Flow 5 – ML-KEM-512 Non-Streaming Encrypt / Decrypt (Compact JWE)

/*
 * 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.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 5 — ML-KEM-512 Bulk Helpers (Compact JWE).
 *
 * <p>This scenario demonstrates the <strong>non-streaming</strong> helper
 * methods that work with RFC&nbsp;7516 <em>Compact&nbsp;JWE</em> tokens:</p>
 * <ol>
 *   <li>Generate an <code>ML-KEM-512</code> key-pair.</li>
 *   <li>Export the key's public metadata to JSON.</li>
 *   <li>Encrypt a file via {@link AuthenticatedSdk#encryptFile(String, Path, Path)}
 *       (compact token written to disk).</li>
 *   <li>Decrypt via {@link AuthenticatedSdk#decryptFile(Path, Path)}.</li>
 *   <li>Print rich metadata for both operations.</li>
 *   <li>Validate round-trip integrity.</li>
 * </ol>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>All filesystem interactions use the {@link java.nio.file.Path} API.</li>
 *   <li>UTF-8 is enforced explicitly for deterministic encoding.</li>
 *   <li>Temporary artefacts are written 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 ExampleScenario5 {

    /** No instantiation &mdash; this class only exposes {@link #main(String[])}. */
    private ExampleScenario5() { }

    /**
     * Runs the ML-KEM-512 compact JWE encrypt/decrypt 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 5 START =====");
        System.out.println("""
                Purpose :
                  * ML-KEM-512 compact-JWE encrypt / decrypt helpers
                  * Non-streaming - full token handled in memory
                Steps   :
                  1) Generate ML-KEM-512 key
                  2) Export public metadata
                  3) Encrypt payload (compact 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 5 failed", ex);
        }

        System.out.println("===== SCENARIO 5 END =====");
    }

    /**
     * Executes the 6-step ML-KEM-512 compact JWE scenario.
     *
     * <ol>
     *   <li>Prepare plaintext file.</li>
     *   <li>Generate ML-KEM-512 key.</li>
     *   <li>Export key metadata.</li>
     *   <li>Encrypt file (compact JWE).</li>
     *   <li>Decrypt compact JWE.</li>
     *   <li>Validate round-trip integrity.</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 {

        /* 1 -- prepare plaintext -------------------------------------------- */
        Path plainFile = TEMP_DIR.resolve("scenario5_plain.txt");
        FileIO.writeUtf8(plainFile,
                "Scenario-5 - ML-KEM-512 compact-JWE encryption demo.");
        System.out.println("[1] Plaintext ready          -> " + plainFile.toAbsolutePath());

        /* 2 -- generate ML-KEM-512 key -------------------------------------- */
        String kid = "sc5_kem_" + System.currentTimeMillis();
        sdk.generateKey(new GenerateKeySpec()
                .setKid(kid)
                .setKty("ML-KEM")
                .setAlg("ML-KEM-512"));
        System.out.println("[2] Key generated            -> kid = " + kid);

        /* 3 -- export metadata ---------------------------------------------- */
        Path exportJson = TEMP_DIR.resolve("scenario5_key.json");
        FileIO.writeUtf8(exportJson, toJson(sdk.exportKey(kid)));
        System.out.println("[3] Metadata exported        -> " + exportJson.toAbsolutePath());

        /* 4 -- encrypt (compact JWE) ---------------------------------------- */
        Path cipherFile = TEMP_DIR.resolve("scenario5.cipher.jwe");
        EncryptResult encMeta = sdk.encryptFile(kid, plainFile, cipherFile);
        System.out.println("[4] Ciphertext written       -> " + cipherFile.toAbsolutePath());
        printEncryptMeta(encMeta);

        /* 5 -- decrypt ------------------------------------------------------ */
        Path decFile = TEMP_DIR.resolve("scenario5_decrypted.txt");
        DecryptResultMetadata decMeta = sdk.decryptFile(cipherFile, 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!");
    }
}