diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadManager.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadManager.java
new file mode 100644
index 000000000..8a5c851ea
--- /dev/null
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadManager.java
@@ -0,0 +1,137 @@
+package org.jackhuang.hmcl.task;
+
+import com.google.gson.JsonParseException;
+import org.jackhuang.hmcl.util.gson.JsonUtils;
+import org.jackhuang.hmcl.util.io.FileUtils;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+class DownloadManager {
+
+    static DownloadState ne(int contentLength, int initialParts) {
+
+    }
+
+    static DownloadTaskState download(List<String> urls, Path file, int initialParts) throws IOException {
+        Path downloadingFile = file.resolveSibling(FileUtils.getName(file) + ".download");
+        Path stateFile = file.resolveSibling(FileUtils.getName(file) + ".status");
+        DownloadState state;
+        if (Files.exists(downloadingFile) && Files.exists(stateFile)) {
+            // Resume downloading from state
+            try {
+                String status = FileUtils.readText(stateFile);
+                state = JsonUtils.fromNonNullJson(status, DownloadState.class);
+            } catch (JsonParseException e) {
+                state =
+            }
+        }
+    }
+
+    protected static class DownloadTaskState {
+        private final List<String> urls;
+        private final List<DownloadSegment> segments;
+
+        DownloadTaskState(DownloadState state) {
+            urls = new ArrayList<>(state.urls);
+            segments = new ArrayList<>(state.segments);
+        }
+
+        DownloadTaskState(List<String> urls, int contentLength, int initialParts) {
+            urls = new ArrayList<>(urls);
+            segments = new ArrayList<>(initialParts);
+            int partLength = contentLength / initialParts;
+            for (int i = 0; i < initialParts; i++) {
+                int begin = partLength * i;
+                int end = Math.min((partLength + 1) * i, contentLength);
+                segments.add(new DownloadSegment(begin, end, 0));
+            }
+        }
+
+        public static DownloadTaskState newWithLengthUnknown(List<String> urls, int initialParts) {
+            return
+        }
+
+        public List<String> getUrls() {
+            return urls;
+        }
+
+        public List<DownloadSegment> getSegments() {
+            return segments;
+        }
+    }
+
+    protected static class DownloadState {
+        private final List<String> urls;
+        private final List<DownloadSegment> segments;
+
+        /**
+         * Constructor for Gson
+         */
+        public DownloadState() {
+            this(Collections.emptyList(), Collections.emptyList());
+        }
+
+        public DownloadState(List<String> urls, List<DownloadSegment> segments) {
+            this.urls = urls;
+            this.segments = segments;
+        }
+
+        public List<String> getUrls() {
+            return urls;
+        }
+
+        public List<DownloadSegment> getSegments() {
+            return segments;
+        }
+    }
+
+    protected static class DownloadSegment {
+        private final int startPosition;
+        private final int endPosition;
+        private int currentPosition;
+
+        /**
+         * Constructor for Gson
+         */
+        public DownloadSegment() {
+            this(0, 0, 0);
+        }
+
+        public DownloadSegment(int startPosition, int endPosition, int currentPosition) {
+            if (currentPosition < startPosition || currentPosition > endPosition) {
+                throw new IllegalArgumentException("Illegal download state: start " + startPosition + ", end " + endPosition + ", cur " + currentPosition);
+            }
+            this.startPosition = startPosition;
+            this.endPosition = endPosition;
+            this.currentPosition = currentPosition;
+        }
+
+        public int getStartPosition() {
+            return startPosition;
+        }
+
+        public int getEndPosition() {
+            return endPosition;
+        }
+
+        public int getCurrentPosition() {
+            return currentPosition;
+        }
+
+        public void setCurrentPosition(int currentPosition) {
+            this.currentPosition = currentPosition;
+        }
+
+        public boolean isFinished() {
+            return currentPosition == endPosition;
+        }
+
+        public boolean isWaiting() { return startPosition == endPosition && startPosition == 0; }
+    }
+
+}
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadTask.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadTask.java
new file mode 100644
index 000000000..ffe71c6b6
--- /dev/null
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/DownloadTask.java
@@ -0,0 +1,5 @@
+package org.jackhuang.hmcl.task;
+
+class DownloadTask {
+
+}
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FetchTask.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FetchTask.java
index ecc1041f6..11f78d3c8 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FetchTask.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FetchTask.java
@@ -226,39 +226,6 @@ public abstract class FetchTask<T> extends Task<T> {
         NOT_CHECK_E_TAG,
         CACHED
     }
-    
-    protected class DownloadState {
-        private final int startPosition;
-        private final int endPosition;
-        private final int currentPosition;
-        private final boolean finished;
-
-        public DownloadState(int startPosition, int endPosition, int currentPosition) {
-            if (currentPosition < startPosition || currentPosition > endPosition) {
-                throw new IllegalArgumentException("Illegal download state: start " + startPosition + ", end " + endPosition + ", cur " + currentPosition);
-            }
-            this.startPosition = startPosition;
-            this.endPosition = endPosition;
-            this.currentPosition = currentPosition;
-            finished = currentPosition == endPosition;
-        }
-
-        public int getStartPosition() {
-            return startPosition;
-        }
-
-        public int getEndPosition() {
-            return endPosition;
-        }
-
-        public int getCurrentPosition() {
-            return currentPosition;
-        }
-
-        public boolean isFinished() {
-            return finished;
-        }
-    }
 
     protected class DownloadMission {