Add the option to use an asynchronous command execution coordinator

cloud-core/src/main/java/com/intellectualsites/commands/execution/AsynchronousCommandExecutionCoordinator.java

@@ -0,0 +1,156 @@
+//
+// MIT License
+//
+// Copyright (c) 2020 Alexander Söderberg
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall 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 com.intellectualsites.commands.execution;
+
+import com.intellectualsites.commands.Command;
+import com.intellectualsites.commands.CommandTree;
+import com.intellectualsites.commands.context.CommandContext;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Optional;
+import java.util.Queue;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+/**
+ * Execution coordinator parses and/or executes commands on a separate thread from the calling thread
+ *
+ * @param <C> Command sender type
+ */
+public final class AsynchronousCommandExecutionCoordinator<C> extends CommandExecutionCoordinator<C> {
+
+    private final Executor executor;
+    private final boolean synchronizeParsing;
+
+    private AsynchronousCommandExecutionCoordinator(@Nullable final Executor executor,
+                                                    final boolean synchronizeParsing,
+                                                    @Nonnull final CommandTree<C> commandTree) {
+        super(commandTree);
+        this.executor = executor;
+        this.synchronizeParsing = synchronizeParsing;
+    }
+
+    /**
+     * Create a new {@link Builder} instance
+     *
+     * @param <C> Command sender type
+     * @return Builder
+     */
+    @Nonnull
+    public static <C> Builder<C> newBuilder() {
+        return new Builder<>();
+    }
+
+    @Override
+    public CompletableFuture<CommandResult<C>> coordinateExecution(@Nonnull final CommandContext<C> commandContext,
+                                                                   @Nonnull final Queue<String> input) {
+
+        final Supplier<CommandResult<C>> supplier;
+        if (this.synchronizeParsing) {
+            final Optional<Command<C>> commandOptional = this.getCommandTree().parse(commandContext, input);
+            supplier = () -> {
+                commandOptional.ifPresent(command -> command.getCommandExecutionHandler().execute(commandContext));
+                return new CommandResult<>(commandContext);
+            };
+        } else {
+            supplier = () -> {
+                this.getCommandTree().parse(commandContext, input).ifPresent(
+                        command -> command.getCommandExecutionHandler().execute(commandContext));
+                return new CommandResult<>(commandContext);
+            };
+        }
+        if (this.executor != null) {
+            return CompletableFuture.supplyAsync(supplier, this.executor);
+        } else {
+            return CompletableFuture.supplyAsync(supplier);
+        }
+    }
+
+
+    /**
+     * Builder for {@link AsynchronousCommandExecutionCoordinator} instances
+     *
+     * @param <C> Command sender type
+     */
+    public static final class Builder<C> {
+
+        private Executor executor = null;
+        private boolean synchronizeParsing = false;
+
+        private Builder() {
+        }
+
+        /**
+         * This forces the command parsing to run on the calling thread,
+         * and only the actual command execution will run using the executor
+         *
+         * @return Builder instance
+         */
+        @Nonnull
+        public Builder<C> withSynchronousParsing() {
+            this.synchronizeParsing = true;
+            return this;
+        }
+
+        /**
+         * Both command parsing and execution will run using the executor
+         *
+         * @return Builder instance
+         */
+        @Nonnull
+        public Builder<C> withAsynchronousParsing() {
+            this.synchronizeParsing = false;
+            return this;
+        }
+
+        /**
+         * Specify an executor that will be used to coordinate tasks.
+         * By default the executor uses {@link java.util.concurrent.ForkJoinPool#commonPool()}
+         *
+         * @param executor Executor to use
+         * @return Builder instance
+         */
+        @Nonnull
+        public Builder<C> withExecutor(@Nonnull final Executor executor) {
+            this.executor = executor;
+            return this;
+        }
+
+        /**
+         * Builder a function that generates a command execution coordinator
+         * using the options specified in this builder
+         *
+         * @return Function that builds the coordinator
+         */
+        @Nonnull
+        public Function<CommandTree<C>, CommandExecutionCoordinator<C>> build() {
+            return tree -> new AsynchronousCommandExecutionCoordinator<>(this.executor, this.synchronizeParsing, tree);
+        }
+
+    }
+
+}