import {BarCodeEvent, BarCodeScanner, PermissionResponse} from 'expo-barcode-scanner';
import React, {ReactElement, useEffect, useState} from 'react';
import {AppRegistry, SafeAreaView, View} from 'react-native';
import {
  Appbar,
  Button, DarkTheme,
  DefaultTheme,
  HelperText,
  Provider as PaperProvider,
  Snackbar, Subheading,
  TextInput,
  Title
} from 'react-native-paper';
import {expo as appExpo} from './app.json';
import {CancelButton} from './components/Common';
import {BarCodeDisplay, PrintButton, PrintingMessage} from './components/Print';
import {ScanButton, Scanner} from './components/Scan';
import {colors, styles} from './components/Styles';
import {BarcodeScannerAppState} from './models/BarcodeScannerAppState';
import {ElementProps, StateProps} from './models/ElementProps';

const theme = {
  ...DefaultTheme,
  colors: colors,
}

export default function Main() {
  const [appState, setAppState] = useState<BarcodeScannerAppState>(BarcodeScannerAppState.INITIAL);
  const [barCodeData, setBarCodeData] = useState<string>('');
  const [date, setDate] = useState<Date>(new Date());
  const [locationStr, setLocationStr] = useState<string>('4321');

  useEffect(() => {
    BarCodeScanner.requestPermissionsAsync().then((value: PermissionResponse) => {
      if (value.granted) {
        setAppState(BarcodeScannerAppState.DEFAULT);
      } else {
        setAppState(BarcodeScannerAppState.ERROR);
      }
    });
  }, []);

  const _doNothing = () => {};
  const _scan = () => setAppState(BarcodeScannerAppState.SCANNING);
  const _print = () => setAppState(BarcodeScannerAppState.PRINTING);
  const _home = () => setAppState(BarcodeScannerAppState.DEFAULT);
  const _settings = () => setAppState(BarcodeScannerAppState.SETTINGS);

  const handleBarCodeScanned = (e: BarCodeEvent) => {
    // Make sure the data is the right length.
    const barCodeString = e.data;
    const pattern = /^[\d]{14}$/;
    if (pattern.test(barCodeString)) {
      setBarCodeData(e.data);
      setDate(new Date());
      setAppState(BarcodeScannerAppState.SCANNED);
    } else {
      setAppState(BarcodeScannerAppState.ERROR);
    }
  };

  function ErrorMessage(props: ElementProps): ReactElement {
    return <View style={styles.fullScreen}>
      <View style={styles.container}>
        <ScanButton onClicked={_scan}/>
      </View>
      <Snackbar
        visible={appState === BarcodeScannerAppState.ERROR}
        onDismiss={_doNothing}
        style={styles.error}
      >Something went wrong. Try again.</Snackbar>
    </View>
  }

  function LoadingMessage(props: ElementProps): ReactElement {
    return <Snackbar
      visible={appState === BarcodeScannerAppState.INITIAL}
      onDismiss={_doNothing}
    >Loading...</Snackbar>;
  }

  function SuccessMessage(props: ElementProps): ReactElement {
    return <Title>Your barcode label has printed successfully.</Title>;
  }

  function ActionButtons(props: ElementProps): ReactElement {
    return <View>
      <PrintButton onClicked={_print}/>
      <CancelButton onClicked={_home}/>
    </View>
  }

  function SettingsModal(props: ElementProps): ReactElement {
    const [inputStr, setInputStr] = useState<string>(locationStr);
    const pattern = /^[\d]{4}$/;
    const hasErrors = () => {
      return !pattern.test(inputStr);
    };

    return <View style={styles.settings}>
      <Title style={styles.headingInverse}>Settings</Title>
      <View style={{marginBottom: 10}}>
        <Subheading style={{color: DefaultTheme.colors.text, marginBottom: 60}}>
          Please do NOT change this unless you know what you are doing. Entering an incorrect location number may prevent patients from getting accurate info about their test results.
        </Subheading>
        <TextInput
          label="Location #"
          value={inputStr}
          onChangeText={inputStr => setInputStr(inputStr)}
          mode="outlined"
          theme={DefaultTheme}
        />
        <HelperText type="error" visible={hasErrors()}>
          Location number must be exactly 4 digits. No other characters are allowed.
        </HelperText>
        <Button
          icon="save"
          mode="contained"
          color={colors.primary}
          style={{marginBottom: 10}}
          disabled={hasErrors()}
          onPress={() => {
            setLocationStr(inputStr);
            _home();
          }}
        >Save</Button>
        <Button
          icon="cancel"
          mode="outlined"
          color={colors.primary}
          onPress={_home}
        >Cancel</Button>
      </View>
    </View>
  }

  function App(props: StateProps): ReactElement {
    switch (props.appState) {
      case BarcodeScannerAppState.INITIAL:
        return <LoadingMessage/>;
      case BarcodeScannerAppState.DEFAULT:
        return <View style={styles.container}>
          <ScanButton onClicked={_scan}/>
        </View>;
      case BarcodeScannerAppState.PRINTED:
        return <SuccessMessage/>;
      case BarcodeScannerAppState.PRINTING:
        return <PrintingMessage
          onCancel={_home}
          id={barCodeData}
          date={date} location={locationStr}
        />;
      case BarcodeScannerAppState.SCANNED:
        return <View style={styles.container}>
          <BarCodeDisplay id={barCodeData} date={date} location={locationStr}/>
          <ActionButtons/>
        </View>;
      case BarcodeScannerAppState.SCANNING:
        return <Scanner
          onScanned={handleBarCodeScanned}
          onCancel={_home}
        />;
      case BarcodeScannerAppState.SETTINGS:
        return <SettingsModal/>;
      default:
        return <ErrorMessage/>;
    }
  }

  return (
    <PaperProvider theme={theme}>
      <Appbar.Header dark={true}>
        <Appbar.Content title={`${appExpo.description} #${locationStr}`}/>
        <Appbar.Action icon="home" onPress={_home}/>
        <Appbar.Action icon="settings" onPress={_settings}/>
      </Appbar.Header>
      <SafeAreaView style={styles.safeAreaView}>
        <App appState={appState}/>
      </SafeAreaView>
    </PaperProvider>
  );
};

AppRegistry.registerComponent(appExpo.name, () => Main);