/*
 * Copyright (c) 2008, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.attributes;

import org.glassfish.grizzly.utils.NullaryFunction;

Class used to define dynamic typed attributes on AttributeHolder instances. Storing attribute values in AttributeHolder has two advantage comparing to Map storage: 1) Attribute value is typed, and could be checked at
        compile time.
     2) Access to Attribute value, if used with IndexedAttributeHolder, could be as fast as access to array. 
Type parameters:
<T> – /** 
 * Class used to define dynamic typed attributes on {@link AttributeHolder}
 * instances.
 * Storing attribute values in {@link AttributeHolder} has two advantage
 * comparing to Map storage:
 *      1) <tt>Attribute</tt> value is typed, and could be checked at
 *         compile time.
 *      2) Access to <tt>Attribute</tt> value, if used with
 *         {@link IndexedAttributeHolder}, could be as fast as access to array.
 * @param <T>
 */
public final class Attribute<T> {
    
AttributeBuilder, which was used to create this attribute
/**
     * AttributeBuilder, which was used to create this attribute
     */
    private final AttributeBuilder builder;
    
Attribute name
/**
     * Attribute name
     */
    private final String name;
    
Attribute initializer, which will be called, if attribute is not set.
/**
     * Attribute initializer, which will be called, if attribute is not set.
     */
    private final NullaryFunction<T> initializer;
    
Attribute index in AttributeBuilder
/**
     * Attribute index in AttributeBuilder
     */
    private final int attributeIndex;

    @Override
    public String toString() {
        return "Attribute[" + name + ':' + attributeIndex + ']';
    }

    protected Attribute(final AttributeBuilder builder, final String name,
            final int index, final T defaultValue) {
        this(builder, name, index, new NullaryFunction<T>() {

            @Override
            public T evaluate() {
                return defaultValue;
            }
        });
    }

    protected Attribute(final AttributeBuilder builder, final String name,
            final int index, final NullaryFunction<T> initializer) {
        this.builder = builder;
        this.name = name;
        this.attributeIndex = index;
        this.initializer = initializer;
    }

    
Get attribute value, stored on the AttributeHolder, the difference from get(AttributeHolder) is that default value or NullaryFunction won't be invoked. 
Params:
attributeHolder – AttributeHolder.
Returns:
attribute value/**
     * Get attribute value, stored on the {@link AttributeHolder},
     * the difference from {@link #get(org.glassfish.grizzly.attributes.AttributeHolder)} is
     * that default value or {@link NullaryFunction} won't be invoked.
     *
     * @param attributeHolder {@link AttributeHolder}.
     * @return attribute value
     */
    public T peek(final AttributeHolder attributeHolder) {
        return get0(attributeHolder, null);
    }

    
Get attribute value, stored on the AttributeStorage, the difference from get(AttributeStorage) is that default value or NullaryFunction won't be invoked. 
Params:
storage – AttributeStorage.
Returns:
attribute value/**
     * Get attribute value, stored on the {@link AttributeStorage},
     * the difference from {@link #get(AttributeStorage)} is
     * that default value or {@link NullaryFunction} won't be invoked.
     *
     * @param storage {@link AttributeStorage}.
     * @return attribute value
     */
    public T peek(final AttributeStorage storage) {
        final AttributeHolder holder = storage.getAttributes();
        if (holder != null) {
            return peek(holder);
        }

        return null;
    }

    
Get attribute value, stored on the AttributeHolder. 
Params:
attributeHolder – AttributeHolder.
Returns:
attribute value/**
     * Get attribute value, stored on the {@link AttributeHolder}.
     * 
     * @param attributeHolder {@link AttributeHolder}.
     * @return attribute value
     */
    public T get(final AttributeHolder attributeHolder) {
        return get0(attributeHolder, initializer);
    }

    
Get attribute value, stored on the AttributeStorage. 
Params:
storage – AttributeStorage.
Returns:
attribute value/**
     * Get attribute value, stored on the {@link AttributeStorage}.
     *
     * @param storage {@link AttributeStorage}.
     * @return attribute value
     */
    public T get(final AttributeStorage storage) {
        return get(storage.getAttributes());
    }

    
Set attribute value, stored on the AttributeHolder. 
Params:
attributeHolder – AttributeHolder.
value – attribute value to set./**
     * Set attribute value, stored on the {@link AttributeHolder}.
     *
     * @param attributeHolder {@link AttributeHolder}.
     * @param value attribute value to set.
     */
    public void set(final AttributeHolder attributeHolder, final T value) {
        final IndexedAttributeAccessor indexedAccessor =
                attributeHolder.getIndexedAttributeAccessor();
        
        if (indexedAccessor != null) {
            indexedAccessor.setAttribute(attributeIndex, value);
        } else {
            attributeHolder.setAttribute(name, value);
        }
    }

    
Set attribute value, stored on the AttributeStorage. 
Params:
storage – AttributeStorage.
value – attribute value to set./**
     * Set attribute value, stored on the {@link AttributeStorage}.
     *
     * @param storage {@link AttributeStorage}.
     * @param value attribute value to set.
     */
    public void set(final AttributeStorage storage, final T value) {
        set(storage.getAttributes(), value);
    }

    
Remove attribute value, stored on the AttributeHolder. 
Params:
attributeHolder – AttributeHolder.
Returns:
the previous value associated with the attribute/**
     * Remove attribute value, stored on the {@link AttributeHolder}.
     *
     * @param attributeHolder {@link AttributeHolder}.
     * @return the previous value associated with the attribute
     */
    @SuppressWarnings("unchecked")
    public T remove(final AttributeHolder attributeHolder) {
        final IndexedAttributeAccessor indexedAccessor =
                attributeHolder.getIndexedAttributeAccessor();
        
        return indexedAccessor != null
                ? (T) indexedAccessor.removeAttribute(attributeIndex)
                : (T) attributeHolder.removeAttribute(name);
    }

    
Remove attribute value, stored on the AttributeStorage. 
Params:
storage – AttributeStorage./**
     * Remove attribute value, stored on the {@link AttributeStorage}.
     *
     * @param storage {@link AttributeStorage}.
     */
    public T remove(final AttributeStorage storage) {
        final AttributeHolder holder = storage.getAttributes();
        if (holder != null) {
            return remove(holder);
        }

        return null;
    }
    
    
Checks if this attribute is set on the AttributeHolder. Returns true, if attribute is set, of false otherwise.
Params:
attributeHolder – AttributeHolder.
Returns:
true, if attribute is set, of false otherwise./**
     * Checks if this attribute is set on the {@link AttributeHolder}.
     * Returns <tt>true</tt>, if attribute is set, of <tt>false</tt> otherwise.
     * 
     * @param attributeHolder {@link AttributeHolder}.
     * 
     * @return <tt>true</tt>, if attribute is set, of <tt>false</tt> otherwise.
     */
    public boolean isSet(final AttributeHolder attributeHolder) {
        return get0(attributeHolder, null) != null;
    }

    
Checks if this attribute is set on the AttributeStorage. Returns true, if attribute is set, of false otherwise.
Params:
storage – AttributeStorage.
Returns:
true, if attribute is set, of false otherwise./**
     * Checks if this attribute is set on the {@link AttributeStorage}.
     * Returns <tt>true</tt>, if attribute is set, of <tt>false</tt> otherwise.
     *
     * @param storage {@link AttributeStorage}.
     *
     * @return <tt>true</tt>, if attribute is set, of <tt>false</tt> otherwise.
     */
    public boolean isSet(final AttributeStorage storage) {
        final AttributeHolder holder = storage.getAttributes();
        return holder != null && isSet(holder);

    }
    
    
Return attribute name, which is used as attribute key on non-indexed AttributeHolders. 
Returns:
attribute name./**
     * Return attribute name, which is used as attribute key on
     * non-indexed {@link AttributeHolder}s.
     * 
     * @return attribute name.
     */
    public String name() {
        return name;
    }

    
Return attribute name, which is used as attribute key on indexed AttributeHolders. 
Returns:
attribute indexed./**
     * Return attribute name, which is used as attribute key on
     * indexed {@link AttributeHolder}s.
     *
     * @return attribute indexed.
     */
    public int index() {
        return attributeIndex;
    }
    
    @SuppressWarnings("unchecked")
    private T get0(final AttributeHolder attributeHolder,
            final NullaryFunction<T> initializer) {
        final IndexedAttributeAccessor indexedAccessor =
                attributeHolder.getIndexedAttributeAccessor();
        
        return indexedAccessor != null
                ? (T) indexedAccessor.getAttribute(attributeIndex, initializer)
                : (T) attributeHolder.getAttribute(name, initializer);
    }
}