Refactoring.

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/Handler.java

@@ -3,6 +3,10 @@
 import java.util.List;
 
 public interface Handler {
+    /**
+     * The default handler.  It holds no state.
+     */
+    Handler DEFAULT = new Handler() {};
 
     default void log(LogLevel level, String message) throws WasmException {}
 

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/ProxyWasm.java

@@ -22,7 +22,6 @@
 public final class ProxyWasm implements Closeable {
 
     private final ABI abi;
-    private final Handler pluginHandler;
     private final WasiPreview1 wasi;
 
     private final AtomicInteger nextContextID = new AtomicInteger(1);
@@ -33,6 +32,7 @@ public final class ProxyWasm implements Closeable {
     private ProxyMap httpCallResponseHeaders;
     private ProxyMap httpCallResponseTrailers;
     private byte[] httpCallResponseBody;
+    private Handler pluginHandler;
 
     private ProxyWasm(Builder other) throws StartException {
         this.pluginHandler = Objects.requireNonNullElse(other.pluginHandler, new Handler() {});
@@ -52,6 +52,14 @@ private ProxyWasm(Builder other) throws StartException {
         }
     }
 
+    public Handler getPluginHandler() {
+        return pluginHandler;
+    }
+
+    public void setPluginHandler(Handler pluginHandler) {
+        this.pluginHandler = pluginHandler;
+    }
+
     public void start() throws StartException {
         if (pluginContext != null) {
             return;

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/plugin/HttpCallResponse.java

@@ -0,0 +1,16 @@
+package io.roastedroot.proxywasm.plugin;
+
+import io.roastedroot.proxywasm.ProxyMap;
+
+public class HttpCallResponse {
+
+    public final int statusCode;
+    public final ProxyMap headers;
+    public final byte[] body;
+
+    public HttpCallResponse(int statusCode, ProxyMap headers, byte[] body) {
+        this.statusCode = statusCode;
+        this.headers = headers;
+        this.body = body;
+    }
+}

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/plugin/HttpCallResponseHandler.java

@@ -0,0 +1,5 @@
+package io.roastedroot.proxywasm.plugin;
+
+public interface HttpCallResponseHandler {
+    void call(HttpCallResponse response);
+}

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/plugin/HttpContext.java

@@ -126,10 +126,11 @@ public SendResponse consumeSentHttpResponse() {
     }
 
     class HandlerImpl extends ChainedHandler {
+        private final Handler next = plugin.wasm.getPluginHandler();
 
         @Override
         protected Handler next() {
-            return plugin.handler;
+            return next;
         }
 
         public ProxyMap getHttpRequestHeaders() {

proxy-wasm-java-host/src/main/java/io/roastedroot/proxywasm/plugin/Metric.java

@@ -0,0 +1,33 @@
+package io.roastedroot.proxywasm.plugin;
+
+import io.roastedroot.proxywasm.MetricType;
+
+public class Metric {
+
+    final int id;
+    final MetricType type;
+    final String name;
+    long value;
+
+    public Metric(int id, MetricType type, String name) {
+        this.id = id;
+        this.type = type;
+        this.name = name;
+    }
+
+    public int id() {
+        return id;
+    }
+
+    public MetricType type() {
+        return type;
+    }
+
+    public String name() {
+        return name;
+    }
+
+    public long value() {
+        return value;
+    }
+}