webview: Implement voting on polls.

Related: zulip#3205

Author: WesleyAC

src/webview/handleOutboundEvents.js

@@ -131,6 +131,13 @@ type WebViewOutboundEventTimeDetails = {|
   originalText: string,
 |};
 
+type WebViewOutboundEventVote = {|
+  type: 'vote',
+  messageId: number,
+  key: string,
+  vote: number,
+|};
+
 export type WebViewOutboundEvent =
   | WebViewOutboundEventReady
   | WebViewOutboundEventScroll
@@ -145,7 +152,8 @@ export type WebViewOutboundEvent =
   | WebViewOutboundEventWarn
   | WebViewOutboundEventError
   | WebViewOutboundEventMention
-  | WebViewOutboundEventTimeDetails;
+  | WebViewOutboundEventTimeDetails
+  | WebViewOutboundEventVote;
 
 // TODO: Consider completing this and making it exact, once
 // `MessageList`'s props are type-checked.
@@ -311,6 +319,19 @@ export const handleWebViewOutboundEvent = (
       break;
     }
 
+    case 'vote': {
+      api.sendSubmessage(
+        props.backgroundData.auth,
+        event.messageId,
+        JSON.stringify({
+          type: 'vote',
+          key: event.key,
+          vote: event.vote,
+        }),
+      );
+      break;
+    }
+
     case 'debug':
       console.debug(props, event); // eslint-disable-line
       break;

src/webview/js/generatedEs3.js

@@ -980,6 +980,27 @@ var compiledWebviewJs = (function (exports) {
       return;
     }
 
+    if (target.matches('.poll-vote')) {
+      var _messageElement = target.closest('.message');
+
+      if (_messageElement) {
+        var current_vote = requireAttribute(target, 'data-voted') === 'true';
+        var vote = current_vote ? -1 : 1;
+        sendMessage({
+          type: 'vote',
+          messageId: requireNumericAttribute(_messageElement, 'data-msg-id'),
+          key: requireAttribute(target, 'data-key'),
+          vote: vote
+        });
+        target.setAttribute('data-voted', (!current_vote).toString());
+        target.innerText = (parseInt(target.innerText, 10) + vote).toString();
+      } else {
+        throw new Error('Message element not found');
+      }
+
+      return;
+    }
+
     if (target.matches('time')) {
       var originalText = requireAttribute(target, 'original-text');
       sendMessage({

src/webview/js/js.js

@@ -904,6 +904,27 @@ documentBody.addEventListener('click', (e: MouseEvent) => {
     return;
   }
 
+  if (target.matches('.poll-vote')) {
+    const messageElement = target.closest('.message');
+    if (!messageElement) {
+      throw new Error('Message element not found');
+    }
+    // This duplicates some logic from PollData.handle.vote.outbound, but it's
+    // much simpler to just duplicate it than it is to thread a callback all
+    // the way over here.
+    const current_vote = requireAttribute(target, 'data-voted') === 'true';
+    const vote = current_vote ? -1 : 1;
+    sendMessage({
+      type: 'vote',
+      messageId: requireNumericAttribute(messageElement, 'data-msg-id'),
+      key: requireAttribute(target, 'data-key'),
+      vote,
+    });
+    target.setAttribute('data-voted', (!current_vote).toString());
+    target.innerText = (parseInt(target.innerText, 10) + vote).toString();
+    return;
+  }
+
   if (target.matches('time')) {
     const originalText = requireAttribute(target, 'original-text');
     sendMessage({