/* 
@VaadinApache2LicenseForJavaFiles@
 */

package com.vaadin.data;

import java.io.Serializable;

import com.vaadin.terminal.ErrorMessage;
import com.vaadin.terminal.PaintException;
import com.vaadin.terminal.PaintTarget;
import com.vaadin.terminal.gwt.server.AbstractApplicationServlet;

/**
 * Interface that implements a method for validating if an {@link Object} is
 * valid or not.
 * <p>
 * Implementors of this class can be added to any
 * {@link com.vaadin.data.Validatable Validatable} implementor to verify its
 * value.
 * </p>
 * <p>
 * {@link #isValid(Object)} and {@link #validate(Object)} can be used to check
 * if a value is valid. {@link #isValid(Object)} and {@link #validate(Object)}
 * must use the same validation logic so that iff {@link #isValid(Object)}
 * returns false, {@link #validate(Object)} throws an
 * {@link InvalidValueException}.
 * </p>
 * <p>
 * Validators must not have any side effects.
 * </p>
 * 
 * @author Vaadin Ltd.
 * @version
 * @VERSION@
 * @since 3.0
 */
public interface Validator extends Serializable {

    /**
     * Checks the given value against this validator. If the value is valid the
     * method does nothing. If the value is invalid, an
     * {@link InvalidValueException} is thrown.
     * 
     * @param value
     *            the value to check
     * @throws Validator.InvalidValueException
     *             if the value is invalid
     */
    public void validate(Object value) throws Validator.InvalidValueException;

    /**
     * Tests if the given value is valid. This method must be symmetric with
     * {@link #validate(Object)} so that {@link #validate(Object)} throws an
     * error iff this method returns false.
     * 
     * @param value
     *            the value to check
     * @return <code>true</code> if the value is valid, <code>false</code>
     *         otherwise.
     */
    public boolean isValid(Object value);

    /**
     * Exception that is thrown by a {@link Validator} when a value is invalid.
     * 
     * <p>
     * The default implementation of InvalidValueException does not support HTML
     * in error messages. To enable HTML support, override
     * {@link #getHtmlMessage()} and use the subclass in validators.
     * </p>
     * 
     * @author Vaadin Ltd.
     * @version
     * @VERSION@
     * @since 3.0
     */
    @SuppressWarnings("serial")
    public class InvalidValueException extends RuntimeException implements
            ErrorMessage {

        /**
         * Array of one or more validation errors that are causing this
         * validation error.
         */
        private InvalidValueException[] causes = null;

        /**
         * Constructs a new {@code InvalidValueException} with the specified
         * message.
         * 
         * @param message
         *            The detail message of the problem.
         */
        public InvalidValueException(String message) {
            this(message, new InvalidValueException[] {});
        }

        /**
         * Constructs a new {@code InvalidValueException} with a set of causing
         * validation exceptions. The causing validation exceptions are included
         * when the exception is painted to the client.
         * 
         * @param message
         *            The detail message of the problem.
         * @param causes
         *            One or more {@code InvalidValueException}s that caused
         *            this exception.
         */
        public InvalidValueException(String message,
                InvalidValueException[] causes) {
            super(message);
            if (causes == null) {
                throw new NullPointerException(
                        "Possible causes array must not be null");
            }

            this.causes = causes;
        }

        /**
         * Check if the error message should be hidden.
         * 
         * An empty (null or "") message is invisible unless it contains nested
         * exceptions that are visible.
         * 
         * @return true if the error message should be hidden, false otherwise
         */
        public boolean isInvisible() {
            String msg = getMessage();
            if (msg != null && msg.length() > 0) {
                return false;
            }
            if (causes != null) {
                for (int i = 0; i < causes.length; i++) {
                    if (!causes[i].isInvisible()) {
                        return false;
                    }
                }
            }
            return true;
        }

        /*
         * (non-Javadoc)
         * 
         * @see com.vaadin.terminal.ErrorMessage#getErrorLevel()
         */
        public final int getErrorLevel() {
            return ErrorMessage.ERROR;
        }

        /*
         * (non-Javadoc)
         * 
         * @see
         * com.vaadin.terminal.Paintable#paint(com.vaadin.terminal.PaintTarget)
         */
        public void paint(PaintTarget target) throws PaintException {
            target.startTag("error");
            target.addAttribute("level", "error");

            // Error message
            final String message = getHtmlMessage();
            if (message != null) {
                target.addText(message);
            }

            // Paint all the causes
            for (int i = 0; i < causes.length; i++) {
                causes[i].paint(target);
            }

            target.endTag("error");
        }

        /**
         * Returns the message of the error in HTML.
         * 
         * Note that this API may change in future versions.
         */
        protected String getHtmlMessage() {
            return AbstractApplicationServlet
                    .safeEscapeForHtml(getLocalizedMessage());
        }

        /*
         * (non-Javadoc)
         * 
         * @see
         * com.vaadin.terminal.ErrorMessage#addListener(com.vaadin.terminal.
         * Paintable.RepaintRequestListener)
         */
        public void addListener(RepaintRequestListener listener) {
        }

        /*
         * (non-Javadoc)
         * 
         * @see
         * com.vaadin.terminal.ErrorMessage#removeListener(com.vaadin.terminal
         * .Paintable.RepaintRequestListener)
         */
        public void removeListener(RepaintRequestListener listener) {
        }

        /*
         * (non-Javadoc)
         * 
         * @see com.vaadin.terminal.ErrorMessage#requestRepaint()
         */
        public void requestRepaint() {
        }

        /*
         * (non-Javadoc)
         * 
         * @see com.vaadin.terminal.Paintable#requestRepaintRequests()
         */
        public void requestRepaintRequests() {
        }

        /*
         * (non-Javadoc)
         * 
         * @see com.vaadin.terminal.Paintable#getDebugId()
         */
        public String getDebugId() {
            return null;
        }

        /*
         * (non-Javadoc)
         * 
         * @see com.vaadin.terminal.Paintable#setDebugId(java.lang.String)
         */
        public void setDebugId(String id) {
            throw new UnsupportedOperationException(
                    "InvalidValueException cannot have a debug id");
        }

        /**
         * Returns the {@code InvalidValueExceptions} that caused this
         * exception.
         * 
         * @return An array containing the {@code InvalidValueExceptions} that
         *         caused this exception. Returns an empty array if this
         *         exception was not caused by other exceptions.
         */
        public InvalidValueException[] getCauses() {
            return causes;
        }

    }

    /**
     * A specific type of {@link InvalidValueException} that indicates that
     * validation failed because the value was empty. What empty means is up to
     * the thrower.
     * 
     * @author Vaadin Ltd.
     * @version
     * @VERSION@
     * @since 5.3.0
     */
    @SuppressWarnings("serial")
    public class EmptyValueException extends Validator.InvalidValueException {

        public EmptyValueException(String message) {
            super(message);
        }

    }
}