package com.yahoo.dtf.config.transform;

import java.util.HashMap;

import com.yahoo.dtf.config.transform.Transformer;
import com.yahoo.dtf.config.transform.converters.Converter;
import com.yahoo.dtf.config.transform.converters.FromHexConverter;
import com.yahoo.dtf.config.transform.converters.ToHexConverter;
import com.yahoo.dtf.exception.ParseException;
import com.yahoo.dtf.util.StringUtil;

/**
 * @dtf.feature Convert Transformer
 * @dtf.feature.group Transformers
 * 
 * @dtf.feature.desc <p>
 *                   This is the DTF string conversion transformer and it can be 
 *                   used to convert between various formats such as hex to 
 *                   string and string to hex. In the currently available 
 *                   functions are:
 *                   </p>
 *                   <p> 
 *                   <b>to-hex([padding])</b><br/>
 *                   The to-hex function obviously converts an integer to a hex 
 *                   format. The padding argument is optional and if set will 
 *                   pad the resulting number with 0's on the left side.
 *                   </p>
 *                   <p>
 *                   <b>from-hex</b><br/>
 *                   The from-hex does the opposite of to-hex and converts a 
 *                   hexa-decimal number back to its decimal representation.
 *                   </p>
 *                   
 * @dtf.example
 * <sequence>
 *     <property name="int1" value="1234"/> 
 *     <property name="int2" value="42"/> 
 *
 *     <log>${int1:convert:to-hex}</log> 
 *     <log>${int2:convert:to-hex(4)}</log> 
 * </sequence>
 *
 * @dtf.example
 * <sequence>
 *     <property name="hex1" value="FFFF"/>
 *     <property name="hex2" value="FFFFFFFF"/>
 *     
 *     <log>${hex1:convert:from-hex}</log> 
 *     <log>${hex2:convert:from-hex}</log> 
 * </sequence>
 * 
 */
public class ConvertTransformer implements Transformer {
    
    private static HashMap<String, Converter> converters = 
                                               new HashMap<String, Converter>();
    
    static { 
        converters.put("to-hex", new ToHexConverter());
        converters.put("from-hex", new FromHexConverter());
    }
    
    public String apply(String data, String expression) throws ParseException {
        int bracketIndex = expression.indexOf('(');
        String operator = null;
        String result = null;
        int padding = 0;
        
        if ( bracketIndex != -1 ) {
            operator = expression.substring(0,bracketIndex);
            padding = Integer.valueOf(expression.substring(bracketIndex+1,
                                                           expression.length()-1));
        } else { 
            operator = expression;
        }
        
        Converter converter = converters.get(operator);

        if ( converter != null ) { 
            result = converter.convert(data);
           return "" + StringUtil.padString(result, padding, '0');
        } 
        
        throw new ParseException("Unkown convert expression [" + operator + "]");
    }
}