Option to delete old cached covers

app/src/main/java/eu/kanade/tachiyomi/data/cache/CoverCache.kt

@@ -1,7 +1,18 @@
 package eu.kanade.tachiyomi.data.cache
 
 import android.content.Context
+import android.text.format.Formatter
+import eu.kanade.tachiyomi.R
+import eu.kanade.tachiyomi.data.database.DatabaseHelper
 import eu.kanade.tachiyomi.util.storage.DiskUtil
+import eu.kanade.tachiyomi.util.system.executeOnIO
+import eu.kanade.tachiyomi.util.system.toast
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import uy.kohesive.injekt.Injekt
+import uy.kohesive.injekt.api.get
 import java.io.File
 import java.io.IOException
 import java.io.InputStream
@@ -23,6 +34,34 @@ class CoverCache(private val context: Context) {
     private val cacheDir = context.getExternalFilesDir("covers")
             ?: File(context.filesDir, "covers").also { it.mkdirs() }
 
+    fun deleteOldCovers() {
+        GlobalScope.launch(Dispatchers.Default) {
+            val db = Injekt.get<DatabaseHelper>()
+            var deletedSize = 0L
+            val urls = db.getLibraryMangas().executeOnIO().mapNotNull {
+                it.thumbnail_url?.let { url ->
+                    return@mapNotNull DiskUtil.hashKeyForDisk(url)
+                }
+                null
+            }
+            val files = cacheDir.listFiles()?.iterator() ?: return@launch
+            while (files.hasNext()) {
+                val file = files.next()
+                if (file.name !in urls) {
+                    deletedSize += file.length()
+                    file.delete()
+                }
+            }
+            withContext(Dispatchers.Main) {
+                context.toast(
+                    context.getString(
+                        R.string.deleted_, Formatter.formatFileSize(context, deletedSize)
+                    )
+                )
+            }
+        }
+    }
+
     /**
      * Returns the cover from cache.
      *

app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsAdvancedController.kt

@@ -14,6 +14,7 @@ import androidx.preference.PreferenceScreen
 import com.afollestad.materialdialogs.MaterialDialog
 import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.data.cache.ChapterCache
+import eu.kanade.tachiyomi.data.cache.CoverCache
 import eu.kanade.tachiyomi.data.database.DatabaseHelper
 import eu.kanade.tachiyomi.data.download.DownloadManager
 import eu.kanade.tachiyomi.data.library.LibraryUpdateService
@@ -43,6 +44,8 @@ class SettingsAdvancedController : SettingsController() {
 
     private val db: DatabaseHelper by injectLazy()
 
+    private val coverCache: CoverCache by injectLazy()
+
     @SuppressLint("BatteryLife")
     override fun setupPreferenceScreen(screen: PreferenceScreen) = with(screen) {
         titleRes = R.string.advanced
@@ -97,6 +100,17 @@ class SettingsAdvancedController : SettingsController() {
 
             onClick { cleanupDownloads() }
         }
+
+        preference {
+            titleRes = R.string.clean_up_cached_covers
+
+            summaryRes = R.string.delete_old_covers_in_library
+
+            onClick {
+                context.toast(R.string.starting_cleanup)
+                coverCache.deleteOldCovers()
+            }
+        }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
             val pm = context.getSystemService(Context.POWER_SERVICE) as? PowerManager?
             if (pm != null) preference {

app/src/main/res/values/strings.xml

@@ -537,6 +537,9 @@
         <item quantity="one">Cleanup done. Removed %d folder</item>
         <item quantity="other">Cleanup done. Removed %d folders</item>
     </plurals>
+    <string name="clean_up_cached_covers">Clean up cached covers</string>
+    <string name="delete_old_covers_in_library">Delete old and unused cached covers of
+        manga in your library that has been updated</string>
 
     <!-- About section -->
     <string name="version">Version</string>
@@ -653,6 +656,7 @@
     <string name="create">Create</string>
     <string name="default_value">Default</string>
     <string name="delete">Delete</string>
+    <string name="deleted_">Deleted: %1$s</string>
     <string name="display">Display</string>
     <string name="drag_handle">Drag handle</string>
     <string name="edit">Edit</string>