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YAML for Java 8 and above. Very similar to the JSON-P api.
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/**
 * Copyright (c) 2016-2024, Mihai Emil Andronache
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *  Redistributions in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 * Neither the name of the copyright holder nor the names of its
 *  contributors may be used to endorse or promote products derived from
 *  this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
package com.amihaiemil.eoyaml;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * Decorator over some YamlLines which makes sure that lines
 * which satisfy one of the given conditions are ignored from
 * iteration.
 * @author Mihai Andronache ([email protected])
 * @version $Id: 7aadc97f6a26fadd1c4b683e31a3004a527ec551 $
 * @since 4.2.0
 */
final class Skip implements YamlLines {

    /**
     * YamlLines.
     */
    private final YamlLines yamlLines;

    /**
     * If a YamlLine meets any of these conditions, it is skipped.
     */
    private final Condition[] conditions;

    /**
     * Ctor.
     * @param yamlLines The Yaml lines.
     * @param conditions Conditions.
     *  If a YamlLine meets any of these conditions, it is skipped.
     */
    Skip(final YamlLines yamlLines, final Condition... conditions) {
        this.yamlLines = yamlLines;
        this.conditions = conditions;
    }

    @Override
    public Iterator iterator() {
        Iterator iterator = this.yamlLines.iterator();
        if (iterator.hasNext()) {
            final List notSkipped = new ArrayList<>();
            YamlLine previous = new YamlLine.NullYamlLine();
            while (iterator.hasNext()) {
                boolean skip = false;
                final YamlLine next = iterator.next();
                final Skip.Line current = new Skip.Line(next, previous);
                previous = current;
                for(int idx = 0; idx < this.conditions.length; idx++) {
                    if(this.conditions[idx].isMet(current)) {
                        skip = true;
                        break;
                    }
                }
                if(!skip) {
                    notSkipped.add(current.unwrap());
                }
            }
            iterator = notSkipped.iterator();
        }
        return iterator;
    }

    @Override
    public YamlNode nextYamlNode(final YamlLine prev) {
        return this.yamlLines.nextYamlNode(prev);
    }

    /**
     * Condition that a YamlLine has to satisfy in order to be
     * skipped/ignored from iteration.
     * @author Mihai Andronache ([email protected])
     * @version $Id: 7aadc97f6a26fadd1c4b683e31a3004a527ec551 $
     * @since 4.2.0
     */
    interface Condition {

        /**
         * Is this condition met or not?
         * @param line YamlLine.
         * @return True or false.
         */
        boolean isMet(final YamlLine line);

    }

    /**
     * A wrapper line that keeps track of current and previous line.
     * 

     * It also can arbitrary store a line in order to be used as a reference
     * downstream when evaluating the current iteration line condition.
     * 

     * The current line is used as delegate for {@link YamlLine} API
     * and previous line is a {@link Line} in order to carry over the
     * "stored" state.
     * 

     * 

     * 

     * Used by {@link Skip#iterator()} to feed current line {@link Condition}.
     */
    static final class Line implements YamlLine {

        /**
         * Current line.
         */
        private final YamlLine current;

        /**
         * Previous line.
         */
        private final YamlLine previous;

        /**
         * Arbitrary stored line.
         */
        private YamlLine stored;

        /**
         * Ctor.
         * @param current Current line.
         * @param previous Previous line.
         */
        private Line(final YamlLine current, final YamlLine previous) {
            this.current = current;
            this.previous = previous;
            final YamlLine store;
            if (previous instanceof Line) {
                final Line prevLine = (Line) previous;
                store = prevLine.stored;
            } else {
                store = new NullYamlLine();
            }
            this.stored = store;
        }

        @Override
        public String value() {
            return this.current.value();
        }

        @Override
        public int number() {
            return this.current.number();
        }

        @Override
        public int indentation() {
            return this.current.indentation();
        }

        /**
         * Previous line. Usually a skip {@link Line}
         * @return YamlLine.
         */
        YamlLine getPrevious() {
            return this.previous;
        }

        /**
         * Stores a line.
         * @param line A {@link YamlLine}.
         */
        void store(final YamlLine line){
            this.stored = line;
        }

        /**
         * Get currently stored line.
         * @return YamlLine
         */
        YamlLine getStored() {
            return this.stored;
        }

        /**
         * Unwraps to current line.
         * @return YamlLine.
         */
        private YamlLine unwrap() {
            return this.current;
        }
    }
}