1 files changed, 55 insertions, 0 deletions
diff --git a/src/main/java/com/keuin/kbackupfabric/backup/incremental/ObjectCollectionFactory.java b/src/main/java/com/keuin/kbackupfabric/backup/incremental/ObjectCollectionFactory.java
new file mode 100644
index 0000000..0e02606
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+++ b/src/main/java/com/keuin/kbackupfabric/backup/incremental/ObjectCollectionFactory.java
@@ -0,0 +1,55 @@
+package com.keuin.kbackupfabric.backup.incremental;
+
+import com.keuin.kbackupfabric.backup.incremental.identifier.FileIdentifierProvider;
+import com.keuin.kbackupfabric.backup.incremental.identifier.ObjectIdentifier;
+import com.keuin.kbackupfabric.util.PrintUtil;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+
+/**
+ * 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 ObjectCollectionFactory<T extends ObjectIdentifier> {
+
+    private final FileIdentifierProvider<T> identifierFactory;
+
+    public ObjectCollectionFactory(FileIdentifierProvider<T> identifierFactory) {
+        this.identifierFactory = identifierFactory;
+    }
+
+    public ObjectCollection fromDirectory(File directory, Set<String> ignoredFiles) throws IOException {
+        final Set<ObjectElement> subFiles = new HashSet<>();
+        final Map<String, ObjectCollection> subCollections = new HashMap<>();
+
+        if (!Objects.requireNonNull(directory).isDirectory())
+            throw new IllegalArgumentException("given file is not a directory");
+
+        for (Iterator<Path> iter = Files.walk(directory.toPath(), 1).iterator(); iter.hasNext(); ) {
+            Path path = iter.next();
+            if (Files.isSameFile(path, directory.toPath()))
+                continue;
+            File file = path.toFile();
+            if (file.isDirectory()) {
+                subCollections.put(file.getName(), fromDirectory(file, ignoredFiles));
+            } else if (!ignoredFiles.contains(file.getName())) {
+                subFiles.add(new ObjectElement(file.getName(), identifierFactory.fromFile(file)));
+            } else {
+                PrintUtil.info(String.format("Skipping file %s.", file.getName()));
+            }
+        }
+
+        return new ObjectCollection(directory.getName(), subFiles, subCollections);
+    }
+
+    public ObjectCollection fromDirectory(File directory) throws IOException {
+        return fromDirectory(directory, Collections.emptySet());
+    }
+
+}