/*

 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.jshell;

import jdk.jshell.Snippet.Status;

/**

 * A description of a change to a Snippet. These are generated by direct changes

 * to state with {@link JShell#eval(java.lang.String) JShell.eval(String)} or

 * {@link JShell#drop(jdk.jshell.PersistentSnippet) JShell.drop(PersistentSnippet)},

 * or indirectly by these same methods as

 * dependencies change or Snippets are overwritten. For direct changes, the

 * {@link SnippetEvent#causeSnippet()} is <code>null</code>.

 * <p>

 * <code>SnippetEvent</code> is immutable: an access to

 * any of its methods will always return the same result.

 * and thus is thread-safe.

 * @author Robert Field

 */

public class SnippetEvent {

    SnippetEvent(Snippet snippet, Status previousStatus, Status status,

            boolean isSignatureChange, Snippet causeSnippet,

            String value, Exception exception) {

        this.snippet = snippet;

        this.previousStatus = previousStatus;

        this.status = status;

        this.isSignatureChange = isSignatureChange;

        this.causeSnippet = causeSnippet;

        this.value = value;

        this.exception = exception;

    }

    private final Snippet snippet;

    private final Status previousStatus;

    private final Status status;

    private final boolean isSignatureChange;

    private final Snippet causeSnippet;

    private final String value;

    private final Exception exception;

    /**

     * The Snippet which has changed

     * @return the return the Snippet whose <code>Status</code> has changed.

     */

    public Snippet snippet() {

        return snippet;

    }

    /**

     * The status before the transition. If this event describes a Snippet

     * creation return {@link Snippet.Status#NONEXISTENT NONEXISTENT}.

     * @return the previousStatus

     */

    public Status previousStatus() {

        return previousStatus;

    }

    /**

     * The after status. Note: this may be the same as the previous status (not

     * all changes cause a <code>Status</code> change.

     * @return the status

     */

    public Status status() {

        return status;

    }

    /**

     * Has the signature changed? Coming in or out of definition

     * (status.isDefined) is always a signature change. An overwritten Snippet

     * {@link jdk.jshell.Snippet.Status#OVERWRITTEN (status == OVERWRITTEN)}

     * is always <code>false</code> as responsibility for the

     * definition has passed to the overwriting definition.

     * @return <code>true</code> if the signature changed.

     */

    public boolean isSignatureChange() {

        return isSignatureChange;

    }

    /**

     * Either the snippet whose change caused this update or

     * <code>null</code>. This returns <code>null</code> if this change is the

     * creation of a new Snippet via

     * {@link jdk.jshell.JShell#eval(java.lang.String) eval} or it is the

     * explicit drop of a Snippet with

     * {@link jdk.jshell.JShell#drop(jdk.jshell.PersistentSnippet) drop}.

     *

     * @return the Snippet which caused this change or <code>null</code> if

     * directly caused by an API action.

     */

    public Snippet causeSnippet() {

        return causeSnippet;

    }

    /**

     * An instance of {@link jdk.jshell.UnresolvedReferenceException}, if an unresolved reference was

     * encountered, or an instance of {@link jdk.jshell.EvalException} if an exception was thrown

     * during execution, otherwise <code>null</code>.

     * @return the exception or <code>null</code>.

     */

    public Exception exception() {

        return exception;

    }

    /**

     * The result value of successful run. The value is null if not executed

     * or an exception was thrown.

     * @return the value or <code>null</code>.

     */

    public String value() {

        return value;

    }

    /**

     * Return a string representation of the event

     * @return a descriptive representation of the SnippetEvent

     */

    @Override

    public String toString() {

        return "SnippetEvent(snippet=" + snippet +

                ",previousStatus=" + previousStatus +

                ",status=" + status +

                ",isSignatureChange=" + isSignatureChange +

                ",causeSnippet" + causeSnippet +

                (value == null? "" : "value=" + value) +

                (exception == null? "" : "exception=" + exception) +

                ")";

    }

}