feat: process manual channel mentions and emoji shortcodes

Signed-off-by: Infi <infi@infi.sh>

app/src/main/java/chat/revolt/api/internals/MessageProcessor.kt

@@ -1,14 +1,26 @@
 package chat.revolt.api.internals
 
 import chat.revolt.api.RevoltAPI
+import chat.revolt.api.schemas.ChannelType
+import chat.revolt.internals.EmojiImpl
 
 object MessageProcessor {
     private val MentionRegex = Regex("@((?:\\p{L}|[\\d_.-])+)#([0-9]{4})", RegexOption.IGNORE_CASE)
+    private val ChannelRegex = Regex("(?:\\s|^)#(.+?)(?:\\s|\$)", RegexOption.IGNORE_CASE)
+    private val EmojiRegex = Regex(":(.+?):", RegexOption.IGNORE_CASE)
 
-    fun processOutgoing(content: String): String {
+    private val emojiMetadata = EmojiImpl()
+
+    /**
+     * Processes an outgoing message for sending.
+     * 1. Replaces @mentions#0000 with <@userId>
+     * 2. Replaces #channel with <#channelId> if the current server has a channel with that name
+     * 2. Replaces :emoji-shortcode: with the emoji's unicode character, if it exists
+     */
+    fun processOutgoing(content: String, serverId: String?): String {
         val mentions = MentionRegex.findAll(content).map { it.value }.toList()
 
-        return mentions.fold(content) { acc, mention ->
+        var returnable = mentions.fold(content) { acc, mention ->
             val (username, discriminator) = MentionRegex.matchEntire(mention)?.destructured
                 ?: return@fold acc
 
@@ -18,5 +30,34 @@ object MessageProcessor {
             val userId = user?.id ?: return@fold acc
             acc.replace(mention, "<@$userId>")
         }
+
+        val channels = ChannelRegex.findAll(returnable).map { it.value }.toList()
+
+        returnable = channels.fold(returnable) { acc, channel ->
+            val channelName = ChannelRegex.matchEntire(channel)?.destructured?.component1()
+                ?: return@fold acc
+
+            val fetchedChannel =
+                RevoltAPI.channelCache.values.find {
+                    it.name == channelName && it.server == serverId && it.channelType == ChannelType.TextChannel
+                }
+                    ?: return@fold acc
+
+            fetchedChannel.name?.let { acc.replace("#${it}", "<#${fetchedChannel.id}>") } ?: acc
+        }
+
+        val emojis = EmojiRegex.findAll(returnable).map { it.value }.toList()
+
+        returnable = emojis.fold(returnable) { acc, emoji ->
+            val emojiName = EmojiRegex.matchEntire(emoji)?.destructured?.component1()
+                ?: return@fold acc
+
+            val byShortcode = emojiMetadata.unicodeByShortcode(emojiName)
+                ?: return@fold acc
+
+            acc.replace(":$emojiName:", byShortcode)
+        }
+
+        return returnable
     }
 }

app/src/main/java/chat/revolt/internals/EmojiImpl.kt

@@ -247,6 +247,18 @@ class EmojiImpl {
         return list
     }
 
+    fun unicodeByShortcode(shortcode: String): String? {
+        return metadata.asSequence().mapNotNull { group ->
+            group.emoji.find { emoji ->
+                emoji.shortcodes.any { code ->
+                    code == ":${shortcode}:"
+                }
+            }
+        }.firstOrNull().let { emoji ->
+            emoji?.base?.joinToString("") { String(Character.toChars(it.toInt())) }
+        }
+    }
+
     init {
         metadata = initMetadata(RevoltApplication.instance.applicationContext)
     }

app/src/main/java/chat/revolt/screens/chat/views/channel/ChannelScreenViewModel.kt

@@ -212,7 +212,10 @@ class ChannelScreenViewModel : ViewModel() {
 
             sendMessage(
                 activeChannel!!.id!!,
-                MessageProcessor.processOutgoing(pendingMessageContent.trimIndent()),
+                MessageProcessor.processOutgoing(
+                    pendingMessageContent.trimIndent(),
+                    activeChannel?.server
+                ),
                 attachments = if (attachmentIds.isEmpty()) null else attachmentIds,
                 replies = pendingReplies
             )