Add WebSocket support in plugins (#5662)

#### What type of PR is this?

/kind feature
/area core
/area plugin

#### What this PR does / why we need it:

This PR allows plugin developers defining WebSocket endpoints in plugins.

#### Which issue(s) this PR fixes:

Fixes #5285 

#### Does this PR introduce a user-facing change?

```release-note
支持在插件中实现 WebSocket
```

api/src/main/java/run/halo/app/core/endpoint/WebSocketEndpoint.java

@@ -0,0 +1,34 @@
+package run.halo.app.core.endpoint;
+
+import org.springframework.web.reactive.socket.WebSocketHandler;
+import run.halo.app.extension.GroupVersion;
+
+/**
+ * Endpoint for WebSocket.
+ *
+ * @author johnniang
+ */
+public interface WebSocketEndpoint {
+
+    /**
+     * Path of the URL after group version.
+     *
+     * @return path of the URL.
+     */
+    String urlPath();
+
+    /**
+     * Group and version parts of the endpoint.
+     *
+     * @return GroupVersion.
+     */
+    GroupVersion groupVersion();
+
+    /**
+     * Real WebSocket handler for the endpoint.
+     *
+     * @return WebSocket handler.
+     */
+    WebSocketHandler handler();
+
+}

application/src/main/java/run/halo/app/config/WebFluxConfig.java

@@ -38,6 +38,7 @@
 import reactor.core.publisher.Mono;
 import run.halo.app.console.ProxyFilter;
 import run.halo.app.console.WebSocketRequestPredicate;
+import run.halo.app.core.endpoint.WebSocketHandlerMapping;
 import run.halo.app.core.extension.endpoint.CustomEndpoint;
 import run.halo.app.core.extension.endpoint.CustomEndpointsBuilder;
 import run.halo.app.infra.properties.HaloProperties;
@@ -100,6 +101,13 @@ RouterFunction<ServerResponse> customEndpoints(ApplicationContext context) {
         return builder.build();
     }
 
+    @Bean
+    public WebSocketHandlerMapping webSocketHandlerMapping() {
+        WebSocketHandlerMapping handlerMapping = new WebSocketHandlerMapping();
+        handlerMapping.setOrder(-2);
+        return handlerMapping;
+    }
+
     @Bean
     RouterFunction<ServerResponse> consoleIndexRedirection() {
         var consolePredicate = method(HttpMethod.GET)

application/src/main/java/run/halo/app/console/WebSocketUtils.java

@@ -1,5 +1,6 @@
 package run.halo.app.console;
 
+import java.util.Objects;
 import org.springframework.http.HttpHeaders;
 
 public enum WebSocketUtils {
@@ -8,8 +9,11 @@ public enum WebSocketUtils {
     public static boolean isWebSocketUpgrade(HttpHeaders headers) {
         // See io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil
         // .isWebsocketUpgrade for more.
+        var upgradeConnection = headers.getConnection().stream().map(String::toLowerCase)
+            .anyMatch(conn -> Objects.equals(conn, "upgrade"));
+
         return headers.containsKey(HttpHeaders.UPGRADE)
-            && headers.getConnection().contains(HttpHeaders.UPGRADE)
+            && upgradeConnection
             && "websocket".equalsIgnoreCase(headers.getUpgrade());
     }
 

application/src/main/java/run/halo/app/core/endpoint/WebSocketEndpointManager.java

@@ -0,0 +1,16 @@
+package run.halo.app.core.endpoint;
+
+import java.util.Collection;
+
+/**
+ * Interface for managing WebSocket endpoints, including registering and unregistering.
+ *
+ * @author johnniang
+ */
+public interface WebSocketEndpointManager {
+
+    void register(Collection<WebSocketEndpoint> endpoints);
+
+    void unregister(Collection<WebSocketEndpoint> endpoints);
+
+}

application/src/main/java/run/halo/app/core/endpoint/WebSocketHandlerMapping.java

@@ -0,0 +1,140 @@
+package run.halo.app.core.endpoint;
+
+import com.google.common.collect.BiMap;
+import com.google.common.collect.HashBiMap;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import org.apache.commons.lang3.StringUtils;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.server.reactive.observation.ServerRequestObservationContext;
+import org.springframework.lang.NonNull;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.web.reactive.handler.AbstractHandlerMapping;
+import org.springframework.web.reactive.socket.WebSocketHandler;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.util.pattern.PathPattern;
+import reactor.core.publisher.Mono;
+import run.halo.app.console.WebSocketUtils;
+
+public class WebSocketHandlerMapping extends AbstractHandlerMapping
+    implements WebSocketEndpointManager, InitializingBean {
+
+    private final BiMap<PathPattern, WebSocketEndpoint> endpointMap;
+
+    private final ReadWriteLock rwLock;
+
+    public WebSocketHandlerMapping() {
+        this.endpointMap = HashBiMap.create();
+        this.rwLock = new ReentrantReadWriteLock();
+    }
+
+    @Override
+    @NonNull
+    public Mono<WebSocketHandler> getHandlerInternal(ServerWebExchange exchange) {
+        var request = exchange.getRequest();
+        if (!HttpMethod.GET.equals(request.getMethod())
+            || !WebSocketUtils.isWebSocketUpgrade(request.getHeaders())) {
+            // skip getting handler if the request is not a WebSocket.
+            return Mono.empty();
+        }
+
+        var lock = rwLock.readLock();
+        lock.lock();
+        try {
+            // Refer to org.springframework.web.reactive.handler.AbstractUrlHandlerMapping
+            // .lookupHandler
+            var pathContainer = request.getPath().pathWithinApplication();
+            List<PathPattern> matches = null;
+            for (var pattern : this.endpointMap.keySet()) {
+                if (pattern.matches(pathContainer)) {
+                    if (matches == null) {
+                        matches = new ArrayList<>();
+                    }
+                    matches.add(pattern);
+                }
+            }
+            if (matches == null) {
+                return Mono.empty();
+            }
+
+            if (matches.size() > 1) {
+                matches.sort(PathPattern.SPECIFICITY_COMPARATOR);
+            }
+
+            var pattern = matches.get(0);
+            exchange.getAttributes().put(BEST_MATCHING_PATTERN_ATTRIBUTE, pattern);
+
+            var handler = endpointMap.get(pattern).handler();
+            exchange.getAttributes().put(BEST_MATCHING_HANDLER_ATTRIBUTE, handler);
+
+            ServerRequestObservationContext.findCurrent(exchange.getAttributes())
+                .ifPresent(context -> context.setPathPattern(pattern.toString()));
+
+            var pathWithinMapping = pattern.extractPathWithinPattern(pathContainer);
+            exchange.getAttributes().put(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);
+
+            var matchInfo = pattern.matchAndExtract(pathContainer);
+            Assert.notNull(matchInfo, "Expect a match");
+            exchange.getAttributes()
+                .put(URI_TEMPLATE_VARIABLES_ATTRIBUTE, matchInfo.getUriVariables());
+            return Mono.just(handler);
+        } catch (Exception e) {
+            return Mono.error(e);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void register(Collection<WebSocketEndpoint> endpoints) {
+        if (CollectionUtils.isEmpty(endpoints)) {
+            return;
+        }
+        var lock = rwLock.writeLock();
+        lock.lock();
+        try {
+            endpoints.forEach(endpoint -> {
+                var urlPath = endpoint.urlPath();
+                urlPath = StringUtils.prependIfMissing(urlPath, "/");
+                var groupVersion = endpoint.groupVersion();
+                var parser = getPathPatternParser();
+                var pattern = parser.parse("/apis/" + groupVersion + urlPath);
+                endpointMap.put(pattern, endpoint);
+            });
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void unregister(Collection<WebSocketEndpoint> endpoints) {
+        if (CollectionUtils.isEmpty(endpoints)) {
+            return;
+        }
+        var lock = rwLock.writeLock();
+        lock.lock();
+        try {
+            BiMap<WebSocketEndpoint, PathPattern> inverseMap = endpointMap.inverse();
+            endpoints.forEach(inverseMap::remove);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void afterPropertiesSet() {
+        var endpoints = obtainApplicationContext().getBeanProvider(WebSocketEndpoint.class)
+            .orderedStream()
+            .toList();
+        register(endpoints);
+    }
+
+    BiMap<PathPattern, WebSocketEndpoint> getEndpointMap() {
+        return endpointMap;
+    }
+}

application/src/main/java/run/halo/app/plugin/DefaultPluginApplicationContextFactory.java

@@ -29,6 +29,8 @@
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.ServerResponse;
 import reactor.core.Exceptions;
+import run.halo.app.core.endpoint.WebSocketEndpoint;
+import run.halo.app.core.endpoint.WebSocketEndpointManager;
 import run.halo.app.extension.ReactiveExtensionClient;
 import run.halo.app.infra.properties.HaloProperties;
 import run.halo.app.plugin.event.HaloPluginBeforeStopEvent;
@@ -125,6 +127,10 @@ public ApplicationContext create(String pluginId) {
                 beanFactory.registerSingleton("finderManager", finderManager);
             });
 
+        rootContext.getBeanProvider(WebSocketEndpointManager.class)
+            .ifUnique(manager -> beanFactory.registerSingleton("pluginWebSocketEndpointManager",
+                new PluginWebSocketEndpointManager(manager)));
+
         rootContext.getBeanProvider(PluginRouterFunctionRegistry.class)
             .ifUnique(registry -> {
                 var pluginRouterFunctionManager = new PluginRouterFunctionManager(registry);
@@ -219,6 +225,31 @@ public void onApplicationEvent(ContextRefreshedEvent event) {
 
     }
 
+    private static class PluginWebSocketEndpointManager {
+
+        private final WebSocketEndpointManager manager;
+
+        private List<WebSocketEndpoint> endpoints;
+
+        private PluginWebSocketEndpointManager(WebSocketEndpointManager manager) {
+            this.manager = manager;
+        }
+
+        @EventListener
+        public void onApplicationEvent(ContextRefreshedEvent event) {
+            var context = event.getApplicationContext();
+            this.endpoints = context.getBeanProvider(WebSocketEndpoint.class)
+                .orderedStream()
+                .toList();
+            manager.register(this.endpoints);
+        }
+
+        @EventListener
+        public void onApplicationEvent(ContextClosedEvent ignored) {
+            manager.unregister(this.endpoints);
+        }
+    }
+
     private static class PluginRouterFunctionManager {
 
         private final PluginRouterFunctionRegistry routerFunctionRegistry;

application/src/main/java/run/halo/app/security/authorization/RequestInfoFactory.java

@@ -6,6 +6,7 @@
 import org.apache.commons.lang3.StringUtils;
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.reactive.ServerHttpRequest;
+import run.halo.app.console.WebSocketUtils;
 
 /**
  * Creates {@link RequestInfo} from {@link ServerHttpRequest}.
@@ -215,6 +216,10 @@ public RequestInfo newRequestInfo(ServerHttpRequest request) {
                 requestInfo.verb = "deletecollection";
             }
         }
+        if ("list".equals(requestInfo.verb)
+            && WebSocketUtils.isWebSocketUpgrade(request.getHeaders())) {
+            requestInfo.verb = "watch";
+        }
         return requestInfo;
     }