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/*
 * Copyright (c) 2024 Oracle and/or its affiliates.
 *
 * 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 io.helidon.build.maven.cache;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import io.helidon.build.common.xml.XMLElement;

import org.codehaus.plexus.util.xml.Xpp3Dom;

/**
 * Config support.
 */
class ConfigHelper {

    private ConfigHelper() {
        // cannot be instantiated
    }

    /**
     * Compute the path of an element.
     *
     * @param elt element
     * @return path
     */
    static String path(XMLElement elt) {
        return subpath(null, elt);
    }

    /**
     * Compute the path of an element.
     *
     * @param begin element
     * @param end   element
     * @return path
     */
    static String subpath(XMLElement begin, XMLElement end) {
        StringBuilder sb = new StringBuilder();
        XMLElement e = end;
        while (e != null && e != begin) {
            String segment = e.name();
            int index = index(e);
            if (index >= 0) {
                segment += "[" + index + "]";
            }
            if (e != end) {
                segment += "/";
            }
            sb.insert(0, segment);
            e = e.parent();
        }
        return sb.toString();
    }

    /**
     * Compute the index among the siblings with the same name.
     *
     * @param elt element
     * @return index, or {@code -1} if there are no siblings
     */
    static int index(XMLElement elt) {
        int count = 0;
        if (elt.parent() != null) {
            List elements = elt.parent().children(elt.name());
            if (elements.size() > 1) {
                for (XMLElement e : elements) {
                    if (e == elt) {
                        return count;
                    }
                    count++;
                }
            }
        }
        return -1;
    }

    /**
     * Convert an {@link Xpp3Dom} to {@link XMLElement}.
     *
     * @param elt element
     * @return XMLElement
     */
    static XMLElement toXMLElement(Xpp3Dom elt) {
        Xpp3Converter converter = new Xpp3Converter();
        Deque stack = new ArrayDeque<>();
        stack.push(elt);
        Xpp3Dom parent = elt.getParent();
        while (!stack.isEmpty()) {
            Xpp3Dom e = stack.peek();
            if (parent == e) {
                // leaving node
                parent = e.getParent();
                stack.pop();
                converter.postVisitElement();
            } else {
                converter.visitElement(e);
                parent = e;
                Xpp3Dom[] children = e.getChildren();
                for (int i = children.length - 1; i >= 0; i--) {
                    stack.push(children[i]);
                }
            }
        }
        return converter.stack.pop().build();
    }

    private static final class Xpp3Converter {

        private final Deque stack = new ArrayDeque<>();

        void visitElement(Xpp3Dom elt) {
            XMLElement.Builder builder = XMLElement.builder()
                    .modifiable(true)
                    .name(elt.getName())
                    .attributes(attributes(elt))
                    .value(elt.getValue());

            if (!stack.isEmpty()) {
                stack.peek().child(builder);
            }
            stack.push(builder);
        }

        void postVisitElement() {
            if (stack.size() > 1) {
                stack.pop();
            }
        }

        static Map attributes(Xpp3Dom elt) {
            Map attributes = new HashMap<>();
            for (String attrName : elt.getAttributeNames()) {
                attributes.put(attrName, elt.getAttribute(attrName));
            }
            return attributes;
        }
    }
}