/*
 * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.mdsal.eos.common.api;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMap.Builder;
import java.util.Map;

/**
 * Enumerates the ownership change states for an entity.
 *
 * @author Thomas Pantelis
 */
public enum EntityOwnershipChangeState {
    /**
     * The local process instance has been granted ownership.
     */
    LOCAL_OWNERSHIP_GRANTED(false, true, true),

    /**
     * The local process instance has lost ownership and another process instance is now the owner.
     */
    LOCAL_OWNERSHIP_LOST_NEW_OWNER(true, false, true),

    /**
     * The local process instance has lost ownership and there are no longer any candidates for the entity and
     * thus has no owner.
     */
    LOCAL_OWNERSHIP_LOST_NO_OWNER(true, false, false),

    /**
     * The local process instance ownership has not changed but some other aspect has changed (for example inJeopardy).
     */
    LOCAL_OWNERSHIP_RETAINED_WITH_NO_CHANGE(true, true, true),

    /**
     * Entity ownership has transitioned to another process instance and this instance was not the previous owner.
     */
    REMOTE_OWNERSHIP_CHANGED(false, false, true),

    /**
     * A remote process instance has lost ownership and there are no longer any candidates for the entity and
     * thus has no owner.
     */
    REMOTE_OWNERSHIP_LOST_NO_OWNER(false, false, false);

    private static final Map<Key, EntityOwnershipChangeState> BY_KEY;
    static {
        final Builder<Key, EntityOwnershipChangeState> builder = ImmutableMap.<Key, EntityOwnershipChangeState>builder();
        for(final EntityOwnershipChangeState e: values()) {
            builder.put(new Key(e.wasOwner, e.isOwner, e.hasOwner), e);
        }

        BY_KEY = builder.build();
    }

    private final boolean wasOwner;
    private final boolean isOwner;
    private final boolean hasOwner;

    private EntityOwnershipChangeState(final boolean wasOwner, final boolean isOwner, final boolean hasOwner) {
        this.wasOwner = wasOwner;
        this.isOwner = isOwner;
        this.hasOwner = hasOwner;
    }

    /**
     * Returns the previous ownership status of the entity for this process instance.
     * @return true if this process was the owner of the entity at the time this notification was generated
     */
    public boolean wasOwner() {
        return wasOwner;
    }

    /**
     * Returns the current ownership status of the entity for this process instance.
     * @return true if this process is now the owner of the entity
     */
    public boolean isOwner() {
        return isOwner;
    }

    /**
     * Returns the current ownership status of the entity across all process instances.
     * @return true if the entity has an owner which may or may not be this process. If false, then
     *         the entity has no candidates and thus no owner.
     */
    public boolean hasOwner() {
        return hasOwner;
    }

    @Override
    public String toString() {
        return name() + " [wasOwner=" + wasOwner + ", isOwner=" + isOwner + ", hasOwner=" + hasOwner + "]";
    }

    public static EntityOwnershipChangeState from(final boolean wasOwner, final boolean isOwner, final boolean hasOwner) {
        final EntityOwnershipChangeState state = BY_KEY.get(new Key(wasOwner, isOwner, hasOwner));
        Preconditions.checkArgument(state != null, "Invalid combination of wasOwner: %s, isOwner: %s, hasOwner: %s",
                wasOwner, isOwner, hasOwner);
        return state;
    }

    private static final class Key {
        private final boolean wasOwner;
        private final boolean isOwner;
        private final boolean hasOwner;

        Key(final boolean wasOwner, final boolean isOwner, final boolean hasOwner) {
            this.wasOwner = wasOwner;
            this.isOwner = isOwner;
            this.hasOwner = hasOwner;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + (hasOwner ? 1231 : 1237);
            result = prime * result + (isOwner ? 1231 : 1237);
            result = prime * result + (wasOwner ? 1231 : 1237);
            return result;
        }

        @Override
        public boolean equals(final Object obj) {
            final Key other = (Key) obj;
            return hasOwner == other.hasOwner && isOwner == other.isOwner && wasOwner == other.wasOwner;
        }
    }
}