/*
 * The contents of this file are subject to the terms of the Common Development and
 * Distribution License (the License). You may not use this file except in compliance with the
 * License.
 *
 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
 * specific language governing permission and limitations under the License.
 *
 * When distributing Covered Software, include this CDDL Header Notice in each file and include
 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Copyright 2008 Sun Microsystems, Inc.
 * Portions Copyright 2014-2015 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<>(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<>(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<>(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<>(Type.SUCCESS, new ArrayList<>(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 values.iterator().next();
        }
        return null;
    }

    /**
     * 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<>(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;
    }

    @Override
    public String toString() {
        return getClass().getSimpleName() + "(type=" + type + ", values=" + values + ")";
    }
}