Flow 6 – ML-DSA-87 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.
 */

package co.ankatech.ankasecure.sdk.examples;

import co.ankatech.ankasecure.sdk.AuthenticatedSdk;
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 6 — ML-DSA-87 Bulk Helpers (Compact JWS).
 *
 * <p>This scenario signs and verifies a document with <strong>non-streaming</strong>
 * helpers that operate on RFC&nbsp;7515 <em>Compact&nbsp;JWS</em> tokens:</p>
 * <ol>
 *   <li>Resolve a pre-provisioned <code>ML-DSA-87</code> key from the demo
 *       playground (the SDK is data-plane-only — it does not create keys).</li>
 *   <li>Create a Compact JWS on disk via {@link AuthenticatedSdk#signFileCompact(String, Path, Path)}.</li>
 *   <li>Verify it via {@link AuthenticatedSdk#verifySignature(Path)}.</li>
 *   <li>Print server metadata and validate integrity.</li>
 * </ol>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>Filesystem interactions rely on the {@link java.nio.file.Path} API.</li>
 *   <li>UTF-8 is enforced explicitly for deterministic encoding.</li>
 *   <li>Temporary artefacts reside under <kbd>temp_files/</kbd>.</li>
 * </ul>
 *
 * <p><b>Thread-safety:</b> this class is stateless and immutable.</p>
 *
 * @see ExampleUtil
 * @see ExamplePlaygroundKeys
 * @see AuthenticatedSdk
 */
public final class ExampleScenario6 {

    /** No instantiation &mdash; this class only exposes {@link #main(String[])}. */
    private ExampleScenario6() { }

    /**
     * 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 6 START =====");
        System.out.println("""
                Purpose :
                  * ML-DSA-87 compact-JWS sign / verify helpers
                  * Non-streaming - token handled as text
                  * Operates on a pre-provisioned playground key
                Steps   :
                  1) Resolve pre-provisioned ML-DSA-87 key
                  2) Sign payload (compact JWS)
                  3) Verify signature
                  4) Validate integrity
                --------------------------------------------------------------""");

        try {
            prepareWorkingDir();

            Properties            props      = loadProperties();
            AuthenticatedSdk      sdk        = authenticate(props);
            ExamplePlaygroundKeys playground = ExamplePlaygroundKeys.from(props, sdk);

            runScenario(sdk, playground);

        } catch (Exception ex) {
            fatal("Scenario 6 failed", ex);
        }

        System.out.println("===== SCENARIO 6 END =====");
    }

    /**
     * Executes the ML-DSA-87 sign/verify scenario on a pre-provisioned key.
     *
     * <ol>
     *   <li>Prepare document file.</li>
     *   <li>Resolve a pre-provisioned ML-DSA-87 signing key.</li>
     *   <li>Sign document (compact JWS).</li>
     *   <li>Verify signature and report result.</li>
     * </ol>
     *
     * @param sdk        an authenticated {@link AuthenticatedSdk} instance; must not be {@code null}
     * @param playground the pre-provisioned playground key resolver; must not be {@code null}
     * @throws Exception if any step fails
     */
    private static void runScenario(final AuthenticatedSdk sdk,
                                    final ExamplePlaygroundKeys playground) throws Exception {

        /* 1 -- prepare document --------------------------------------------- */
        Path doc = TEMP_DIR.resolve("scenario6_doc.txt");
        FileIO.writeUtf8(doc,
                "Scenario-6 - ML-DSA-87 compact-JWS sign / verify demo.");
        System.out.println("[1] Document ready          -> " + doc.toAbsolutePath());

        /* 2 -- resolve pre-provisioned key (data-plane SDK: no key creation) */
        final String kid = playground.kidForAlgorithm("ML-DSA-87");
        System.out.println("[2] Using pre-provisioned key -> kid = " + kid);

        /* 3 -- sign (compact JWS) ------------------------------------------- */
        Path jwsFile = TEMP_DIR.resolve("scenario6.jws");
        SignResult signMeta = sdk.signFileCompact(kid, doc, jwsFile);
        System.out.println("[3] JWS written              -> " + jwsFile.toAbsolutePath());
        printSignMeta(signMeta);

        /* 4 -- verify ------------------------------------------------------- */
        VerifySignatureResult verMeta = sdk.verifySignature(jwsFile);
        System.out.println(MessageFormat.format(
                "[4] Signature valid?        : {0}", verMeta.isValid()));
        printVerifyMeta(verMeta);

        System.out.println(verMeta.isValid()
                ? "[5] SUCCESS - signature verified."
                : "[5] FAILURE - signature invalid.");
    }
}