/*
    * 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.encrypt;
  
  import io.github.tonywasher.joceanus.gordianknot.api.digest.GordianDigestSpec;
  import io.github.tonywasher.joceanus.gordianknot.api.digest.GordianDigestType;
  import io.github.tonywasher.joceanus.gordianknot.api.keypair.GordianKeyPairType;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.Objects;
  
  /**
   * Asymmetric Encryption Specification.
   */
  public final class GordianEncryptorSpec {
      /**
       * The EC-ElGamal name.
       */
      private static final String ECELGAMAL = "ElGamal";
  
      /**
       * The Separator.
       */
      static final String SEP = "-";
  
      /**
       * KeyPairType.
       */
      private final GordianKeyPairType theKeyPairType;
  
      /**
       * EncryptorType.
       */
      private final Object theEncryptorType;
  
      /**
       * The Validity.
       */
      private final boolean isValid;
  
      /**
       * The String name.
       */
      private String theName;
  
      /**
       * Constructor.
       *
       * @param pKeyPairType   the keyPairType
       * @param pEncryptorType the encryptor type
       */
      public GordianEncryptorSpec(final GordianKeyPairType pKeyPairType,
                                  final Object pEncryptorType) {
          theKeyPairType = pKeyPairType;
          theEncryptorType = pEncryptorType;
          isValid = checkValidity();
      }
  
      /**
       * Obtain the keyPairType.
       *
       * @return the keyPairType.
       */
      public GordianKeyPairType getKeyPairType() {
          return theKeyPairType;
      }
  
      /**
       * Obtain the encryptorType.
       *
       * @return the encryptorType.
       */
      public Object getEncryptorType() {
          return theEncryptorType;
      }
  
      /**
       * Obtain the digestSpec.
       *
       * @return the digestSpec.
       */
      public GordianDigestSpec getDigestSpec() {
          if (theEncryptorType instanceof GordianDigestSpec mySpec) {
              return mySpec;
         }
         throw new IllegalArgumentException();
     }
 
     /**
      * Obtain the SM2 encryption Spec.
      *
      * @return the encryptionSpec.
      */
     public GordianSM2EncryptionSpec getSM2EncryptionSpec() {
         if (theEncryptorType instanceof GordianSM2EncryptionSpec mySpec) {
             return mySpec;
         }
         throw new IllegalArgumentException();
     }
 
     /**
      * Obtain the composite encryptorSpec iterator.
      *
      * @return the encryptorSpec iterator.
      */
     @SuppressWarnings("unchecked")
     public Iterator<GordianEncryptorSpec> encryptorSpecIterator() {
         if (theEncryptorType instanceof List) {
             return ((List<GordianEncryptorSpec>) theEncryptorType).iterator();
         }
         throw new IllegalArgumentException();
     }
 
     /**
      * Is the encryptorSpec valid?
      *
      * @return true/false.
      */
     public boolean isValid() {
         return isValid;
     }
 
     /**
      * Check spec validity.
      *
      * @return valid true/false
      */
     private boolean checkValidity() {
         if (theKeyPairType == null) {
             return false;
         }
         switch (theKeyPairType) {
             case RSA:
             case ELGAMAL:
                 return theEncryptorType instanceof GordianDigestSpec s
                         && s.isValid();
             case SM2:
                 return theEncryptorType == null
                         || (theEncryptorType instanceof GordianSM2EncryptionSpec s
                         && s.isValid());
             case EC:
             case GOST2012:
                 return theEncryptorType == null;
             case COMPOSITE:
                 return theEncryptorType instanceof List && checkComposite();
             default:
                 return false;
         }
     }
 
     /**
      * Is the Spec supported?
      *
      * @return true/false
      */
     public boolean isSupported() {
         switch (theKeyPairType) {
             case RSA:
             case ELGAMAL:
                 final GordianDigestSpec mySpec = getDigestSpec();
                 return GordianDigestType.SHA2.equals(mySpec.getDigestType()) && !mySpec.isSha2Hybrid();
             case EC:
             case GOST2012:
             case SM2:
             case COMPOSITE:
                 return true;
             default:
                 return false;
         }
     }
 
     /**
      * Check composite spec validity.
      *
      * @return valid true/false
      */
     private boolean checkComposite() {
         final Iterator<GordianEncryptorSpec> myIterator = encryptorSpecIterator();
         while (myIterator.hasNext()) {
             /* Check that each spec is valid */
             final GordianEncryptorSpec mySpec = myIterator.next();
             if (mySpec == null || !mySpec.isValid()) {
                 return false;
             }
         }
         return true;
     }
 
     @Override
     public String toString() {
         /* If we have not yet loaded the name */
         if (theName == null) {
             /* If the encryptorSpec is valid */
             if (isValid) {
                 /* Load the name */
                 theName = theKeyPairType.toString();
                 switch (theKeyPairType) {
                     case RSA:
                     case ELGAMAL:
                         theName += SEP + theEncryptorType;
                         break;
                     case EC:
                     case GOST2012:
                         theName += SEP + ECELGAMAL;
                         break;
                     case SM2:
                         theName += SEP + (theEncryptorType == null ? ECELGAMAL : theEncryptorType);
                         break;
                     case COMPOSITE:
                         final Iterator<GordianEncryptorSpec> myIterator = encryptorSpecIterator();
                         final StringBuilder myBuilder = new StringBuilder(theName);
                         while (myIterator.hasNext()) {
                             myBuilder.append(SEP).append(myIterator.next().toString());
                         }
                         theName = myBuilder.toString();
                         break;
                     default:
                         break;
                 }
             } else {
                 /* Report invalid spec */
                 theName = "InvalidEncryptorSpec: " + theKeyPairType + ":" + theEncryptorType;
             }
         }
 
         /* 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;
         }
 
         /* Match fields */
         return pThat instanceof GordianEncryptorSpec myThat
                 && theKeyPairType == myThat.getKeyPairType()
                 && Objects.equals(theEncryptorType, myThat.theEncryptorType);
     }
 
     @Override
     public int hashCode() {
         return Objects.hash(theKeyPairType, theEncryptorType);
     }
 }