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package redis;

import java.io.IOException;

import com.google.common.base.Charsets;

import org.jboss.netty.buffer.ChannelBuffer;

import static redis.util.Encoding.numToBytes;

/**
 * Command serialization.  We special case when there are few 4 or fewer parameters
 * since most commands fall into that category. Passing bytes, channelbuffers and
 * strings / objects are all allowed. All strings are assumed to be UTF-8.
 */
public class Command {
  public static final byte[] ARGS_PREFIX = "*".getBytes();
  public static final byte[] CRLF = "\r\n".getBytes();
  public static final byte[] BYTES_PREFIX = "$".getBytes();
  public static final byte[] EMPTY_BYTES = new byte[0];

  private final Object name;
  private final Object[] objects;
  private final Object object1;
  private final Object object2;
  private final Object object3;

  public Command(Object[] objects) {
    this(null, null, null, null, objects);
  }

  public Command(Object name) {
    this(name, null, null, null, null);
  }

  public Command(Object name, Object[] objects) {
    this(name, null, null, null, objects);
  }

  public Command(Object name, Object object1) {
    this(name, object1, null, null, null);
  }

  public Command(Object name, Object object1, Object object2) {
    this(name, object1, object2, null, null);
  }

  public Command(Object name, Object object1, Object object2, Object object3) {
    this(name, object1, object2, object3, null);
  }

  private Command(Object name, Object object1, Object object2, Object object3, Object[] objects) {
    this.name = name;
    this.object1 = object1;
    this.object2 = object2;
    this.object3 = object3;
    this.objects = objects;
  }

  public void write(ChannelBuffer os) throws IOException {
    writeDirect(os, name, object1, object2, object3, objects);
  }

  public static void writeDirect(ChannelBuffer os, Object name, Object object1, Object object2, Object object3, Object[] objects) throws IOException {
    int others = (object1 == null ? 0 : 1) + (object2 == null ? 0 : 1) +
            (object3 == null ? 0 : 1) + (name == null ? 0 : 1);
    int length = objects == null ? 0 : objects.length;
    os.writeBytes(ARGS_PREFIX);
    os.writeBytes(numToBytes(length + others, true));
    if (name != null) writeObject(os, name);
    if (object1 != null) writeObject(os, object1);
    if (object2 != null) writeObject(os, object2);
    if (object3 != null) writeObject(os, object3);
    if (objects != null) {
      for (Object object : objects) {
        writeObject(os, object);
      }
    }
  }

  private static void writeObject(ChannelBuffer os, Object object) throws IOException {
    byte[] argument;
    if (object == null) {
      argument = EMPTY_BYTES;
    } else if (object instanceof byte[]) {
      argument = (byte[]) object;
    } else if (object instanceof ChannelBuffer) {
      writeArgument(os, (ChannelBuffer) object);
      return;
    } else if (object instanceof String) {
      argument = ((String) object).getBytes(Charsets.UTF_8);
    } else {
      argument = object.toString().getBytes(Charsets.UTF_8);
    }
    writeArgument(os, argument);
  }

  private static void writeArgument(ChannelBuffer os, byte[] argument) throws IOException {
    os.writeBytes(BYTES_PREFIX);
    os.writeBytes(numToBytes(argument.length, true));
    os.writeBytes(argument);
    os.writeBytes(CRLF);
  }

  private static void writeArgument(ChannelBuffer os, ChannelBuffer argument) throws IOException {
    os.writeBytes(BYTES_PREFIX);
    os.writeBytes(numToBytes(argument.readableBytes(), true));
    os.writeBytes(argument);
    os.writeBytes(CRLF);
  }

}