AssertStatement.java

package calculator.interpreter.ast.logic;

import net.sf.etl.parsers.TermToken;
import net.sf.etl.parsers.beans.TokenCollector;
import calculator.interpreter.Cell;
import calculator.interpreter.Environment;
import calculator.interpreter.EvalException;
import calculator.interpreter.ast.Expression;
import calculator.interpreter.ast.Statement;

/**
 * The assert statement
 */
public class AssertStatement extends Statement implements TokenCollector {
  /** The condition to assert */
  public Expression condition;
  /** The message to use in case of assertion failure */
  public Expression message;
  /** The text of the assert statement */
  private StringBuilder textBuilder = new StringBuilder();
  /** The text of the condition */
  private String conditionText;

  @Override
  public Environment eval(Environment env, Cell result) {
    Object c = condition.eval(env);
    if (!(c instanceof Boolean)) {
      throw new EvalException(this, "The condition " + conditionText() + " at "
          + condition.location.toShortString()
          + " did not evaluated to the boolean: " + c);
    }
    if (!(Boolean) c) {
      throw new EvalException(this, "The assertion " + conditionText()
          + " failed" + (message == null ? "." : ": " + message.eval(env)));
    }
    return env;
  }

  /**
   * @return the text of condition
   */
  private String conditionText() {
    if (conditionText == null) {
      int start = (int) (condition.location.start().offset() - location.start()
          .offset());
      int end = (int) (condition.location.end().offset() - location.start()
          .offset());
      conditionText = textBuilder.substring(start, end);
      textBuilder = null;
    }
    return conditionText;
  }

  /** {@inheritDoc} */
  public void collect(TermToken token) {
    if (token.hasLexicalToken()) {
      textBuilder.append(token.token().token().text());
    }
  }
}