/*
    * 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.sign;
  
  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.keypair.GordianKeyPairType;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.Objects;
  
  /**
   * Signature Specification.
   */
  public final class GordianSignatureSpec {
      /**
       * The Separator.
       */
      private static final String SEP = "-";
  
      /**
       * KeyPairType.
       */
      private final GordianKeyPairType theKeyPairType;
  
      /**
       * SignatureType.
       */
      private final GordianSignatureType theSignatureType;
  
      /**
       * SignatureSpec.
       */
      private final Object theSignatureSpec;
  
      /**
       * The Validity.
       */
      private final boolean isValid;
  
      /**
       * The String name.
       */
      private String theName;
  
      /**
       * Constructor.
       *
       * @param pKeyPairType   the keyPairType
       * @param pSignatureSpec the signatureSpec
       */
      public GordianSignatureSpec(final GordianKeyPairType pKeyPairType,
                                  final Object pSignatureSpec) {
          /* Store parameters */
          this(pKeyPairType, GordianSignatureType.NATIVE, pSignatureSpec);
      }
  
      /**
       * Constructor.
       *
       * @param pKeyPairType   the keyPairType
       * @param pSignatureType the signatureType
       */
      public GordianSignatureSpec(final GordianKeyPairType pKeyPairType,
                                  final GordianSignatureType pSignatureType) {
          /* Store parameters */
          this(pKeyPairType, pSignatureType, null);
      }
  
      /**
       * Constructor.
       *
       * @param pKeyPairType   the keyPairType
       * @param pSignatureType the signatureType
       * @param pSignatureSpec the signatureSpec
       */
      public GordianSignatureSpec(final GordianKeyPairType pKeyPairType,
                                  final GordianSignatureType pSignatureType,
                                  final Object pSignatureSpec) {
          /* Store parameters */
          theKeyPairType = pKeyPairType;
          theSignatureType = pSignatureType;
          theSignatureSpec = pSignatureSpec;
          isValid = checkValidity();
     }
 
     /**
      * Obtain the keyPairType.
      *
      * @return the keyPairType.
      */
     public GordianKeyPairType getKeyPairType() {
         return theKeyPairType;
     }
 
     /**
      * Obtain the SignatureType.
      *
      * @return the signatureType.
      */
     public GordianSignatureType getSignatureType() {
         return theSignatureType;
     }
 
     /**
      * Obtain the signatureSpec.
      *
      * @return the signatureSpec.
      */
     public Object getSignatureSpec() {
         return theSignatureSpec;
     }
 
     /**
      * Obtain the DigestSpec.
      *
      * @return the digestSpec.
      */
     public GordianDigestSpec getDigestSpec() {
         if (!(theSignatureSpec instanceof GordianDigestSpec)) {
             throw new IllegalArgumentException();
         }
         return (GordianDigestSpec) theSignatureSpec;
     }
 
     /**
      * Obtain the composite signatureSpec iterator.
      *
      * @return the signatureeSpec iterator.
      */
     @SuppressWarnings("unchecked")
     public Iterator<GordianSignatureSpec> signatureSpecIterator() {
         if (!(theSignatureSpec instanceof List)) {
             throw new IllegalArgumentException();
         }
         return ((List<GordianSignatureSpec>) theSignatureSpec).iterator();
     }
 
     /**
      * Is the signatureSpec valid?
      *
      * @return true/false.
      */
     public boolean isValid() {
         return isValid;
     }
 
     /**
      * Does this signatureSpec support context?
      *
      * @return true/false
      */
     public boolean supportsContext() {
         switch (theKeyPairType) {
             case MLDSA:
             case SLHDSA:
                 return true;
             default:
                 return false;
         }
     }
 
     /**
      * Check spec validity.
      *
      * @return valid true/false
      */
     private boolean checkValidity() {
         if (theKeyPairType == null || theSignatureType == null) {
             return false;
         }
         switch (theKeyPairType) {
             case RSA:
             case DSA:
             case EC:
             case DSTU4145:
             case GOST2012:
                 if (!(theSignatureSpec instanceof GordianDigestSpec)) {
                     return false;
                 }
                 final GordianDigestSpec mySpec = getDigestSpec();
                 return mySpec.isValid() && mySpec.getDigestType().supportsLargeData();
             case EDDSA:
             case SLHDSA:
             case MLDSA:
             case FALCON:
             case MAYO:
             case SNOVA:
             case XMSS:
             case LMS:
                 return theSignatureSpec == null;
             case PICNIC:
                 return theSignatureSpec == null || checkPICNICDigest();
             case SM2:
                 return checkSM2Digest();
             case COMPOSITE:
                 return theSignatureSpec instanceof List && checkComposite();
             default:
                 return false;
         }
     }
 
     /**
      * Check composite spec validity.
      *
      * @return valid true/false
      */
     private boolean checkComposite() {
         final Iterator<GordianSignatureSpec> myIterator = signatureSpecIterator();
         while (myIterator.hasNext()) {
             /* Check that each spec is valid */
             final GordianSignatureSpec mySpec = myIterator.next();
             if (mySpec == null || !mySpec.isValid()) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Check picnic spec validity.
      *
      * @return valid true/false
      */
     private boolean checkPICNICDigest() {
         /* Check that signature length is 512 */
         final GordianDigestSpec myDigest = getDigestSpec();
         if (!GordianLength.LEN_512.equals(myDigest.getDigestLength())) {
             return false;
         }
 
         /* Switch on DigestType */
         switch (myDigest.getDigestType()) {
             case SHA2:
             case SHA3:
             case SHAKE:
                 return true;
             default:
                 return false;
         }
     }
 
     /**
      * Check sm2 spec validity.
      *
      * @return valid true/false
      */
     private boolean checkSM2Digest() {
         /* Switch on DigestType */
         final GordianDigestSpec myDigest = getDigestSpec();
         switch (myDigest.getDigestType()) {
             case SM3:
                 return true;
             case SHA2:
                 return GordianLength.LEN_256.equals(myDigest.getDigestLength())
                         && !myDigest.isSha2Hybrid();
             default:
                 return false;
         }
     }
 
     @Override
     public String toString() {
         /* If we have not yet loaded the name */
         if (theName == null) {
             /* Load the name */
             theName = theKeyPairType.toString();
             if (theSignatureType != GordianSignatureType.NATIVE) {
                 theName += SEP + theSignatureType.toString();
             }
             if (theSignatureSpec != null) {
                 if (theKeyPairType == GordianKeyPairType.COMPOSITE) {
                     final Iterator<GordianSignatureSpec> myIterator = signatureSpecIterator();
                     final StringBuilder myBuilder = new StringBuilder(theName);
                     while (myIterator.hasNext()) {
                         myBuilder.append(SEP).append(myIterator.next().toString());
                     }
                     theName = myBuilder.toString();
                 } else {
                     theName += SEP + theSignatureSpec.toString();
                 }
             }
         }
 
         /* 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 KeyPairType, signatureType and signatureSpec */
         return pThat instanceof GordianSignatureSpec myThat
                 && theKeyPairType == myThat.getKeyPairType()
                 && theSignatureType == myThat.getSignatureType()
                 && Objects.equals(theSignatureSpec, myThat.theSignatureSpec);
     }
 
     @Override
     public int hashCode() {
         return Objects.hash(theKeyPairType, theSignatureType, theSignatureSpec);
     }
 }