/*
 * Jooby https://jooby.io
 * Apache License Version 2.0 https://jooby.io/LICENSE.txt
 * Copyright 2014 Edgar Espina
 */
package io.jooby.internal.x509;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.KeyException;
import java.security.cert.CertificateException;
import java.util.ArrayList;
import java.util.Base64;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import io.jooby.internal.IOUtils;

/**
 * Reads a PEM file and converts it into a list of DERs.
 *
 * <p>Borrowed from <a href="http://netty.io">Netty</a>
 */
final class PemReader {

  private static final Pattern CERT_PATTERN =
      Pattern.compile(
          "-+BEGIN\\s+.*CERTIFICATE[^-]*-+(?:\\s|\\r|\\n)+"
              + // Header
              "([a-z0-9+/=\\r\\n]+)"
              + // Base64 text
              "-+END\\s+.*CERTIFICATE[^-]*-+", // Footer
          Pattern.CASE_INSENSITIVE);

  private static final Pattern KEY_PATTERN =
      Pattern.compile(
          "-+BEGIN\\s+.*PRIVATE\\s+KEY[^-]*-+(?:\\s|\\r|\\n)+"
              + // Header
              "([a-z0-9+/=\\r\\n]+)"
              + // Base64 text
              "-+END\\s+.*PRIVATE\\s+KEY[^-]*-+", // Footer
          Pattern.CASE_INSENSITIVE);

  static List<ByteBuffer> readCertificates(final InputStream file)
      throws CertificateException, IOException {
    String content = IOUtils.toString(file, StandardCharsets.UTF_8);

    List<ByteBuffer> certs = new ArrayList<>();
    Matcher m = CERT_PATTERN.matcher(content);
    int start = 0;
    while (m.find(start)) {
      ByteBuffer buffer = ByteBuffer.wrap(decode(m.group(1)));
      certs.add(buffer);
      start = m.end();
    }

    if (certs.isEmpty()) {
      throw new CertificateException("found no certificates: " + file);
    }

    return certs;
  }

  private static byte[] decode(String value) {
    // MimeDecoder automatically strips out \r and \n characters
    return Base64.getMimeDecoder().decode(value);
  }

  static ByteBuffer readPrivateKey(final InputStream file) throws KeyException, IOException {
    String content = IOUtils.toString(file, StandardCharsets.US_ASCII);

    Matcher m = KEY_PATTERN.matcher(content);
    if (!m.find()) {
      throw new KeyException("found no private key: " + file);
    }

    String value = m.group(1);
    return ByteBuffer.wrap(decode(value));
  }

  private PemReader() {}
}
