/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.ignite.internal.network.direct.state;

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.function.Supplier;

/**
 * Message state.
 */
public class DirectMessageState<T extends DirectMessageStateItem> {
    /** Initial array size. */
    private static final int INIT_SIZE = 10;

    /** Item factory. */
    private final Supplier<T> factory;

    /** Stack array. */
    private T[] stack;

    /** Current position. */
    private int pos;

    /**
     * Constructor.
     *
     * @param cls     State item type.
     * @param factory Item factory.
     */
    public DirectMessageState(Class<T> cls, Supplier<T> factory) {
        this.factory = factory;

        stack = (T[]) Array.newInstance(cls, INIT_SIZE);

        stack[0] = factory.get();
    }

    /**
     * Returns current item.
     *
     * @return Current item.
     */
    public T item() {
        return stack[pos];
    }

    /**
     * Go forward.
     */
    public void forward() {
        pos++;

        if (pos == stack.length) {
            stack = Arrays.copyOf(stack, stack.length << 1);
        }

        if (stack[pos] == null) {
            stack[pos] = factory.get();
        }
    }

    /**
     * Go backward.
     *
     * @param reset Whether to reset current item.
     */
    public void backward(boolean reset) {
        if (reset) {
            stack[pos].reset();
        }

        pos--;
    }

    /**
     * Resets state.
     */
    public void reset() {
        assert pos == 0;

        stack[0].reset();
    }
}
