/*
    * 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.myfaces.view.facelets.el;
  
  import java.io.IOException;
  import java.io.Writer;
  import java.util.ArrayList;
  import java.util.List;
  
  import javax.el.ELContext;
  import javax.el.ELException;
  import javax.el.ExpressionFactory;
  import javax.el.ValueExpression;
  import javax.faces.component.UIComponent;
  import javax.faces.context.ResponseWriter;
  import javax.faces.view.Location;
  
  import org.apache.myfaces.util.ExternalSpecifications;
  import org.apache.myfaces.view.facelets.AbstractFaceletContext;
  
  /**
   * Handles parsing EL Strings in accordance with the EL-API Specification.
   * The parser accepts either <code>${..}</code>
   * or <code>#{..}</code>.
   * 
   * @author Jacob Hookom
   * @version $Id$
   */
  public class ELText
  {
  
      private static final class LiteralValueExpression extends ValueExpression
      {
  
          /**
           * 
           */
          private static final long serialVersionUID = 1L;
  
          private final String text;
  
          public LiteralValueExpression(String text)
          {
              this.text = text;
          }
  
          public boolean isLiteralText()
          {
              return false;
          }
  
          public int hashCode()
          {
              return 0;
          }
  
          public String getExpressionString()
          {
              return this.text;
          }
  
          public boolean equals(Object obj)
          {
              return false;
          }
  
          public void setValue(ELContext context, Object value)
          {
          }
  
          public boolean isReadOnly(ELContext context)
          {
              return false;
          }
  
          public Object getValue(ELContext context)
          {
              return null;
          }
  
          public Class<?> getType(ELContext context)
          {
              return null;
         }
 
         public Class<?> getExpectedType()
         {
             return null;
         }
 
     }
 
     private static final class ELTextComposite extends ELText
     {
         private final ELText[] txt;
 
         public ELTextComposite(ELText[] txt)
         {
             super(null);
             this.txt = txt;
         }
 
         public void write(Writer out, ELContext ctx) throws ELException, IOException
         {
             for (int i = 0; i < this.txt.length; i++)
             {
                 this.txt[i].write(out, ctx);
             }
         }
 
         public void writeText(ResponseWriter out, ELContext ctx) throws ELException, IOException
         {
             for (int i = 0; i < this.txt.length; i++)
             {
                 this.txt[i].writeText(out, ctx);
             }
         }
 
         public String toString(ELContext ctx)
         {
             StringBuffer sb = new StringBuffer();
             for (int i = 0; i < this.txt.length; i++)
             {
                 sb.append(this.txt[i].toString(ctx));
             }
             return sb.toString();
         }
 
         /*
          * public String toString(ELContext ctx) { StringBuffer sb = new StringBuffer(); for (int i = 0; i <
          * this.txt.length; i++) { sb.append(this.txt[i].toString(ctx)); } return sb.toString(); }
          */
 
         public String toString()
         {
             StringBuffer sb = new StringBuffer();
             for (int i = 0; i < this.txt.length; i++)
             {
                 sb.append(this.txt[i].toString());
             }
             return sb.toString();
         }
 
         public boolean isLiteral()
         {
             return false;
         }
 
         public ELText apply(ExpressionFactory factory, ELContext ctx)
         {
             int len = this.txt.length;
             ELText[] nt = new ELText[len];
             for (int i = 0; i < len; i++)
             {
                 nt[i] = this.txt[i].apply(factory, ctx);
             }
             return new ELTextComposite(nt);
         }
     }
 
     private static final class ELTextVariable extends ELText
     {
         private final ValueExpression ve;
 
         public ELTextVariable(ValueExpression ve)
         {
             super(ve.getExpressionString());
             this.ve = ve;
         }
 
         public boolean isLiteral()
         {
             return false;
         }
 
         public ELText apply(ExpressionFactory factory, ELContext ctx)
         {
             return new ELTextVariable(factory.createValueExpression(ctx, this.ve.getExpressionString(), String.class));
         }
 
         public void write(Writer out, ELContext ctx) throws ELException, IOException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 out.write((String) v);
             }
         }
 
         public String toString(ELContext ctx) throws ELException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 return v.toString();
             }
 
             return null;
         }
 
         public void writeText(ResponseWriter out, ELContext ctx) throws ELException, IOException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 out.writeText((String) v, null);
             }
         }
     }
     
     private static final class ELCacheableTextVariable extends ELText
     {
         private final ValueExpression ve;
         
         //Just like TagAttributeImpl
         private final static int EL_CC = 2;
         
         private final static int EL_RESOURCE = 8;
         
         private final int capabilities;
         
         private volatile ELTextVariable cached;
         
         public ELCacheableTextVariable(ValueExpression ve)
         {
             super(ve.getExpressionString());
             this.ve = ve;
             boolean compositeComponentExpression
                     = CompositeComponentELUtils.isCompositeComponentExpression(ve.getExpressionString());
             boolean resourceExpression = ResourceELUtils.isResourceExpression(ve.getExpressionString());
             this.capabilities = (compositeComponentExpression ? EL_CC : 0) | ( resourceExpression ? EL_RESOURCE : 0);
         }
 
         public boolean isLiteral()
         {
             return false;
         }
 
         public ELText apply(ExpressionFactory factory, ELContext ctx)
         {
             AbstractFaceletContext actx = (AbstractFaceletContext) ctx;
             
             if (actx.isAllowCacheELExpressions() && cached != null)
             {
                 // In TagAttributeImpl.getValueExpression(), it is necessary to do an
                 // special logic to detect the cases where #{cc} is included into the
                 // EL expression and set the proper ccLevel. In this case, it is usual
                 // the parent composite component is always on top, but it is possible to
                 // write a nesting case with <composite:insertChildren>, and
                 // pass a flat EL expression over itself. So, it is necessary to update
                 // the ccLevel to make possible to find the right parent where this 
                 // expression belongs to.
                 if ((this.capabilities & EL_CC) != 0)
                 {
                     UIComponent cc = actx.getFaceletCompositionContext().getCompositeComponentFromStack();
                     if (cc != null)
                     {
                         Location location = (Location) cc.getAttributes().get(CompositeComponentELUtils.LOCATION_KEY);
                         if (location != null)
                         {
                             return new ELTextVariable(((LocationValueExpression)cached.ve).apply(
                                     actx.getFaceletCompositionContext().getCompositeComponentLevel(), location));
                         }
                     }
                     return new ELTextVariable(((LocationValueExpression)cached.ve).apply(
                             actx.getFaceletCompositionContext().getCompositeComponentLevel()));
                 }
                 return cached;
             }
             
             actx.beforeConstructELExpression();
             try
             {
                 ValueExpression valueExpression
                         = factory.createValueExpression(ctx, this.ve.getExpressionString(), String.class);
               
                 if ((this.capabilities & EL_CC) != 0)
                 {
                     UIComponent cc = actx.getFaceletCompositionContext().getCompositeComponentFromStack();
                     if (cc != null)
                     {
                         Location location = (Location) cc.getAttributes().get(CompositeComponentELUtils.LOCATION_KEY);
                         if (location != null)
                         {
                             if (ExternalSpecifications.isUnifiedELAvailable())
                             {
                                 valueExpression = new LocationValueExpressionUEL(location, valueExpression,
                                         actx.getFaceletCompositionContext().getCompositeComponentLevel());
                             }
                             else
                             {
                                 valueExpression = new LocationValueExpression(location, valueExpression,
                                         actx.getFaceletCompositionContext().getCompositeComponentLevel());
                             }
                         }
                     }
                 }
                 else if ((this.capabilities & EL_RESOURCE) != 0)
                 {
                     UIComponent cc = actx.getFaceletCompositionContext().getCompositeComponentFromStack();
                     if (cc != null)
                     {
                         Location location = (Location) cc.getAttributes().get(CompositeComponentELUtils.LOCATION_KEY);
                         if (location != null)
                         {
                             if (ExternalSpecifications.isUnifiedELAvailable())
                             {
                                 valueExpression = new ResourceLocationValueExpressionUEL(location, valueExpression);
                             }
                             else
                             {
                                 valueExpression = new ResourceLocationValueExpression(location, valueExpression);
                             }
                         }
                     }
                 }
                 
                 ELTextVariable eltv = new ELTextVariable(valueExpression);
                 
                 if (actx.isAllowCacheELExpressions() && !actx.isAnyFaceletsVariableResolved())
                 {
                      cached = eltv;
                 }
                 return eltv;
             }
             finally
             {
                 actx.afterConstructELExpression();
             }
         }
 
         public void write(Writer out, ELContext ctx) throws ELException, IOException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 out.write((String) v);
             }
         }
 
         public String toString(ELContext ctx) throws ELException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 return v.toString();
             }
 
             return null;
         }
 
         public void writeText(ResponseWriter out, ELContext ctx) throws ELException, IOException
         {
             Object v = this.ve.getValue(ctx);
             if (v != null)
             {
                 out.writeText((String) v, null);
             }
         }
     }
 
     protected final String literal;
 
     public ELText(String literal)
     {
         this.literal = literal;
     }
 
     /**
      * If it's literal text
      * 
      * @return true if the String is literal (doesn't contain <code>#{..}</code> or <code>${..}</code>)
      */
     public boolean isLiteral()
     {
         return true;
     }
 
     /**
      * Return an instance of <code>this</code> that is applicable given the ELContext and ExpressionFactory state.
      * 
      * @param factory
      *            the ExpressionFactory to use
      * @param ctx
      *            the ELContext to use
      * @return an ELText instance
      */
     public ELText apply(ExpressionFactory factory, ELContext ctx)
     {
         return this;
     }
 
     /**
      * Allow this instance to write to the passed Writer, given the ELContext state
      * 
      * @param out
      *            Writer to write to
      * @param ctx
      *            current ELContext state
      * @throws ELException
      * @throws IOException
      */
     public void write(Writer out, ELContext ctx) throws ELException, IOException
     {
         out.write(this.literal);
     }
 
     public void writeText(ResponseWriter out, ELContext ctx) throws ELException, IOException
     {
         out.writeText(this.literal, null);
     }
 
     /**
      * Evaluates the ELText to a String
      * 
      * @param ctx
      *            current ELContext state
      * @throws ELException
      * @return the evaluated String
      */
     public String toString(ELContext ctx) throws ELException
     {
         return this.literal;
     }
 
     public String toString()
     {
         return this.literal;
     }
 
     /**
      * Parses the passed string to determine if it's literal or not
      * 
      * @param in
      *            input String
      * @return true if the String is literal (doesn't contain <code>#{..}</code> or <code>${..}</code>)
      */
     public static boolean isLiteral(String in)
     {
         //ELText txt = parse(in);
         //return txt == null || txt.isLiteral();
         return isLiteral(null, null, in);
     }
 
     /**
      * Factory method for creating an unvalidated ELText instance. NOTE: All expressions in the passed String are
      * treated as {@link org.apache.myfaces.view.facelets.el.LiteralValueExpression LiteralValueExpressions}.
      * 
      * @param in
      *            String to parse
      * @return ELText instance that knows if the String was literal or not
      * @throws javax.el.ELException
      */
     public static ELText parse(String in) throws ELException
     {
         return parse(null, null, in);
     }
     
     public static ELText parseAllowEmptyString(String in) throws ELException
     {
         if (in != null && in.length() == 0)
         {
             return new ELText(in);
         }
         else
         {
             return parse(null, null, in);
         }
     }
 
     /**
      * Factory method for creating a validated ELText instance. When an Expression is hit, it will use the
      * ExpressionFactory to create a ValueExpression instance, resolving any functions at that time. <p/> Variables and
      * properties will not be evaluated.
      * 
      * @param fact
      *            ExpressionFactory to use
      * @param ctx
      *            ELContext to validate against
      * @param in
      *            String to parse
      * @return ELText that can be re-applied later
      * @throws javax.el.ELException
      */
     public static ELText parse(ExpressionFactory fact, ELContext ctx, String in) throws ELException
     {
         char[] ca = in.toCharArray();
         int i = 0;
         char c = 0;
         int len = ca.length;
         int end = len - 1;
         boolean esc = false;
         int vlen = 0;
 
         StringBuffer buff = new StringBuffer(128);
         List<ELText> text = new ArrayList<ELText>();
         ELText t = null;
         ValueExpression ve = null;
 
         while (i < len)
         {
             c = ca[i];
             if ('\\' == c)
             {
                 esc = !esc;
                 if (esc && i < end && (ca[i + 1] == '$' || ca[i + 1] == '#'))
                 {
                     i++;
                     continue;
                 }
             }
             else if (!esc && ('$' == c || '#' == c))
             {
                 if (i < end)
                 {
                     if ('{' == ca[i + 1])
                     {
                         if (buff.length() > 0)
                         {
                             text.add(new ELText(buff.toString()));
                             buff.setLength(0);
                         }
                         vlen = findVarLength(ca, i);
                         if (ctx != null && fact != null)
                         {
                             ve = fact.createValueExpression(ctx, new String(ca, i, vlen), String.class);
                             t = new ELCacheableTextVariable(ve);
                         }
                         else
                         {
                             t = new ELCacheableTextVariable(new LiteralValueExpression(new String(ca, i, vlen)));
                         }
                         text.add(t);
                         i += vlen;
                         continue;
                     }
                 }
             }
             esc = false;
             buff.append(c);
             i++;
         }
 
         if (buff.length() > 0)
         {
             text.add(new ELText(buff.toString()));
             buff.setLength(0);
         }
 
         if (text.size() == 0)
         {
             return null;
         }
         else if (text.size() == 1)
         {
             return (ELText) text.get(0);
         }
         else
         {
             ELText[] ta = (ELText[]) text.toArray(new ELText[text.size()]);
             return new ELTextComposite(ta);
         }
     }
 
     public static ELText[] parseAsArray(String in) throws ELException
     {
         return parseAsArray(null, null, in);
     }
     
     public static ELText[] parseAsArray(ExpressionFactory fact, ELContext ctx, String in) throws ELException
     {
         char[] ca = in.toCharArray();
         int i = 0;
         char c = 0;
         int len = ca.length;
         int end = len - 1;
         boolean esc = false;
         int vlen = 0;
 
         StringBuffer buff = new StringBuffer(128);
         List<ELText> text = new ArrayList<ELText>();
         ELText t = null;
         ValueExpression ve = null;
 
         while (i < len)
         {
             c = ca[i];
             if ('\\' == c)
             {
                 esc = !esc;
                 if (esc && i < end && (ca[i + 1] == '$' || ca[i + 1] == '#'))
                 {
                     i++;
                     continue;
                 }
             }
             else if (!esc && ('$' == c || '#' == c))
             {
                 if (i < end)
                 {
                     if ('{' == ca[i + 1])
                     {
                         if (buff.length() > 0)
                         {
                             text.add(new ELText(buff.toString()));
                             buff.setLength(0);
                         }
                         vlen = findVarLength(ca, i);
                         if (ctx != null && fact != null)
                         {
                             ve = fact.createValueExpression(ctx, new String(ca, i, vlen), String.class);
                             t = new ELCacheableTextVariable(ve);
                         }
                         else
                         {
                             t = new ELCacheableTextVariable(new LiteralValueExpression(new String(ca, i, vlen)));
                         }
                         text.add(t);
                         i += vlen;
                         continue;
                     }
                 }
             }
             esc = false;
             buff.append(c);
             i++;
         }
 
         if (buff.length() > 0)
         {
             text.add(new ELText(buff.toString()));
             buff.setLength(0);
         }
 
         if (text.size() == 0)
         {
             return null;
         }
         else if (text.size() == 1)
         {
             return new ELText[]{text.get(0)};
         }
         else
         {
             ELText[] ta = (ELText[]) text.toArray(new ELText[text.size()]);
             return ta;
         }
     }
     
     public static boolean isLiteral(ExpressionFactory fact, ELContext ctx, String in) throws ELException
     {
         char[] ca = in.toCharArray();
         int i = 0;
         char c = 0;
         int len = ca.length;
         int end = len - 1;
         boolean esc = false;
         //int vlen = 0;
 
         while (i < len)
         {
             c = ca[i];
             if ('\\' == c)
             {
                 esc = !esc;
                 if (esc && i < end && (ca[i + 1] == '$' || ca[i + 1] == '#'))
                 {
                     i++;
                     continue;
                 }
             }
             else if (!esc && ('$' == c || '#' == c))
             {
                 if (i < end)
                 {
                     if ('{' == ca[i + 1])
                     {
                         //vlen = findVarLength(ca, i);
                         //In this point we have at least 1 EL expression, so it is not literal
                         return false;
                     }
                 }
             }
             esc = false;
             i++;
         }
         return true;
     }
 
     private static int findVarLength(char[] ca, int s) throws ELException
     {
         int i = s;
         int len = ca.length;
         char c = 0;
         int str = 0;
         int nest = 0;
         while (i < len)
         {
             c = ca[i];
             if ('\\' == c && i < len - 1)
             {
                 i++;
             }
             else if ('\'' == c || '"' == c)
             {
                 if (str == c)
                 {
                     str = 0;
                 }
                 else
                 {
                     str = c;
                 }
             }
             else if ('{' == c && str == 0)
             {
                 ++nest;
             }
             else if ('}' == c && str == 0 && nest > 1)
             {
                 --nest;
             }
             else if (str == 0 && ('}' == c && nest == 1))
             {
                 return i - s + 1;
             }
             i++;
         }
         throw new ELException("EL Expression Unbalanced: ... " + new String(ca, s, i - s));
     }
 
 }