refactor(NormalizeStopTimesModal): disable if too few timepoints

i18n/english.yml

@@ -824,6 +824,7 @@ components:
     normalizeStopTimes: Normalize stop times
     normalizeStopTimesQuestion: Normalize stop times?
     selectBeginningPatternStop: "Select beginning pattern stop:"
+    tooFewTimepoints: "You must have more than 1 timepoint to interpolate times"
     usageExplanationOne: This feature is useful when the travel times for one or more
       pattern stops change. Take for example a pattern
       that has been re-routed along to travel a longer distance, has had a

i18n/german.yml

@@ -836,6 +836,7 @@ components:
     normalizeStopTimes: Normalize stop times
     normalizeStopTimesQuestion: Normalize stop times?
     selectBeginningPatternStop: "Select beginning pattern stop:"
+    tooFewTimepoints: "You must have more than 1 timepoint to interpolate times"
     usageExplanationOne: This feature is useful when the travel times for one or more
       pattern stops change. Take for example a pattern
       that has been re-routed along to travel a longer distance, has had a

i18n/polish.yml

@@ -827,6 +827,7 @@ components:
     normalizeStopTimes: Normalize stop times
     normalizeStopTimesQuestion: Normalize stop times?
     selectBeginningPatternStop: "Select beginning pattern stop:"
+    tooFewTimepoints: "You must have more than 1 timepoint to interpolate times"
     usageExplanationOne: This feature is useful when the travel times for one or more
       pattern stops change. Take for example a pattern
       that has been re-routed along to travel a longer distance, has had a

lib/editor/components/pattern/NormalizeStopTimesModal.js

@@ -2,7 +2,7 @@
 
 import Icon from '@conveyal/woonerf/components/icon'
 import React, { Component } from 'react'
-import { Alert, Button, Checkbox, ControlLabel, FormControl, Modal } from 'react-bootstrap'
+import { Alert, Button, Checkbox, ControlLabel, FormControl, Modal, OverlayTrigger, Tooltip } from 'react-bootstrap'
 
 import * as tripPatternActions from '../../actions/tripPattern'
 import type { GtfsStop, Pattern } from '../../../types'
@@ -48,6 +48,8 @@ export default class NormalizeStopTimesModal extends Component<Props, State> {
   render () {
     const { Body, Footer, Header, Title } = Modal
     const { activePattern, stops } = this.props
+    const timepoints = activePattern.patternStops.filter(ps => ps.timepoint === 1)
+    const interpolationDisabled = timepoints.length < 2
     return (
       <Modal show={this.props.show || this.state.show} onHide={this._onClose}>
         <Header>
@@ -77,12 +79,20 @@ export default class NormalizeStopTimesModal extends Component<Props, State> {
             }
             )}
           </FormControl>
-          <Checkbox
-            onChange={this._onChangeInterpolation}
-            value={this.state.interpolateStopTimes}
-          >
-            {this.messages('interpolateStopTimes')}
-          </Checkbox>
+          <div style={{alignContent: 'center', alignItems: 'center', display: 'flex'}}>
+            <OverlayTrigger
+              overlay={<Tooltip>{this.messages('tooFewTimepoints')}</Tooltip>}
+              placement='bottom'
+            >
+              <Checkbox
+                disabled={interpolationDisabled}
+                onChange={this._onChangeInterpolation}
+                value={this.state.interpolateStopTimes}
+              />
+            </OverlayTrigger>
+            {/* Separate label so that tooltip appears over checkbox. Hack: Padding to align center with checkbox */}
+            <span style={{paddingBottom: '2px'}}>{this.messages('interpolateStopTimes')}</span>
+          </div>
           <br />
           <Alert bsStyle='warning'>
             {this.state.patternStopIndex === 0