/**
    * Copyright (C) 2005-2009 Alfresco Software Limited.
    *
    * This file is part of the Spring Surf Extension project.
    *
    * 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.springframework.extensions.webscripts.json;
  
  import java.io.IOException;
  import java.io.Writer;
  import java.util.Stack;
  
  /**
   * Fast and simple JSON stream writer. Wraps a Writer to output a JSON object stream.
   * No intermediate objects are created - writes are immediate to the underlying stream.
   * Quoted and correct JSON encoding is performed on string values, - encoding is
   * not performed on key names - it is assumed they are simple strings. The developer must
   * call JSONWriter.encodeJSONString() on the key name if required.
   * 
   * @author Kevin Roast
   */
  public final class JSONWriter
  {
     private Writer out;
     private Stack<Boolean> stack = new Stack<Boolean>();
     
     public JSONWriter(Writer out)
     {
        this.out = out;
        stack.push(Boolean.FALSE);
     }
     
     public void startArray() throws IOException
     {
        if (stack.peek() == true) out.write(", ");
        out.write("[");
        stack.pop();
        stack.push(Boolean.TRUE);
        stack.push(Boolean.FALSE);
     }
     
     public void endArray() throws IOException
     {
        out.write("]");
        stack.pop();
     }
     
     public void startObject() throws IOException
     {
        if (stack.peek() == true) out.write(", ");
        out.write("{");
        stack.pop();
        stack.push(Boolean.TRUE);
        stack.push(Boolean.FALSE);
     }
     
     public void endObject() throws IOException
     {
        out.write("}");
        stack.pop();
     }
     
     public void startValue(String name) throws IOException
     {
        if (stack.peek() == true) out.write(", ");
        out.write('"');
        out.write(name);
        out.write("\": ");
        stack.pop();
        stack.push(Boolean.TRUE);
        stack.push(Boolean.FALSE);
     }
     
     public void endValue()
     {
        stack.pop();
     }
     
     public void writeValue(String name, String value) throws IOException
     {
        if (stack.peek() == true) out.write(", ");
        out.write('"');
        out.write(name);
        out.write("\": \"");
        out.write(encodeJSONString(value));
        out.write('"');
        stack.pop();
       stack.push(Boolean.TRUE);
    }
    
    public void writeValue(String name, int value) throws IOException
    {
       if (stack.peek() == true) out.write(", ");
       out.write('"');
       out.write(name);
       out.write("\": ");
       out.write(Integer.toString(value));
       stack.pop();
       stack.push(Boolean.TRUE);
    }
    
    public void writeValue(String name, boolean value) throws IOException
    {
       if (stack.peek() == true) out.write(", ");
       out.write('"');
       out.write(name);
       out.write("\": ");
       out.write(Boolean.toString(value));
       stack.pop();
       stack.push(Boolean.TRUE);
    }
    
    public void writeNullValue(String name) throws IOException
    {
       if (stack.peek() == true) out.write(", ");
       out.write('"');
       out.write(name);
       out.write("\": null");
       stack.pop();
       stack.push(Boolean.TRUE);
    }
 
    public static String encodeJSONString(final String s)
    {
        if (s == null || s.length() == 0)
        {
            return "";
        }
        
        StringBuilder sb = null;      // create on demand
        String enc;
        char c;
        int len = s.length();
        for (int i = 0; i < len; i++)
        {
            enc = null;
            c = s.charAt(i);
            switch (c)
            {
                case '\\':
                    enc = "\\\\";
                    break;
                case '"':
                    enc = "\\\"";
                    break;
                case '/':
                    enc = "\\/";
                    break;
                case '\b':
                    enc = "\\b";
                    break;
                case '\t':
                    enc = "\\t";
                    break;
                case '\n':
                    enc = "\\n";
                    break;
                case '\f':
                    enc = "\\f";
                    break;
                case '\r':
                    enc = "\\r";
                    break;
 
                default:
                    if (((int)c) >= 0x80)
                    {
                        //encode all non basic latin characters
                        String u = "000" + Integer.toHexString((int)c);
                        enc = "\\u" + u.substring(u.length() - 4);
 
                    }
                break;
            }
 
            if (enc != null)
            {
                if (sb == null)
                {
                    String soFar = s.substring(0, i);
                    sb = new StringBuilder(i + 8);
                    sb.append(soFar);
                }
                sb.append(enc);
            }
            else
            {
                if (sb != null)
                {
                    sb.append(c);
                }
            }
        }
 
        if (sb == null)
        {
            return s;
        }
        else
        {
            return sb.toString();
        }
    }
 }