Feature/decouple thumbnail downloads and cache (#581)

* Rename "DownloadedFilesProvider" to "ChaptersFilesProvider"

* Move files into sub packages

* Further abstract "DownloadedFilesProvider"

* Rename "getCachedImageResponse" to "getImageResponse"

* Extract getting cached image response into new function

* Decouple thumbnail cache and download

* Download and delete permanent thumbnails

When adding/removing manga from/to the library make sure the permanent thumbnail files will get handled properly

* Move thumbnail cache to actual temp folder

* Rename "mangaDownloadsRoot" to "downloadRoot"

* Move manga downloads into "mangas" subfolder

* Clear downloaded thumbnail

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Library.kt

@@ -7,6 +7,10 @@ package suwayomi.tachidesk.manga.impl
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
 import org.jetbrains.exposed.sql.and
 import org.jetbrains.exposed.sql.insert
 import org.jetbrains.exposed.sql.select
@@ -19,6 +23,8 @@ import suwayomi.tachidesk.manga.model.table.MangaTable
 import java.time.Instant
 
 object Library {
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
+
     suspend fun addMangaToLibrary(mangaId: Int) {
         val manga = getManga(mangaId)
         if (!manga.inLibrary) {
@@ -41,6 +47,8 @@ object Library {
                         }
                     }
                 }
+            }.apply {
+                handleMangaThumbnail(mangaId, true)
             }
         }
     }
@@ -52,6 +60,22 @@ object Library {
                 MangaTable.update({ MangaTable.id eq manga.id }) {
                     it[inLibrary] = false
                 }
+            }.apply {
+                handleMangaThumbnail(mangaId, false)
+            }
+        }
+    }
+
+    fun handleMangaThumbnail(mangaId: Int, inLibrary: Boolean) {
+        scope.launch {
+            try {
+                if (inLibrary) {
+                    ThumbnailDownloadHelper.download(mangaId)
+                } else {
+                    ThumbnailDownloadHelper.delete(mangaId)
+                }
+            } catch (e: Exception) {
+                // ignore
             }
         }
     }