Implement simple API listing

pom.xml

@@ -210,6 +210,30 @@
         </annotationProcessorPaths>
       </configuration>
     </plugin>
+    <plugin>
+      <artifactId>maven-resources-plugin</artifactId>
+      <version>${org.apache.maven.plugins.resources.version}</version>
+      <executions>
+        <execution>
+          <id>copy-apidoc-resource</id>
+          <phase>prepare-package</phase>
+          <goals>
+            <goal>copy-resources</goal>
+          </goals>
+          <configuration>
+            <resources>
+              <resource>
+                <directory>${project.basedir}</directory>
+                <includes>
+                  <include>HTTP_API.md</include>
+                </includes>
+              </resource>
+            </resources>
+            <outputDirectory>${project.build.directory}/assets/app/resources/io/cryostat/net/web</outputDirectory>
+          </configuration>
+        </execution>
+      </executions>
+    </plugin>
     <plugin>
       <groupId>org.codehaus.mojo</groupId>
       <artifactId>exec-maven-plugin</artifactId>
@@ -662,7 +686,7 @@
                   <resource>
                     <directory>web-client/dist</directory>
                     <excludes>
-                        <exclude>cache/**/*</exclude>
+                      <exclude>cache/**/*</exclude>
                     </excludes>
                   </resource>
                 </resources>

src/main/java/io/cryostat/net/web/http/api/v2/ApiGetHandler.java

@@ -0,0 +1,166 @@
+/*
+ * Copyright The Cryostat Authors
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or data
+ * (collectively the "Software"), free of charge and under any and all copyright
+ * rights in the Software, and any and all patent rights owned or freely
+ * licensable by each licensor hereunder covering either (i) the unmodified
+ * Software as contributed to or provided by such licensor, or (ii) the Larger
+ * Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software (each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ * The above copyright notice and either this complete permission notice or at
+ * a minimum a reference to the UPL must be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package io.cryostat.net.web.http.api.v2;
+
+import java.net.URI;
+import java.net.URL;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import javax.inject.Inject;
+
+import io.cryostat.net.AuthManager;
+import io.cryostat.net.web.WebServer;
+import io.cryostat.net.web.http.HttpMimeType;
+import io.cryostat.net.web.http.RequestHandler;
+import io.cryostat.net.web.http.api.ApiVersion;
+
+import com.google.gson.Gson;
+import com.google.gson.annotations.SerializedName;
+import dagger.Lazy;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import io.vertx.core.http.HttpMethod;
+import org.apache.commons.lang3.builder.HashCodeBuilder;
+
+class ApiGetHandler extends AbstractV2RequestHandler<ApiGetHandler.ApiResponse> {
+
+    private final Lazy<WebServer> webServer;
+    private final Lazy<Set<RequestHandler>> handlers;
+
+    @Inject
+    ApiGetHandler(
+            Lazy<WebServer> webServer,
+            Lazy<Set<RequestHandler>> handlers,
+            AuthManager auth,
+            Gson gson) {
+        super(auth, gson);
+        this.webServer = webServer;
+        this.handlers = handlers;
+    }
+
+    @Override
+    public HttpMethod httpMethod() {
+        return HttpMethod.GET;
+    }
+
+    @Override
+    public ApiVersion apiVersion() {
+        return ApiVersion.GENERIC;
+    }
+
+    @Override
+    public String path() {
+        return basePath() + "api";
+    }
+
+    @Override
+    HttpMimeType mimeType() {
+        return HttpMimeType.JSON;
+    }
+
+    @Override
+    public boolean requiresAuthentication() {
+        return false;
+    }
+
+    @Override
+    IntermediateResponse<ApiResponse> handle(RequestParameters requestParams) throws Exception {
+        List<SerializedHandler> serializedHandlers =
+                handlers.get().stream()
+                        .filter(RequestHandler::isAvailable)
+                        .filter(handler -> !ApiVersion.GENERIC.equals(handler.apiVersion()))
+                        .sorted((h1, h2) -> h1.path().compareTo(h2.path()))
+                        .map(SerializedHandler::new)
+                        .distinct()
+                        .collect(Collectors.toList());
+
+        URL resourceFilePath = new URL(webServer.get().getHostUrl(), "HTTP_API.md");
+
+        return new IntermediateResponse<ApiResponse>()
+                .body(new ApiResponse(resourceFilePath, serializedHandlers));
+    }
+
+    @SuppressFBWarnings("URF_UNREAD_FIELD")
+    static class ApiResponse {
+        @SerializedName("overview")
+        final URL resourceFilePath;
+
+        @SerializedName("endpoints")
+        final List<SerializedHandler> handlers;
+
+        ApiResponse(URL resourceFilePath, List<SerializedHandler> handlers) {
+            this.resourceFilePath = resourceFilePath;
+            this.handlers = handlers;
+        }
+    }
+
+    @SuppressFBWarnings("URF_UNREAD_FIELD")
+    static class SerializedHandler {
+        @SerializedName("version")
+        final ApiVersion apiVersion;
+
+        @SerializedName("verb")
+        final HttpMethod httpMethod;
+
+        final String path;
+
+        SerializedHandler(RequestHandler handler) {
+            this.apiVersion = handler.apiVersion();
+            this.httpMethod = handler.httpMethod();
+            this.path = URI.create(handler.path()).normalize().toString();
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (!(o instanceof SerializedHandler)) {
+                return false;
+            }
+            SerializedHandler osh = (SerializedHandler) o;
+            return Objects.equals(apiVersion, osh.apiVersion)
+                    && Objects.equals(httpMethod, osh.httpMethod)
+                    && Objects.equals(path, osh.path);
+        }
+
+        @Override
+        public int hashCode() {
+            return new HashCodeBuilder().append(apiVersion).append(httpMethod).append(path).build();
+        }
+    }
+}

src/main/java/io/cryostat/net/web/http/api/v2/HttpApiV2Module.java

@@ -56,6 +56,10 @@
 @Module
 public abstract class HttpApiV2Module {
 
+    @Binds
+    @IntoSet
+    abstract RequestHandler bindApiGetHandler(ApiGetHandler handler);
+
     @Binds
     @IntoSet
     abstract RequestHandler bindTargetsPostHandler(TargetsPostHandler handler);