Add /velocity plugins command.

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommand.java

@@ -1,19 +1,27 @@
 package com.velocitypowered.proxy.command;
 
+import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.velocitypowered.api.command.Command;
 import com.velocitypowered.api.command.CommandSource;
 import com.velocitypowered.api.permission.Tristate;
+import com.velocitypowered.api.plugin.PluginContainer;
+import com.velocitypowered.api.plugin.PluginDescription;
 import com.velocitypowered.api.proxy.ProxyServer;
 import com.velocitypowered.api.util.ProxyVersion;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import net.kyori.text.Components;
 import net.kyori.text.TextComponent;
 import net.kyori.text.event.ClickEvent;
+import net.kyori.text.event.HoverEvent;
+import net.kyori.text.event.HoverEvent.Action;
 import net.kyori.text.format.TextColor;
 import net.kyori.text.format.TextDecoration;
 import org.checkerframework.checker.nullness.qual.NonNull;
@@ -25,6 +33,7 @@ public class VelocityCommand implements Command {
   public VelocityCommand(ProxyServer server) {
     this.subcommands = ImmutableMap.<String, Command>builder()
         .put("version", new Info(server))
+        .put("plugins", new Plugins(server))
         .build();
   }
 
@@ -132,4 +141,75 @@ public class VelocityCommand implements Command {
       return source.getPermissionValue("velocity.command.info") != Tristate.FALSE;
     }
   }
+
+  private static class Plugins implements Command {
+
+    private final ProxyServer server;
+
+    private Plugins(ProxyServer server) {
+      this.server = server;
+    }
+
+    @Override
+    public void execute(CommandSource source, String @NonNull [] args) {
+      if (args.length != 0) {
+        source.sendMessage(TextComponent.of("/velocity plugins", TextColor.RED));
+        return;
+      }
+
+      List<PluginContainer> plugins = ImmutableList.copyOf(server.getPluginManager().getPlugins());
+      int pluginCount = plugins.size();
+
+      if (pluginCount == 0) {
+        source.sendMessage(TextComponent.of("No plugins installed.", TextColor.YELLOW));
+        return;
+      }
+
+      TextComponent.Builder output = TextComponent.builder("Plugins: ")
+          .color(TextColor.YELLOW);
+      for (int i = 0; i < pluginCount; i++) {
+        PluginContainer plugin = plugins.get(i);
+        output.append(componentForPlugin(plugin.getDescription()));
+        if (i + 1 < pluginCount) {
+          output.append(TextComponent.of(", "));
+        }
+      }
+
+      source.sendMessage(output.build());
+    }
+
+    private TextComponent componentForPlugin(PluginDescription description) {
+      TextComponent pluginSelf = TextComponent.of(description.getId(), TextColor.GRAY);
+      String pluginInfo = description.getName().orElse(description.getId())
+          + description.getVersion().map(v -> " " + v).orElse("");
+
+      TextComponent.Builder hoverText = TextComponent.builder(pluginInfo);
+
+      description.getUrl().ifPresent(url -> {
+        hoverText.append(Components.newline());
+        hoverText.append(TextComponent.of("Website: " + url));
+      });
+      if (!description.getAuthors().isEmpty()) {
+        hoverText.append(Components.newline());
+        if (description.getAuthors().size() == 1) {
+          hoverText.append(TextComponent.of("Author: " + description.getAuthors().get(0)));
+        } else {
+          hoverText.append(TextComponent.of("Author: " + Joiner.on(", ")
+              .join(description.getAuthors())));
+        }
+      }
+      description.getDescription().ifPresent(pdesc -> {
+        hoverText.append(Components.newline());
+        hoverText.append(Components.newline());
+        hoverText.append(TextComponent.of(pdesc));
+      });
+
+      return pluginSelf.hoverEvent(new HoverEvent(Action.SHOW_TEXT, hoverText.build()));
+    }
+
+    @Override
+    public boolean hasPermission(CommandSource source, String @NonNull [] args) {
+      return source.getPermissionValue("velocity.command.plugins") == Tristate.TRUE;
+    }
+  }
 }