Implementing incremental backup. (in progress)

6 files changed, 57 insertions, 5 deletions

diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java b/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
index 54c2f58..d0c7500 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
@@ -70,7 +70,7 @@ public final class BackupFilesystemUtil {
         return -1;
     }
 
-    public static String humanFileSize(long size) {
+    public static String getFriendlyFileSizeString(long size) {
         double fileSize = size * 1.0 / 1024 / 1024; // Default unit is MB
         if (fileSize > 1000)
             //msgInfo(context, String.format("File size: %.2fGB", fileSize / 1024));
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/builder/ObjectTreeBackupFileNameBuilder.java b/src/main/java/com/keuin/kbackupfabric/util/backup/builder/ObjectTreeBackupFileNameBuilder.java
index 3c15741..c3d8257 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/builder/ObjectTreeBackupFileNameBuilder.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/builder/ObjectTreeBackupFileNameBuilder.java
@@ -8,13 +8,13 @@ import java.time.LocalDateTime;
 public class ObjectTreeBackupFileNameBuilder implements BackupFileNameBuilder {
     private static final ObjectTreeBackupFileNameBuilder instance = new ObjectTreeBackupFileNameBuilder();
 
-    public static ObjectTreeBackupFileNameBuilder getInstance()  {
+    public static ObjectTreeBackupFileNameBuilder getInstance() {
         return instance;
     }
 
     @Override
     public String build(LocalDateTime time, String backupName) {
         String timeString = BackupNameTimeFormatter.localDateTimeToString(time);
-        return String.format("%s%s_%s%s", BackupFilesystemUtil.getBackupFileNamePrefix(),timeString,backupName,".json");
+        return String.format("%s%s_%s%s", BackupFilesystemUtil.getBackupFileNamePrefix(), timeString, backupName, ".json");
     }
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/builder/PrimitiveZipBackupFileNameBuilder.java b/src/main/java/com/keuin/kbackupfabric/util/backup/builder/PrimitiveZipBackupFileNameBuilder.java
index f910c37..6d8b5f5 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/builder/PrimitiveZipBackupFileNameBuilder.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/builder/PrimitiveZipBackupFileNameBuilder.java
@@ -9,14 +9,14 @@ public class PrimitiveZipBackupFileNameBuilder implements BackupFileNameBuilder
 
     private static final PrimitiveZipBackupFileNameBuilder instance = new PrimitiveZipBackupFileNameBuilder();
 
-    public static PrimitiveZipBackupFileNameBuilder getInstance()  {
+    public static PrimitiveZipBackupFileNameBuilder getInstance() {
         return instance;
     }
 
     @Override
     public String build(LocalDateTime time, String backupName) {
         String timeString = BackupNameTimeFormatter.localDateTimeToString(time);
-        return String.format("%s%s_%s%s", BackupFilesystemUtil.getBackupFileNamePrefix(),timeString,backupName,".zip");
+        return String.format("%s%s_%s%s", BackupFilesystemUtil.getBackupFileNamePrefix(), timeString, backupName, ".zip");
     }
 
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/inc/ObjectCollectionManager.java b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/ObjectCollectionManager.java
new file mode 100644
index 0000000..9560261
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/ObjectCollectionManager.java
@@ -0,0 +1,11 @@
+package com.keuin.kbackupfabric.util.backup.inc;
+
+/**
+ * Incremental backup is implemented as git-like file collection.
+ * Files are called `objects`, the collection contains all files distinguished by their
+ * identifiers. Usually, identifier is the combination of hash and other short information (such as size and another hash).
+ * The identifier should use hashes that are strong enough, to prevent possible collisions.
+ */
+public class ObjectCollectionManager {
+
+}
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/ObjectIdentifier.java b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/ObjectIdentifier.java
new file mode 100644
index 0000000..079f49d
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/ObjectIdentifier.java
@@ -0,0 +1,9 @@
+package com.keuin.kbackupfabric.util.backup.inc.identifier;
+
+/**
+ * The identifier distinguishing files in the object collection.
+ * It should be based on cryptographic hash function in order to prevent possible attacks to the backup system.
+ * All identifiers should be immutable and implement their own equals method.
+ */
+public interface ObjectIdentifier {
+}
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/SingleHashIdentifier.java b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/SingleHashIdentifier.java
new file mode 100644
index 0000000..50b23bb
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/inc/identifier/SingleHashIdentifier.java
@@ -0,0 +1,32 @@
+package com.keuin.kbackupfabric.util.backup.inc.identifier;
+
+import java.io.File;
+import java.util.Arrays;
+
+/**
+ * A simple identifier based on a single hash function.
+ */
+public abstract class SingleHashIdentifier implements ObjectIdentifier {
+
+    private final byte[] hash;
+
+    protected SingleHashIdentifier(byte[] hash) {
+        this.hash = Arrays.copyOf(hash, hash.length);
+    }
+
+    /**
+     * The hash function.
+     *
+     * @param file the file to be hashed.
+     * @return the hash bytes.
+     */
+    protected abstract byte[] hash(File file);
+
+    @Override
+    public boolean equals(Object obj) {
+        if (!(obj instanceof SingleHashIdentifier)) {
+            return false;
+        }
+        return Arrays.equals(hash, ((SingleHashIdentifier) obj).hash);
+    }
+}