On file-drag, show a border around textarea

app/assets/javascripts/components/components/autosuggest_textarea.jsx

@@ -32,6 +32,7 @@ const AutosuggestTextarea = React.createClass({
     value: React.PropTypes.string,
     suggestions: ImmutablePropTypes.list,
     disabled: React.PropTypes.bool,
+    fileDropDate: React.PropTypes.instanceOf(Date),
     placeholder: React.PropTypes.string,
     onSuggestionSelected: React.PropTypes.func.isRequired,
     onSuggestionsClearRequested: React.PropTypes.func.isRequired,
@@ -42,6 +43,8 @@ const AutosuggestTextarea = React.createClass({
 
   getInitialState () {
     return {
+      isFileDragging: false,
+      fileDraggingDate: undefined,
       suggestionsHidden: false,
       selectedSuggestion: 0,
       lastToken: null,
@@ -120,21 +123,51 @@ const AutosuggestTextarea = React.createClass({
     if (nextProps.suggestions !== this.props.suggestions && nextProps.suggestions.size > 0 && this.state.suggestionsHidden) {
       this.setState({ suggestionsHidden: false });
     }
+
+    const fileDropDate = nextProps.fileDropDate;
+    const { isFileDragging, fileDraggingDate } = this.state;
+
+    /*
+     * We can't detect drop events, because they might not be on the textarea (the app allows dropping anywhere in the
+     * window). Instead, on-drop, we notify this textarea to stop its hover effect by passing in a prop with the
+     * drop-date.
+     */
+    if (isFileDragging && fileDraggingDate && fileDropDate // if dragging when props updated, and dates aren't undefined
+      && fileDropDate > fileDraggingDate) { // and if the drop date is now greater than when we started dragging
+      // then we should stop dragging
+      this.setState({
+        isFileDragging: false
+      });
+    }
   },
 
   setTextarea (c) {
     this.textarea = c;
   },
 
+  onDragEnter () {
+    this.setState({
+      isFileDragging: true,
+      fileDraggingDate: new Date()
+    })
+  },
+
+  onDragExit () {
+    this.setState({
+      isFileDragging: false
+    })
+  },
+
   render () {
-    const { value, suggestions, disabled, placeholder, onKeyUp } = this.props;
-    const { suggestionsHidden, selectedSuggestion } = this.state;
+    const { value, suggestions, fileDropDate, disabled, placeholder, onKeyUp } = this.props;
+    const { isFileDragging, suggestionsHidden, selectedSuggestion } = this.state;
+    const className = isFileDragging ? 'autosuggest-textarea__textarea file-drop' : 'autosuggest-textarea__textarea';
 
     return (
       <div className='autosuggest-textarea'>
         <textarea
           ref={this.setTextarea}
-          className='autosuggest-textarea__textarea'
+          className={className}
           disabled={disabled}
           placeholder={placeholder}
           value={value}
@@ -142,6 +175,8 @@ const AutosuggestTextarea = React.createClass({
           onKeyDown={this.onKeyDown}
           onKeyUp={onKeyUp}
           onBlur={this.onBlur}
+          onDragEnter={this.onDragEnter}
+          onDragExit={this.onDragExit}
         />
 
         <div style={{ display: (suggestions.size > 0 && !suggestionsHidden) ? 'block' : 'none' }} className='autosuggest-textarea__suggestions'>