package nodebox.node;

public class StampExpression {

private Parameter parameter;

private String stampKey;

private Expression expression;

/**

* Create a new stamp expression. The stamp expression should be set as the value of the given parameter,

* in the format "width = CNUM * 5"

*

* @param node the node this expression operates on.

* @param parameterName the name of the parameter for this expression.

*/

public StampExpression(Node node, String parameterName) {

if (!node.hasParameter(parameterName)) {

throw new IllegalArgumentException("The node \"" + node.getName() + "\" has no parameter \"" + parameterName + "\".");

}

parameter = node.getParameter(parameterName);

String stampExpression = parameter.asString();

if (stampExpression.trim().length() == 0) return;

// Split the stamp expression into the key and the actual expression.

int equalsPos = stampExpression.indexOf('=');

if (equalsPos < 0) {

throw new IllegalArgumentException("The stamp expression \"" + stampExpression + "\" is not in the format \"width = CNUM * 5\"");

}

stampKey = stampExpression.substring(0, equalsPos);

String expressionString = stampExpression.substring(equalsPos + 1);

// Convert the expression string to an Expression object.

expression = new Expression(parameter, expressionString);

}

public Parameter getParameter() {

return parameter;

}

public String getStampKey() {

return stampKey;

}

public Expression getExpression() {

return expression;

}

/**

* Evaluate the expression and store the result under the stamp expression key.

*

* @param context the current processing context

* @throws ExpressionError if an error occurs in the expression

*/

public void evaluate(ProcessingContext context) throws ExpressionError {

if (expression == null) return;

Object result = expression.evaluate(context);

context.put(stampKey, result);

}

}