/*
 * ContentParser.java February 2001
 *
 * Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed 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.simpleframework.http.parse;

import org.simpleframework.http.ContentType;
import org.simpleframework.util.KeyMap;
import org.simpleframework.util.parse.ParseBuffer;
import org.simpleframework.util.parse.Parser;

/** 
 * This provides access to the MIME type parts, that is the primary 
 * type, the secondary type and an optional character set parameter.
 * The <code>charset</code> parameter is one of many parameters that 
 * can be associated with a MIME type. This however this exposes this
 * parameter with a typed method.
 * <p>
 * The <code>getCharset</code> will return the character encoding the
 * content type is encoded within. This allows the user of the content
 * to decode it correctly. Other parameters can be acquired from this
 * by simply providing the name of the parameter. 
 *
 * @author Niall Gallagher
 */
public class ContentParser extends Parser implements ContentType {

   /** 
    * Used to store the characters consumed for the subtype.
    */
   private ParseBuffer subtype;

   /** 
    * Used to store the characters for the <code>charset</code>.
    */
   private ParseBuffer charset;

   /** 
    * Used to store the characters consumed for the type.
    */
   private ParseBuffer type;
   
   /**
    * Used to collect the name of a content type parameter.
    */
   private ParseBuffer name;
   
   /**
    * Used to collect the value of the content type parameter.
    */
   private ParseBuffer value;
   
   /**
    * Used to store the name value pairs of the parameters.
    */
   private KeyMap<String> map;
   
   /** 
    * The default constructor will create a <code>ContentParser</code>
    * that contains no charset, type or subtype. This can be used to 
    * extract the type, subtype and the optional <code>charset</code> 
    * parameter by using the parser's <code>parse(String)</code> 
    * method.
    */   
   public ContentParser(){
      this.subtype = new ParseBuffer();
      this.charset = new ParseBuffer();
      this.value = new ParseBuffer();
      this.name = new ParseBuffer(); 
      this.type = new ParseBuffer();  
      this.map = new KeyMap<String>();
   }

   /** 
    * This is primarily a convenience constructor. This will parse 
    * the <code>String</code> given to extract the MIME type. This 
    * could be achived by calling the default no-arg constructor 
    * and then using the instance to invoke the <code>parse</code> 
    * method on that <code>String</code>.
    *
    * @param header <code>String</code> containing a MIME type value
    */
   public ContentParser(String header){
      this();
      parse(header);
   }      

   /** 
    * This sets the primary type to whatever value is in the string 
    * provided is. If the string is null then this will contain a 
    * null string for the primary type of the parameter, which is 
    * likely invalid in most cases.
    * 
    * @param primary the type to set for the primary type of this
    */ 
   public void setPrimary(String primary) {      
      type.reset(primary);
   }
   
   /** 
    * This is used to retrieve the primary type of this MIME type. The 
    * primary type part within the MIME type defines the generic type.
    * For example <code>text/plain; charset=UTF-8</code>. This will 
    * return the text value. If there is no primary type then this 
    * will return <code>null</code> otherwise the string value.
    *
    * @return the primary type part of this MIME type
    */  
   public String getPrimary() {
      return type.toString();
   }   
   
   /** 
    * This sets the secondary type to whatever value is in the string 
    * provided is. If the string is null then this will contain a 
    * null string for the secondary type of the parameter, which is 
    * likely invalid in most cases.
    * 
    * @param type the type to set for the primary type of this
    */ 
   public void setSecondary(String type) {
      subtype.reset(type);
   }   

   /** 
    * This is used to retrieve the secondary type of this MIME type. 
    * The secondary type part within the MIME type defines the generic 
    * type. For example <code>text/html; charset=UTF-8</code>. This 
    * will return the HTML value. If there is no secondary type then 
    * this will return <code>null</code> otherwise the string value.
    *
    * @return the primary type part of this MIME type
    */ 
   public String getSecondary(){
      return subtype.toString();
   }   

   /** 
    * This will set the <code>charset</code> to whatever value the
    * string contains. If the string is null then this will not set 
    * the parameter to any value and the <code>toString</code> method 
    * will not contain any details of the parameter.
    *
    * @param enc parameter value to add to the MIME type
    */ 
   public void setCharset(String enc) {
      charset.reset(enc);  
   }   

   /** 
    * This is used to retrieve the <code>charset</code> of this MIME 
    * type. This is a special parameter associated with the type, if
    * the parameter is not contained within the type then this will
    * return null, which typically means the default of ISO-8859-1.
    *
    * @return the value that this parameter contains
    */  
   public String getCharset() {
      return charset.toString();   
   }  
   
   /**
    * This is used to retrieve an arbitrary parameter from the MIME
    * type header. This ensures that values for <code>boundary</code>
    * or other such parameters are not lost when the header is parsed.
    * This will return the value, unquoted if required, as a string. 
    * 
    * @param name this is the name of the parameter to be retrieved
    * 
    * @return this is the value for the parameter, or null if empty
    */
   public String getParameter(String name) {
      return map.get(name);
   }
   
   /**
    * This will add a named parameter to the content type header. If
    * a parameter of the specified name has already been added to the
    * header then that value will be replaced by the new value given.
    * Parameters such as the <code>boundary</code> as well as other
    * common parameters can be set with this method.
    * 
    * @param name this is the name of the parameter to be added     
    * @param value this is the value to associate with the name
    */
   public void setParameter(String name, String value) {
      map.put(name, value);
   }

   /** 
    * This will initialize the parser when it is ready to parse 
    * a new <code>String</code>. This will reset the parser to a 
    * ready state. The init method is invoked by the parser when 
    * the <code>Parser.parse</code> method is invoked.
    */
   protected void init(){
      if(count > 0) { 
         pack();
      }
      clear();
   }
   
   /**
    * This is used to clear all previously collected tokens. This 
    * allows the parser to be reused when there are multiple source
    * strings to be parsed. Clearing of the tokens is performed 
    * when the parser is initialized.
    */
   private void clear() {
      type.clear();
      subtype.clear();
      charset.clear();
      name.clear();
      value.clear();
      map.clear();
      off = 0;
   }
   
   /** 
    * Reads and parses the MIME type from the given <code>String</code> 
    * object. This uses the syntax defined by RFC 2616 for the media-type 
    * syntax. This parser is only concerned with one parameter, the 
    * <code>charset</code> parameter. The syntax for the media type is 
    * <pre>
    * media-type = token "/" token *( ";" parameter )
    * parameter = token | literal 
    * </pre>
    */
   protected void parse(){
      type();
      off++;
      subtype();
      parameters();
   }
   
   /** 
    * This is used to remove all whitespace characters from the 
    * <code>String</code> excluding the whitespace within literals. 
    * The definition of a literal can be found in RFC 2616. 
    * <p>
    * The definition of a literal for RFC 2616 is anything between 2 
    * quotes but excluding quotes that are prefixed with the backward 
    * slash character.
    */
   private void pack() {
      char old = buf[0];
      int len = count;
      int seek = 0;
      int pos = 0;

      while(seek < len){
         char ch = buf[seek++];
         
         if(ch == '"' && old != '\\'){  /* qd-text*/
            buf[pos++] = ch;
            
            while(seek < len){
               old = buf[seek-1];
               ch = buf[seek++];  
               buf[pos++] = ch;  
               
               if(ch =='"'&& old!='\\'){  /*qd-text*/
                  break;
               }
            }
         }else if(!space(ch)){            
            old = buf[seek - 1];  
            buf[pos++] = old;                   
         }         
      }
      count = pos;
   }
   
   /** 
    * This reads the type from the MIME type. This will fill the 
    * type <code>ParseBuffer</code>. This will read all chars 
    * upto but not including the first instance of a '/'. The type 
    * of a media-type as defined by RFC 2616 is
    * <code>type/subtype;param=val;param2=val</code>.
    */  
   private void type(){
      while(off < count){
         if(buf[off] =='/'){
            break;
         }
         type.append(buf[off]);
         off++;
      }
   }
  
   /** 
    * This reads the subtype from the MIME type. This will fill the 
    * subtype <code>ParseBuffer</code>. This will read all chars 
    * upto but not including the first instance of a ';'. The subtype 
    * of a media-type as defined by RFC 2616 is
    * <code>type/subtype;param=val;param2=val</code>.
    */
   private void subtype(){
      while(off < count){
         if(buf[off] ==';'){
            break;
         }
         subtype.append(buf[off]);
         off++;
      }      
   }
   
   /** 
    * This will read the parameters from the MIME type. This will search 
    * for the <code>charset</code> parameter within the set of parameters 
    * which are given to the type. The <code>charset</code> param is the 
    * only parameter that this parser will tokenize. 
    * <p>
    * This will remove any parameters that preceed the charset parameter. 
    * Once the <code>charset</code> is retrived the MIME type is considered 
    * to be parsed.
    */
   private void parameters(){   
      while(skip(";")){
         if(skip("charset=")){
            charset();
            break;
         }else{
            parameter();
            insert();
         }
      }
   }   
   
   /**
    * This will add the name and value tokens to the parameters map.
    * If any previous value of the given name has been inserted
    * into the map then this will overwrite that value. This is
    * used to ensure that the string value is inserted to the map.
    */
   private void insert() {
      insert(name, value);
   }
   
   /**
    * This will add the given name and value to the parameters map.
    * If any previous value of the given name has been inserted
    * into the map then this will overwrite that value. This is
    * used to ensure that the string value is inserted to the map.
    *
    * @param name this is the name of the value to be inserted
    * @param value this is the value of a that is to be inserted
    */
   private void insert(ParseBuffer name, ParseBuffer value) {
	   map.put(name.toString(), value.toString());
   }
   
   /** 
    * This is a parameter as defined by RFC 2616. The parameter is added to a 
    * MIME type e.g. <code>type/subtype;param=val</code> etc.  The parameter 
    * name and value are not stored. This is used to simply update the read 
    * offset past the parameter. The reason for reading the parameters is to 
    * search for the <code>charset</code> parameter which will indicate the 
    * encoding.
    */
   private void parameter(){
      name();
      off++; /* = */
      value();
   }
   
   /** 
    * This will simply read all characters from the buffer before the first '=' 
    * character. This represents a parameter name (see RFC 2616 for token). The 
    * parameter name is not buffered it is simply read from the buffer. This will
    * not cause an <code>IndexOutOfBoundsException</code> as each offset
    * is checked before it is acccessed.
    */
   private void name(){
      while(off < count){
         if(buf[off] =='='){
            break;
         }
         name.append(buf[off]);
         off++;
      }   
   }
   
   /** 
    * This is used to read a parameters value from the buf. This will read all 
    * <code>char</code>'s upto but excluding the first terminal <code>char</code> 
    * encountered from the off within the buf, or if the value is a literal 
    * it will read a literal from the buffer (literal is any data between 
    * quotes except if the quote is prefixed with a backward slash character).    
    */
   private void value(){
      if(quote(buf[off])){         
         for(off++; off < count;){
            if(quote(buf[off])){
               if(buf[++off-2]!='\\'){
                  break;
               }
            }
            value.append(buf[off++]);
         }
      }else{   
         while(off < count){
            if(buf[off] ==';') {
               break;           
            }
            value.append(buf[off]);
            off++;
         }
      }
   }
   
   /**
    * This method is used to determine if the specified character is a quote
    * character. The quote character is typically used as a boundary for the
    * values within the header. This accepts a single or double quote.
    * 
    * @param ch the character to determine if it is a quotation
    * 
    * @return true if the character provided is a quotation character
    */
   private boolean quote(char ch) {
      return ch == '\'' || ch == '"';
   }
   
   /** 
    * This is used to read the value from the <code>charset</code> param.
    * This will fill the <code>charset</code> <code>ParseBuffer</code> and with 
    * the <code>charset</code> value. This will read a literal or a token as 
    * the <code>charset</code> value. If the <code>charset</code> is a literal 
    * then the quotes will be read as part of the charset.
    */ 
   private void charset(){
      if(buf[off] == '"'){         
         charset.append('"');
         for(off++; off < count;){
            charset.append(buf[off]);
            if(buf[off++]=='"')
               if(buf[off-2]!='\\'){
                  break;
               }            
         }
      }else{   
         while(off < count){
            if(buf[off]==';') {
               break;          
            }
            charset.append(buf[off]);
            off++;
         }
      }   
   }
   
   /** 
    * This will return the value of the MIME type as a string. This
    * will concatenate the primary and secondary type values and 
    * add the <code>charset</code> parameter to the type which will
    * recreate the content type.
    * 
    * @return this returns the string representation of the type
    */
   private String encode() {
      StringBuilder text = new StringBuilder();
      
      if(type != null) {
         text.append(type);
         text.append("/");
         text.append(subtype);
      }
      if(charset.length() > 0) {
         text.append("; charset=");
         text.append(charset);
      }
      return encode(text);
   }
   
   /** 
    * This will return the value of the MIME type as a string. This
    * will concatenate the primary and secondary type values and 
    * add the <code>charset</code> parameter to the type which will
    * recreate the content type.
    * 
    * @param text this is the buffer to encode the parameters to
    * 
    * @return this returns the string representation of the type
    */
   private String encode(StringBuilder text) {
      for(String name : map) {
         String value = map.get(name);
         
         text.append("; ");
         text.append(name);
         
         if(value != null) {
            text.append("=");
            text.append(value);;
         }
      }
      return text.toString();
   }

   /** 
    * This will return the value of the MIME type as a string. This
    * will concatenate the primary and secondary type values and 
    * add the <code>charset</code> parameter to the type which will
    * recreate the content type.
    * 
    * @return this returns the string representation of the type
    */
   public String toString() {
      return encode();
   }
}