/*

* Copyright (c) 2023-2026 Ronald Brill.

*

* 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

* https://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 org.htmlunit.csp.value;

import java.util.Locale;

import java.util.Optional;

import org.htmlunit.csp.Utils;

/**

* Represents a CSP nonce-source value, e.g. {@code 'nonce-abc123...'}.

* <p>

* A nonce-source consists of the keyword prefix {@code nonce-} followed by a

* Base64-encoded value, all enclosed in single quotes. The prefix is parsed

* case-insensitively, but the Base64 nonce value itself is case-sensitive.

* </p>

*

* @param base64ValuePart the Base64-encoded nonce value (case-sensitive)

* @see <a href="https://w3c.github.io/webappsec-csp/#grammardef-nonce-source">

* nonce-source grammar</a>

*/

public record Nonce(String base64ValuePart) {

/**

* Parses a nonce-source from its CSP string representation.

* <p>

* The input must be a single-quoted string of the form {@code 'nonce-<base64>'}.

* The prefix is matched case-insensitively; the Base64 portion is preserved as-is.

* </p>

*

* @param value the CSP nonce-source token (e.g. {@code 'nonce-abc123...'})

* @return an {@link Optional} containing the parsed {@link Nonce},

* or empty if the value does not match the nonce-source grammar

*/

public static Optional<Nonce> parseNonce(final String value) {

final String lowercaseValue = value.toLowerCase(Locale.ROOT);

if (lowercaseValue.startsWith("'nonce-") && lowercaseValue.endsWith("'")) {

final String nonce = value.substring(7, value.length() - 1);

if (Utils.IS_BASE64_VALUE.test(nonce)) {

// Note that nonces _are_ case-sensitive, even though the grammar is not

return Optional.of(new Nonce(nonce));

}

}

return Optional.empty();

}

/**

* Returns the CSP string representation of this nonce-source,

* e.g. {@code 'nonce-abc123...'}.

*

* @return the single-quoted nonce-source string

*/

@Override

public String toString() {

return "'nonce-" + base64ValuePart + "'";

}

}