don't restore files that still exist unchanged

(same size and lastModified)

storage/lib/src/main/java/org/calyxos/backup/storage/restore/AbstractChunkRestore.kt

@@ -46,8 +46,6 @@ internal abstract class AbstractChunkRestore(
         tag: String,
         streamWriter: suspend (outputStream: OutputStream) -> Long,
     ) {
-        // TODO check if the file exists already (same name, size, chunk IDs)
-        //  and skip it in this case
         fileRestore.restoreFile(file, observer, tag, streamWriter)
     }
 

storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileRestore.kt

@@ -24,7 +24,6 @@ import kotlin.random.Random
 
 private const val TAG = "FileRestore"
 
-@Suppress("BlockingMethodInNonBlockingContext")
 internal class FileRestore(
     private val context: Context,
     private val mediaScanner: MediaScanner,
@@ -46,10 +45,12 @@ internal class FileRestore(
                 bytes = restoreFile(file.mediaFile, streamWriter)
                 finalTag = "M$tag"
             }
+
             file.docFile != null -> {
                 bytes = restoreFile(file, streamWriter)
                 finalTag = "D$tag"
             }
+
             else -> {
                 error("unexpected file: $file")
             }
@@ -63,16 +64,21 @@ internal class FileRestore(
         streamWriter: suspend (outputStream: OutputStream) -> Long,
     ): Long {
         // ensure directory exists
-        @Suppress("DEPRECATION")
         val dir = File("${getExternalStorageDirectory()}/${docFile.dir}")
         if (!dir.mkdirs() && !dir.isDirectory) {
             throw IOException("Could not create ${dir.absolutePath}")
         }
-        // find non-existing file-name
         var file = File(dir, docFile.name)
+        // TODO should we also calculate and check the chunk IDs?
+        if (file.isFile && file.length() == docFile.size &&
+            file.lastModified() == docFile.lastModified
+        ) {
+            Log.i(TAG, "Not restoring $file, already there unchanged.")
+            return file.length() // not restoring existing file with same length and date
+        } else {
             var i = 0
-        // we don't support existing files, but at least don't overwrite them when they do exist
-        while (file.exists()) {
+            // don't overwrite existing files, if they exist
+            while (file.exists()) { // find non-existing file-name
                 i++
                 val lastDot = docFile.name.lastIndexOf('.')
                 val newName = if (lastDot == -1) "${docFile.name} ($i)"
@@ -97,12 +103,21 @@ internal class FileRestore(
 
             return bytesWritten
         }
+    }
 
     @Throws(IOException::class)
     private suspend fun restoreFile(
         mediaFile: BackupMediaFile,
         streamWriter: suspend (outputStream: OutputStream) -> Long,
     ): Long {
+        // TODO should we also calculate and check the chunk IDs?
+        if (mediaScanner.existsMediaFileUnchanged(mediaFile)) {
+            Log.i(
+                TAG,
+                "Not restoring ${mediaFile.path}/${mediaFile.name}, already there unchanged."
+            )
+            return mediaFile.size
+        }
         // Insert pending media item into MediaStore
         val contentValues = ContentValues().apply {
             put(MediaColumns.DISPLAY_NAME, mediaFile.name)
@@ -143,7 +158,6 @@ internal class FileRestore(
     }
 
     private fun setLastModifiedOnMediaFile(mediaFile: BackupMediaFile, uri: Uri) {
-        @Suppress("DEPRECATION")
         val extDir = getExternalStorageDirectory()
 
         // re-set lastModified as we can't use the MediaStore for this (read-only property)

storage/lib/src/main/java/org/calyxos/backup/storage/scanner/DocumentScanner.kt

@@ -56,7 +56,7 @@ public class DocumentScanner(context: Context) {
             queryUri, PROJECTION, null, null, null
         )
         val documentFiles = ArrayList<DocFile>(cursor?.count ?: 0)
-        cursor?.use { it ->
+        cursor?.use {
             while (it.moveToNext()) {
                 val id = it.getString(PROJECTION_ID)
                 val documentUri = DocumentsContract.buildDocumentUriUsingTree(uri, id)

storage/lib/src/main/java/org/calyxos/backup/storage/scanner/FileScanner.kt

@@ -16,7 +16,6 @@ import org.calyxos.backup.storage.content.DocFile
 import org.calyxos.backup.storage.content.MediaFile
 import org.calyxos.backup.storage.db.UriStore
 import org.calyxos.backup.storage.measure
-import kotlin.time.ExperimentalTime
 
 internal class FileScannerResult(
     val smallFiles: List<ContentFile>,
@@ -36,7 +35,6 @@ internal class FileScanner(
         private const val FILES_LARGE = "large"
     }
 
-    @OptIn(ExperimentalTime::class)
     fun getFiles(): FileScannerResult {
         // scan both APIs
         val mediaFiles = ArrayList<ContentFile>()

storage/lib/src/main/java/org/calyxos/backup/storage/scanner/MediaScanner.kt

@@ -6,6 +6,7 @@
 package org.calyxos.backup.storage.scanner
 
 import android.content.ContentResolver.QUERY_ARG_SQL_SELECTION
+import android.content.ContentResolver.QUERY_ARG_SQL_SELECTION_ARGS
 import android.content.ContentUris
 import android.content.Context
 import android.database.Cursor
@@ -21,6 +22,7 @@ import androidx.core.database.getLongOrNull
 import androidx.core.database.getStringOrNull
 import org.calyxos.backup.storage.api.BackupFile
 import org.calyxos.backup.storage.api.MediaType
+import org.calyxos.backup.storage.backup.BackupMediaFile
 import org.calyxos.backup.storage.content.MediaFile
 import java.io.File
 
@@ -79,6 +81,37 @@ public class MediaScanner(context: Context) {
         }
     }
 
+    internal fun existsMediaFileUnchanged(mediaFile: BackupMediaFile): Boolean {
+        val uri = MediaType.fromBackupMediaType(mediaFile.type).contentUri
+        val extras = Bundle().apply {
+            // search for files with same path and name
+            val query = StringBuilder().apply {
+                append("${MediaStore.MediaColumns.MIME_TYPE}!='$MIME_TYPE_DIR'")
+                append(" AND ")
+                append("${MediaStore.MediaColumns.RELATIVE_PATH}=?")
+                append(" AND ")
+                append("${MediaStore.MediaColumns.DISPLAY_NAME}=?")
+            }
+            putString(QUERY_ARG_SQL_SELECTION, query.toString())
+            val args = arrayOf(
+                mediaFile.path + "/", // Note trailing slash that is important
+                mediaFile.name,
+            )
+            putStringArray(QUERY_ARG_SQL_SELECTION_ARGS, args)
+        }
+
+        contentResolver.query(uri, PROJECTION, extras, null)?.use { c ->
+            while (c.moveToNext()) {
+                val f = createMediaFile(c, uri)
+                // note that we get seconds, but store milliseconds
+                if (f.dateModified == mediaFile.lastModified / 1000 && f.size == mediaFile.size) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+
     internal fun getPath(uri: Uri): String? {
         val projection = arrayOf(
             MediaStore.MediaColumns.RELATIVE_PATH,