Voice messages: Don't crash if mxc uri is invalid (#1756)

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## Type of change

- [ ] Feature
- [x] Bugfix
- [ ] Technical
- [ ] Other :

## Content

Code now checks whether the mx uri is invalid and handles the error condition properly.

## Motivation and context

https://github.com/vector-im/element-x-android/pull/1748#discussion_r1384557443

## Screenshots / GIFs

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## Tests

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## Checklist

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- [ ] Changes have been tested on an Android device or Android emulator with API 23
- [ ] UI change has been tested on both light and dark themes
- [ ] Accessibility has been taken into account. See https://github.com/vector-im/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
- [ ] Pull request is based on the develop branch
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features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/voicemessages/timeline/VoiceMessageMediaRepo.kt

@@ -83,13 +83,15 @@ class DefaultVoiceMessageMediaRepo @AssistedInject constructor(
         ): DefaultVoiceMessageMediaRepo
     }
 
-    override suspend fun getMediaFile(): Result<File> = if (!isInCache()) {
-        matrixMediaLoader.downloadMediaFile(
+    override suspend fun getMediaFile(): Result<File> = when {
+        cachedFile == null -> Result.failure(IllegalStateException("Invalid mxcUri."))
+        cachedFile.exists() -> Result.success(cachedFile)
+        else -> matrixMediaLoader.downloadMediaFile(
             source = mediaSource,
             mimeType = mimeType,
             body = body,
         ).mapCatching {
-            val dest = cachedFilePath.apply { parentFile?.mkdirs() }
+            val dest = cachedFile.apply { parentFile?.mkdirs() }
             // TODO By not closing the MediaFile we're leaking the rust file handle here.
             // Not that big of a deal but better to avoid it someday.
             if (it.toFile().renameTo(dest)) {
@@ -98,13 +100,11 @@ class DefaultVoiceMessageMediaRepo @AssistedInject constructor(
                 error("Failed to move file to cache.")
             }
         }
-    } else {
-        Result.success(cachedFilePath)
     }
 
-    private val cachedFilePath: File = File("${cacheDir.path}/$CACHE_VOICE_SUBDIR/${mxcUri2FilePath(mediaSource.url)}")
-
-    private fun isInCache(): Boolean = cachedFilePath.exists()
+    private val cachedFile: File? = mxcUri2FilePath(mediaSource.url)?.let {
+        File("${cacheDir.path}/$CACHE_VOICE_SUBDIR/$it")
+    }
 }
 
 /**
@@ -123,12 +123,9 @@ private val mxcRegex = Regex("""^mxc:\/\/([^\/]+)\/([^\/]+)$""")
  * Sanitizes an mxcUri to be used as a relative file path.
  *
  * @param mxcUri the Matrix Content (mxc://) URI of the voice message.
- * @return the relative file path as "<server-name>/<media-id>".
- * @throws IllegalStateException if the mxcUri is invalid.
+ * @return the relative file path as "<server-name>/<media-id>" or null if the mxcUri is invalid.
  */
-private fun mxcUri2FilePath(mxcUri: String): String = checkNotNull(mxcRegex.matchEntire(mxcUri)) {
-    "mxcUri2FilePath: Invalid mxcUri: $mxcUri"
-}.let { match ->
+private fun mxcUri2FilePath(mxcUri: String): String? = mxcRegex.matchEntire(mxcUri)?.let { match ->
     buildString {
         append(match.groupValues[1])
         append("/")