Implement a storage plugin method to get free space

app/src/androidTest/java/com/stevesoltys/seedvault/PluginTest.kt

@@ -70,6 +70,17 @@ class PluginTest : KoinComponent {
         assertNotNull(storagePlugin.providerPackageName)
     }
 
+    @Test
+    fun testTest() = runBlocking(Dispatchers.IO) {
+        assertTrue(storagePlugin.test())
+    }
+
+    @Test
+    fun testGetFreeSpace() = runBlocking(Dispatchers.IO) {
+        val freeBytes = storagePlugin.getFreeSpace() ?: error("no free space retrieved")
+        assertTrue(freeBytes > 0)
+    }
+
     /**
      * This test initializes the storage three times while creating two new restore sets.
      *

app/src/main/java/com/stevesoltys/seedvault/plugins/StoragePlugin.kt

@@ -13,6 +13,13 @@ interface StoragePlugin<T> {
      */
     suspend fun test(): Boolean
 
+    /**
+     * Retrieves the available storage space in bytes.
+     * @return the number of bytes available or null if the number is unknown.
+     * Returning a negative number or zero to indicate unknown is discouraged.
+     */
+    suspend fun getFreeSpace(): Long?
+
     /**
      * Start a new [RestoreSet] with the given token.
      *

app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderStoragePlugin.kt

@@ -3,13 +3,21 @@ package com.stevesoltys.seedvault.plugins.saf
 import android.content.Context
 import android.content.pm.PackageManager
 import android.net.Uri
+import android.os.Environment
+import android.os.StatFs
+import android.provider.DocumentsContract
+import android.provider.DocumentsContract.Root.COLUMN_AVAILABLE_BYTES
+import android.provider.DocumentsContract.Root.COLUMN_ROOT_ID
 import android.util.Log
+import androidx.core.database.getIntOrNull
 import androidx.documentfile.provider.DocumentFile
 import com.stevesoltys.seedvault.getStorageContext
 import com.stevesoltys.seedvault.plugins.EncryptedMetadata
 import com.stevesoltys.seedvault.plugins.StoragePlugin
 import com.stevesoltys.seedvault.plugins.chunkFolderRegex
 import com.stevesoltys.seedvault.plugins.tokenRegex
+import com.stevesoltys.seedvault.ui.storage.AUTHORITY_STORAGE
+import com.stevesoltys.seedvault.ui.storage.ROOT_ID_DEVICE
 import org.calyxos.backup.storage.plugin.PluginConstants.SNAPSHOT_EXT
 import java.io.FileNotFoundException
 import java.io.IOException
@@ -35,6 +43,32 @@ internal class DocumentsProviderStoragePlugin(
         return dir != null && dir.exists()
     }
 
+    override suspend fun getFreeSpace(): Long? {
+        val rootId = storage.safStorage.rootId ?: return null
+        val authority = storage.safStorage.uri.authority
+        // using DocumentsContract#buildRootUri(String, String) with rootId directly doesn't work
+        val rootUri = DocumentsContract.buildRootsUri(authority)
+        val projection = arrayOf(COLUMN_AVAILABLE_BYTES)
+        // query directly for our rootId
+        val bytesAvailable = context.contentResolver.query(
+            rootUri, projection, "$COLUMN_ROOT_ID=?", arrayOf(rootId), null
+        )?.use { c ->
+            if (!c.moveToNext()) return@use null // no results
+            val bytes = c.getIntOrNull(c.getColumnIndex(COLUMN_AVAILABLE_BYTES))
+            if (bytes != null && bytes >= 0) return@use bytes.toLong()
+            else return@use null
+        }
+        // if we didn't get anything from SAF, try some known hacks
+        return if (bytesAvailable == null && authority == AUTHORITY_STORAGE) {
+            if (rootId == ROOT_ID_DEVICE) {
+                StatFs(Environment.getDataDirectory().absolutePath).availableBytes
+            } else if (storage.safStorage.isUsb) {
+                val documentId = storage.safStorage.uri.lastPathSegment ?: return null
+                StatFs("/mnt/media_rw/${documentId.trimEnd(':')}").availableBytes
+            } else null
+        } else bytesAvailable
+    }
+
     @Throws(IOException::class)
     override suspend fun startNewRestoreSet(token: Long) {
         // reset current storage

app/src/main/java/com/stevesoltys/seedvault/plugins/saf/SafHandler.kt

@@ -40,7 +40,7 @@ internal class SafHandler(
         } else {
             safOption.title
         }
-        return SafStorage(uri, name, safOption.isUsb, safOption.requiresNetwork)
+        return SafStorage(uri, name, safOption.isUsb, safOption.requiresNetwork, safOption.rootId)
     }
 
     /**

app/src/main/java/com/stevesoltys/seedvault/plugins/saf/SafStorage.kt

@@ -7,6 +7,7 @@ package com.stevesoltys.seedvault.plugins.saf
 
 import android.content.Context
 import android.net.Uri
+import android.provider.DocumentsContract.Root.COLUMN_ROOT_ID
 import androidx.annotation.WorkerThread
 import androidx.documentfile.provider.DocumentFile
 import com.stevesoltys.seedvault.plugins.StorageProperties
@@ -16,6 +17,11 @@ data class SafStorage(
     override val name: String,
     override val isUsb: Boolean,
     override val requiresNetwork: Boolean,
+    /**
+     * The [COLUMN_ROOT_ID] for the [uri].
+     * This is only nullable for historic reasons, because we didn't always store it.
+     */
+    val rootId: String?,
 ) : StorageProperties<Uri>() {
 
     val uri: Uri = config

app/src/main/java/com/stevesoltys/seedvault/plugins/webdav/WebDavStoragePlugin.kt

@@ -6,6 +6,7 @@ import at.bitfire.dav4jvm.DavCollection
 import at.bitfire.dav4jvm.Response.HrefRelation.SELF
 import at.bitfire.dav4jvm.exception.NotFoundException
 import at.bitfire.dav4jvm.property.DisplayName
+import at.bitfire.dav4jvm.property.QuotaAvailableBytes
 import at.bitfire.dav4jvm.property.ResourceType
 import com.stevesoltys.seedvault.plugins.EncryptedMetadata
 import com.stevesoltys.seedvault.plugins.StoragePlugin
@@ -43,6 +44,25 @@ internal class WebDavStoragePlugin(
         return webDavSupported
     }
 
+    override suspend fun getFreeSpace(): Long? {
+        val location = url.toHttpUrl()
+        val davCollection = DavCollection(okHttpClient, location)
+
+        val availableBytes = suspendCoroutine { cont ->
+            davCollection.propfind(depth = 0, QuotaAvailableBytes.NAME) { response, _ ->
+                debugLog { "getFreeSpace() = $response" }
+                val quota = response.properties.getOrNull(0) as? QuotaAvailableBytes
+                val availableBytes = quota?.quotaAvailableBytes ?: -1
+                if (availableBytes > 0) {
+                    cont.resume(availableBytes)
+                } else {
+                    cont.resume(null)
+                }
+            }
+        }
+        return availableBytes
+    }
+
     @Throws(IOException::class)
     override suspend fun startNewRestoreSet(token: Long) {
         val location = "$url/$token".toHttpUrl()

app/src/main/java/com/stevesoltys/seedvault/settings/SettingsManager.kt

@@ -32,6 +32,7 @@ internal enum class StoragePluginType { // don't rename, will break existing ins
 }
 
 private const val PREF_KEY_STORAGE_URI = "storageUri"
+private const val PREF_KEY_STORAGE_ROOT_ID = "storageRootId"
 private const val PREF_KEY_STORAGE_NAME = "storageName"
 private const val PREF_KEY_STORAGE_IS_USB = "storageIsUsb"
 private const val PREF_KEY_STORAGE_REQUIRES_NETWORK = "storageRequiresNetwork"
@@ -136,6 +137,7 @@ class SettingsManager(private val context: Context) {
     fun setSafStorage(safStorage: SafStorage) {
         prefs.edit()
             .putString(PREF_KEY_STORAGE_URI, safStorage.uri.toString())
+            .putString(PREF_KEY_STORAGE_ROOT_ID, safStorage.rootId)
             .putString(PREF_KEY_STORAGE_NAME, safStorage.name)
             .putBoolean(PREF_KEY_STORAGE_IS_USB, safStorage.isUsb)
             .putBoolean(PREF_KEY_STORAGE_REQUIRES_NETWORK, safStorage.requiresNetwork)
@@ -149,7 +151,8 @@ class SettingsManager(private val context: Context) {
             ?: throw IllegalStateException("no storage name")
         val isUsb = prefs.getBoolean(PREF_KEY_STORAGE_IS_USB, false)
         val requiresNetwork = prefs.getBoolean(PREF_KEY_STORAGE_REQUIRES_NETWORK, false)
-        return SafStorage(uri, name, isUsb, requiresNetwork)
+        val rootId = prefs.getString(PREF_KEY_STORAGE_ROOT_ID, null)
+        return SafStorage(uri, name, isUsb, requiresNetwork, rootId)
     }
 
     fun setFlashDrive(usb: FlashDrive?) {

app/src/test/java/com/stevesoltys/seedvault/plugins/webdav/WebDavStoragePluginTest.kt

@@ -41,6 +41,12 @@ internal class WebDavStoragePluginTest : TransportTest() {
         println(e)
     }
 
+    @Test
+    fun `test getting free space`() = runBlocking {
+        val freeBytes = plugin.getFreeSpace() ?: fail()
+        assertTrue(freeBytes > 0)
+    }
+
     @Test
     fun `test restore sets and reading+writing`() = runBlocking {
         val token = System.currentTimeMillis()

app/src/test/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinatorTest.kt

@@ -64,6 +64,7 @@ internal class BackupCoordinatorTest : BackupTest() {
         name = getRandomString(),
         isUsb = false,
         requiresNetwork = false,
+        rootId = null,
     )
 
     init {