RandomSec/src/main/java/com/metaweb/gridworks/expr/JythonEvaluable.java

package com.metaweb.gridworks.expr;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Properties;

import org.python.core.PyException;
import org.python.core.PyNone;
import org.python.core.PyObject;
import org.python.core.PyString;
import org.python.util.PythonInterpreter;

public class JythonEvaluable implements Evaluable {
	private static final String s_functionName = "___temp___";
	
    private static PythonInterpreter _engine = new PythonInterpreter();

    public JythonEvaluable(String s) {
    	// indent and create a function out of the code
    	String[] lines = s.split("\r\n|\r|\n");
    	
    	StringBuffer sb = new StringBuffer();
    	sb.append("def " + s_functionName + "():");
    	for (int i = 0; i < lines.length; i++) {
    		sb.append("\n  " + lines[i]);    		
    	}
    	
        _engine.exec(sb.toString());
    }
    
	public Object evaluate(Properties bindings) {
		try {
		    for (Object key : bindings.keySet()) {
		        String k = (String) key;
				Object v = bindings.get(k);
				
				_engine.set(
				    k,
				    (v instanceof HasFields) ?
				        new JythonHasFieldsWrapper((HasFields) v, bindings) :
			            v
			    );
			}
			
			Object result = _engine.eval(s_functionName + "()");

			return unwrap(result);
		} catch (PyException e) {
			return new EvalError(e.toString());
		}
	}
	
	protected Object unwrap(Object result) {
        if (result != null) {
            if (result instanceof JythonObjectWrapper) {
                return ((JythonObjectWrapper) result)._obj;
            } else if (result instanceof JythonHasFieldsWrapper) {
                return ((JythonHasFieldsWrapper) result)._obj;
            } else if (result instanceof PyString) {
                return ((PyString) result).asString();
            } else if (result instanceof PyObject) {
                return unwrap((PyObject) result);
            }
        }
        
        return result;	    
	}
	
	protected Object unwrap(PyObject po) {
	    if (po instanceof PyNone) {
	        return null;
	    } else if (po.isNumberType()) {
            return po.asDouble();
        } else if (po.isSequenceType()) {
            Iterator<PyObject> i = po.asIterable().iterator();
            
            List<Object> list = new ArrayList<Object>();
            while (i.hasNext()) {
                list.add(unwrap(i.next()));
            }
            
            return list.toArray();
        } else {
            return po;
        }
	}
}