Minor refactor

app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadProvider.kt

@@ -83,7 +83,7 @@ class DownloadProvider(private val context: Context) {
      * @param manga the manga to query.
      */
     fun getMangaDirName(manga: Manga): String {
-        return DiskUtil.buildValidFatFilename(manga.title)
+        return DiskUtil.buildValidFilename(manga.title)
     }
 
     /**
@@ -92,7 +92,7 @@ class DownloadProvider(private val context: Context) {
      * @param chapter the chapter to query.
      */
     fun getChapterDirName(chapter: Chapter): String {
-        return DiskUtil.buildValidFatFilename(chapter.name)
+        return DiskUtil.buildValidFilename(chapter.name)
     }
 
 }

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPresenter.kt

@@ -570,17 +570,16 @@ class ReaderPresenter : BasePresenter<ReaderActivity>() {
                     val destDir = File(pictureDirectory)
                     destDir.mkdirs()
 
-                    // Find out file extension.
+                    // Find out file mime type.
                     val mime = context.contentResolver.getType(page.uri)
                     ?: context.contentResolver.openInputStream(page.uri).buffered().use {
                         URLConnection.guessContentTypeFromStream(it)
                     }
-                    val ext = MimeTypeMap.getSingleton().getExtensionFromMimeType(mime) ?: "jpg"
-
-                    // Destination file.
 
-                    val filename = "${manga.title} - ${chapter.name} - ${page.index + 1}.$ext"
-                    val destFile = File(destDir, DiskUtil.buildValidFatFilename(filename))
+                    // Build destination file.
+                    val ext = MimeTypeMap.getSingleton().getExtensionFromMimeType(mime) ?: "jpg"
+                    val filename = "${manga.title} - ${chapter.name} - ${page.index + 1}"
+                    val destFile = File(destDir, DiskUtil.buildValidFilename(filename) + ".$ext")
 
                     context.contentResolver.openInputStream(page.uri).use { input ->
                         destFile.outputStream().use { output ->

app/src/main/java/eu/kanade/tachiyomi/util/DiskUtil.kt

@@ -36,7 +36,7 @@ object DiskUtil {
      * replacing any invalid characters with "_". This method doesn't allow private files (starting
      * with a dot), but you can manually add it later.
      */
-    fun buildValidFatFilename(origName: String): String {
+    fun buildValidFilename(origName: String): String {
         val name = origName.trim('.', ' ')
         if (name.isNullOrEmpty()) {
             return "(invalid)"