/**
 * This file Copyright (c) 2010-2013 Magnolia International
 * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
 *
 *
 * This file is dual-licensed under both the Magnolia
 * Network Agreement and the GNU General Public License.
 * You may elect to use one or the other of these licenses.
 *
 * This file is distributed in the hope that it will be
 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
 * Redistribution, except as permitted by whichever of the GPL
 * or MNA you select, is prohibited.
 *
 * 1. For the GPL license (GPL), you can redistribute and/or
 * modify this file under the terms of the GNU General
 * Public License, Version 3, as published by the Free Software
 * Foundation.  You should have received a copy of the GNU
 * General Public License, Version 3 along with this program;
 * if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * 2. For the Magnolia Network Agreement (MNA), this file
 * and the accompanying materials are made available under the
 * terms of the MNA which accompanies this distribution, and
 * is available at http://www.magnolia-cms.com/mna.html
 *
 * Any modifications to this file must keep this entire header
 * intact.
 *
 */
package info.magnolia.module.blossom.support;

import java.util.Enumeration;
import java.util.NoSuchElementException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.lang.ObjectUtils;
import org.springframework.web.util.WebUtils;

/**
 * Request wrapper for overriding special attributes.
 *
 * @since 1.2
 */
public class SpecialAttributeRequestWrapper extends HttpServletRequestWrapper {

    private static final String[] SPECIAL_ATTRIBUTE_NAMES = new String[]{
            WebUtils.INCLUDE_REQUEST_URI_ATTRIBUTE,
            WebUtils.INCLUDE_CONTEXT_PATH_ATTRIBUTE,
            WebUtils.INCLUDE_SERVLET_PATH_ATTRIBUTE,
            WebUtils.INCLUDE_PATH_INFO_ATTRIBUTE,
            WebUtils.INCLUDE_QUERY_STRING_ATTRIBUTE,
            WebUtils.FORWARD_REQUEST_URI_ATTRIBUTE,
            WebUtils.FORWARD_CONTEXT_PATH_ATTRIBUTE,
            WebUtils.FORWARD_SERVLET_PATH_ATTRIBUTE,
            WebUtils.FORWARD_PATH_INFO_ATTRIBUTE,
            WebUtils.FORWARD_QUERY_STRING_ATTRIBUTE /*,
            WebUtils.ERROR_STATUS_CODE_ATTRIBUTE,
            WebUtils.ERROR_EXCEPTION_TYPE_ATTRIBUTE,
            WebUtils.ERROR_MESSAGE_ATTRIBUTE,
            WebUtils.ERROR_EXCEPTION_ATTRIBUTE,
            WebUtils.ERROR_REQUEST_URI_ATTRIBUTE,
            WebUtils.ERROR_SERVLET_NAME_ATTRIBUTE*/
    };

    private final Object[] localValues = new Object[SPECIAL_ATTRIBUTE_NAMES.length];
    private final Object[] originalValues = new Object[SPECIAL_ATTRIBUTE_NAMES.length];
    private boolean enabled = true;

    public SpecialAttributeRequestWrapper(HttpServletRequest request) {
        super(request);
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public boolean setSpecialAttribute(String name, Object value) {
        for (int i = 0; i < SPECIAL_ATTRIBUTE_NAMES.length; i++) {
            if (name.equals(SPECIAL_ATTRIBUTE_NAMES[i])) {
                localValues[i] = value;
                originalValues[i] = super.getAttribute(name);
                return true;
            }
        }
        return false;
    }

    @Override
    public Object getAttribute(String name) {
        if (enabled) {
            for (int i = 0; i < SPECIAL_ATTRIBUTE_NAMES.length; i++) {
                if (localValues[i] != null && SPECIAL_ATTRIBUTE_NAMES[i].equals(name)) {
                    if (shouldMasquerade(name)) {
                        return localValues[i];
                    } else {
                        break;
                    }
                }
            }
        }
        return super.getAttribute(name);
    }

    protected boolean shouldMasquerade(String name) {
        for (int i = 0; i < SPECIAL_ATTRIBUTE_NAMES.length; i++) {
            if (localValues[i] != null && !ObjectUtils.equals(super.getAttribute(SPECIAL_ATTRIBUTE_NAMES[i]), originalValues[i])) {
                return false;
            }
        }
        return true;
    }

    @Override
    public Enumeration getAttributeNames() {

        return new Enumeration() {

            private int pos = 0;
            private String next = null;
            private Enumeration parentEnumeration = getRequest().getAttributeNames();

            @Override
            public boolean hasMoreElements() {
                if (enabled) {
                    while (pos < localValues.length) {
                        if (localValues[pos] != null) {
                            return true;
                        }
                        pos++;
                    }
                }
                if (next != null) {
                    return true;
                }
                next = findNext();
                return next != null;
            }

            @Override
            public Object nextElement() {
                if (enabled) {
                    while (pos < localValues.length) {
                        if (localValues[pos] != null) {
                            String name = SPECIAL_ATTRIBUTE_NAMES[pos];
                            pos++;
                            return name;
                        }
                        pos++;
                    }
                }
                if (next == null) {
                    next = findNext();
                    if (next == null) {
                        throw new NoSuchElementException();
                    }
                }
                Object result = next;
                next = null;
                return result;
            }

            private String findNext() {
                while (parentEnumeration.hasMoreElements()) {
                    String name = (String) parentEnumeration.nextElement();
                    if (!enabled || !hasLocalValue(name)) {
                        return name;
                    }
                }
                return null;
            }
        };
    }

    @Override
    public void setAttribute(String name, Object o) {
        if (!hasLocalValue(name)) {
            super.setAttribute(name, o);
        }
    }

    @Override
    public void removeAttribute(String name) {
        if (!hasLocalValue(name)) {
            super.removeAttribute(name);
        }
    }

    private boolean hasLocalValue(String name) {
        for (int i = 0; i < SPECIAL_ATTRIBUTE_NAMES.length; i++) {
            if (localValues[i] != null && name.equals(SPECIAL_ATTRIBUTE_NAMES[i])) {
                return true;
            }
        }
        return false;
    }
}