Flow 1 – ML-KEM-512 Stream Encrypt / Decrypt (Detached JWET)

/*
 * 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.DecryptResultMetadata;
import co.ankatech.ankasecure.sdk.model.EncryptResult;
import co.ankatech.ankasecure.sdk.model.ExportedKeySpec;
import co.ankatech.ankasecure.sdk.model.GenerateKeySpec;
import co.ankatech.ankasecure.sdk.util.FileIO;
import java.nio.file.Path;
import java.util.Properties;

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

/**
 * Scenario 1 — End-to-End ML-KEM-512 Life-cycle (Streaming).
 *
 * <p>This scenario walks through a complete post-quantum key life-cycle using
 * the <strong>streaming</strong> endpoints of ANKASecure&copy;. In streaming mode the
 * service produces a <em>detached&nbsp;JWE</em> (General-JSON header + raw
 * ciphertext stream) instead of a single compact JWE string.</p>
 *
 * <ol>
 *   <li>Generate an <code>ML-KEM-512</code> key-pair.</li>
 *   <li>Export its public metadata to JSON.</li>
 *   <li>Stream-encrypt a local file (detached JWE).</li>
 *   <li>Stream-decrypt the ciphertext.</li>
 *   <li>Validate round-trip integrity.</li>
 * </ol>
 *
 * <p><strong>Prerequisite:</strong> a valid access-token must be present in the
 * CLI configuration.</p>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>All file handling relies on the {@link java.nio.file.Path} API.</li>
 *   <li>UTF-8 is enforced explicitly to avoid platform-dependent defaults.</li>
 *   <li>Temporary artefacts are written under <kbd>temp_files/</kbd>.</li>
 * </ul>
 *
 * <p><b>Thread-safety:</b> the class is stateless and immutable; a fresh
 * {@link AuthenticatedSdk} instance is created inside {@link #main(String[])}.</p>
 *
 * @author ANKATech Solutions Inc.
 * @since 3.0.0
 * @see ExampleUtil
 * @see AuthenticatedSdk
 */
public final class ExampleScenario1 {

    /** No instantiation &mdash; this class only exposes {@link #main(String[])}. */
    private ExampleScenario1() { }

    /**
     * Runs the 5-step ML-KEM-512 streaming life-cycle 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(String[] args) {

        System.out.println("===== SCENARIO 1 START =====");
        System.out.println("""
                Purpose :
                  * End-to-end ML-KEM-512 life-cycle in streaming mode
                  * Demonstrates detached-JWE pipeline (encrypt -> decrypt)
                Steps   :
                  1) Generate ML-KEM-512 key
                  2) Export public metadata
                  3) Encrypt payload (detached JWE)
                  4) Decrypt ciphertext
                  5) Validate integrity
                --------------------------------------------------------------""");

        try {
            ensureTempDir(TEMP_DIR);

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

            runScenario(sdk);

        } catch (Exception ex) {
            fatal("Scenario 1 failed", ex);
        }

        System.out.println("===== SCENARIO 1 END =====");
    }

    /**
     * Executes the 5-step ML-KEM-512 streaming encryption scenario.
     *
     * <ol>
     *   <li>Create plaintext file.</li>
     *   <li>Generate ML-KEM-512 key.</li>
     *   <li>Export key metadata.</li>
     *   <li>Stream-encrypt to detached JWE.</li>
     *   <li>Stream-decrypt and validate integrity.</li>
     * </ol>
     *
     * @param sdk an authenticated {@link AuthenticatedSdk} instance;
     *            must not be {@code null}
     * @throws Exception on any I/O or cryptographic failure
     */
    private static void runScenario(final AuthenticatedSdk sdk) throws Exception {

        final String kid = "sc1_kem_" + System.currentTimeMillis();

        /* -- file system artefacts ----------------------------------------- */
        Path plainFile  = TEMP_DIR.resolve("scenario1_plain.txt");
        Path encFile    = TEMP_DIR.resolve("scenario1.enc");
        Path decFile    = TEMP_DIR.resolve("scenario1.dec");
        Path exportJson = TEMP_DIR.resolve("scenario1_keydata.json");

        /* 1 -- plaintext ---------------------------------------------------- */
        FileIO.writeUtf8(plainFile,
                "Hello Scenario-1 - streaming encryption demo!");
        System.out.println("[1] Plaintext ready          -> " + plainFile.toAbsolutePath());

        /* 2 -- key generation ----------------------------------------------- */
        sdk.generateKey(new GenerateKeySpec()
                .setKid(kid)
                .setKty("ML-KEM")
                .setAlg("ML-KEM-512"));
        System.out.println("[2] Key generated            -> kid = " + kid);

        /* 3 -- export metadata ---------------------------------------------- */
        ExportedKeySpec exported = sdk.exportKey(kid);
        FileIO.writeUtf8(exportJson, toJson(exported));
        System.out.println("[3] Metadata exported        -> " + exportJson.toAbsolutePath());

        /* 4 -- streaming encrypt (detached JWE) ----------------------------- */
        EncryptResult encMeta = sdk.encryptFileStream(kid, plainFile, encFile);
        System.out.println("[4] Ciphertext written       -> " + encFile.toAbsolutePath());
        printEncryptMeta(encMeta);

        /* 5 -- streaming decrypt -------------------------------------------- */
        DecryptResultMetadata decMeta = sdk.decryptFileStream(encFile, decFile);
        System.out.println("[5] Decrypted file           -> " + decFile.toAbsolutePath());
        printDecryptMeta(decMeta);

        /* 6 -- validation --------------------------------------------------- */
        String original  = FileIO.readUtf8(plainFile);
        String recovered = FileIO.readUtf8(decFile);
        System.out.println(original.equals(recovered)
                ? "[6] Validation OK - plaintext matches."
                : "[6] WARNING - plaintext mismatch!");
    }
}