1 files changed, 90 insertions, 0 deletions
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/backup/IncrementalBackupUtil.java b/src/main/java/com/keuin/kbackupfabric/operation/backup/IncrementalBackupUtil.java
new file mode 100644
index 0000000..f90aef1
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/operation/backup/IncrementalBackupUtil.java
@@ -0,0 +1,90 @@
+package com.keuin.kbackupfabric.operation.backup;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.keuin.kbackupfabric.util.FilesystemUtil;
+import org.apache.commons.codec.digest.DigestUtils;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.*;
+import java.util.Map;
+
+public class IncrementalBackupUtil {
+    /**
+     * Generate a json object representing a directory and its all sub files and directories.
+     * @param path path to the directory.
+     * @return a json object.
+     */
+    public static JsonObject generateDirectoryJsonObject(String path) throws IOException {
+        JsonObject json = new JsonObject();
+        File directory = new File(path);
+        if (!(directory.isDirectory() && directory.exists()))
+            throw new IOException(String.format("Path %s is not a valid directory.", path));
+
+        // Iterate all sub files using BFS.
+        try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(Paths.get(path))) {
+            for (Path sub : directoryStream) {
+                if (sub.toFile().isFile()) {
+                    // A sub file
+                    // Just hash and add it as a string
+                    try (InputStream is = Files.newInputStream(sub)) {
+                        String md5 = org.apache.commons.codec.digest.DigestUtils.md5Hex(is);
+                        json.addProperty(sub.getFileName().toString(), md5);
+                    }
+                } else {
+                    // A sub directory
+                    // Search into
+                    json.addProperty(String.valueOf(sub.getFileName()), sub.toString());
+                }
+            }
+        }
+
+        return json;
+    }
+
+    /**
+     * Save new (or modified) files to target path, based on hash json.
+     * @param targetSavePath where we should save new files.
+     * @param sourcePath where new files come from. This path must be the base directory of given hash json.
+     * @param hashJson the json object obtained by calling generateDirectoryJsonObject method.
+     * @return total size of new files. If failed, will return -1.
+     */
+    public static long saveNewFiles(String targetSavePath, String sourcePath, JsonObject hashJson) throws IOException {
+        long bytesCopied = 0;
+        for (Map.Entry<String, JsonElement> entry : hashJson.entrySet()) {
+            String key = entry.getKey();
+            JsonElement value = entry.getValue();
+            if (value.isJsonPrimitive() && value.getAsJsonPrimitive().isString()) {
+                // A sub file
+                // key is file name
+                // value is file md5
+                String md5 = value.getAsJsonPrimitive().getAsString();
+                File saveTarget = new File(targetSavePath, md5);
+                if (!saveTarget.exists()) {
+                    // Target file does not exist. We have to copy this to the target.
+                    File sourceFile = new File(sourcePath, key);
+                    Files.copy(sourceFile.toPath(), saveTarget.toPath(), StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES);
+                    try {
+                        bytesCopied += sourceFile.length();
+                    } catch (SecurityException ignored) {
+                        // failed to get the file size. Just ignore this.
+                    }
+                }
+            } else if (value.isJsonObject()) {
+                // A sub directory
+                // key is directory name
+                // value is directory json object
+                // Go into
+                if(!value.isJsonObject())
+                    throw new IllegalArgumentException(String.format("Hash json contains illegal argument of a directory item: %s -> %s.", key, value));
+                Path pathSource = Paths.get(sourcePath, key);
+                bytesCopied += saveNewFiles(targetSavePath, pathSource.toString(), value.getAsJsonObject());
+            } else {
+                throw new IllegalArgumentException(String.format("Hash json contains illegal element: %s -> %s.", key, value));
+            }
+        }
+        return bytesCopied;
+    }
+}