Fragmentless GalleryDetailScene (#202)

* Initial fragmentless port

* Compile it

* Refine

* Refine

* All

* Fix

---------

Co-authored-by: Lokesh Gidra <lokeshgidra@google.com>

app/src/main/kotlin/com/hippo/ehviewer/client/data/GalleryInfo.kt

@@ -16,6 +16,7 @@
 package com.hippo.ehviewer.client.data
 
 import java.util.regex.Pattern
+import moe.tarsin.kt.unreachable
 
 interface GalleryInfo {
     var gid: Long
@@ -133,3 +134,15 @@ interface GalleryInfo {
         const val LOCAL_FAVORITED = -1
     }
 }
+
+fun GalleryInfo.findBaseInfo(): BaseGalleryInfo {
+    return when (this) {
+        is BaseGalleryInfo -> this
+        is GalleryDetail -> galleryInfo
+        else -> unreachable()
+    }
+}
+
+fun GalleryInfo.asGalleryDetail(): GalleryDetail? {
+    return this as? GalleryDetail
+}