/*
    * Copyright 2024–2026 Michael Osipov
    *
    * 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 net.sf.michaelo.tomcat.pac;
  
  import java.nio.charset.StandardCharsets;
  import java.util.Objects;
  
  import net.sf.michaelo.tomcat.realm.Sid;
  
  /**
   * A class representing the <a href=
   * "https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-pac/1c0d6e11-6443-4846-b744-f9f810a504eb">{@code UPN_DNS_INFO}</a>
   * structure from MS-PAC.
   */
  public class UpnDnsInfo {
  
  	public static final long UPN_CONSTRUCTED_FLAG = 0x00000001L;
  	public static final long SAM_NAME_AND_SID_FLAG = 0x00000002L;
  
  	private final String upn;
  	private final String dnsDomainName;
  
  	private final long flags;
  
  	private String samName;
  	private Sid sid;
  
  	/**
  	 * Parses a UPN DNS info object from a byte array.
  	 *
  	 * @param infoBytes UPN DNS info structure encoded as bytes
  	 * @throws NullPointerException if {@code infoBytes} is null
  	 * @throws IllegalArgumentException if {@code infoBytes} is empty
  	 */
  	public UpnDnsInfo(byte[] infoBytes) {
  		Objects.requireNonNull(infoBytes, "infoBytes cannot be null");
  		if (infoBytes.length == 0) throw new IllegalArgumentException("infoBytes cannot be empty");
  
  		PacDataBuffer buf = new PacDataBuffer(infoBytes);
  
  		// UpnLength
  		int upnLength = buf.getUnsignedShort();
  		// UpnOffset
  		int upnOffset = buf.getUnsignedShort();
  		// DnsDomainNameLength
  		int dnsDomainNameLength = buf.getUnsignedShort();
  		// DnsDomainNameOffset
  		int dnsDomainNameOffset = buf.getUnsignedShort();
  		// Flags
  		/* Something isn't right, it appears to be that the bits are in reverse order
  		 * or the documentation is wrong:
  		 * - flag U should be at bit 31, but is at bit 0
  		 * - flag S should be at bit 30, but is at bit 1
  		 *
  		 * Samba has the same reversed order: https://github.com/samba-team/samba/blob/9844ac289be3430fd3f72c5e57fa00e012c5d417/librpc/idl/krb5pac.idl#L93-L96
  		 */
  		this.flags = buf.getUnsignedInt();
  
  		int pos = buf.position();
  		buf.position(upnOffset);
  		this.upn = getUnicodeString(buf, upnLength);
  		buf.position(dnsDomainNameOffset);
  		this.dnsDomainName = getUnicodeString(buf, dnsDomainNameLength);
  		buf.position(pos);
  
  		if ((flags & SAM_NAME_AND_SID_FLAG) != 0L) {
  			// SamNameLength
  			int samNameLength = buf.getUnsignedShort();
  			// SamNameOffset
  			int samNameOffset = buf.getUnsignedShort();
  			// SidLength
  			int sidLength = buf.getUnsignedShort();
  			// SidOffset
  			int sidOffset = buf.getUnsignedShort();
  
  			pos = buf.position();
  			buf.position(samNameOffset);
  			this.samName = getUnicodeString(buf, samNameLength);
  			byte[] dst = new byte[sidLength];
  			buf.position(sidOffset);
  			buf.get(dst);
  			this.sid = new Sid(dst);
  		}
  	}
  
  	public String getUpn() {
 		return upn;
 	}
 
 	public String getDnsDomainName() {
 		return dnsDomainName;
 	}
 
 	public long getFlags() {
 		return flags;
 	}
 
 	public String getSamName() {
 		return samName;
 	}
 
 	public Sid getSid() {
 		return sid;
 	}
 
 	private String getUnicodeString(PacDataBuffer buf, int length) {
 		byte[] dst = new byte[length];
 		buf.get(dst);
 		return new String(dst, StandardCharsets.UTF_16LE);
 	}
 }