/*

 * Copyright (c) 2015, 2017, 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 sun.security.util;

import java.util.HashSet;

import java.util.Set;

import java.util.Arrays;

import java.util.Collection;

import java.util.regex.Pattern;

/**

 * The class decomposes standard algorithms into sub-elements.

 */

public class AlgorithmDecomposer {

    // '(?<!padd)in': match 'in' but not preceded with 'padd'.

    private static final Pattern PATTERN =

            Pattern.compile("with|and|(?<!padd)in", Pattern.CASE_INSENSITIVE);

    private static Set<String> decomposeImpl(String algorithm) {

        Set<String> elements = new HashSet<>();

        // algorithm/mode/padding

        String[] transTokens = algorithm.split("/");

        for (String transToken : transTokens) {

            if (transToken == null || transToken.isEmpty()) {

                continue;

            }

            // PBEWith<digest>And<encryption>

            // PBEWith<prf>And<encryption>

            // OAEPWith<digest>And<mgf>Padding

            // <digest>with<encryption>

            // <digest>with<encryption>and<mgf>

            // <digest>with<encryption>in<format>

            String[] tokens = PATTERN.split(transToken);

            for (String token : tokens) {

                if (token == null || token.isEmpty()) {

                    continue;

                }

                elements.add(token);

            }

        }

        return elements;

    }

    /**

     * Decompose the standard algorithm name into sub-elements.

     * <p>

     * For example, we need to decompose "SHA1WithRSA" into "SHA1" and "RSA"

     * so that we can check the "SHA1" and "RSA" algorithm constraints

     * separately.

     * <p>

     * Please override the method if need to support more name pattern.

     */

    public Set<String> decompose(String algorithm) {

            return new HashSet<>();

        }

        Set<String> elements = decomposeImpl(algorithm);

        // In Java standard algorithm name specification, for different

        // purpose, the SHA-1 and SHA-2 algorithm names are different. For

        // example, for MessageDigest, the standard name is "SHA-256", while

        // for Signature, the digest algorithm component is "SHA256" for

        // signature algorithm "SHA256withRSA". So we need to check both

        // "SHA-256" and "SHA256" to make the right constraint checking.

        // handle special name: SHA-1 and SHA1

        if (elements.contains("SHA1") && !elements.contains("SHA-1")) {

            elements.add("SHA-1");

        }

        if (elements.contains("SHA-1") && !elements.contains("SHA1")) {

            elements.add("SHA1");

        }

        // handle special name: SHA-224 and SHA224

        if (elements.contains("SHA224") && !elements.contains("SHA-224")) {

            elements.add("SHA-224");

        }

        if (elements.contains("SHA-224") && !elements.contains("SHA224")) {

            elements.add("SHA224");

        }

        // handle special name: SHA-256 and SHA256

        if (elements.contains("SHA256") && !elements.contains("SHA-256")) {

            elements.add("SHA-256");

        }

        if (elements.contains("SHA-256") && !elements.contains("SHA256")) {

            elements.add("SHA256");

        }

        // handle special name: SHA-384 and SHA384

        if (elements.contains("SHA384") && !elements.contains("SHA-384")) {

            elements.add("SHA-384");

        }

        if (elements.contains("SHA-384") && !elements.contains("SHA384")) {

            elements.add("SHA384");

        }

        // handle special name: SHA-512 and SHA512

        if (elements.contains("SHA512") && !elements.contains("SHA-512")) {

            elements.add("SHA-512");

        }

        if (elements.contains("SHA-512") && !elements.contains("SHA512")) {

            elements.add("SHA512");

        }

        return elements;

    }

    /**

     * Get aliases of the specified algorithm.

     *

     * May support more algorithms in the future.

     */

    public static Collection<String> getAliases(String algorithm) {

        String[] aliases;

        if (algorithm.equalsIgnoreCase("DH") ||

                algorithm.equalsIgnoreCase("DiffieHellman")) {

            aliases = new String[] {"DH", "DiffieHellman"};

        } else {

            aliases = new String[] {algorithm};

        }

        return Arrays.asList(aliases);

    }

    private static void hasLoop(Set<String> elements, String find, String replace) {

        if (elements.contains(find)) {

            if (!elements.contains(replace)) {

                elements.add(replace);

            }

            elements.remove(find);

        }

    }

    /*

     * This decomposes a standard name into sub-elements with a consistent

     * message digest algorithm name to avoid overly complicated checking.

     */

    public static Set<String> decomposeOneHash(String algorithm) {

            return new HashSet<>();

        }

        Set<String> elements = decomposeImpl(algorithm);

        hasLoop(elements, "SHA-1", "SHA1");

        hasLoop(elements, "SHA-224", "SHA224");

        hasLoop(elements, "SHA-256", "SHA256");

        hasLoop(elements, "SHA-384", "SHA384");

        hasLoop(elements, "SHA-512", "SHA512");

        return elements;

    }

    /*

     * The provided message digest algorithm name will return a consistent

     * naming scheme.

     */

    public static String hashName(String algorithm) {

        return algorithm.replace("-", "");

    }

}