/*
 * Copyright 2009-2017 java-diff-utils.
 *
 * Licensed 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 com.github.difflib.algorithm.myers;

/**
 * A node in a diffpath.
 *
 * @author <a href="mailto:juanco@suigeneris.org">Juanco Anez</a>
 */
public final class PathNode {

    /**
     * Position in the original sequence.
     */
    public final int i;
    /**
     * Position in the revised sequence.
     */
    public final int j;
    /**
     * The previous node in the path.
     */
    public final PathNode prev;

    public final boolean snake;

    public final boolean bootstrap;

    /**
     * Concatenates a new path node with an existing diffpath.
     *
     * @param i The position in the original sequence for the new node.
     * @param j The position in the revised sequence for the new node.
     * @param prev The previous node in the path.
     */
    public PathNode(int i, int j, boolean snake, boolean bootstrap, PathNode prev) {
        this.i = i;
        this.j = j;
        this.bootstrap = bootstrap;
        if (snake) {
            this.prev = prev;
        } else {
            this.prev = prev == null ? null : prev.previousSnake();
        }
        this.snake = snake;
    }

    public boolean isSnake() {
        return snake;
    }

    /**
     * Is this a bootstrap node?
     * <p>
     * In bottstrap nodes one of the two corrdinates is less than zero.
     *
     * @return tru if this is a bootstrap node.
     */
    public boolean isBootstrap() {
        return bootstrap;
    }

    /**
     * Skips sequences of {@link PathNode PathNodes} until a snake or bootstrap node is found, or the end of the
     * path is reached.
     *
     * @return The next first {@link PathNode} or bootstrap node in the path, or <code>null</code> if none found.
     */
    public final PathNode previousSnake() {
        if (isBootstrap()) {
            return null;
        }
        if (!isSnake() && prev != null) {
            return prev.previousSnake();
        }
        return this;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        StringBuilder buf = new StringBuilder("[");
        PathNode node = this;
        while (node != null) {
            buf.append("(");
            buf.append(node.i);
            buf.append(",");
            buf.append(node.j);
            buf.append(")");
            node = node.prev;
        }
        buf.append("]");
        return buf.toString();
    }
}