/*
    * Copyright 2014 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.handler.codec.base64.Base64;
  import io.netty5.util.internal.logging.InternalLogger;
  import io.netty5.util.internal.logging.InternalLoggerFactory;
  
  import java.io.ByteArrayOutputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.security.KeyException;
  import java.security.KeyStore;
  import java.security.cert.CertificateException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import static io.netty5.buffer.api.DefaultBufferAllocators.onHeapAllocator;
  import static java.nio.charset.StandardCharsets.US_ASCII;
  
  /**
   * Reads a PEM file and converts it into a list of DERs so that they are imported into a {@link KeyStore} easily.
   */
  final class PemReader {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(PemReader.class);
  
      private static final Pattern CERT_HEADER = Pattern.compile(
              "-+BEGIN\\s[^-\\r\\n]*CERTIFICATE[^-\\r\\n]*-+(?:\\s|\\r|\\n)+");
      private static final Pattern CERT_FOOTER = Pattern.compile(
              "-+END\\s[^-\\r\\n]*CERTIFICATE[^-\\r\\n]*-+(?:\\s|\\r|\\n)*");
      private static final Pattern KEY_HEADER = Pattern.compile(
              "-+BEGIN\\s[^-\\r\\n]*PRIVATE\\s+KEY[^-\\r\\n]*-+(?:\\s|\\r|\\n)+");
      private static final Pattern KEY_FOOTER = Pattern.compile(
              "-+END\\s[^-\\r\\n]*PRIVATE\\s+KEY[^-\\r\\n]*-+(?:\\s|\\r|\\n)*");
      private static final Pattern BODY = Pattern.compile("[a-z0-9+/=][a-z0-9+/=\\r\\n]*", Pattern.CASE_INSENSITIVE);
  
      static Buffer[] readCertificates(File file) throws CertificateException {
          try {
              InputStream in = new FileInputStream(file);
  
              try {
                  return readCertificates(in);
              } finally {
                  safeClose(in);
              }
          } catch (FileNotFoundException e) {
              throw new CertificateException("could not find certificate file: " + file);
          }
      }
  
      static Buffer[] readCertificates(InputStream in) throws CertificateException {
          String content;
          try {
              content = readContent(in);
          } catch (IOException e) {
              throw new CertificateException("failed to read certificate input stream", e);
          }
  
          List<Buffer> certs = new ArrayList<>();
          Matcher m = CERT_HEADER.matcher(content);
          int start = 0;
          while (m.find(start)) {
              m.usePattern(BODY);
              if (!m.find()) {
                  break;
              }
  
              try (Buffer base64 = onHeapAllocator().copyOf(m.group(0), US_ASCII)) {
                  m.usePattern(CERT_FOOTER);
                  if (!m.find()) {
                      // Certificate is incomplete.
                      break;
                  }
                  certs.add(Base64.decode(base64));
  
                  start = m.end();
                  m.usePattern(CERT_HEADER);
              }
         }
 
         if (certs.isEmpty()) {
             throw new CertificateException("found no certificates in input stream");
         }
 
         return certs.toArray(Buffer[]::new);
     }
 
     static Buffer readPrivateKey(File file) throws KeyException {
         try {
             InputStream in = new FileInputStream(file);
 
             try {
                 return readPrivateKey(in);
             } finally {
                 safeClose(in);
             }
         } catch (FileNotFoundException e) {
             throw new KeyException("could not find key file: " + file);
         }
     }
 
     static Buffer readPrivateKey(InputStream in) throws KeyException {
         String content;
         try {
             content = readContent(in);
         } catch (IOException e) {
             throw new KeyException("failed to read key input stream", e);
         }
 
         Matcher m = KEY_HEADER.matcher(content);
         if (!m.find()) {
             throw keyNotFoundException();
         }
         m.usePattern(BODY);
         if (!m.find()) {
             throw keyNotFoundException();
         }
 
         try (Buffer base64 = onHeapAllocator().copyOf(m.group(0), US_ASCII)) {
             m.usePattern(KEY_FOOTER);
             if (!m.find()) {
                 // Key is incomplete.
                 throw keyNotFoundException();
             }
             return Base64.decode(base64);
         }
     }
 
     private static KeyException keyNotFoundException() {
         return new KeyException("could not find a PKCS #8 private key in input stream" +
                 " (see https://netty.io/wiki/sslcontextbuilder-and-private-key.html for more information)");
     }
 
     private static String readContent(InputStream in) throws IOException {
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         try {
             byte[] buf = new byte[8192];
             for (;;) {
                 int ret = in.read(buf);
                 if (ret < 0) {
                     break;
                 }
                 out.write(buf, 0, ret);
             }
             return out.toString(US_ASCII);
         } finally {
             safeClose(out);
         }
     }
 
     private static void safeClose(InputStream in) {
         try {
             in.close();
         } catch (IOException e) {
             logger.warn("Failed to close a stream.", e);
         }
     }
 
     private static void safeClose(OutputStream out) {
         try {
             out.close();
         } catch (IOException e) {
             logger.warn("Failed to close a stream.", e);
         }
     }
 
     private PemReader() { }
 }