Move code to get highest message UID from K9BackendFolder to MessageStore

app/core/src/main/java/com/fsck/k9/mailstore/K9BackendFolder.kt

@@ -18,34 +18,30 @@ class K9BackendFolder(
 ) : BackendFolder {
     private val database = localStore.database
     private val databaseId: String
+    private val folderId: Long
     private val localFolder = localStore.getFolder(folderServerId)
     override val name: String
     override val visibleLimit: Int
 
     init {
-        data class Init(val databaseId: String, val name: String, val visibleLimit: Int)
+        data class Init(val folderId: Long, val name: String, val visibleLimit: Int)
 
         val init = messageStore.getFolder(folderServerId) { folder ->
             Init(
-                databaseId = folder.id.toString(),
+                folderId = folder.id,
                 name = folder.name,
                 visibleLimit = folder.visibleLimit
             )
         } ?: error("Couldn't find folder $folderServerId")
 
-        databaseId = init.databaseId
+        databaseId = init.folderId.toString()
+        folderId = init.folderId
         name = init.name
         visibleLimit = init.visibleLimit
     }
 
     override fun getLastUid(): Long? {
-        return database.rawQuery("SELECT MAX(uid) FROM messages WHERE folder_id = ?", databaseId) { cursor ->
-            if (cursor.moveToFirst()) {
-                cursor.getLongOrNull(0)
-            } else {
-                null
-            }
-        }
+        return messageStore.getLastUid(folderId)
     }
 
     override fun getMessageServerIds(): Set<String> {

app/core/src/main/java/com/fsck/k9/mailstore/MessageStore.kt

@@ -56,6 +56,11 @@ interface MessageStore {
      */
     fun getHeaders(folderId: Long, messageServerId: String): List<Header>
 
+    /**
+     * Get highest UID (message server ID)
+     */
+    fun getLastUid(folderId: Long): Long?
+
     /**
      * Create folders.
      */

app/storage/src/main/java/com/fsck/k9/storage/messages/K9MessageStore.kt

@@ -53,6 +53,10 @@ class K9MessageStore(
         return retrieveMessageOperations.getHeaders(folderId, messageServerId)
     }
 
+    override fun getLastUid(folderId: Long): Long? {
+        return retrieveMessageOperations.getLastUid(folderId)
+    }
+
     override fun createFolders(folders: List<CreateFolderInfo>) {
         createFolderOperations.createFolders(folders)
     }

app/storage/src/main/java/com/fsck/k9/storage/messages/RetrieveMessageOperations.kt

@@ -1,5 +1,6 @@
 package com.fsck.k9.storage.messages
 
+import androidx.core.database.getLongOrNull
 import com.fsck.k9.mail.Header
 import com.fsck.k9.mail.MessagingException
 import com.fsck.k9.mail.internet.MimeHeader
@@ -52,7 +53,6 @@ internal class RetrieveMessageOperations(private val lockableDatabase: LockableD
                         databaseIdToServerIdMapping[databaseId] = serverId
                     }
                 }
-                Unit
             }
 
             databaseIdToServerIdMapping
@@ -80,4 +80,19 @@ internal class RetrieveMessageOperations(private val lockableDatabase: LockableD
             }
         }
     }
+
+    fun getLastUid(folderId: Long): Long? {
+        return lockableDatabase.execute(false) { database ->
+            database.rawQuery(
+                "SELECT MAX(uid) FROM messages WHERE folder_id = ?",
+                arrayOf(folderId.toString())
+            ).use { cursor ->
+                if (cursor.moveToFirst()) {
+                    cursor.getLongOrNull(0)
+                } else {
+                    null
+                }
+            }
+        }
+    }
 }

app/storage/src/test/java/com/fsck/k9/storage/messages/RetrieveMessageOperationsTest.kt

@@ -73,4 +73,25 @@ class RetrieveMessageOperationsTest : RobolectricTest() {
             )
         )
     }
+
+    @Test
+    fun `get highest message uid`() {
+        val folderId = sqliteDatabase.createFolder()
+        sqliteDatabase.createMessage(uid = "42", folderId = folderId)
+        sqliteDatabase.createMessage(uid = "23", folderId = folderId)
+        sqliteDatabase.createMessage(uid = "27", folderId = folderId)
+
+        val highestUid = retrieveMessageOperations.getLastUid(folderId)
+
+        assertThat(highestUid).isEqualTo(42)
+    }
+
+    @Test
+    fun `get highest message uid should return null if there are no messages`() {
+        val folderId = sqliteDatabase.createFolder()
+
+        val highestUid = retrieveMessageOperations.getLastUid(folderId)
+
+        assertThat(highestUid).isNull()
+    }
 }