/*
 * $Id: JSONParser.java,v 1.1 2006/04/15 14:10:48 platform Exp $
 * Created on 2006-4-15
 */
package org.zkoss.json.parser;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.zkoss.json.JSONArray;
import org.zkoss.json.JSONObject;


/**
 * Parser for JSON text. Please note that JSONParser is NOT thread-safe.
 * 
 * @author FangYidong<fangyidong@yahoo.com.cn>
 */
@SuppressWarnings("unchecked")
public class JSONParser {
	public static final int S_INIT=0;
	public static final int S_IN_FINISHED_VALUE=1;//string,number,boolean,null,object,array
	public static final int S_IN_OBJECT=2;
	public static final int S_IN_ARRAY=3;
	public static final int S_PASSED_PAIR_KEY=4;
	public static final int S_IN_PAIR_VALUE=5;
	public static final int S_END=6;
	public static final int S_IN_ERROR=-1;
	
	private LinkedList handlerStatusStack;
	private Yylex lexer = new Yylex((Reader)null);
	private Yytoken token = null;
	private int status = S_INIT;
	
	private int peekStatus(LinkedList statusStack){
		if(statusStack.size()==0)
			return -1;
		Integer status=(Integer)statusStack.getFirst();
		return status.intValue();
	}
	
    /**
     *  Reset the parser to the initial state without resetting the underlying reader.
     *
     */
    public void reset(){
        token = null;
        status = S_INIT;
        handlerStatusStack = null;
    }
    
    /**
     * Reset the parser to the initial state with a new character reader.
     * 
     * @param in - The new character reader.
     * @throws IOException
     * @throws ParseException
     */
	public void reset(Reader in){
		lexer.yyreset(in);
		reset();
	}
	
	/**
	 * @return The position of the beginning of the current token.
	 */
	public int getPosition(){
		return lexer.getPosition();
	}
	
	public Object parse(String s) throws ParseException{
		return parse(s, (ContainerFactory)null);
	}
	
	public Object parse(String s, ContainerFactory containerFactory) throws ParseException{
		StringReader in=new StringReader(s);
		try{
			return parse(in, containerFactory);
		}
		catch(IOException ie){
			/*
			 * Actually it will never happen.
			 */
			throw new ParseException(-1, ParseException.ERROR_UNEXPECTED_EXCEPTION, ie);
		}
	}
	
	public Object parse(Reader in) throws IOException, ParseException{
		return parse(in, (ContainerFactory)null);
	}
	
	/**
	 * Parse JSON text into java object from the input source.
	 * 	
	 * @param in
     * @param containerFactory - Use this factory to create your own JSON object and JSON array containers.
	 * @return Instance of the following:
	 *  org.zkoss.json.JSONObject,
	 * 	org.zkoss.json.JSONArray,
	 * 	java.lang.String,
	 * 	java.lang.Number,
	 * 	java.lang.Boolean,
	 * 	null
	 * 
	 * @throws IOException
	 * @throws ParseException
	 */
	public Object parse(Reader in, ContainerFactory containerFactory) throws IOException, ParseException{
		reset(in);
		LinkedList statusStack = new LinkedList();
		LinkedList valueStack = new LinkedList();
		
		try{
			do{
				nextToken();
				switch(status){
				case S_INIT:
					switch(token.type){
					case Yytoken.TYPE_VALUE:
						status=S_IN_FINISHED_VALUE;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(token.value);
						break;
					case Yytoken.TYPE_LEFT_BRACE:
						status=S_IN_OBJECT;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(createObjectContainer(containerFactory));
						break;
					case Yytoken.TYPE_LEFT_SQUARE:
						status=S_IN_ARRAY;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(createArrayContainer(containerFactory));
						break;
					default:
						status=S_IN_ERROR;
					}//inner switch
					break;
					
				case S_IN_FINISHED_VALUE:
					if(token.type==Yytoken.TYPE_EOF)
						return valueStack.removeFirst();
					else
						throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token);
					
				case S_IN_OBJECT:
					switch(token.type){
					case Yytoken.TYPE_COMMA:
						break;
					case Yytoken.TYPE_VALUE:
						if(token.value instanceof String){
							String key=(String)token.value;
							valueStack.addFirst(key);
							status=S_PASSED_PAIR_KEY;
							statusStack.addFirst(new Integer(status));
						}
						else{
							status=S_IN_ERROR;
						}
						break;
					case Yytoken.TYPE_RIGHT_BRACE:
						if(valueStack.size()>1){
							statusStack.removeFirst();
							valueStack.removeFirst();
							status=peekStatus(statusStack);
						}
						else{
							status=S_IN_FINISHED_VALUE;
						}
						break;
					default:
						status=S_IN_ERROR;
						break;
					}//inner switch
					break;
					
				case S_PASSED_PAIR_KEY:
					switch(token.type){
					case Yytoken.TYPE_COLON:
						break;
					case Yytoken.TYPE_VALUE:
						statusStack.removeFirst();
						String key=(String)valueStack.removeFirst();
						Map parent=(Map)valueStack.getFirst();
						parent.put(key,token.value);
						status=peekStatus(statusStack);
						break;
					case Yytoken.TYPE_LEFT_SQUARE:
						statusStack.removeFirst();
						key=(String)valueStack.removeFirst();
						parent=(Map)valueStack.getFirst();
						List newArray=createArrayContainer(containerFactory);
						parent.put(key,newArray);
						status=S_IN_ARRAY;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(newArray);
						break;
					case Yytoken.TYPE_LEFT_BRACE:
						statusStack.removeFirst();
						key=(String)valueStack.removeFirst();
						parent=(Map)valueStack.getFirst();
						Map newObject=createObjectContainer(containerFactory);
						parent.put(key,newObject);
						status=S_IN_OBJECT;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(newObject);
						break;
					default:
						status=S_IN_ERROR;
					}
					break;
					
				case S_IN_ARRAY:
					switch(token.type){
					case Yytoken.TYPE_COMMA:
						break;
					case Yytoken.TYPE_VALUE:
						List val=(List)valueStack.getFirst();
						val.add(token.value);
						break;
					case Yytoken.TYPE_RIGHT_SQUARE:
						if(valueStack.size()>1){
							statusStack.removeFirst();
							valueStack.removeFirst();
							status=peekStatus(statusStack);
						}
						else{
							status=S_IN_FINISHED_VALUE;
						}
						break;
					case Yytoken.TYPE_LEFT_BRACE:
						val=(List)valueStack.getFirst();
						Map newObject=createObjectContainer(containerFactory);
						val.add(newObject);
						status=S_IN_OBJECT;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(newObject);
						break;
					case Yytoken.TYPE_LEFT_SQUARE:
						val=(List)valueStack.getFirst();
						List newArray=createArrayContainer(containerFactory);
						val.add(newArray);
						status=S_IN_ARRAY;
						statusStack.addFirst(new Integer(status));
						valueStack.addFirst(newArray);
						break;
					default:
						status=S_IN_ERROR;
					}//inner switch
					break;
				case S_IN_ERROR:
					throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token);
				}//switch
				if(status==S_IN_ERROR){
					throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token);
				}
			}while(token.type!=Yytoken.TYPE_EOF);
		}
		catch(IOException ie){
			throw ie;
		}
		
		throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token);
	}
	
	private void nextToken() throws ParseException, IOException{
		token = lexer.yylex();
		if(token == null)
			token = new Yytoken(Yytoken.TYPE_EOF, null);
	}
	
	private Map createObjectContainer(ContainerFactory containerFactory){
		if(containerFactory == null)
			return new JSONObject();
		Map m = containerFactory.createObjectContainer();
		
		if(m == null)
			return new JSONObject();
		return m;
	}
	
	private List createArrayContainer(ContainerFactory containerFactory){
		if(containerFactory == null)
			return new JSONArray();
		List l = containerFactory.creatArrayContainer();
		
		if(l == null)
			return new JSONArray();
		return l;
	}
}
