/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you 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:
 *
 *   http://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.netty.util;

import io.netty.util.internal.ObjectUtil;

import java.util.HashMap;
import java.util.Map;

/**
 * A pool of {@link Constant}s.
 *
 * @param <T> the type of the constant
 */
public abstract class ConstantPool<T extends Constant<T>> {

    private final Map<String, T> constants = new HashMap<String, T>();

    private int nextId = 1;

    /**
     * Shortcut of {@link #valueOf(String) valueOf(firstNameComponent.getName() + "#" + secondNameComponent)}.
     */
    public T valueOf(Class<?> firstNameComponent, String secondNameComponent) {
        if (firstNameComponent == null) {
            throw new NullPointerException("firstNameComponent");
        }
        if (secondNameComponent == null) {
            throw new NullPointerException("secondNameComponent");
        }

        return valueOf(firstNameComponent.getName() + '#' + secondNameComponent);
    }

    /**
     * Returns the {@link Constant} which is assigned to the specified {@code name}.
     * If there's no such {@link Constant}, a new one will be created and returned.
     * Once created, the subsequent calls with the same {@code name} will always return the previously created one
     * (i.e. singleton.)
     *
     * @param name the name of the {@link Constant}
     */
    public T valueOf(String name) {
        if (name == null) {
            throw new NullPointerException("name");
        }

        if (name.isEmpty()) {
            throw new IllegalArgumentException("empty name");
        }

        synchronized (constants) {
            T c = constants.get(name);
            if (c == null) {
                c = newConstant(nextId, name);
                constants.put(name, c);
                nextId ++;
            }

            return c;
        }
    }

    /**
     * Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
     */
    public boolean exists(String name) {
        ObjectUtil.checkNotNull(name, "name");
        synchronized (constants) {
            return constants.containsKey(name);
        }
    }

    /**
     * Creates a new {@link Constant} for the given {@param name} or fail with an
     * {@link IllegalArgumentException} if a {@link Constant} for the given {@param name} exists.
     */
    @SuppressWarnings("unchecked")
    public T newInstance(String name) {
        if (name == null) {
            throw new NullPointerException("name");
        }

        if (name.isEmpty()) {
            throw new IllegalArgumentException("empty name");
        }

        synchronized (constants) {
            T c = constants.get(name);
            if (c == null) {
                c = newConstant(nextId, name);
                constants.put(name, c);
                nextId ++;
            } else {
                throw new IllegalArgumentException(String.format("'%s' is already in use", name));
            }
            return c;
        }
    }

    protected abstract T newConstant(int id, String name);
}

@@ -1956,242 +1956,96 @@
     
-if (name == null) %7B%0A            throw new NullPointerException(%22name%22);
+T c;%0A%0A        synchronized (constants) %7B
 %0A      
-  %7D%0A%0A
       
-  
 if (
-name.isEmpty()) %7B%0A            throw new IllegalArgumentException(%22empty name%22);%0A        %7D%0A%0A        synchronized (constants) %7B%0A            T
+exists(name)) %7B%0A               
  c =
@@ -2074,38 +2074,30 @@
             
-if (c == null)
+%7D else
  %7B%0A         
@@ -2114,69 +2114,22 @@
  new
-Co
+I
 nstan
-t(nextId, name);%0A                constants.put
+ce0
 (name
-, c
 );%0A 
@@ -2143,42 +2143,21 @@
     
-    nextId ++;%0A            %7D%0A%0A    
+%7D%0A        %7D%0A%0A
     
@@ -2166,34 +2166,24 @@
   return c;%0A
-        %7D%0A
     %7D%0A%0A    /
@@ -2335,19 +2335,8 @@
     
-ObjectUtil.
 chec
@@ -2347,21 +2347,24 @@
 Null
-(name, %22
+AndNotEmpty(
 name
-%22
 );%0A 
@@ -2749,20 +2749,20 @@
 if (
-name == null
+exists(name)
 ) %7B%0A
@@ -2787,35 +2787,78 @@
 new 
-NullPointerException(%22
+IllegalArgumentException(String.format(%22'%25s' is already in use%22, 
 name
-%22
+)
 );%0A 
@@ -2879,102 +2879,183 @@
     
-if (name.isEmpty()) %7B
+T c = newInstance0(name);%0A%0A        return c;
 %0A    
+%7D%0A%0A
     
-    throw new IllegalArgumentException(%22empty name%22);%0A        %7D%0A
+// Be careful that this dose not check whether the argument is null or empty.%0A    private T newInstance0(String name) %7B
 %0A   
@@ -3100,38 +3100,44 @@
       T c = 
-c
+newC
 onstant
-s.get(
+(nextId, 
 name);%0A     
@@ -3147,70 +3147,74 @@
     
-if (c == null) %7B%0A                c = newConstant(nextId, name)
+constants.put(name, c);%0A            nextId++;%0A            return c
 ;%0A  
@@ -3223,92 +3223,153 @@
     
+%7D%0A
     
+%7D%0A%0A
     
-constants.put(name, c);%0A                nextId ++;%0A            %7D else %7B%0A    
+private String checkNotNullAndNotEmpty(String name) %7B%0A        ObjectUtil.checkNotNull(name, %22name%22);%0A%0A        if (name.isEmpty()) %7B%0A
     
@@ -3415,53 +3415,20 @@
 ion(
-String.format(%22'%25s' is already in use%22,
+%22empty
  name
-)
+%22
 );%0A 
@@ -3430,34 +3430,27 @@
 %22);%0A        
-    %7D%0A    
+%7D%0A%0A
         retu
@@ -3448,36 +3448,29 @@
      return 
-c;%0A        %7D
+name;
 %0A    %7D%0A%0A    

Remove duplicate code in ConstantPool class