Flow 11 --- ML-DSA-87 Compact-JWS Sign / Verify (Non-Streaming)

/*
 * Copyright 2025 ANKATech Solutions Inc
 *
 * 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.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
package co.ankatech.ankasecure.sdk.examples;

import co.ankatech.ankasecure.sdk.AuthenticatedSdk;
import co.ankatech.ankasecure.sdk.model.GenerateKeySpec;
import co.ankatech.ankasecure.sdk.model.SignResult;
import co.ankatech.ankasecure.sdk.model.VerifySignatureResult;
import co.ankatech.ankasecure.sdk.util.FileIO;

import java.nio.file.Path;
import java.text.MessageFormat;
import java.util.Properties;

import static co.ankatech.ankasecure.sdk.examples.ExampleUtil.*;

/**
 * Scenario 11 — ML-DSA-87 Bulk Helpers (Compact JWS).
 *
 * <p>This scenario shows the <strong>non-streaming</strong> helper methods for
 * RFC&nbsp;7515 <em>Compact&nbsp;JWS</em> using an ML-DSA-87 key:</p>
 * <ol>
 *   <li>Generate an <code>ML-DSA-87</code> key.</li>
 *   <li>Sign a plaintext document.</li>
 *   <li>Export the key's public metadata.</li>
 *   <li>Verify the resulting JWS.</li>
 * </ol>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>Filesystem operations use {@link java.nio.file.Path}.</li>
 *   <li>UTF-8 encoding is enforced for deterministic behaviour.</li>
 *   <li>Temporary artefacts reside under <kbd>temp_files/</kbd>.</li>
 * </ul>
 *
 * <p><b>Thread-safety:</b> this class is stateless and immutable.</p>
 *
 * @author ANKATech Solutions Inc.
 * @since 3.0.0
 * @see ExampleUtil
 * @see AuthenticatedSdk
 */
public final class ExampleScenario11 {

    /** No instantiation &mdash; this class only exposes {@link #main(String[])}. */
    private ExampleScenario11() { }

    /**
     * Runs the ML-DSA-87 compact JWS sign/verify scenario.
     *
     * <p>Loads CLI properties, authenticates against ANKASecure&copy;,
     * and delegates to the scenario logic. On any unrecoverable error
     * the JVM terminates via
     * {@link ExampleUtil#fatal(String, Throwable)}.</p>
     *
     * @param args command-line arguments (ignored)
     */
    public static void main(final String[] args) {

        System.out.println("===== SCENARIO 11 START =====");
        System.out.println("""
                Purpose :
                  * Demonstrate Compact-JWS helpers with an ML-DSA-87 key
                Steps   :
                  1) Generate ML-DSA-87 key
                  2) Sign payload (compact JWS)
                  3) Export public metadata
                  4) Verify JWS and validate integrity
                --------------------------------------------------------------""");

        try {
            ensureTempDir(TEMP_DIR);

            Properties   props = loadProperties();
            AuthenticatedSdk sdk  = authenticate(props);

            runScenario(sdk);

        } catch (Exception ex) {
            fatal("Scenario 11 failed", ex);
        }

        System.out.println("===== SCENARIO 11 END =====");
    }

    /**
     * Executes the 4-step ML-DSA-87 sign/verify scenario.
     *
     * <ol>
     *   <li>Create document file.</li>
     *   <li>Generate ML-DSA-87 signing key.</li>
     *   <li>Sign document (compact JWS).</li>
     *   <li>Export metadata and verify signature.</li>
     * </ol>
     *
     * @param sdk an authenticated {@link AuthenticatedSdk} instance;
     *            must not be {@code null}
     * @throws Exception if any step fails
     */
    private static void runScenario(final AuthenticatedSdk sdk) throws Exception {

        Path docFile  = TEMP_DIR.resolve("scenario11_doc.txt");
        Path jwsFile  = TEMP_DIR.resolve("scenario11.jws");
        Path metaJson = TEMP_DIR.resolve("scenario11_keydata.json");

        /* 1 -- create document ---------------------------------------------- */
        FileIO.writeUtf8(docFile,
                "Scenario-11 - ML-DSA-87 non-streaming sign / verify demo.");
        System.out.println("[1] Document ready          -> " + docFile.toAbsolutePath());

        /* 2 -- generate ML-DSA-87 key -------------------------------------- */
        String kid = "sc11_dsa87_" + System.currentTimeMillis();
        sdk.generateKey(new GenerateKeySpec()
                .setKid(kid)
                .setKty("ML-DSA")
                .setAlg("ML-DSA-87"));
        System.out.println("[2] Key generated           -> kid = " + kid);

        /* 3 -- sign document (compact JWS) --------------------------------- */
        SignResult signMeta = sdk.signFile(kid, docFile, jwsFile);
        System.out.println("[3] JWS written             -> " + jwsFile.toAbsolutePath());
        printSignMeta(signMeta);

        /* 4 -- export key metadata ---------------------------------------- */
        FileIO.writeUtf8(metaJson, toJson(sdk.exportKey(kid)));
        System.out.println("[4] Metadata exported       -> " + metaJson.toAbsolutePath());

        /* 5 -- verify signature ------------------------------------------- */
        VerifySignatureResult verMeta = sdk.verifySignature(jwsFile);
        System.out.println(MessageFormat.format(
                "[5] Signature valid?        -> {0}", verMeta.isValid()));
        printVerifyMeta(verMeta);

        System.out.println(verMeta.isValid()
                ? "[6] SUCCESS - JWS verified."
                : "[6] FAILURE - verification failed.");
    }
}