text: /*
   * Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <AK/Debug.h>
  #include <LibCore/DateTime.h>
  #include <LibCore/Timer.h>
  #include <LibCrypto/PK/Code/EMSA_PSS.h>
  #include <LibTLS/TLSv12.h>
  
  namespace TLS {
  
  Optional<ByteBuffer> TLSv12::read()
  {
      if (m_context.application_buffer.size()) {
          auto buf = m_context.application_buffer.slice(0, m_context.application_buffer.size());
          m_context.application_buffer.clear();
          return buf;
      }
      return {};
  }
  
  ByteBuffer TLSv12::read(size_t max_size)
  {
      if (m_context.application_buffer.size()) {
          auto length = min(m_context.application_buffer.size(), max_size);
          auto buf = m_context.application_buffer.slice(0, length);
          m_context.application_buffer = m_context.application_buffer.slice(length, m_context.application_buffer.size() - length);
          return buf;
      }
      return {};
  }
  
  String TLSv12::read_line(size_t max_size)
  {
      if (!can_read_line())
          return {};
  
      auto* start = m_context.application_buffer.data();
      auto* newline = (u8*)memchr(m_context.application_buffer.data(), '\n', m_context.application_buffer.size());
      VERIFY(newline);
  
      size_t offset = newline - start;
  
      if (offset > max_size)
          return {};
  
      auto buffer = ByteBuffer::copy(start, offset);
      m_context.application_buffer = m_context.application_buffer.slice(offset + 1, m_context.application_buffer.size() - offset - 1);
  
      return String::copy(buffer, Chomp);
  }
  
  bool TLSv12::write(ReadonlyBytes buffer)
  {
      if (m_context.connection_status != ConnectionStatus::Established) {
          dbgln_if(TLS_DEBUG, "write request while not connected");
          return false;
      }
  
      PacketBuilder builder { MessageType::ApplicationData, m_context.options.version, buffer.size() };
      builder.append(buffer);
      auto packet = builder.build();
  
      update_packet(packet);
      write_packet(packet);
  
      return true;
  }
  
  bool TLSv12::connect(const String& hostname, int port)
  {
      set_sni(hostname);
      return Core::Socket::connect(hostname, port);
  }
  
  bool TLSv12::common_connect(const struct sockaddr* saddr, socklen_t length)
  {
      if (m_context.critical_error)
          return false;
  
      if (Core::Socket::is_connected()) {
          if (is_established()) {
              VERIFY_NOT_REACHED();
          } else {
              Core::Socket::close(); // reuse?
          }
      }
  
      Core::Socket::on_connected = [this] {
          Core::Socket::on_ready_to_read = [this] {
              read_from_socket();
          };
  
          auto packet = build_hello();
          write_packet(packet);
  
          deferred_invoke([&](auto&) {
              m_handshake_timeout_timer = Core::Timer::create_single_shot(
                  m_max_wait_time_for_handshake_in_seconds * 1000, [&] {
                      auto timeout_diff = Core::DateTime::now().timestamp() - m_context.handshake_initiation_timestamp;
                      // If the timeout duration was actually within the max wait time (with a margin of error),
                      // we're not operating slow, so the server timed out.
                      // otherwise, it's our fault that the negotiation is taking too long, so extend the timer :P
                      if (timeout_diff < m_max_wait_time_for_handshake_in_seconds + 1) {
                          // The server did not respond fast enough,
                          // time the connection out.
                          alert(AlertLevel::Critical, AlertDescription::UserCanceled);
                          m_context.connection_finished = true;
                          m_context.tls_buffer.clear();
                          m_context.error_code = Error::TimedOut;
                          m_context.critical_error = (u8)Error::TimedOut;
                          check_connection_state(false); // Notify the client.
                      } else {
                          // Extend the timer, we are too slow.
                          m_handshake_timeout_timer->restart(m_max_wait_time_for_handshake_in_seconds * 1000);
                      }
                  },
                  this);
              write_into_socket();
              m_handshake_timeout_timer->start();
              m_context.handshake_initiation_timestamp = Core::DateTime::now().timestamp();
          });
          m_has_scheduled_write_flush = true;
  
          if (on_tls_connected)
              on_tls_connected();
      };
      bool success = Core::Socket::common_connect(saddr, length);
      if (!success)
          return false;
  
      return true;
  }
  
  void TLSv12::read_from_socket()
  {
      auto did_schedule_read = false;
      auto notify_client_for_app_data = [&] {
          if (m_context.application_buffer.size() > 0) {
              if (!did_schedule_read) {
                  deferred_invoke([&](auto&) { read_from_socket(); });
                  did_schedule_read = true;
              }
              if (on_tls_ready_to_read)
                  on_tls_ready_to_read(*this);
          }
      };
  
      // If there's anything before we consume stuff, let the client know
      // since we won't be consuming things if the connection is terminated.
      notify_client_for_app_data();
  
      if (!check_connection_state(true))
          return;
  
      consume(Core::Socket::read(4096));
  
      // If anything new shows up, tell the client about the event.
      notify_client_for_app_data();
  }
  
  void TLSv12::write_into_socket()
  {
      dbgln_if(TLS_DEBUG, "Flushing cached records: {} established? {}", m_context.tls_buffer.size(), is_established());
  
      m_has_scheduled_write_flush = false;
      if (!check_connection_state(false))
          return;
      flush();
  
      if (!is_established())
          return;
  
      if (!m_context.application_buffer.size()) // hey client, you still have stuff to read...
          if (on_tls_ready_to_write)
              on_tls_ready_to_write(*this);
  }
  
  bool TLSv12::check_connection_state(bool read)
  {
      if (!Core::Socket::is_open() || !Core::Socket::is_connected() || Core::Socket::eof()) {
          // an abrupt closure (the server is a jerk)
          dbgln_if(TLS_DEBUG, "Socket not open, assuming abrupt closure");
          m_context.connection_finished = true;
      }
      if (m_context.critical_error) {
          dbgln_if(TLS_DEBUG, "CRITICAL ERROR {} :(", m_context.critical_error);
  
          if (on_tls_error)
              on_tls_error((AlertDescription)m_context.critical_error);
          return false;
      }
      if (((read && m_context.application_buffer.size() == 0) || !read) && m_context.connection_finished) {
          if (m_context.application_buffer.size() == 0 && m_context.connection_status != ConnectionStatus::Disconnected) {
              if (on_tls_finished)
                  on_tls_finished();
          }
          if (m_context.tls_buffer.size()) {
              dbgln_if(TLS_DEBUG, "connection closed without finishing data transfer, {} bytes still in buffer and {} bytes in application buffer",
                  m_context.tls_buffer.size(),
                  m_context.application_buffer.size());
          } else {
              m_context.connection_finished = false;
              dbgln_if(TLS_DEBUG, "FINISHED");
          }
          if (!m_context.application_buffer.size()) {
              m_context.connection_status = ConnectionStatus::Disconnected;
              return false;
          }
      }
      return true;
  }
  
  bool TLSv12::flush()
  {
      auto out_buffer = write_buffer().data();
      size_t out_buffer_index { 0 };
      size_t out_buffer_length = write_buffer().size();
  
      if (out_buffer_length == 0)
          return true;
  
      if constexpr (TLS_DEBUG) {
          dbgln("SENDING...");
          print_buffer(out_buffer, out_buffer_length);
      }
      if (Core::Socket::write(&out_buffer[out_buffer_index], out_buffer_length)) {
          write_buffer().clear();
          return true;
      }
      if (m_context.send_retries++ == 10) {
          // drop the records, we can't send
          dbgln_if(TLS_DEBUG, "Dropping {} bytes worth of TLS records as max retries has been reached", write_buffer().size());
          write_buffer().clear();
          m_context.send_retries = 0;
      }
      return false;
  }
  
  }
  