/*
    * GordianKnot: Security Suite
    * Copyright 2012-2026. Tony Washer
    *
    * 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 io.github.tonywasher.joceanus.gordianknot.api.keypair;
  
  import io.github.tonywasher.joceanus.gordianknot.api.base.GordianLength;
  import io.github.tonywasher.joceanus.gordianknot.api.digest.GordianDigestSpec;
  import io.github.tonywasher.joceanus.gordianknot.api.digest.GordianDigestSpecBuilder;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Objects;
  
  /**
   * XMSS KeySpec.
   */
  public class GordianXMSSKeySpec {
      /**
       * The Separator.
       */
      private static final String SEP = "-";
  
      /**
       * The key type.
       */
      private final GordianXMSSKeyType theKeyType;
  
      /**
       * The digest type.
       */
      private final GordianXMSSDigestType theDigestType;
  
      /**
       * The height.
       */
      private final GordianXMSSHeight theHeight;
  
      /**
       * The layers.
       */
      private final GordianXMSSMTLayers theLayers;
  
      /**
       * The Validity.
       */
      private final boolean isValid;
  
      /**
       * The String name.
       */
      private String theName;
  
      /**
       * Constructor.
       *
       * @param pDigestType the digestType
       * @param pHeight     the height
       */
      public GordianXMSSKeySpec(final GordianXMSSDigestType pDigestType,
                                final GordianXMSSHeight pHeight) {
          this(GordianXMSSKeyType.XMSS, pDigestType, pHeight, null);
      }
  
      /**
       * Constructor.
       *
       * @param pDigestType the digestType
       * @param pHeight     the height
       * @param pLayers     the layers
       */
      public GordianXMSSKeySpec(final GordianXMSSDigestType pDigestType,
                                final GordianXMSSHeight pHeight,
                                final GordianXMSSMTLayers pLayers) {
          this(GordianXMSSKeyType.XMSSMT, pDigestType, pHeight, pLayers);
      }
  
      /**
       * Constructor.
       *
       * @param pKeyType    the keyType
       * @param pDigestType the digestType
       * @param pHeight     the height
       * @param pLayers     the layers
       */
      public GordianXMSSKeySpec(final GordianXMSSKeyType pKeyType,
                                final GordianXMSSDigestType pDigestType,
                               final GordianXMSSHeight pHeight,
                               final GordianXMSSMTLayers pLayers) {
         theKeyType = pKeyType;
         theDigestType = pDigestType;
         theHeight = pHeight;
         theLayers = pLayers;
         isValid = checkValidity();
     }
 
     /**
      * Is this key MT?
      *
      * @return true/false
      */
     public boolean isMT() {
         return theKeyType.isMT();
     }
 
     /**
      * Obtain the keyType.
      *
      * @return the keyType
      */
     public GordianXMSSKeyType getKeyType() {
         return theKeyType;
     }
 
     /**
      * Obtain the digestType.
      *
      * @return the digestType
      */
     public GordianXMSSDigestType getDigestType() {
         return theDigestType;
     }
 
     /**
      * Obtain the height.
      *
      * @return the height
      */
     public GordianXMSSHeight getHeight() {
         return theHeight;
     }
 
     /**
      * Obtain the layers.
      *
      * @return the layers
      */
     public GordianXMSSMTLayers getLayers() {
         return theLayers;
     }
 
     /**
      * Is the keySpec valid?
      *
      * @return true/false.
      */
     public boolean isValid() {
         return isValid;
     }
 
     /**
      * Is the keySpec high (height > 15)?
      *
      * @return true/false.
      */
     public boolean isHigh() {
         return isValid && theHeight.isHigh(theKeyType);
     }
 
     /**
      * Create XMSS keySpec.
      *
      * @param pDigestType the digestType
      * @param pHeight     the height
      * @return the keySpec
      */
     public static GordianXMSSKeySpec xmss(final GordianXMSSDigestType pDigestType,
                                           final GordianXMSSHeight pHeight) {
         return new GordianXMSSKeySpec(pDigestType, pHeight);
     }
 
     /**
      * Create XMSS keySpec.
      *
      * @param pDigestType the digestType
      * @param pHeight     the height
      * @param pLayers     the layers
      * @return the keySpec
      */
     public static GordianXMSSKeySpec xmssmt(final GordianXMSSDigestType pDigestType,
                                             final GordianXMSSHeight pHeight,
                                             final GordianXMSSMTLayers pLayers) {
         return new GordianXMSSKeySpec(pDigestType, pHeight, pLayers);
     }
 
     /**
      * Check spec validity.
      *
      * @return valid true/false
      */
     private boolean checkValidity() {
         /* Check that required elements are present */
         if (theKeyType == null || theDigestType == null || theHeight == null) {
             return false;
         }
 
         /* Check that the height is valid for the keyType */
         if (!theHeight.validForKeyType(theKeyType)) {
             return false;
         }
 
         /* Check layers is valid for keyType/height */
         return theKeyType == GordianXMSSKeyType.XMSS
                 ? theLayers == null
                 : theLayers != null && theHeight.hasValidLayers(theLayers);
     }
 
     @Override
     public String toString() {
         /* If we have not yet loaded the name */
         if (theName == null) {
             /* If the keySpec is valid */
             if (isValid) {
                 /* Load the name */
                 theName = theKeyType.toString()
                         + SEP + theDigestType.toString()
                         + SEP + theHeight.toString();
                 if (isMT()) {
                     theName += SEP + theLayers.toString();
                 }
 
             } else {
                 /* Report invalid spec */
                 theName = "InvalidXMSSKeySpec: " + theKeyType + ":" + theDigestType
                         + ":" + theHeight + ":" + theLayers;
             }
         }
 
         /* return the name */
         return theName;
     }
 
     @Override
     public boolean equals(final Object pThat) {
         /* Handle the trivial cases */
         if (this == pThat) {
             return true;
         }
         if (pThat == null) {
             return false;
         }
 
         /* Check KeyType, digestType, height and layers */
         return pThat instanceof GordianXMSSKeySpec myThat
                 && theKeyType == myThat.getKeyType()
                 && theDigestType == myThat.getDigestType()
                 && theHeight == myThat.getHeight()
                 && theLayers == myThat.getLayers();
     }
 
     @Override
     public int hashCode() {
         return Objects.hash(theKeyType, theDigestType, theHeight, theLayers);
     }
 
     /**
      * Obtain a list of all possible specs.
      *
      * @return the list
      */
     public static List<GordianXMSSKeySpec> listPossibleKeySpecs() {
         /* Create the list */
         final List<GordianXMSSKeySpec> mySpecs = new ArrayList<>();
 
         /* Add the specs */
         for (final GordianXMSSDigestType myType : GordianXMSSDigestType.values()) {
             mySpecs.addAll(listPossibleKeySpecs(myType));
         }
 
         /* Return the list */
         return mySpecs;
     }
 
     /**
      * Obtain a list of all possible specs.
      *
      * @param pDigestType the digestType
      * @return the list
      */
     public static List<GordianXMSSKeySpec> listPossibleKeySpecs(final GordianXMSSDigestType pDigestType) {
         /* Create the list */
         final List<GordianXMSSKeySpec> mySpecs = new ArrayList<>();
 
         /* For all heights */
         for (final GordianXMSSHeight myHeight : GordianXMSSHeight.values()) {
             /* Add XMSS Spec if valid */
             if (myHeight.validForKeyType(GordianXMSSKeyType.XMSS)) {
                 mySpecs.add(xmss(pDigestType, myHeight));
             }
 
             /* Add XMSSMT Specs if valid */
             if (myHeight.validForKeyType(GordianXMSSKeyType.XMSSMT)) {
                 /* For all heights */
                 for (final GordianXMSSMTLayers myLayers : myHeight.getValidLayers()) {
                     mySpecs.add(xmssmt(pDigestType, myHeight, myLayers));
                 }
             }
         }
 
         /* Return the list */
         return mySpecs;
     }
 
     /**
      * XMSS keyTypes.
      */
     public enum GordianXMSSKeyType {
         /**
          * XMSS.
          */
         XMSS,
 
         /**
          * XMSSMT.
          */
         XMSSMT;
 
         /**
          * Is this key MT?
          *
          * @return true/false
          */
         public boolean isMT() {
             return this == XMSSMT;
         }
 
         @Override
         public String toString() {
             return this == XMSSMT ? "XMSS^MT" : "XMSS";
         }
     }
 
     /**
      * XMSS digestType.
      */
     public enum GordianXMSSDigestType {
         /**
          * SHA256.
          */
         SHA256,
 
         /**
          * SHA512.
          */
         SHA512,
 
         /**
          * SHAKE128.
          */
         SHAKE128,
 
         /**
          * SHAKE256.
          */
         SHAKE256;
 
         /**
          * Obtain the required digestSpec.
          *
          * @return the digestSpec
          */
         public GordianDigestSpec getDigestSpec() {
             switch (this) {
                 case SHA256:
                     return GordianDigestSpecBuilder.sha2(GordianLength.LEN_256);
                 case SHA512:
                     return GordianDigestSpecBuilder.sha2(GordianLength.LEN_512);
                 case SHAKE128:
                     return GordianDigestSpecBuilder.shake128();
                 case SHAKE256:
                     return GordianDigestSpecBuilder.shake256();
                 default:
                     throw new IllegalStateException();
             }
         }
     }
 
     /**
      * XMSS Height.
      */
     public enum GordianXMSSHeight {
         /**
          * 10.
          */
         H10(10),
 
         /**
          * 16.
          */
         H16(16),
 
         /**
          * 20.
          */
         H20(20, new GordianXMSSMTLayers[]{GordianXMSSMTLayers.L2, GordianXMSSMTLayers.L4}),
 
         /**
          * 40.
          */
         H40(40, new GordianXMSSMTLayers[]{GordianXMSSMTLayers.L2, GordianXMSSMTLayers.L4, GordianXMSSMTLayers.L8}),
 
         /**
          * 12.
          */
         H60(12, new GordianXMSSMTLayers[]{GordianXMSSMTLayers.L3, GordianXMSSMTLayers.L6, GordianXMSSMTLayers.L12});
 
         /**
          * The Height.
          */
         private final int theHeight;
 
         /**
          * The Layers.
          */
         private final GordianXMSSMTLayers[] theLayers;
 
         /**
          * Constructor.
          *
          * @param pHeight the height
          */
         GordianXMSSHeight(final int pHeight) {
             this(pHeight, null);
         }
 
         /**
          * Constructor.
          *
          * @param pHeight the height
          * @param pLayers the layers
          */
         GordianXMSSHeight(final int pHeight,
                           final GordianXMSSMTLayers[] pLayers) {
             theHeight = pHeight;
             theLayers = pLayers;
         }
 
         /**
          * Obtain the height.
          *
          * @return the height
          */
         public int getHeight() {
             return theHeight;
         }
 
 
         /**
          * Is the height valid for the keyType.
          *
          * @param pKeyType the keyType
          * @return true/false
          */
         boolean validForKeyType(final GordianXMSSKeyType pKeyType) {
             switch (this) {
                 case H10:
                 case H16:
                     return pKeyType == GordianXMSSKeyType.XMSS;
                 case H40:
                 case H60:
                     return pKeyType == GordianXMSSKeyType.XMSSMT;
                 default:
                     return true;
             }
         }
 
         /**
          * Is the layers valid for the height.
          *
          * @param pLayers the layers
          * @return true/false
          */
         boolean hasValidLayers(final GordianXMSSMTLayers pLayers) {
             if (theLayers != null) {
                 for (GordianXMSSMTLayers myLayers : theLayers) {
                     if (myLayers == pLayers) {
                         return true;
                     }
                 }
             }
             return false;
         }
 
         /**
          * Obtain the valid XMSSMT layers.
          *
          * @return the height
          */
         GordianXMSSMTLayers[] getValidLayers() {
             return theLayers;
         }
 
         /**
          * Is the parameter high?
          *
          * @param pKeyType the keyTypoe
          * @return true/false.
          */
         public boolean isHigh(final GordianXMSSKeyType pKeyType) {
             switch (this) {
                 case H16:
                 case H20:
                     return pKeyType == GordianXMSSKeyType.XMSS;
                 case H40:
                 case H60:
                     return true;
                 default:
                     return false;
             }
         }
     }
 
     /**
      * XMSSMT Layers.
      */
     public enum GordianXMSSMTLayers {
         /**
          * 2.
          */
         L2(2),
 
         /**
          * 3.
          */
         L3(3),
 
         /**
          * 4.
          */
         L4(4),
 
         /**
          * 6.
          */
         L6(6),
 
         /**
          * 40.
          */
         L8(8),
 
         /**
          * 12.
          */
         L12(12);
 
         /**
          * The layers.
          */
         private final int theLayers;
 
         /**
          * Constructor.
          *
          * @param pLayers the layers
          */
         GordianXMSSMTLayers(final int pLayers) {
             theLayers = pLayers;
         }
 
         /**
          * Obtain the layers.
          *
          * @return the layers
          */
         public int getLayers() {
             return theLayers;
         }
     }
 }