/*

 * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.javadoc.internal.doclets.toolkit.util;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

/**

 * Abstraction for immutable relative paths.

 * Paths always use '/' as a separator, and never begin or end with '/'.

 *

 *  <p><b>This is NOT part of any supported API.

 *  If you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class DocPath {

    private final String path;

    /** The empty path. */

    public static final DocPath empty = new DocPath("");

    /** The empty path. */

    public static final DocPath parent = new DocPath("..");

    /**

     * Creates a path from a string.

     * @param p the string

     * @return the path

     */

    public static DocPath create(String p) {

        return (p == null) || p.isEmpty() ? empty : new DocPath(p);

    }

    protected DocPath(String p) {

        path = (p.endsWith("/") ? p.substring(0, p.length() - 1) : p);

    }

    /** {@inheritDoc} */

    @Override

    public boolean equals(Object other) {

        return (other instanceof DocPath) && path.equals(((DocPath)other).path);

    }

    /** {@inheritDoc} */

    @Override

    public int hashCode() {

        return path.hashCode();

    }

    public DocPath basename() {

        int sep = path.lastIndexOf("/");

        return (sep == -1) ? this : new DocPath(path.substring(sep + 1));

    }

    public DocPath parent() {

        int sep = path.lastIndexOf("/");

        return (sep == -1) ? empty : new DocPath(path.substring(0, sep));

    }

    /**

     * Returns the path formed by appending the specified string to the current path.

     * @param p the string

     * @return the path

     */

    public DocPath resolve(String p) {

        if (p == null || p.isEmpty())

            return this;

        if (path.isEmpty())

            return new DocPath(p);

        return new DocPath(path + "/" + p);

    }

    /**

     * Returns the path by appending the specified path to the current path.

     * @param p the path

     * @return the path

     */

    public DocPath resolve(DocPath p) {

        if (p == null || p.isEmpty())

            return this;

        if (path.isEmpty())

            return p;

        return new DocPath(path + "/" + p.getPath());

    }

    /**

     * Return the inverse path for this path.

     * For example, if the path is a/b/c, the inverse path is ../../..

     * @return the path

     */

    public DocPath invert() {

        return new DocPath(path.replaceAll("[^/]+", ".."));

    }

    /**

     * Returns the path formed by eliminating empty components,

     * '.' components, and redundant name/.. components.

     * @return the path

     */

    public DocPath normalize() {

        return path.isEmpty()

                ? this

                : new DocPath(String.join("/", normalize(path)));

    }

    private static List<String> normalize(String path) {

        return normalize(Arrays.asList(path.split("/")));

    }

    private static List<String> normalize(List<String> parts) {

        if (parts.stream().noneMatch(s -> s.isEmpty() || s.equals(".") || s.equals(".."))) {

            return parts;

        }

        List<String> normalized = new ArrayList<>();

        for (String part : parts) {

            switch (part) {

                case "":

                case ".":

                    break;

                case "..":

                    int n = normalized.size();

                    if (n > 0 && !normalized.get(n - 1).equals("..")) {

                        normalized.remove(n - 1);

                    } else {

                        normalized.add(part);

                    }

                    break;

                default:

                    normalized.add(part);

            }

        }

        return normalized;

    }

    /**

     * Normalize and relativize a path against this path,

     * assuming that this path is for a file (not a directory),

     * in which the other path will appear.

     *

     * @param other the path to be relativized.

     * @return the simplified path

     */

    public DocPath relativize(DocPath other) {

        if (other == null || other.path.isEmpty()) {

            return this;

        }

        if (path.isEmpty()) {

            return other;

        }

        List<String> originParts = normalize(path);

        int sep = path.lastIndexOf("/");

        List<String> destParts = sep == -1

                ? normalize(other.path)

                : normalize(path.substring(0, sep + 1) + other.path);

        int common = 0;

        while (common < originParts.size()

                && common < destParts.size()

                && originParts.get(common).equals(destParts.get(common))) {

            common++;

        }

        List<String> newParts;

        if (common == originParts.size()) {

            newParts = destParts.subList(common, destParts.size());

        } else {

            newParts = new ArrayList<>();

            newParts.addAll(Collections.nCopies(originParts.size() - common - 1, ".."));

            newParts.addAll(destParts.subList(common, destParts.size()));

        }

        return new DocPath(String.join("/", newParts));

    }

    /**

     * Return true if this path is empty.

     * @return true if this path is empty

     */

    public boolean isEmpty() {

        return path.isEmpty();

    }

    /**

     * Creates a DocLink formed from this path and a fragment identifier.

     * @param fragment the fragment

     * @return the link

     */

    public DocLink fragment(String fragment) {

        return new DocLink(path, null, fragment);

    }

    /**

     * Creates a DocLink formed from this path and a query string.

     * @param query the query string

     * @return the link

     */

    public DocLink query(String query) {

        return new DocLink(path, query, null);

    }

    /**

     * Returns this path as a string.

     * @return the path

     */

    // This is provided instead of using toString() to help catch

    // unintended use of toString() in string concatenation sequences.

    public String getPath() {

        return path;

    }

}