/*
 * 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.commons.el;

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
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: mbenson $
 **/

public class ImplicitObjects
{
  //-------------------------------------
  // Constants
  //-------------------------------------

  static final String sAttributeName = 
    "org.apache.commons.el.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 e = request.getHeaders ((String) pKey);
            if (e != null) {
              while (e.hasMoreElements ()) {
                l.add (e.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;
  }

  //-------------------------------------
}