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Advanced and thread-safe Java Redis client for synchronous, asynchronous, and reactive usage. Supports Cluster, Sentinel, Pipelining, Auto-Reconnect, Codecs and much more.
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/*
 * Copyright 2011-Present, Redis Ltd. and Contributors
 * All rights reserved.
 *
 * Licensed under the MIT License.
 *
 * This file contains contributions from third-party contributors
 * licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.lettuce.core.protocol;

import io.lettuce.core.internal.LettuceAssert;
import io.lettuce.core.output.CommandOutput;
import io.netty.buffer.ByteBuf;

/**
 * A Redis command with a {@link ProtocolKeyword command type}, {@link CommandArgs arguments} and an optional
 * {@link CommandOutput output}. All successfully executed commands will eventually return a {@link CommandOutput} object.
 *
 * @param  Key type.
 * @param  Value type.
 * @param  Command output type.
 *
 * @author Will Glozer
 * @author Mark Paluch
 */
public class Command implements RedisCommand {

    protected static final byte ST_INITIAL = 0;

    protected static final byte ST_COMPLETED = 1;

    protected static final byte ST_CANCELLED = 2;

    private final ProtocolKeyword type;

    protected CommandArgs args;

    protected CommandOutput output;

    protected Throwable exception;

    protected volatile byte status = ST_INITIAL;

    /**
     * Create a new command with the supplied type.
     *
     * @param type Command type, must not be {@code null}.
     * @param output Command output, can be {@code null}.
     */
    public Command(ProtocolKeyword type, CommandOutput output) {
        this(type, output, null);
    }

    /**
     * Create a new command with the supplied type and args.
     *
     * @param type Command type, must not be {@code null}.
     * @param output Command output, can be {@code null}.
     * @param args Command args, can be {@code null}
     */
    public Command(ProtocolKeyword type, CommandOutput output, CommandArgs args) {
        LettuceAssert.notNull(type, "Command type must not be null");
        this.type = type;
        this.output = output;
        this.args = args;
    }

    /**
     * Get the object that holds this command's output.
     *
     * @return The command output object.
     */
    @Override
    public CommandOutput getOutput() {
        return output;
    }

    @Override
    public boolean completeExceptionally(Throwable throwable) {
        if (output != null) {
            output.setError(throwable.getMessage());
        }

        exception = throwable;
        this.status = ST_COMPLETED;
        return true;
    }

    /**
     * Mark this command complete and notify all waiting threads.
     */
    @Override
    public void complete() {
        this.status = ST_COMPLETED;
    }

    @Override
    public void cancel() {
        this.status = ST_CANCELLED;
    }

    /**
     * Encode and write this command to the supplied buffer using the new Unified
     * Request Protocol.
     *
     * @param buf Buffer to write to.
     */
    public void encode(ByteBuf buf) {

        buf.touch("Command.encode(…)");
        buf.writeByte('*');
        CommandArgs.IntegerArgument.writeInteger(buf, 1 + (args != null ? args.count() : 0));

        buf.writeBytes(CommandArgs.CRLF);

        CommandArgs.BytesArgument.writeBytes(buf, type.getBytes());

        if (args != null) {
            args.encode(buf);
        }
    }

    public String getError() {
        return output.getError();
    }

    @Override
    public CommandArgs getArgs() {
        return args;
    }

    /**
     *
     * @return the resut from the output.
     */
    public T get() {
        if (output != null) {
            return output.get();
        }
        return null;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        sb.append(getClass().getSimpleName());
        sb.append(" [type=").append(type);
        sb.append(", output=").append(output);
        sb.append(']');
        return sb.toString();
    }

    public void setOutput(CommandOutput output) {
        if (this.status != ST_INITIAL) {
            throw new IllegalStateException("Command is completed/cancelled. Cannot set a new output");
        }
        this.output = output;
    }

    @Override
    public ProtocolKeyword getType() {
        return type;
    }

    @Override
    public boolean isCancelled() {
        return status == ST_CANCELLED;
    }

    @Override
    public boolean isDone() {
        return status != ST_INITIAL;
    }

}