/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.taglibs.standard.lang.jstl;


import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletContext;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.PageContext;


/**
 * <p>This class is used to generate the implicit Map and List objects
 * that wrap various elements of the PageContext.  It also returns the
 * correct implicit object for a given implicit object name.
 *
 * @author Nathan Abramson - Art Technology Group
 */
public class ImplicitObjects
{
    //-------------------------------------
    // Constants
    //-------------------------------------

    static final String sAttributeName =
            "org.apache.taglibs.standard.ImplicitObjects";

    //-------------------------------------
    // Member variables
    //-------------------------------------

    PageContext mContext;

    Map mPage;

    Map mRequest;

    Map mSession;

    Map mApplication;

    Map mParam;

    Map mParams;

    Map mHeader;

    Map mHeaders;

    Map mInitParam;

    Map mCookie;

    //-------------------------------------

    /**
     * Constructor
     */
    public ImplicitObjects(PageContext pContext)
    {
        mContext = pContext;
    }

    //-------------------------------------

    /**
     * Finds the ImplicitObjects associated with the PageContext,
     * creating it if it doesn't yet exist.
     */
    public static ImplicitObjects getImplicitObjects(PageContext pContext)
    {
        ImplicitObjects objs =
                (ImplicitObjects)
                        pContext.getAttribute(sAttributeName,
                                PageContext.PAGE_SCOPE);
        if (objs == null) {
            objs = new ImplicitObjects(pContext);
            pContext.setAttribute(sAttributeName,
                    objs,
                    PageContext.PAGE_SCOPE);
        }
        return objs;
    }

    //-------------------------------------

    /**
     * Returns the Map that "wraps" page-scoped attributes
     */
    public Map getPageScopeMap()
    {
        if (mPage == null) {
            mPage = createPageScopeMap(mContext);
        }
        return mPage;
    }

    //-------------------------------------

    /**
     * Returns the Map that "wraps" request-scoped attributes
     */
    public Map getRequestScopeMap()
    {
        if (mRequest == null) {
            mRequest = createRequestScopeMap(mContext);
        }
        return mRequest;
    }

    //-------------------------------------

    /**
     * Returns the Map that "wraps" session-scoped attributes
     */
    public Map getSessionScopeMap()
    {
        if (mSession == null) {
            mSession = createSessionScopeMap(mContext);
        }
        return mSession;
    }

    //-------------------------------------
    /**
     * Returns the Map that "wraps" application-scoped attributes
     */
    public Map getApplicationScopeMap()
    {
        if (mApplication == null) {
            mApplication = createApplicationScopeMap(mContext);
        }
        return mApplication;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps parameter name to a single parameter
     * values.
     */
    public Map getParamMap()
    {
        if (mParam == null) {
            mParam = createParamMap(mContext);
        }
        return mParam;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps parameter name to an array of parameter
     * values.
     */
    public Map getParamsMap()
    {
        if (mParams == null) {
            mParams = createParamsMap(mContext);
        }
        return mParams;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps header name to a single header
     * values.
     */
    public Map getHeaderMap()
    {
        if (mHeader == null) {
            mHeader = createHeaderMap(mContext);
        }
        return mHeader;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps header name to an array of header
     * values.
     */
    public Map getHeadersMap()
    {
        if (mHeaders == null) {
            mHeaders = createHeadersMap(mContext);
        }
        return mHeaders;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps init parameter name to a single init
     * parameter values.
     */
    public Map getInitParamMap()
    {
        if (mInitParam == null) {
            mInitParam = createInitParamMap(mContext);
        }
        return mInitParam;
    }

    //-------------------------------------

    /**
     * Returns the Map that maps cookie name to the first matching
     * Cookie in request.getCookies().
     */
    public Map getCookieMap()
    {
        if (mCookie == null) {
            mCookie = createCookieMap(mContext);
        }
        return mCookie;
    }

    //-------------------------------------
    // Methods for generating wrapper maps
    //-------------------------------------

    /**
     * Creates the Map that "wraps" page-scoped attributes
     */
    public static Map createPageScopeMap(PageContext pContext)
    {
        final PageContext context = pContext;

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return context.getAttributeNamesInScope
                        (PageContext.PAGE_SCOPE);
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return context.getAttribute
                            ((String) pKey,
                                    PageContext.PAGE_SCOPE);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return true;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that "wraps" request-scoped attributes
     */
    public static Map createRequestScopeMap(PageContext pContext)
    {
        final PageContext context = pContext;

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return context.getAttributeNamesInScope
                        (PageContext.REQUEST_SCOPE);
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return context.getAttribute
                            ((String) pKey,
                                    PageContext.REQUEST_SCOPE);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return true;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that "wraps" session-scoped attributes
     */
    public static Map createSessionScopeMap(PageContext pContext)
    {
        final PageContext context = pContext;

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return context.getAttributeNamesInScope
                        (PageContext.SESSION_SCOPE);
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return context.getAttribute
                            ((String) pKey,
                                    PageContext.SESSION_SCOPE);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return true;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that "wraps" application-scoped attributes
     */
    public static Map createApplicationScopeMap(PageContext pContext)
    {
        final PageContext context = pContext;

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return context.getAttributeNamesInScope
                        (PageContext.APPLICATION_SCOPE);
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return context.getAttribute
                            ((String) pKey,
                                    PageContext.APPLICATION_SCOPE);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return true;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps parameter name to single parameter
     * value.
     */
    public static Map createParamMap(PageContext pContext)
    {
        final HttpServletRequest request =
                (HttpServletRequest) pContext.getRequest();
        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return request.getParameterNames();
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return request.getParameter((String) pKey);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return false;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps parameter name to an array of parameter
     * values.
     */
    public static Map createParamsMap(PageContext pContext)
    {
        final HttpServletRequest request =
                (HttpServletRequest) pContext.getRequest();

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return request.getParameterNames();
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return request.getParameterValues((String) pKey);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return false;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps header name to single header
     * value.
     */
    public static Map createHeaderMap(PageContext pContext)
    {
        final HttpServletRequest request =
                (HttpServletRequest) pContext.getRequest();

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return request.getHeaderNames();
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return request.getHeader((String) pKey);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return false;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps header name to an array of header
     * values.
     */
    public static Map createHeadersMap(PageContext pContext)
    {
        final HttpServletRequest request =
                (HttpServletRequest) pContext.getRequest();

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return request.getHeaderNames();
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    // Drain the header enumeration
                    List l = new ArrayList();
                    Enumeration enum_ = request.getHeaders((String) pKey);
                    if (enum_ != null) {
                        while (enum_.hasMoreElements()) {
                            l.add(enum_.nextElement());
                        }
                    }
                    String[] ret = (String[]) l.toArray(new String[l.size()]);
                    return ret;
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return false;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps init parameter name to single init
     * parameter value.
     */
    public static Map createInitParamMap(PageContext pContext)
    {
        final ServletContext context = pContext.getServletContext();

        return new EnumeratedMap()
        {
            public Enumeration enumerateKeys()
            {
                return context.getInitParameterNames();
            }

            public Object getValue(Object pKey)
            {
                if (pKey instanceof String) {
                    return context.getInitParameter((String) pKey);
                } else {
                    return null;
                }
            }

            public boolean isMutable()
            {
                return false;
            }
        };
    }

    //-------------------------------------

    /**
     * Creates the Map that maps cookie name to the first matching
     * Cookie in request.getCookies().
     */
    public static Map createCookieMap(PageContext pContext)
    {
        // Read all the cookies and construct the entire map
        HttpServletRequest request = (HttpServletRequest) pContext.getRequest();
        Cookie[] cookies = request.getCookies();
        Map ret = new HashMap();

        for (int i = 0; cookies != null && i < cookies.length; i++) {
            Cookie cookie = cookies[i];
            if (cookie != null) {
                String name = cookie.getName();
                if (!ret.containsKey(name)) {
                    ret.put(name, cookie);
                }
            }
        }
        return ret;
    }

    //-------------------------------------

}
