/*
    * Copyright 2016 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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.netty5.handler.ssl;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.buffer.api.BufferAllocator;
  import io.netty5.util.Resource;
  import io.netty5.util.Send;
  import io.netty5.buffer.api.internal.ResourceSupport;
  import io.netty5.buffer.api.internal.Statics;
  import io.netty5.util.CharsetUtil;
  
  import java.math.BigInteger;
  import java.security.Principal;
  import java.security.PublicKey;
  import java.security.cert.CertificateEncodingException;
  import java.security.cert.X509Certificate;
  import java.util.Arrays;
  import java.util.Date;
  import java.util.Set;
  
  import static io.netty5.buffer.api.DefaultBufferAllocators.offHeapAllocator;
  import static io.netty5.util.internal.ObjectUtil.checkNonEmpty;
  import static java.util.Objects.requireNonNull;
  
  /**
   * This is a special purpose implementation of a {@link X509Certificate} which allows
   * the user to pass PEM/PKCS#8 encoded data straight into {@link OpenSslContext} without
   * having to parse and re-encode bytes in Java land.
   *
   * All methods other than what's implemented in {@link PemEncoded}'s throw
   * {@link UnsupportedOperationException}s.
   *
   * @see PemEncoded
   * @see OpenSslContext
   * @see #valueOf(byte[])
   * @see #valueOf(Buffer)
   */
  public final class PemX509Certificate extends X509Certificate implements PemEncoded, Resource<PemX509Certificate> {
  
      private static final byte[] BEGIN_CERT = "-----BEGIN CERTIFICATE-----\n".getBytes(CharsetUtil.US_ASCII);
      private static final byte[] END_CERT = "\n-----END CERTIFICATE-----\n".getBytes(CharsetUtil.US_ASCII);
  
      /**
       * Creates a {@link PemEncoded} value from the {@link X509Certificate}s.
       */
      static PemEncoded toPEM(BufferAllocator alloc, X509Certificate... chain) throws CertificateEncodingException {
          checkNonEmpty(chain, "chain");
  
          // We can take a shortcut if there is only one certificate, and
          // it already happens to be a PemEncoded instance. This is the
          // ideal case and reason why all this exists. It allows the user
          // to pass pre-encoded bytes straight into OpenSSL without having
          // to do any of the extra work.
          if (chain.length == 1) {
              X509Certificate first = chain[0];
              if (first instanceof PemEncoded) {
                  return ((PemEncoded) first).copy();
              }
          }
  
          boolean success = false;
          Buffer pem = null;
          try {
              for (X509Certificate cert : chain) {
  
                  if (cert == null) {
                      throw new IllegalArgumentException("Null element in chain: " + Arrays.toString(chain));
                  }
  
                  if (cert instanceof PemEncoded) {
                      pem = append(alloc, (PemEncoded) cert, chain.length, pem);
                  } else {
                      pem = append(alloc, cert, chain.length, pem);
                  }
              }
  
              PemValue value = new PemValue(pem);
              success = true;
              return value;
          } finally {
              // Make sure we never leak the PEM's Buffer in the event of an Exception
              if (!success && pem != null) {
                  pem.close();
              }
          }
     }
 
     /**
      * Appends the {@link PemEncoded} value to the {@link Buffer} (last arg) and returns it.
      * If the {@link Buffer} didn't exist yet, an off-heap buffer will be created.
      */
     private static Buffer append(
             BufferAllocator alloc, PemEncoded encoded, int count, Buffer pem) {
         Buffer content = encoded.content();
 
         if (pem == null) {
             // see the other append() method
             pem = alloc.allocate(content.readableBytes() * count);
         } else {
             pem.ensureWritable(content.readableBytes());
         }
 
         int length = content.readableBytes();
         pem.skipWritableBytes(length);
         content.copyInto(content.readerOffset(), pem, pem.writerOffset(), length);
         return pem;
     }
 
     /**
      * Appends the {@link X509Certificate} value to the {@link Buffer} (last arg) and returns it.
      * If the {@link Buffer} didn't exist yet, an off-heap buffer will be created.
      */
     private static Buffer append(BufferAllocator alloc, X509Certificate cert, int count, Buffer pem)
             throws CertificateEncodingException {
 
         try (Buffer encoded = alloc.copyOf(cert.getEncoded());
              Buffer base64 = SslUtils.toBase64(alloc, encoded)) {
             int length = BEGIN_CERT.length + base64.readableBytes() + END_CERT.length;
             if (pem == null) {
                 // We try to approximate the buffer's initial size. The sizes of
                 // certificates can vary a lot so it'll be off a bit depending
                 // on the number of elements in the array (count argument).
                 pem = alloc.allocate(length * count);
             } else {
                 pem.ensureWritable(length);
             }
 
             pem.writeBytes(BEGIN_CERT);
             pem.writeBytes(base64);
             pem.writeBytes(END_CERT);
         }
 
         return pem;
     }
 
     /**
      * Creates a {@link PemX509Certificate} from raw {@code byte[]}.
      *
      * ATTENTION: It's assumed that the given argument is a PEM/PKCS#8 encoded value.
      * No input validation is performed to validate it.
      */
     public static PemX509Certificate valueOf(byte[] key) {
         return valueOf(offHeapAllocator().copyOf(key));
     }
 
     /**
      * Creates a {@link PemX509Certificate} from raw {@code Buffer}.
      *
      * ATTENTION: It's assumed that the given argument is a PEM/PKCS#8 encoded value.
      * No input validation is performed to validate it.
      */
     public static PemX509Certificate valueOf(Buffer key) {
         return new PemX509Certificate(key);
     }
 
     private final Buffer content;
 
     private PemX509Certificate(Buffer content) {
         this.content = requireNonNull(content, "content").makeReadOnly();
     }
 
     @Override
     public Buffer content() {
         if (!content.isAccessible()) {
             throw Statics.attachTrace((ResourceSupport<?, ?>) content,
                                       new IllegalStateException("PemX509Certificate is closed."));
         }
 
         return content;
     }
 
     @Override
     public void close() {
         content.close();
     }
 
     @Override
     public PemX509Certificate copy() {
         return new PemX509Certificate(content.copy(true));
     }
 
     @Override
     public Send<PemX509Certificate> send() {
         return content.send().map(PemX509Certificate.class, PemX509Certificate::new);
     }
 
     @Override
     public boolean isAccessible() {
         return content.isAccessible();
     }
 
     @Override
     public byte[] getEncoded() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean hasUnsupportedCriticalExtension() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Set<String> getCriticalExtensionOIDs() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Set<String> getNonCriticalExtensionOIDs() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public byte[] getExtensionValue(String oid) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void checkValidity() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void checkValidity(Date date) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int getVersion() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public BigInteger getSerialNumber() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Principal getIssuerDN() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Principal getSubjectDN() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Date getNotBefore() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Date getNotAfter() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public byte[] getTBSCertificate() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public byte[] getSignature() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public String getSigAlgName() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public String getSigAlgOID() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public byte[] getSigAlgParams() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean[] getIssuerUniqueID() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean[] getSubjectUniqueID() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean[] getKeyUsage() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int getBasicConstraints() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void verify(PublicKey key) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void verify(PublicKey key, String sigProvider) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public PublicKey getPublicKey() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean equals(Object o) {
         if (o == this) {
             return true;
         }
         if (!(o instanceof PemX509Certificate)) {
             return false;
         }
 
         PemX509Certificate other = (PemX509Certificate) o;
         return content.equals(other.content);
     }
 
     @Override
     public int hashCode() {
         return content.hashCode();
     }
 
     @Override
     public String toString() {
         return content.toString(CharsetUtil.UTF_8);
     }
 }