
package epi.test_framework.minimal_json;

/**
 * A handler for parser events. Instances of this class can be given to a {@link
 * JsonParser}. The
 * parser will then call the methods of the given handler while reading the
 * input.
 * <p>
 * The default implementations of these methods do nothing. Subclasses may
 * override only those
 * methods they are interested in. They can use <code>getLocation()</code> to
 * access the current
 * character position of the parser at any point. The <code>start*</code>
 * methods will be called
 * while the location points to the first character of the parsed element. The
 * <code>end*</code>
 * methods will be called while the location points to the character position
 * that directly follows
 * the last character of the parsed element. Example:
 * </p>
 *
 * <pre>
 * ["lorem ipsum"]
 *  ^            ^
 *  startString  endString
 * </pre>
 * <p>
 * Subclasses that build an object representation of the parsed JSON can return
 * arbitrary handler
 * objects for JSON arrays and JSON objects in {@link #startArray()} and {@link
 * #startObject()}.
 * These handler objects will then be provided in all subsequent parser events
 * for this particular
 * array or object. They can be used to keep track the elements of a JSON array
 * or object.
 * </p>
 *
 * @param <A>
 *          The type of handlers used for JSON arrays
 * @param <O>
 *          The type of handlers used for JSON objects
 * @see JsonParser
 */
abstract class JsonHandler<A, O> {
  JsonParser parser;

  /**
   * Returns the current parser location.
   *
   * @return the current parser location
   */
  protected Location getLocation() { return parser.getLocation(); }

  /**
   * Indicates the beginning of a <code>null</code> literal in the JSON input.
   * This method will be
   * called when reading the first character of the literal.
   */
  public void startNull() {}

  /**
   * Indicates the end of a <code>null</code> literal in the JSON input. This
   * method will be called
   * after reading the last character of the literal.
   */
  public void endNull() {}

  /**
   * Indicates the beginning of a boolean literal (<code>true</code> or
   * <code>false</code>) in the
   * JSON input. This method will be called when reading the first character of
   * the literal.
   */
  public void startBoolean() {}

  /**
   * Indicates the end of a boolean literal (<code>true</code> or
   * <code>false</code>) in the JSON
   * input. This method will be called after reading the last character of the
   * literal.
   *
   * @param value
   *          the parsed boolean value
   */
  public void endBoolean(boolean value) {}

  /**
   * Indicates the beginning of a string in the JSON input. This method will be
   * called when reading
   * the opening double quote character (<code>'&quot;'</code>).
   */
  public void startString() {}

  /**
   * Indicates the end of a string in the JSON input. This method will be called
   * after reading the
   * closing double quote character (<code>'&quot;'</code>).
   *
   * @param string
   *          the parsed string
   */
  public void endString(String string) {}

  /**
   * Indicates the beginning of a number in the JSON input. This method will be
   * called when reading
   * the first character of the number.
   */
  public void startNumber() {}

  /**
   * Indicates the end of a number in the JSON input. This method will be called
   * after reading the
   * last character of the number.
   *
   * @param string
   *          the parsed number string
   */
  public void endNumber(String string) {}

  /**
   * Indicates the beginning of an array in the JSON input. This method will be
   * called when reading
   * the opening square bracket character (<code>'['</code>).
   * <p>
   * This method may return an object to handle subsequent parser events for
   * this array. This array
   * handler will then be provided in all calls to {@link
   * #startArrayValue(Object)
   * startArrayValue()}, {@link #endArrayValue(Object) endArrayValue()}, and
   * {@link #endArray(Object) endArray()} for this array.
   * </p>
   *
   * @return a handler for this array, or <code>null</code> if not needed
   */
  public A startArray() { return null; }

  /**
   * Indicates the end of an array in the JSON input. This method will be called
   * after reading the
   * closing square bracket character (<code>']'</code>).
   *
   * @param array
   *          the array handler returned from {@link #startArray()}, or
   * <code>null</code> if not
   *          provided
   */
  public void endArray(A array) {}

  /**
   * Indicates the beginning of an array element in the JSON input. This method
   * will be called when
   * reading the first character of the element, just before the call to the
   * <code>start</code>
   * method for the specific element type ({@link #startString()}, {@link
   * #startNumber()}, etc.).
   *
   * @param array
   *          the array handler returned from {@link #startArray()}, or
   * <code>null</code> if not
   *          provided
   */
  public void startArrayValue(A array) {}

  /**
   * Indicates the end of an array element in the JSON input. This method will
   * be called after
   * reading the last character of the element value, just after the
   * <code>end</code> method for the
   * specific element type (like {@link #endString(String) endString()}, {@link
   * #endNumber(String)
   * endNumber()}, etc.).
   *
   * @param array
   *          the array handler returned from {@link #startArray()}, or
   * <code>null</code> if not
   *          provided
   */
  public void endArrayValue(A array) {}

  /**
   * Indicates the beginning of an object in the JSON input. This method will be
   * called when reading
   * the opening curly bracket character (<code>'{'</code>).
   * <p>
   * This method may return an object to handle subsequent parser events for
   * this object. This
   * object handler will be provided in all calls to {@link
   * #startObjectName(Object)
   * startObjectName()}, {@link #endObjectName(Object, String) endObjectName()},
   * {@link #startObjectValue(Object, String) startObjectValue()},
   * {@link #endObjectValue(Object, String) endObjectValue()}, and {@link
   * #endObject(Object)
   * endObject()} for this object.
   * </p>
   *
   * @return a handler for this object, or <code>null</code> if not needed
   */
  public O startObject() { return null; }

  /**
   * Indicates the end of an object in the JSON input. This method will be
   * called after reading the
   * closing curly bracket character (<code>'}'</code>).
   *
   * @param object
   *          the object handler returned from {@link #startObject()}, or null
   * if not provided
   */
  public void endObject(O object) {}

  /**
   * Indicates the beginning of the name of an object member in the JSON input.
   * This method will be
   * called when reading the opening quote character ('&quot;') of the member
   * name.
   *
   * @param object
   *          the object handler returned from {@link #startObject()}, or
   * <code>null</code> if not
   *          provided
   */
  public void startObjectName(O object) {}

  /**
   * Indicates the end of an object member name in the JSON input. This method
   * will be called after
   * reading the closing quote character (<code>'"'</code>) of the member name.
   *
   * @param object
   *          the object handler returned from {@link #startObject()}, or null
   * if not provided
   * @param name
   *          the parsed member name
   */
  public void endObjectName(O object, String name) {}

  /**
   * Indicates the beginning of the name of an object member in the JSON input.
   * This method will be
   * called when reading the opening quote character ('&quot;') of the member
   * name.
   *
   * @param object
   *          the object handler returned from {@link #startObject()}, or
   * <code>null</code> if not
   *          provided
   * @param name
   *          the member name
   */
  public void startObjectValue(O object, String name) {}

  /**
   * Indicates the end of an object member value in the JSON input. This method
   * will be called after
   * reading the last character of the member value, just after the
   * <code>end</code> method for the
   * specific member type (like {@link #endString(String) endString()}, {@link
   * #endNumber(String)
   * endNumber()}, etc.).
   *
   * @param object
   *          the object handler returned from {@link #startObject()}, or null
   * if not provided
   * @param name
   *          the parsed member name
   */
  public void endObjectValue(O object, String name) {}
}
