/*-
    * #%L
    * io.earcam.instrumental.archive.sign
    * %%
    * Copyright (C) 2018 earcam
    * %%
    * SPDX-License-Identifier: (BSD-3-Clause OR EPL-1.0 OR Apache-2.0 OR MIT)
    * 
    * You <b>must</b> choose to accept, in full - any individual or combination of 
   * the following licenses:
   * <ul>
   * 	<li><a href="https://opensource.org/licenses/BSD-3-Clause">BSD-3-Clause</a></li>
   * 	<li><a href="https://www.eclipse.org/legal/epl-v10.html">EPL-1.0</a></li>
   * 	<li><a href="https://www.apache.org/licenses/LICENSE-2.0">Apache-2.0</a></li>
   * 	<li><a href="https://opensource.org/licenses/MIT">MIT</a></li>
   * </ul>
   * #L%
   */
  package io.earcam.instrumental.archive.sign;
  
  import java.security.MessageDigest;
  import java.util.Base64;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.jar.Attributes;
  import java.util.jar.Manifest;
  
  import io.earcam.instrumental.archive.ArchiveConfigurationPlugin;
  import io.earcam.instrumental.archive.ArchiveRegistrar;
  import io.earcam.instrumental.archive.ArchiveResource;
  import io.earcam.instrumental.archive.ArchiveResourceListener;
  import io.earcam.instrumental.archive.ManifestProcessor;
  
  /**
   * <p>
   * Adds the archive's contents as digests in the manifest.
   * </p>
   *
   */
  public class WithDigest implements ArchiveConfigurationPlugin, ManifestProcessor, ArchiveResourceListener {
  
  	protected MessageDigest digester;
  	private final Map<String, String> digests = new HashMap<>();
  	protected Manifest manifest;
  
  
  	WithDigest()
  	{}
  
  
  	/**
  	 * <p>
  	 * withDigest.
  	 * </p>
  	 *
  	 * @return a {@link io.earcam.instrumental.archive.sign.WithDigest} object.
  	 */
  	public static WithDigest withDigest()
  	{
  		return new WithDigest();
  	}
  
  
  	@Override
  	public void attach(ArchiveRegistrar core)
  	{
  		core.registerManifestProcessor(this);
  		core.registerResourceListener(this);
  	}
  
  
  	@Override
  	public void added(ArchiveResource resource)
  	{
  		digests.put(resource.name(), base64Digest(resource.bytes()));
  	}
  
  
  	/**
  	 * <p>
  	 * base64Digest.
  	 * </p>
  	 *
  	 * @param data an array of {@link byte} objects.
  	 * @return a {@link java.lang.String} object.
  	 */
  	protected String base64Digest(byte[] data)
  	{
  		return base64Digest(digester, data);
  	}
  
  
  	static String base64Digest(MessageDigest digester, byte[] data)
  	{
  		digester.reset();
  		return encodeBase64(digester.digest(data));
  	}
  
 
 	static String encodeBase64(byte[] data)
 	{
 		return Base64.getEncoder().encodeToString(data);
 	}
 
 
 	@Override
 	public void process(Manifest manifest)
 	{
 		this.manifest = manifest;
 
 		Map<String, Attributes> entries = manifest.getEntries();
 
 		for(Entry<String, String> e : digests.entrySet()) {
 			Attributes attributes = entries.computeIfAbsent(e.getKey(), k -> new Attributes());
 			attributes.putValue(digester.getAlgorithm() + "-Digest", e.getValue());
 		}
 	}
 
 
 	/* WithDigest API */
 
 	/**
 	 * Adds digest entries to the manifest. Required for signed JARs.
 	 *
 	 * @param hash the algorithm name
 	 * @return this archive builder
 	 */
 	public WithDigest digestedBy(StandardDigestAlgorithms hash)
 	{
 		return digestedBy(hash.create());
 	}
 
 
 	/**
 	 * Adds digest entries to the manifest. Required for signed JARs.
 	 *
 	 * @param digest the hash algorithm
 	 * @return this archive builder
 	 */
 	public WithDigest digestedBy(MessageDigest digest)
 	{
 		this.digester = digest;
 		return this;
 	}
 
 }