StringJoinFunction.java

package com.googlecode.aviator.runtime.function.string;

import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Map;

import com.googlecode.aviator.exception.ExpressionRuntimeException;
import com.googlecode.aviator.runtime.function.AbstractFunction;
import com.googlecode.aviator.runtime.function.FunctionUtils;
import com.googlecode.aviator.runtime.type.AviatorObject;
import com.googlecode.aviator.runtime.type.AviatorString;


/**
 * string.join function
 * 
 * @author boyan
 * 
 */
public class StringJoinFunction extends AbstractFunction {
    public String getName() {
        return "string.join";
    }


    @Override
    public AviatorObject call(Map<String, Object> env, AviatorObject arg1) {
        Object target = arg1.getValue(env);
        if (target == null)
            throw new ExpressionRuntimeException("Could not replace with null string");
        return join(env, arg1, target, "");
    }


    @Override
    public AviatorObject call(Map<String, Object> env, AviatorObject arg1, AviatorObject arg2) {
        Object target = arg1.getValue(env);
        String split = FunctionUtils.getStringValue(arg2, env);
        if (target == null)
            throw new ExpressionRuntimeException("Could not replace with null string");
        return join(env, arg1, target, split);
    }


    private AviatorObject join(Map<String, Object> env, AviatorObject arg1, Object target, String split) {
        Class<?> clazz = target.getClass();

        StringBuffer sb = new StringBuffer(50);
        if (Collection.class.isAssignableFrom(clazz)) {
            boolean wasFirst = true;
            for (Object obj : (Collection<?>) target) {
                wasFirst = append(sb, split, wasFirst, obj);
            }
        }
        else if (clazz.isArray()) {
            int length = Array.getLength(target);
            boolean wasFirst=true;
            for (int i = 0; i < length; i++) {
                Object obj = Array.get(target, i);
                wasFirst = append(sb, split, wasFirst, obj);
            }
        }
        else {
            throw new IllegalArgumentException(arg1.desc(env) + " is not a seq");
        }
        return new AviatorString(sb.toString());
    }


    private boolean append(StringBuffer sb, String split, boolean wasFirst, Object obj) {
        String str = obj == null ? "null" : obj.toString();
        if (wasFirst) {
            sb.append(str);
            wasFirst = false;
        }
        else {
            sb.append(split).append(str);
        }
        return wasFirst;
    }

}