Fix a minor naming bug.

Code refactor.
Improve test.

4 files changed, 64 insertions, 4 deletions

diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/FileIdentifierProvider.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/FileIdentifierProvider.java
index 9a03371..3fbe284 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/FileIdentifierProvider.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/FileIdentifierProvider.java
@@ -4,5 +4,12 @@ import java.io.File;
 import java.io.IOException;
 
 public interface FileIdentifierProvider<T extends ObjectIdentifier> {
+    /**
+     * Generate file identifier from a random file. The file is not necessarily in the object base.
+     *
+     * @param file the file.
+     * @return the file identifier.
+     * @throws IOException when an I/O error occurs.
+     */
     T fromFile(File file) throws IOException;
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/Sha256Identifier.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/Sha256Identifier.java
index cbf1bb9..c1c87e1 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/Sha256Identifier.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/Sha256Identifier.java
@@ -1,5 +1,7 @@
 package com.keuin.kbackupfabric.util.backup.incremental.identifier;
 
+import com.keuin.kbackupfabric.util.BytesUtil;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -16,20 +18,34 @@ public class Sha256Identifier extends SingleHashIdentifier {
     private static final int SHA256_LENGTH = 32;
     private static final Sha256Identifier DUMMY = new Sha256Identifier(new byte[SHA256_LENGTH]); // only for using its hash method
     private static final FileIdentifierProvider<Sha256Identifier> factory = Sha256Identifier::fromFile;
+    private static final String marker = "S2";
 
     public static Sha256Identifier fromFile(File file) throws IOException {
-        if (!Objects.requireNonNull(file).isFile()) {
+        if (!file.isFile()) {
             throw new IllegalArgumentException("file is not a file");
         }
         return new Sha256Identifier(DUMMY.hash(file));
     }
 
+    /**
+     * Load sha-256 from a named file. Only used in StorageObjectLoader.
+     *
+     * @param fileName the file name.
+     * @return identifier.
+     */
+    static Sha256Identifier fromFileName(String fileName) {
+        if (!fileName.matches(marker + "-[0-9A-Fa-f]{32}"))
+            return null;
+        String hexString = fileName.substring(marker.length() + 1);
+        return new Sha256Identifier(BytesUtil.hexToBytes(hexString));
+    }
+
     public static FileIdentifierProvider<Sha256Identifier> getFactory() {
         return factory;
     }
 
     protected Sha256Identifier(byte[] hash) {
-        super(hash);
+        super(hash, marker);
         Objects.requireNonNull(hash);
         if (hash.length != SHA256_LENGTH) {
             throw new IllegalStateException(String.format("SHA256 must be %d bytes", SHA256_LENGTH));
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/SingleHashIdentifier.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/SingleHashIdentifier.java
index 3b96f79..0f62f2b 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/SingleHashIdentifier.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/SingleHashIdentifier.java
@@ -5,6 +5,7 @@ import com.keuin.kbackupfabric.util.BytesUtil;
 import java.io.File;
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Objects;
 
 /**
  * A simple identifier based on a single hash function.
@@ -13,9 +14,13 @@ import java.util.Arrays;
 public abstract class SingleHashIdentifier implements ObjectIdentifier {
 
     private final byte[] hash;
+    private final String type;
 
-    protected SingleHashIdentifier(byte[] hash) {
+    protected SingleHashIdentifier(byte[] hash, String type) {
+        Objects.requireNonNull(hash);
+        Objects.requireNonNull(type);
         this.hash = Arrays.copyOf(hash, hash.length);
+        this.type = type;
     }
 
     /**
@@ -28,7 +33,7 @@ public abstract class SingleHashIdentifier implements ObjectIdentifier {
 
     @Override
     public String getIdentification() {
-        return BytesUtil.bytesToHex(hash);
+        return type + "-" + BytesUtil.bytesToHex(hash);
     }
 
     @Override
@@ -38,4 +43,11 @@ public abstract class SingleHashIdentifier implements ObjectIdentifier {
         }
         return Arrays.equals(hash, ((SingleHashIdentifier) obj).hash);
     }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hash(type);
+        result = 31 * result + Arrays.hashCode(hash);
+        return result;
+    }
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/StorageObjectLoader.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/StorageObjectLoader.java
new file mode 100644
index 0000000..96bc295
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/identifier/StorageObjectLoader.java
@@ -0,0 +1,25 @@
+package com.keuin.kbackupfabric.util.backup.incremental.identifier;
+
+import java.io.File;
+import java.util.Objects;
+
+public class StorageObjectLoader {
+    /**
+     * Get identifier from storage file.
+     *
+     * @param file storage file.
+     * @return identifier. If failed, return null.
+     */
+    public static ObjectIdentifier asIdentifier(File file) {
+        Objects.requireNonNull(file);
+        String fileName = file.getName();
+        ObjectIdentifier identifier;
+
+        identifier = Sha256Identifier.fromFileName(fileName);
+        if (identifier != null)
+            return identifier;
+
+        // Add more identifiers.
+        return null;
+    }
+}