/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
 * or http://forgerock.org/license/CDDLv1.0.html.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at legal-notices/CDDLv1_0.txt.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Copyright 2008 Sun Microsystems, Inc.
 *      Portions Copyright 2014 ForgeRock AS
 */
package com.forgerock.opendj.cli;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

/**
 * The result of running a {@link Menu}. The result indicates to the
 * application how it should proceed:
 * <ul>
 * <li>{@link #again()} - the menu should be displayed again. A good
 * example of this is when a user chooses to view some help. Normally,
 * after the help is displayed, the user is allowed to select another
 * option
 * <li>{@link #cancel()} - the user chose to cancel any task
 * currently in progress and go back to the previous main menu if
 * applicable
 * <li>{@link #success()} - the user chose to apply any task
 * currently in progress and go back to the previous menu if
 * applicable. Any result values applicable to the chosen option can
 * be retrieved using {@link #getValue()} or {@link #getValues()}
 * <li>{@link #quit()} - the user chose to quit the application and
 * cancel all outstanding tasks.
 * </ul>
 *
 * @param <T>
 *            The type of result value(s) contained in success results. Use <code>Void</code> if success results should
 *            not contain values.
 */
public final class MenuResult<T> {

    /**
     * The type of result returned from the menu.
     */
    private static enum Type {
        /**
         * The user selected an option which did not return a result,
         * so the menu should be displayed again.
         */
        AGAIN,

        /**
         * The user did not select an option and instead
         * chose to cancel the current task.
         */
        CANCEL,

        /**
         * The user did not select an option and instead
         * chose to quit the entire application.
         */
        QUIT,

        /**
         * The user selected an option which succeeded
         * and returned one or more result values.
         */
        SUCCESS
    }

    /**
     * Creates a new menu result indicating that the menu should be displayed again. A good example of this is when a
     * user chooses to view some help. Normally, after the help is displayed, the user is allowed to select another
     * option.
     *
     * @param <T>
     *            The type of result value(s) contained in success results. Use <code>Void</code> if success results
     *            should not contain values.
     * @return Returns a new menu result indicating that the menu should be displayed again.
     */
    public static <T> MenuResult<T> again() {
        return new MenuResult<T>(Type.AGAIN, Collections.<T> emptyList());
    }

    /**
     * Creates a new menu result indicating that the user chose to cancel any task currently in progress and go back to
     * the previous main menu if applicable.
     *
     * @param <T>
     *            The type of result value(s) contained in success results. Use <code>Void</code> if success results
     *            should not contain values.
     * @return Returns a new menu result indicating that the user chose to cancel any task currently in progress and go
     *         back to the previous main menu if applicable.
     */
    public static <T> MenuResult<T> cancel() {
        return new MenuResult<T>(Type.CANCEL, Collections.<T> emptyList());
    }

    /**
     * Creates a new menu result indicating that the user chose to quit the application and cancel all outstanding
     * tasks.
     *
     * @param <T>
     *            The type of result value(s) contained in success results. Use <code>Void</code> if success results
     *            should not contain values.
     * @return Returns a new menu result indicating that the user chose to quit the application and cancel all
     *         outstanding tasks.
     */
    public static <T> MenuResult<T> quit() {
        return new MenuResult<T>(Type.QUIT, Collections.<T> emptyList());
    }

    /**
     * Creates a new menu result indicating that the user chose to apply any task currently in progress and go back to
     * the previous menu if applicable. The menu result will not contain any result values.
     *
     * @param <T>
     *            The type of result value(s) contained in success results. Use <code>Void</code> if success results
     *            should not contain values.
     * @return Returns a new menu result indicating that the user chose to apply any task currently in progress and go
     *         back to the previous menu if applicable.The menu result will not contain any result values.
     */
    public static <T> MenuResult<T> success() {
        return success(Collections.<T> emptySet());
    }

    /**
     * Creates a new menu result indicating that the user chose to apply any task currently in progress and go back to
     * the previous menu if applicable. The menu result will contain the provided values, which can be retrieved using
     * {@link #getValue()} or {@link #getValues()}.
     *
     * @param <T>
     *            The type of the result values.
     * @param values
     *            The result values.
     * @return Returns a new menu result indicating that the user chose to apply any task currently in progress and go
     *         back to the previous menu if applicable. The menu result will contain the provided values, which can be
     *         retrieved using {@link #getValue()} or {@link #getValues()}.
     */
    public static <T> MenuResult<T> success(Collection<T> values) {
        return new MenuResult<T>(Type.SUCCESS, new ArrayList<T>(values));
    }

    /**
     * Creates a new menu result indicating that the user chose to apply any task currently in progress and go back to
     * the previous menu if applicable. The menu result will contain the provided value, which can be retrieved using
     * {@link #getValue()} or {@link #getValues()}.
     *
     * @param <T>
     *            The type of the result value.
     * @param value
     *            The result value.
     * @return Returns a new menu result indicating that the user chose to apply any task currently in progress and go
     *         back to the previous menu if applicable. The menu result will contain the provided value, which can be
     *         retrieved using {@link #getValue()} or {@link #getValues()}.
     */
    public static <T> MenuResult<T> success(T value) {
        return success(Collections.singleton(value));
    }

    /** The type of result returned from the menu. */
    private final Type type;

    /** The menu result value(s). */
    private final Collection<T> values;

    /** Private constructor. */
    private MenuResult(Type type, Collection<T> values) {
        this.type = type;
        this.values = values;
    }

    /**
     * Gets the menu result value if this is a menu result indicating success.
     *
     * @return Returns the menu result value, or <code>null</code> if there was no result value or if this is not a
     *         success menu result.
     * @see #isSuccess()
     */
    public T getValue() {
        if (values.isEmpty()) {
            return null;
        } else {
            return values.iterator().next();
        }
    }

    /**
     * Gets the menu result values if this is a menu result indicating success.
     *
     * @return Returns the menu result values, which may be empty if there were no result values or if this is not a
     *         success menu result.
     * @see #isSuccess()
     */
    public Collection<T> getValues() {
        return new ArrayList<T>(values);
    }

    /**
     * Determines if this menu result indicates that the menu should be displayed again. A good example of this is when
     * a user chooses to view some help. Normally, after the help is displayed, the user is allowed to select another
     * option.
     *
     * @return Returns <code>true</code> if this menu result indicates that the menu should be displayed again.
     */
    public boolean isAgain() {
        return type == Type.AGAIN;
    }

    /**
     * Determines if this menu result indicates that the user chose to cancel any task currently in progress and go back
     * to the previous main menu if applicable.
     *
     * @return Returns <code>true</code> if this menu result indicates that the user chose to cancel any task currently
     *         in progress and go back to the previous main menu if applicable.
     */
    public boolean isCancel() {
        return type == Type.CANCEL;
    }

    /**
     * Determines if this menu result indicates that the user chose to quit the application and cancel all outstanding
     * tasks.
     *
     * @return Returns <code>true</code> if this menu result indicates that the user chose to quit the application and
     *         cancel all outstanding tasks.
     */
    public boolean isQuit() {
        return type == Type.QUIT;
    }

    /**
     * Determines if this menu result indicates that the user chose to apply any task currently in progress and go back
     * to the previous menu if applicable. Any result values can be retrieved using the {@link #getValue()} or
     * {@link #getValues()} methods.
     *
     * @return Returns <code>true</code> if this menu result indicates that the user chose to apply any task currently
     *         in progress and go back to the previous menu if applicable.
     * @see #getValue()
     * @see #getValues()
     */
    public boolean isSuccess() {
        return type == Type.SUCCESS;
    }
}