Add support for slash commands (under Feature Flag) (#6482)

* Add support for slash commands

* Update screenshots

* Rename module `slash` to `slashcommands`

* Rename `SlashCommand` to `SlashCommandService`

* Introduce MsgType in order to send text message with a different msgtype value.

* Format file and add parameter names, add default values and cleanup

* Add isSupported parameter to filter out unsupported yet commands.

* Slash commands: disable suggestions if the feature is disabled.

* Fix sending shrug command.

* Add missing test on SuggestionsProcessor

* Add tests on MessageComposerPresenter about slash command.

* Fix import ordering

* Add missing tests on CommandExecutor

* Add missing tests in MarkdownTextEditorStateTest

* Slash commands: Improve code when sending message with prefix.

* Slash commands: Add support for /unflip

---------

Co-authored-by: ElementBot <android@element.io>

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/core/RoomIdOrAlias.kt

@@ -27,6 +27,16 @@ sealed interface RoomIdOrAlias : Parcelable {
             is Id -> roomId.value
             is Alias -> roomAlias.value
         }
+
+    companion object {
+        fun from(id: String): RoomIdOrAlias? {
+            return when {
+                MatrixPatterns.isRoomId(id) -> Id(RoomId(id))
+                MatrixPatterns.isRoomAlias(id) -> Alias(RoomAlias(id))
+                else -> null
+            }
+        }
+    }
 }
 
 fun RoomId.toRoomIdOrAlias() = RoomIdOrAlias.Id(this)

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/mxc/MxcTools.kt

@@ -17,3 +17,18 @@ interface MxcTools {
      */
     fun mxcUri2FilePath(mxcUri: String): String?
 }
+
+/**
+ * "mxc" scheme, including "://". So "mxc://".
+ */
+const val MATRIX_CONTENT_URI_SCHEME = "mxc://"
+
+/**
+ * Return true if the String starts with "mxc://".
+ */
+fun String.isMxcUrl() = startsWith(MATRIX_CONTENT_URI_SCHEME)
+
+/**
+ * Remove the "mxc://" prefix. No op if the String is not a Mxc URL.
+ */
+fun String.removeMxcPrefix() = removePrefix(MATRIX_CONTENT_URI_SCHEME)

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/MsgType.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.timeline
+
+enum class MsgType {
+    MSG_TYPE_TEXT,
+    MSG_TYPE_EMOTE,
+
+    // For future support
+    MSG_TYPE_SNOW,
+
+    // For future support
+    MSG_TYPE_CONFETTI,
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/Timeline.kt

@@ -69,6 +69,8 @@ interface Timeline : AutoCloseable {
         body: String,
         htmlBody: String?,
         intentionalMentions: List<IntentionalMention>,
+        msgType: MsgType = MsgType.MSG_TYPE_TEXT,
+        asPlainText: Boolean = false,
     ): Result<Unit>
 
     suspend fun editMessage(
@@ -90,6 +92,7 @@ interface Timeline : AutoCloseable {
         htmlBody: String?,
         intentionalMentions: List<IntentionalMention>,
         fromNotification: Boolean = false,
+        msgType: MsgType = MsgType.MSG_TYPE_TEXT,
     ): Result<Unit>
 
     suspend fun sendImage(