/* Copyright 2002-2004 Elliotte Rusty Harold
   
   This library is free software; you can redistribute it and/or modify
   it under the terms of version 2.1 of the GNU Lesser General Public 
   License as published by the Free Software Foundation.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
   GNU Lesser General Public License for more details.
   
   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the 
   Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
   Boston, MA 02111-1307  USA
   
   You can contact Elliotte Rusty Harold by sending e-mail to
   elharo@metalab.unc.edu. Please include the word "XOM" in the
   subject line. The XOM home page is located at http://www.xom.nu/
*/

package nu.xom;

/**
 * <p>
 *  The generic superclass for all the
 *  checked exceptions thrown in XOM. The general
 *  principle followed is that anything that could
 *  plausibly be detected by testing such as 
 *  using spaces in an element name is a runtime exception.
 *  Exceptions that depend on environmental conditions,
 *  such as might occur when parsing an external file,
 *  are checked exceptions, because these depend on variable input,
 *  and thus problems may not all be detected during testing.
 * </p>
 * 
 * @author Elliotte Rusty Harold
 * @version 1.0b6
 *
 */
public class ParsingException extends Exception {

    
    private Throwable cause;
    private int lineNumber = -1;
    private int columnNumber = -1;
    private String uri;

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail message
     * and an underlying root cause.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param cause the original cause of this exception
     */
    public ParsingException(String message, Throwable cause) {
        super(message);
        this.initCause(cause);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail message
     * and an underlying root cause.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param uri the URI of the document that caused this exception
     * @param cause the original cause of this exception
     */
    public ParsingException(String message, String uri, Throwable cause) {
        super(message);
        this.uri = uri;
        this.initCause(cause);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail message
     * and line and column numbers.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param lineNumber the approximate line number 
     *     where the problem occurs
     * @param columnNumber the approximate column number 
     *     where the problem occurs
     */
    public ParsingException(String message, 
      int lineNumber, int columnNumber) {
        this(message, null, lineNumber, columnNumber, null);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail message
     * and line and column numbers.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param uri the URI of the document that caused this exception
     * @param lineNumber the approximate line number 
     *     where the problem occurs
     * @param columnNumber the approximate column number 
     *     where the problem occurs
     */
    public ParsingException(String message, String uri, 
      int lineNumber, int columnNumber) {
        this(message, uri, lineNumber, columnNumber, null);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail 
     * message, line and column numbers, and an underlying exception.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param uri the URI of the document that caused this exception
     * @param lineNumber the approximate line number 
     *     where the problem occurs
     * @param columnNumber the approximate column number 
     *     where the problem occurs
     * @param cause the original cause of this exception
     */
    public ParsingException(String message, String uri, int lineNumber,
      int columnNumber, Throwable cause) {
        super(message);
        this.lineNumber = lineNumber;
        this.columnNumber = columnNumber;
        this.uri = uri;
        this.initCause(cause);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail 
     * message, line and column numbers, and an underlying exception.
     * </p>
     * 
     * @param message a string indicating the specific problem
     * @param lineNumber the approximate line number 
     *     where the problem occurs
     * @param columnNumber the approximate column number 
     *     where the problem occurs
     * @param cause the original cause of this exception
     */
    public ParsingException(String message, int lineNumber,
      int columnNumber, Throwable cause) {
        super(message);
        this.lineNumber = lineNumber;
        this.columnNumber = columnNumber;
        this.initCause(cause);
    }

    
    /**
     * <p>
     * Creates a new <code>ParsingException</code> with a detail message.
     * </p>
     * 
     * @param message a string indicating the specific problem
     */
    public ParsingException(String message) {
        super(message);
    }
    
    
    /**
     * <p>
     * Returns the approximate row number of the construct that
     * caused this exception. If the row number is not known,
     * -1 is returned.
     * </p>
     * 
     * @return row number where the exception occurred
     */
    public int getLineNumber() {
        return this.lineNumber;  
    }

    /**
     * <p>
     * Returns the approximate column number of the construct that
     * caused this exception. If the column number is not known,
     * -1 is returned.
     * </p>
     * 
     * @return column number where the exception occurred
     */
    public int getColumnNumber() {
        return this.columnNumber;  
    }


    /**
     * <p>
     * Returns the system ID (generally a URL) of the document that
     * caused this exception. If this is not known, for instance 
     * because the document was parsed from a raw input stream or from
     * a string, it returns null. 
     * </p>
     * 
     * @return the URI of the document that caused this exception
     */
    public String getURI() {
        return this.uri;  
    }


    // null is insufficient for determining unset cause.
    // The cause may be set to null which may not then be reset.
    private boolean causeSet = false;

    /**
     * <p>
     * Sets the root cause of this exception. This may 
     * only be called once. Subsequent calls throw an 
     * <code>IllegalStateException</code>.
     * </p>
     * 
     * <p>
     * This method is unnecessary in Java 1.4 where it could easily be
     * inherited from the superclass. However, including it here
     * allows this  method to be used in Java 1.3 and earlier.
     * </p>
     *
     * @param cause the root cause of this exception
     * 
     * @return this <code>XMLException</code>
     * 
     * @throws IllegalArgumentException if the cause is this exception
     *   (An exception cannot be its own cause.)
     * @throws IllegalStateException if this method is called twice
     */
    public Throwable initCause(Throwable cause) {
        
        if (causeSet) {
            throw new IllegalStateException("Can't overwrite cause");
        } 
        else if (cause == this) {
            throw new IllegalArgumentException("Self-causation not permitted"); 
        }
        else this.cause = cause;
        causeSet = true;
        return this;
        
    }

    
    /**
     * <p>
     * Returns the underlying exception that caused this exception.
     * </p>
     * 
     * @return the root exception that caused this exception 
     *     to be thrown
     */
    public Throwable getCause() {
        return this.cause;  
    }

    
    /**
     * <p>
     * Returns a string suitable for display to the developer
     * summarizing what went wrong where.
     * </p>
     * 
     * @return an exception message suitable for display to a developer
     */
    public String toString() {
        return super.toString() + " at line " 
          + lineNumber + ", column " + columnNumber + ".";    
    }

    
}