Add MessageViewModel implementation and a mapper for it

app/src/main/java/chat/rocket/android/chatroom/viewmodel/MessageViewModel.kt

+package chat.rocket.android.chatroom.viewmodel
+
+import DateTimeHelper
+import android.content.Context
+import android.graphics.Color
+import android.graphics.Typeface
+import android.text.SpannableString
+import android.text.style.ForegroundColorSpan
+import android.text.style.StyleSpan
+import chat.rocket.android.R
+import chat.rocket.android.app.RocketChatApplication
+import chat.rocket.android.helper.UrlHelper
+import chat.rocket.android.server.domain.USE_REALNAME
+import chat.rocket.core.model.Message
+import chat.rocket.core.model.MessageType.*
+import chat.rocket.core.model.Value
+
+data class MessageViewModel(private val message: Message,
+                            private val settings: Map<String, Value<Any>>?) {
+    val id: String = message.id
+    val time: CharSequence
+    val sender: CharSequence
+    val content: CharSequence
+
+    init {
+        sender = getSenderName()
+        content = getContent(RocketChatApplication.instance)
+        time = getTime()
+    }
+
+    fun getAvatarUrl(serverUrl: String): String? {
+        return message.sender?.username.let {
+            return@let UrlHelper.getAvatarUrl(serverUrl, it.toString())
+        }
+    }
+
+    fun getTime() = DateTimeHelper.getTime(DateTimeHelper.getLocalDateTime(message.timestamp))
+
+    fun getSenderName(): CharSequence {
+        val useRealName = settings?.get(USE_REALNAME)?.value as Boolean
+        val username = message.sender?.username
+        val realName = message.sender?.name
+        val senderName = if (useRealName) realName else username
+        return if (senderName == null) username.toString() else senderName.toString()
+    }
+
+    fun getContent(context: Context): CharSequence {
+        val contentMessage: CharSequence
+        when (message.type) {
+        //TODO: Add implementation for Welcome type.
+            MESSAGE_REMOVED -> contentMessage = getSystemMessage(context.getString(R.string.message_removed))
+            USER_JOINED -> contentMessage = getSystemMessage(context.getString(R.string.message_user_joined_channel))
+            USER_LEFT -> contentMessage = getSystemMessage(context.getString(R.string.message_user_left))
+            USER_ADDED -> contentMessage = getSystemMessage(
+                    context.getString(R.string.message_user_added_by, message.message, message.sender?.username))
+            ROOM_NAME_CHANGED -> contentMessage = getSystemMessage(
+                    context.getString(R.string.message_room_name_changed, message.message, message.sender?.username))
+            USER_REMOVED -> contentMessage = getSystemMessage(
+                    context.getString(R.string.message_user_removed_by, message.message, message.sender?.username))
+            else -> contentMessage = getNormalMessage()
+        }
+        return contentMessage
+    }
+
+    private fun getNormalMessage() = message.message
+
+    private fun getSystemMessage(content: String): CharSequence {
+        val spannableMsg = SpannableString(content)
+        spannableMsg.setSpan(StyleSpan(Typeface.ITALIC), 0, spannableMsg.length,
+                0)
+        spannableMsg.setSpan(ForegroundColorSpan(Color.GRAY), 0, spannableMsg.length,
+                0)
+
+        if (message.type == USER_ADDED) {
+            val userAddedStartIndex = 5
+            val userAddedLastIndex = userAddedStartIndex + message.message.length
+            val addedByStartIndex = userAddedLastIndex + 10
+            val addedByLastIndex = addedByStartIndex + message.sender?.username!!.length
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), userAddedStartIndex, userAddedLastIndex,
+                    0)
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), addedByStartIndex, addedByLastIndex,
+                    0)
+        } else if (message.type == ROOM_NAME_CHANGED) {
+            val userAddedStartIndex = 22
+            val userAddedLastIndex = userAddedStartIndex + message.message.length
+            val addedByStartIndex = userAddedLastIndex + 4
+            val addedByLastIndex = addedByStartIndex + message.sender?.username!!.length
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), userAddedStartIndex, userAddedLastIndex,
+                    0)
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), addedByStartIndex, addedByLastIndex,
+                    0)
+        } else if (message.type == USER_REMOVED) {
+            val userAddedStartIndex = 5
+            val userAddedLastIndex = userAddedStartIndex + message.message.length
+            val addedByStartIndex = userAddedLastIndex + 12
+            val addedByLastIndex = addedByStartIndex + message.sender?.username!!.length
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), userAddedStartIndex, userAddedLastIndex,
+                    0)
+            spannableMsg.setSpan(StyleSpan(Typeface.BOLD_ITALIC), addedByStartIndex, addedByLastIndex,
+                    0)
+        }
+        return spannableMsg
+    }
+}
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app/src/main/java/chat/rocket/android/chatroom/viewmodel/MessageViewModelMapper.kt

+package chat.rocket.android.chatroom.viewmodel
+
+import chat.rocket.core.model.Message
+import chat.rocket.core.model.Value
+
+object MessageViewModelMapper {
+
+    suspend fun mapToViewModel(message: Message, settings: Map<String, Value<Any>>?) = MessageViewModel(message, settings)
+
+    suspend fun mapToViewModelList(messageList: List<Message>, settings: Map<String, Value<Any>>?): List<MessageViewModel> {
+        val vmList = mutableListOf<MessageViewModel>()
+        for (msg in messageList) {
+            vmList.add(MessageViewModel(msg, settings))
+        }
+        return vmList
+    }
+}
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