Add initial Hash configuration. Add the HashDetailsHandler.

src/main/java/io/kamax/mxisd/http/undertow/handler/identity/v2/HashDetailsHandler.java

@@ -0,0 +1,42 @@
+package io.kamax.mxisd.http.undertow.handler.identity.v2;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import io.kamax.mxisd.hash.HashManager;
+import io.kamax.mxisd.http.undertow.handler.BasicHttpHandler;
+import io.undertow.server.HttpServerExchange;
+
+public class HashDetailsHandler extends BasicHttpHandler {
+
+    public static final String PATH = "/_matrix/identity/v2/hash_details";
+
+    private final HashManager hashManager;
+    private volatile JsonObject response = null;
+
+    public HashDetailsHandler(HashManager hashManager) {
+        this.hashManager = hashManager;
+    }
+
+    @Override
+    public void handleRequest(HttpServerExchange exchange) throws Exception {
+        respond(exchange, getResponse());
+    }
+
+    private JsonObject getResponse() {
+        if (response == null) {
+            synchronized (this) {
+                if (response == null) {
+                    response = new JsonObject();
+                    response.addProperty("lookup_pepper", hashManager.getHashEngine().getPepper());
+                    JsonArray algorithms = new JsonArray();
+                    algorithms.add("none");
+                    if (hashManager.getConfig().isEnabled()) {
+                        algorithms.add("sha256");
+                    }
+                    response.add("algorithms", algorithms);
+                }
+            }
+        }
+        return response;
+    }
+}