// SPDX-License-Identifier: BSD-2-Clause
// Copyright (c) 2002-2004 Brian Wellington (bwelling@xbill.org)

package org.xbill.DNS;

import java.io.IOException;
import org.xbill.DNS.utils.base16;

/**
 * DS - contains a Delegation Signer record, which acts as a placeholder for KEY records in the
 * parent zone.
 *
 * @see DNSSEC
 * @author David Blacka
 * @author Brian Wellington
 * @see <a href="https://tools.ietf.org/html/rfc4034">RFC 4034: Resource Records for the DNS
 *     Security Extensions</a>
 */
public class DSRecord extends Record {

  public static class Digest {
    private Digest() {}

    /** SHA-1 */
    public static final int SHA1 = 1;

    /** SHA-256 */
    public static final int SHA256 = 2;

    /** GOST R 34.11-94 */
    public static final int GOST3411 = 3;

    /** SHA-384 */
    public static final int SHA384 = 4;
  }

  public static final int SHA1_DIGEST_ID = Digest.SHA1;
  public static final int SHA256_DIGEST_ID = Digest.SHA256;
  public static final int GOST3411_DIGEST_ID = Digest.GOST3411;
  public static final int SHA384_DIGEST_ID = Digest.SHA384;

  private int footprint;
  private int alg;
  private int digestid;
  private byte[] digest;

  DSRecord() {}

  /**
   * Creates a DS Record from the given data
   *
   * @param footprint The original KEY record's footprint (keyid).
   * @param alg The original key algorithm.
   * @param digestid The digest id code.
   * @param digest A hash of the original key.
   */
  protected DSRecord(
      Name name,
      int type,
      int dclass,
      long ttl,
      int footprint,
      int alg,
      int digestid,
      byte[] digest) {
    super(name, type, dclass, ttl);
    this.footprint = checkU16("footprint", footprint);
    this.alg = checkU8("alg", alg);
    this.digestid = checkU8("digestid", digestid);
    this.digest = digest;
  }

  /**
   * Creates a DS Record from the given data
   *
   * @param footprint The original KEY record's footprint (keyid).
   * @param alg The original key algorithm.
   * @param digestid The digest id code.
   * @param digest A hash of the original key.
   */
  public DSRecord(
      Name name, int dclass, long ttl, int footprint, int alg, int digestid, byte[] digest) {
    this(name, Type.DS, dclass, ttl, footprint, alg, digestid, digest);
  }

  /**
   * Creates a DS Record from the given data
   *
   * @param digestid The digest id code.
   * @param key The key to digest
   */
  public DSRecord(Name name, int dclass, long ttl, int digestid, DNSKEYRecord key) {
    this(
        name,
        dclass,
        ttl,
        key.getFootprint(),
        key.getAlgorithm(),
        digestid,
        DNSSEC.generateDSDigest(key, digestid));
  }

  @Override
  protected void rrFromWire(DNSInput in) throws IOException {
    footprint = in.readU16();
    alg = in.readU8();
    digestid = in.readU8();
    digest = in.readByteArray();
  }

  @Override
  protected void rdataFromString(Tokenizer st, Name origin) throws IOException {
    footprint = st.getUInt16();
    alg = st.getUInt8();
    digestid = st.getUInt8();
    digest = st.getHex();
  }

  /** Converts rdata to a String */
  @Override
  protected String rrToString() {
    StringBuilder sb = new StringBuilder();
    sb.append(footprint);
    sb.append(" ");
    sb.append(alg);
    sb.append(" ");
    sb.append(digestid);
    if (digest != null) {
      sb.append(" ");
      sb.append(base16.toString(digest));
    }

    return sb.toString();
  }

  /** Returns the key's algorithm. */
  public int getAlgorithm() {
    return alg;
  }

  /** Returns the key's Digest ID. */
  public int getDigestID() {
    return digestid;
  }

  /** Returns the binary hash of the key. */
  public byte[] getDigest() {
    return digest;
  }

  /** Returns the key's footprint. */
  public int getFootprint() {
    return footprint;
  }

  @Override
  protected void rrToWire(DNSOutput out, Compression c, boolean canonical) {
    out.writeU16(footprint);
    out.writeU8(alg);
    out.writeU8(digestid);
    if (digest != null) {
      out.writeByteArray(digest);
    }
  }
}
