content: import React from 'react';
  import {
    StyleSheet,
    View,
    Text,
    Dimensions,
    TouchableOpacity,
  } from 'react-native';
  
  import MapView from 'react-native-maps';
  
  const { width, height } = Dimensions.get('window');
  
  const ASPECT_RATIO = width / height;
  const LATITUDE = 37.78825;
  const LONGITUDE = -122.4324;
  const LATITUDE_DELTA = 0.0922;
  const LONGITUDE_DELTA = LATITUDE_DELTA * ASPECT_RATIO;
  let id = 0;
  
  class PolylineCreator extends React.Component {
    constructor(props) {
      super(props);
  
      this.state = {
        region: {
          latitude: LATITUDE,
          longitude: LONGITUDE,
          latitudeDelta: LATITUDE_DELTA,
          longitudeDelta: LONGITUDE_DELTA,
        },
        polylines: [],
        editing: null,
      };
    }
  
    finish() {
      const { polylines, editing } = this.state;
      this.setState({
        polylines: [...polylines, editing],
        editing: null,
      });
    }
  
    onPanDrag(e) {
      const { editing } = this.state;
      if (!editing) {
        this.setState({
          editing: {
            id: id++,
            coordinates: [e.nativeEvent.coordinate],
          },
        });
      } else {
        this.setState({
          editing: {
            ...editing,
            coordinates: [
              ...editing.coordinates,
              e.nativeEvent.coordinate,
            ],
          },
        });
      }
    }
  
    render() {
      return (
        <View style={styles.container}>
          <MapView
            provider={this.props.provider}
            style={styles.map}
            initialRegion={this.state.region}
            scrollEnabled={false}
            onPanDrag={e => this.onPanDrag(e)}
          >
            {this.state.polylines.map(polyline => (
              <MapView.Polyline
                key={polyline.id}
                coordinates={polyline.coordinates}
                strokeColor="#000"
                fillColor="rgba(255,0,0,0.5)"
                strokeWidth={1}
              />
            ))}
            {this.state.editing &&
              <MapView.Polyline
                key="editingPolyline"
                coordinates={this.state.editing.coordinates}
                strokeColor="#F00"
                fillColor="rgba(255,0,0,0.5)"
                strokeWidth={1}
              />
            }
          </MapView>
          <View style={styles.buttonContainer}>
            {this.state.editing && (
              <TouchableOpacity
                onPress={() => this.finish()}
                style={[styles.bubble, styles.button]}
              >
                <Text>Finish</Text>
              </TouchableOpacity>
            )}
          </View>
        </View>
      );
    }
  }
  
  PolylineCreator.propTypes = {
    provider: MapView.ProviderPropType,
  };
  
  const styles = StyleSheet.create({
    container: {
      ...StyleSheet.absoluteFillObject,
      justifyContent: 'flex-end',
      alignItems: 'center',
    },
    map: {
      ...StyleSheet.absoluteFillObject,
    },
    bubble: {
      backgroundColor: 'rgba(255,255,255,0.7)',
      paddingHorizontal: 18,
      paddingVertical: 12,
      borderRadius: 20,
    },
    latlng: {
      width: 200,
      alignItems: 'stretch',
    },
    button: {
      width: 80,
      paddingHorizontal: 12,
      alignItems: 'center',
      marginHorizontal: 10,
    },
    buttonContainer: {
      flexDirection: 'row',
      marginVertical: 20,
      backgroundColor: 'transparent',
    },
  });
  
  module.exports = PolylineCreator;
  