Checker.java

package org.aitools.programd.test.aiml;

import java.io.UnsupportedEncodingException;

import org.aitools.util.runtime.DeveloperError;
import org.aitools.util.xml.Characters;
import org.jdom.Element;

/**
 * Performs a specific test on a given input.
 * 
 * @author Albertas Mickensas
 */
abstract public class Checker {

  /** The string "{@value} ". */
  public static String TAG_EXPECTED_ANSWER = "ExpectedAnswer";

  /** The string "{@value} ". */
  public static String TAG_EXPECTED_KEYWORDS = "ExpectedKeywords";

  /** The string "{@value} ". */
  public static String TAG_EXPECTED_LENGTH = "ExpectedLength";

  /** The string "{@value} ". */
  public static String TAG_EXPECTED_MATCH = "ExpectedMatch";

  /** The string "{@value} ". */
  public static String TAG_ALERT_KEYWORDS = "AlertKeywords";

  /**
   * Creates a new Checker of the correct type based on the contents of the given XML element.
   * 
   * @param element the element from which to create the Input
   * @param encoding the encoding of the document from which this element comes
   * @return the created Input
   */
  public static Checker create(Element element, String encoding) {
    String tagName = element.getName();

    // Create the appropriate type of Checker.
    if (tagName.equals(TAG_ALERT_KEYWORDS)) {
      try {
        return new AlertKeywordChecker(
            new String(Characters.unescapeXMLChars(element.getText()).getBytes(encoding)).intern());
      }
      catch (UnsupportedEncodingException e) {
        throw new DeveloperError(String.format("Platform does not support \"%s\" encoding!", encoding), e);
      }
    }
    else if (tagName.equals(TAG_EXPECTED_ANSWER)) {
      return new AnswerChecker(element, encoding);
    }
    else if (tagName.equals(TAG_EXPECTED_KEYWORDS)) {
      try {
        return new ExpectedKeywordChecker(
            new String(Characters.unescapeXMLChars(element.getText()).getBytes(encoding)).intern());
      }
      catch (UnsupportedEncodingException e) {
        throw new DeveloperError(String.format("Platform does not support \"%s\" encoding!", encoding), e);
      }
    }
    else if (tagName.equals(TAG_EXPECTED_LENGTH)) {
      try {
        return new LengthChecker(new String(element.getText().getBytes(encoding)).intern());
      }
      catch (UnsupportedEncodingException e) {
        throw new DeveloperError(String.format("Platform does not support \"%s\" encoding!", encoding), e);
      }
    }
    else if (tagName.equals(TAG_EXPECTED_MATCH)) {
      try {
        return new MatchChecker(new String(Characters.unescapeXMLChars(element.getText()).getBytes(encoding)).intern());
      }
      catch (UnsupportedEncodingException e) {
        throw new DeveloperError(String.format("Platform does not support \"%s\" encoding!", encoding), e);
      }
    }
    else {
      throw new DeveloperError(String.format("Some invalid element (\"%s\") slipped past the schema!", tagName),
          new IllegalArgumentException());
    }
  }

  /**
   * A protected constructor, for use in persistence.
   */
  protected Checker() {
    // Do nothing.
  }

  /**
   * @return the textual content of the checker
   */
  abstract public String getContent();

  /**
   * @return the result expected by the checker, or a description of it
   */
  abstract public String getExpected();

  /**
   * @return the tag name that the checker uses
   */
  abstract public String getTagName();

  /**
   * Determines whether the given input passes the Checker's test.
   * 
   * @param input the input to test
   * @return whether the given input passes the Checker's test
   */
  abstract public boolean test(String input);
}