          length={MPIN_LENGTH}
          secure
          autoFocus
          editable={!isLoading}
          error={mpinProblem}
        />

        <CodeInput
          label="Confirm MPIN"
          value={confirmMpin}
          onChangeText={setConfirmMpin}
          length={MPIN_LENGTH}
          secure
          editable={!isLoading}
          error={confirmProblem}
          onSubmit={handleSubmit}
        />
      </Card>

      {biometricsAvailable && (
        <Card style={styles.biometricCard}>
          <View style={styles.biometricRow}>
            <Ionicons name="finger-print-outline" size={22} color={theme.colors.primary} />
            <View style={styles.biometricCopy}>
              <Text style={[styles.biometricTitle, { color: theme.colors.textPrimary }]}>
                Sign in with biometrics
              </Text>
              {/* Worth being straight about: the API opens a session only
                  against the MPIN, so enabling this keeps the MPIN on the
                  device behind the system prompt. */}
              <Text style={[styles.biometricNote, { color: theme.colors.textSecondary }]}>
                Stores your MPIN in this device&apos;s secure hardware, unlocked by your
                fingerprint or face.
              </Text>
            </View>
            <Switch
              value={rememberForBiometrics}
              onValueChange={setRememberForBiometrics}
              disabled={isLoading}
            />
          </View>
        </Card>
      )}

      <View style={[styles.noteCard, { backgroundColor: `${theme.colors.warning}14` }]}>
        <Ionicons name="alert-circle-outline" size={18} color={theme.colors.warning} />
        <Text style={[styles.noteText, { color: theme.colors.textSecondary }]}>
          Three wrong MPINs lock your profile, and only your branch can unlock it. Pick
          something you will remember.
        </Text>
      </View>

      <Button
        title="Set MPIN and continue"
        onPress={handleSubmit}
        disabled={!canSubmit}
        loading={isLoading}
        style={styles.submitButton}
      />
    </ScreenShell>
  );
}

const styles = StyleSheet.create({
  container: {
    padding: 16,
    gap: 16,
    flexGrow: 1,
  },
  formCard: {
    padding: 16,
    gap: 16,
  },
  sectionLabel: {
    fontSize: 11,
    fontFamily: fontFamily.bold,
    letterSpacing: 0.5,
    marginLeft: 4,
  },
  biometricCard: {
    padding: 16,
  },
  biometricRow: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: 12,
  },
  biometricCopy: {
    flex: 1,
    gap: 2,
  },
  biometricTitle: {
    fontSize: 15,
    fontFamily: fontFamily.bold,
  },
  biometricNote: {
    fontSize: 12,
    lineHeight: 17,
  },
  noteCard: {
    flexDirection: 'row',
    alignItems: 'flex-start',
    gap: 10,
    padding: 14,
    borderRadius: 12,
  },
  noteText: {
    flex: 1,
    fontSize: 13,
    lineHeight: 18,
  },
  submitButton: {
    marginTop: 'auto',
    height: 54,
  },
});