first commit

services/web/frontend/js/features/chat/utils/message-list-appender.js

@@ -0,0 +1,79 @@
+const TIMESTAMP_GROUP_SIZE = 5 * 60 * 1000 // 5 minutes
+
+export function appendMessage(messageList, message, uniqueMessageIds) {
+  if (uniqueMessageIds.includes(message.id)) {
+    return { messages: messageList, uniqueMessageIds }
+  }
+
+  uniqueMessageIds = uniqueMessageIds.slice(0)
+
+  uniqueMessageIds.push(message.id)
+
+  const lastMessage = messageList[messageList.length - 1]
+
+  const shouldGroup =
+    lastMessage &&
+    message &&
+    message.user &&
+    message.user.id &&
+    message.user.id === lastMessage.user.id &&
+    message.timestamp - lastMessage.timestamp < TIMESTAMP_GROUP_SIZE
+
+  if (shouldGroup) {
+    messageList = messageList.slice(0, messageList.length - 1).concat({
+      ...lastMessage,
+      // the `id` is updated to the latest received content when a new
+      // message is appended or prepended
+      id: message.id,
+      timestamp: message.timestamp,
+      contents: lastMessage.contents.concat(message.content),
+    })
+  } else {
+    messageList = messageList.slice(0).concat({
+      id: message.id,
+      user: message.user,
+      timestamp: message.timestamp,
+      contents: [message.content],
+    })
+  }
+
+  return { messages: messageList, uniqueMessageIds }
+}
+
+export function prependMessages(messageList, messages, uniqueMessageIds) {
+  const listCopy = messageList.slice(0)
+
+  uniqueMessageIds = uniqueMessageIds.slice(0)
+
+  messages
+    .slice(0)
+    .reverse()
+    .forEach(message => {
+      if (uniqueMessageIds.includes(message.id)) {
+        return
+      }
+      uniqueMessageIds.push(message.id)
+      const firstMessage = listCopy[0]
+      const shouldGroup =
+        firstMessage &&
+        message &&
+        message.user &&
+        message.user.id === firstMessage.user.id &&
+        firstMessage.timestamp - message.timestamp < TIMESTAMP_GROUP_SIZE
+
+      if (shouldGroup) {
+        firstMessage.id = message.id
+        firstMessage.timestamp = message.timestamp
+        firstMessage.contents = [message.content].concat(firstMessage.contents)
+      } else {
+        listCopy.unshift({
+          id: message.id,
+          user: message.user,
+          timestamp: message.timestamp,
+          contents: [message.content],
+        })
+      }
+    })
+
+  return { messages: listCopy, uniqueMessageIds }
+}