// Copyright 2024 Google LLC
//
// 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
//
//     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.

#include "internal/platform/implementation/linux/ble_l2cap_socket.h"

#include <bluetooth/bluetooth.h>
#include <bluetooth/l2cap.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <unistd.h>

#include <cerrno>
#include <cstring>
#include <bluetooth/bluetooth.h>
#include <sys/ioctl.h>

#include "absl/strings/escaping.h"
#include "absl/strings/string_view.h"
#include "internal/platform/byte_array.h"
#include "internal/platform/exception.h"
#include "internal/platform/logging.h"

#include "bluetooth_classic_socket.h"

namespace nearby {
namespace linux {

namespace {
constexpr size_t kLogMaxBytes = 64;
constexpr size_t kDefaultBleL2capMtu = 23;

size_t GetSocketMtu(int fd, int option_name) {
  uint16_t mtu = 0;
  socklen_t len = sizeof(mtu);
  if (getsockopt(fd, SOL_BLUETOOTH, option_name, &mtu, &len) == 0 &&
      mtu > 0) {
    return static_cast<size_t>(mtu);
  }
  return 0;
}

std::string HexPreview(const char* data, size_t size) {
  size_t count = std::min(size, kLogMaxBytes);
  std::string hex =
      absl::BytesToHexString(absl::string_view(data, count));
  if (size > count) {
    hex.append("...");
  }
  return hex;
}

size_t GetL2capOutputMtu(int fd) {
  struct l2cap_options opts;
  size_t mtu = GetSocketMtu(fd, BT_SNDMTU);
  if (mtu > 0) {
    return mtu;
  }
  return kDefaultBleL2capMtu;
}

Exception PollSocket(int fd, short event) {
  struct pollfd fds[1];
  fds[0].fd = fd;
  fds[0].events = event;

  while (true) {
    int ret = poll(fds, 1, -1);
    if (ret < 0) {
      if (errno == EINTR) continue;
      LOG(ERROR) << "Error polling L2CAP socket: " << std::strerror(errno);
      return {Exception::kIo};
    }
    if ((fds[0].revents & event) != 0) {
      return {Exception::kSuccess};
    }
    if ((fds[0].revents & POLLHUP) != 0) {
      LOG(ERROR) << "L2CAP socket disconnected";
      return {Exception::kIo};
    }
    if ((fds[0].revents & (POLLERR | POLLNVAL)) != 0) {
      LOG(ERROR) << "Error occurred on L2CAP socket";
      return {Exception::kIo};
    }
  }
}
}  // namespace

BleL2capInputStream::BleL2capInputStream(int fd) : fd_(fd) {}

BleL2capInputStream::~BleL2capInputStream() { Close(); }

static size_t GetBleCocRcvMtu(int fd) {
  // Prefer BT_RCVMTU for LE CoC, but fall back to L2CAP_OPTIONS if needed.
  uint16_t mtu = 0;
  socklen_t len = sizeof(mtu);
  if (getsockopt(fd, SOL_BLUETOOTH, BT_RCVMTU, &mtu, &len) == 0 && mtu > 0)
    return mtu;

  return 512;
}

  static size_t NextPacketSize(int fd) {
  int pending = 0;
  if (ioctl(fd, FIONREAD, &pending) == 0 && pending > 0) {
    return static_cast<size_t>(pending);
  }
  return 0;  // unknown
}
ExceptionOr<ByteArray> BleL2capInputStream::Read(std::int64_t size) {
  int fd = fd_.load();
  if (fd < 0) return Exception{Exception::kIo};

  if (size <= 0) {
    return ExceptionOr<ByteArray>(ByteArray{});
  }
  LOG(INFO) << "Reading";

  auto poller = Poller::CreateOutputPoller(fd);

  while (true) {
    if (fd_.load() != fd) return {Exception::kIo};
    auto result = poller.Ready();
    if (result.Raised()) return result;
    if (fd_.load() != fd) return {Exception::kIo};

    // Read one SDU (kernel gives one per recv on SOCK_SEQPACKET).
    // Always allocate a buffer up to the receive MTU since the kernel may
    // deliver a complete SDU that's larger than the requested size.
    // We'll trim to the requested size afterwards.
    size_t recv_mtu = GetBleCocRcvMtu(fd);
    std::string buffer;
    buffer.resize(recv_mtu);

    if (fd_.load() != fd) return {Exception::kIo};
    ssize_t n = ::recv(fd, buffer.data(), buffer.size(), 0);
    LOG(INFO)<< "Received something";
    if (n < 0) {
      if (errno == EINTR) continue;
      if (errno == EAGAIN || errno == EWOULDBLOCK) continue;
      if (errno == EBADF) {
        LOG(INFO) << __func__ << ": socket was closed during read";
        return {Exception::kIo};
      }
      LOG(ERROR) << __func__ << ": error reading data on bluetooth socket: "
                 << std::strerror(errno);
      return {Exception::kIo};
    }
    // if (n == 0) {
    //   LOG(INFO) << __func__ << ": socket closed (EOF)";
    //   return {Exception::kIo};
    // }
    LOG(INFO)<< "Got this many "<< static_cast<size_t>(n);

    buffer.resize(static_cast<size_t>(n));

    if (buffer.size() != static_cast<size_t>(size)) {
      LOG(WARNING) << __func__ << ": size mismatch recv=" << buffer.size()
                   << " expected=" << size;
    }
    // If the packet is larger than requested size, drop the remainder to stay
    // close to l2test semantics (one recv consumes one frame).
    size_t to_return = std::min(static_cast<size_t>(size), buffer.size());
    std::string out = buffer.substr(0, to_return);
    LOG(INFO) << __func__ << ": returning " << to_return
              << " bytes from SDU size " << buffer.size() << ", data=0x"
              << HexPreview(out.data(), out.size());
    return ExceptionOr<ByteArray>(ByteArray(std::move(out)));
  }
}

Exception BleL2capInputStream::Close() {
  int fd = fd_.exchange(-1);
  if (fd < 0) return {Exception::kSuccess};  // Already closed
  ::shutdown(fd, SHUT_RDWR);
  return {Exception::kSuccess};
}

BleL2capOutputStream::BleL2capOutputStream(int fd) : fd_(fd) {}

BleL2capOutputStream::~BleL2capOutputStream() { Close(); }

Exception BleL2capOutputStream::Write(absl::string_view data) {
  int fd = fd_.load();
  if (fd < 0) return Exception{Exception::kIo};

  auto poller = Poller::CreateOutputPoller(fd);

  if (data.empty()) {
    return {Exception::kSuccess};
  }

  size_t max_chunk_size = GetL2capOutputMtu(fd);
  if (max_chunk_size == 0) {
    max_chunk_size = kDefaultBleL2capMtu;
  }

  LOG(INFO) << "BleL2capOutputStream::Write bytes=" << data.size()
            << " mtu=" << max_chunk_size
            << " data=0x" << HexPreview(data.data(), data.size());

  size_t offset = 0;
  while (offset < data.size()) {
    if (fd_.load() != fd) return {Exception::kIo};
    auto result = poller.Ready();  // wait for POLLOUT/EPOLLOUT
    if (result.Raised()) return result;
    if (fd_.load() != fd) return {Exception::kIo};

    size_t chunk = std::min(max_chunk_size, data.size() - offset);

    ssize_t wrote = ::send(fd,
                           data.data() + offset,
                           chunk,
#ifdef MSG_NOSIGNAL
                           MSG_NOSIGNAL
#else
                           0
#endif
    );

    if (wrote < 0) {
      if (errno == EINTR) continue;
      if (errno == EAGAIN || errno == EWOULDBLOCK) continue;

      if (errno == EMSGSIZE) {
        LOG(ERROR) << __func__
                   << ": EMSGSIZE sending " << chunk
                   << " bytes; peer MTU " << max_chunk_size;
        return {Exception::kIo};
      }

      if (errno == EBADF || errno == EPIPE) {
        LOG(INFO) << __func__ << ": socket was closed during write";
        return {Exception::kIo};
      }

      LOG(ERROR) << __func__
                 << ": error writing data on bluetooth socket: "
                 << std::strerror(errno);
      return {Exception::kIo};
    }

    if (wrote == 0) {
      LOG(INFO) << __func__ << ": peer closed during write";
      return {Exception::kIo};
    }

    if (static_cast<size_t>(wrote) != chunk) {
      LOG(ERROR) << __func__ << ": partial packet write ("
                 << wrote << "/" << chunk << ")";
      return {Exception::kIo};
    }

    offset += static_cast<size_t>(wrote);
  }

  return {Exception::kSuccess};
}

Exception BleL2capOutputStream::Close() {
  int fd = fd_.exchange(-1);
  if (fd < 0) return {Exception::kSuccess};  // Already closed
  ::shutdown(fd, SHUT_RDWR);
  return {Exception::kSuccess};
}

BleL2capSocket::BleL2capSocket(int fd,
                               api::ble::BlePeripheral::UniqueId peripheral_id)
    : peripheral_id_(peripheral_id),
      input_stream_(std::make_unique<BleL2capInputStream>(fd)),
      output_stream_(std::make_unique<BleL2capOutputStream>(fd))
{
  LOG(INFO) << "fd_ " << fd;
  LOG(INFO) << "input_stream_ :" << input_stream_.get();
  LOG(INFO) << "output_stream_ :" << output_stream_.get();
  struct l2cap_options opts;
  size_t snd_mtu = GetSocketMtu(fd, BT_SNDMTU);
  size_t rcv_mtu = GetSocketMtu(fd, BT_RCVMTU);
  LOG(INFO) << "BleL2capSocket MTU fallback snd_mtu=" << snd_mtu
            << " rcv_mtu=" << rcv_mtu;
}

BleL2capSocket::~BleL2capSocket() { Close(); }

Exception BleL2capSocket::Close() {
  absl::MutexLock lock(&mutex_);
  if (closed_) {
    return {Exception::kSuccess};
  }
  DoClose();
  return {Exception::kSuccess};
}

void BleL2capSocket::DoClose() {
  closed_ = true;
  
  if (input_stream_) {
    input_stream_->Close();
  }
  if (output_stream_) {
    output_stream_->Close();
  }
  
  if (close_notifier_) {
    auto notifier = std::move(close_notifier_);
    mutex_.Unlock();
    notifier();
    mutex_.Lock();
  }
}

void BleL2capSocket::SetCloseNotifier(absl::AnyInvocable<void()> notifier) {
  absl::MutexLock lock(&mutex_);
  close_notifier_ = std::move(notifier);
}

bool BleL2capSocket::IsClosed() const {
  absl::MutexLock lock(&mutex_);
  return closed_;
}

}  // namespace linux
}  // namespace nearby