Add FLUSHDB command

kiwi-core/src/main/java/kiwi/core/storage/KeyValueStore.java

@@ -14,4 +14,6 @@ public interface KeyValueStore<K, V> extends AutoCloseable {
     boolean contains(K key);
 
     int size();
+
+    void purge();
 }

kiwi-core/src/main/java/kiwi/core/storage/bitcask/BitcaskStore.java

@@ -154,8 +154,9 @@ public int size() {
         return keyDir.size();
     }
 
-    private Supplier<LogSegment> activeSegmentSupplier() {
-        return () -> activeSegment;
+    @Override
+    public void purge() {
+        keyDir.keys().asIterator().forEachRemaining(this::delete);
     }
 
     @Override
@@ -164,6 +165,10 @@ public void close() {
         writer.close();
     }
 
+    private Supplier<LogSegment> activeSegmentSupplier() {
+        return () -> activeSegment;
+    }
+
     public static Builder Builder() {
         return new Builder();
     }

kiwi-core/src/test/java/kiwi/core/storage/bitcask/BitcaskStoreTest.java

@@ -155,6 +155,21 @@ void testRollActiveSegment() throws IOException {
         assertEquals("3", store.get(Bytes.wrap("c")).orElseThrow().toString());
     }
 
+    @Test
+    void testPurge() {
+        BitcaskStore store = BitcaskStore.open(root);
+        store.put(Bytes.wrap("k1"), Bytes.wrap("v1"));
+        store.put(Bytes.wrap("k2"), Bytes.wrap("v2"));
+        store.put(Bytes.wrap("k3"), Bytes.wrap("v3"));
+        store.delete(Bytes.wrap("k1"));
+
+        assertEquals(2, store.size());
+
+        store.purge();
+
+        assertEquals(0, store.size());
+    }
+
     @Test
     void testFileClose() throws IOException {
         FileChannel channel = FileChannel.open(root.resolve("test.log"), StandardOpenOption.CREATE, StandardOpenOption.READ, StandardOpenOption.WRITE);

kiwi-embedded/src/main/java/kiwi/embedded/Kiwi.java

@@ -58,6 +58,11 @@ public int size() {
         return store.size();
     }
 
+    @Override
+    public void purge() {
+        store.purge();
+    }
+
     @Override
     public void close() throws Exception {
         store.close();

kiwi-server/src/main/java/kiwi/server/resp/command/CommandType.java

@@ -11,5 +11,6 @@ public enum CommandType {
     DEL,
     EXISTS,
     DBSIZE,
+    FLUSHDB,
     UNKNOWN,
 }

kiwi-server/src/main/java/kiwi/server/resp/handler/RESPCommandHandler.java

@@ -32,6 +32,7 @@ protected void channelRead0(ChannelHandlerContext ctx, RESPCommand command) {
             case DEL -> handleDelete(ctx, command);
             case EXISTS -> handleExists(ctx, command);
             case DBSIZE -> handleSize(ctx, command);
+            case FLUSHDB -> handleFlush(ctx, command);
             case UNKNOWN -> handleUnknown(ctx, command);
         }
     }
@@ -118,6 +119,11 @@ private void handleSize(ChannelHandlerContext ctx, RESPCommand ignoredCommand) {
         ctx.writeAndFlush(size);
     }
 
+    private void handleFlush(ChannelHandlerContext ctx, RESPCommand ignoredCommand) {
+        db.purge();
+        ctx.writeAndFlush("OK");
+    }
+
     private void handleUnknown(ChannelHandlerContext ctx, RESPCommand command) {
         ctx.writeAndFlush(new Throwable("unknown command: " + command.commandType()));
     }