#include "server.hh"

#include <algorithm>
#include <cassert>
#include <cerrno>
#include <chrono>
#include <cstring>
#include <signal.h>
#include <unistd.h>

#include "buffer.hh"
#include "logger.hh"
#include "looper.hh"
#include "net.hh"

namespace {

constexpr auto CLIENT_TIMEOUT = std::chrono::seconds(30);
constexpr size_t BUFFER_SIZE = 1 * 1024 * 1024;

int g_signal_pipe[2];

void signal_handler(int) {
  write(g_signal_pipe[1], "1", 1);
}

class ServerImpl : public Server {
 public:
  ServerImpl()
      : looper_(Looper::create()) {}

  ~ServerImpl() override {
    for (auto& fd : listen_) {
      looper_->remove(fd.get());
    }
  }

  bool setup(std::shared_ptr<Logger> logger, std::string const& host,
             uint16_t port) override {
    logger_ = logger;
    listen_ = net::bind_and_listen(logger.get(), host, port);
    if (listen_.empty()) {
      logger->err("Unable to listen");
      return false;
    }

    for (auto& fd : listen_) {
      looper_->add(fd.get(), Looper::EVENT_READ,
                   std::bind(&ServerImpl::listen_read, this, fd.get(),
                             std::placeholders::_1));
    }
    return true;
  }

  bool run(std::shared_ptr<Logger> logger) override {
    logger_ = logger;

    bool close_pipe;
    if (pipe(g_signal_pipe) == 0) {
      close_pipe = true;
      struct sigaction sa;
      sa.sa_handler = signal_handler;
      sigemptyset(&sa.sa_mask);
      sa.sa_flags = SA_RESTART;
      sigaction(SIGINT, &sa, nullptr);
      sigaction(SIGTERM, &sa, nullptr);
      sigaction(SIGQUIT, &sa, nullptr);

      looper_->add(g_signal_pipe[0], Looper::EVENT_READ,
                   std::bind(&ServerImpl::signal, this, std::placeholders::_1));
    } else {
      logger->warn("Unable to create a pipe: %s", strerror(errno));
      close_pipe = false;
    }

    bool ret = looper_->run(logger.get());

    if (close_pipe) {
      looper_->remove(g_signal_pipe[0]);
      close(g_signal_pipe[0]);
      close(g_signal_pipe[1]);
    }
    return ret;
  }

 private:
  void signal(uint8_t) {
    looper_->quit();
  }

  struct Client {
    unique_fd fd_;
    uint8_t events_{Looper::EVENT_WRITE};
    std::unique_ptr<Buffer> in_;
    std::unique_ptr<Buffer> out_;
    uint32_t watchdog_{0};
    std::chrono::steady_clock::time_point last_event_;

    explicit Client(unique_fd fd)
        : fd_(std::move(fd)) {}
  };

  void listen_read(int fd, uint8_t events) {
    if (events & Looper::EVENT_ERROR) {
      auto it = std::find_if(listen_.begin(), listen_.end(),
                             [fd](auto& listen) {
                               return listen.get() == fd;
                             });
      if (it != listen_.end()) {
        logger_->warn("Listening socket error");
        listen_.erase(it);
        if (listen_.empty()) {
          logger_->err("No listening sockets left");
          looper_->quit();
          return;
        }
      } else {
        assert(false);
      }
      return;
    }

    unique_fd client_fd = net::accept(logger_.get(), fd);
    if (client_fd) {
      logger_->dbg("New client: %d", client_fd.get());
      auto client = new Client(std::move(client_fd));
      client->in_ = Buffer::fixed(BUFFER_SIZE);
      client->out_ = Buffer::fixed(BUFFER_SIZE);
      clients_.push_back(client);

      looper_->add(client->fd_.get(), client->events_,
                   std::bind(&ServerImpl::client_event,
                             this, client,
                             std::placeholders::_1));
      client->watchdog_ = looper_->schedule(
          CLIENT_TIMEOUT.count(),
          std::bind(&ServerImpl::client_check_timeout,
                    this, client,
                    std::placeholders::_1));
    }
  }

  void client_event(Client* client, uint8_t events) {
    if (events & Looper::EVENT_ERROR) {
      logger_->warn("%d: Unexpected client error", client->fd_.get());
      remove_client(client);
      return;
    }

    client->last_event_ = std::chrono::steady_clock::now();

    if (events & Looper::EVENT_READ && client->in_) {
      while (true) {
        size_t avail;
        auto* ptr = client->in_->wbuf(65535, avail);
        if (avail == 0)
          break;
        auto ret = read(client->fd_.get(), ptr, avail);
        if (ret < 0) {
          if (errno == EAGAIN || errno == EWOULDBLOCK)
            break;
          if (errno == EINTR)
            continue;
          logger_->warn("%d: Read error: %s", client->fd_.get(),
                        strerror(errno));
          break;
        } else if (ret == 0) {
          logger_->dbg("%d: Connection closed", client->fd_.get());
          if (client->out_->empty()) {
            remove_client(client);
            return;
          } else {
            // Might be only read side that is shutdown, try writing the
            // rest before we give up.
            client->in_.reset();
            break;
          }
        } else {
          client->in_->wcommit(ret);
          if (static_cast<size_t>(ret) < avail)
            break;
        }
      }
    }

    // Always try to write, usually we write as a result of a read above
    // so saves having to call back to the loop just to answer.
    // And if there wasn't a read event then we already know there was an write
    // event.
    if (/* events & Looper::EVENT_WRITE */ true) {
      while (true) {
        size_t avail;
        auto* ptr = client->out_->rbuf(65535, avail);
        if (avail == 0)
          break;
        auto ret = write(client->fd_.get(), ptr, avail);
        if (ret < 0) {
          if (errno == EAGAIN || errno == EWOULDBLOCK)
            break;
          if (errno == EINTR)
            continue;
          logger_->warn("%d: Write error: %s", client->fd_.get(),
                        strerror(errno));
          break;
        } else {
          client->out_->rcommit(ret);
          if (static_cast<size_t>(ret) < avail)
            break;
        }
      }
    }

    auto const old_events = client->events_;
    client->events_ = 0;

    if (client->in_) {
      if (!client->in_->full())
        client->events_ |= Looper::EVENT_READ;
      if (!client->out_->empty())
        client->events_ |= Looper::EVENT_WRITE;
    } else {
      if (client->out_->empty()) {
        remove_client(client);
        return;
      } else {
        client->events_ |= Looper::EVENT_WRITE;
      }
    }

    if (client->events_ != old_events) {
      looper_->update(client->fd_.get(), client->events_);
    }
  }

  void client_check_timeout(Client* client, uint32_t) {
    auto since_last = std::chrono::steady_clock::now() - client->last_event_;
    if (since_last >= CLIENT_TIMEOUT) {
      client->watchdog_ = 0;
      remove_client(client);
      return;
    }
    auto delay = CLIENT_TIMEOUT - since_last;
    client->watchdog_ = looper_->schedule(
        std::chrono::duration_cast<std::chrono::seconds>(delay).count(),
        std::bind(&ServerImpl::client_check_timeout,
                  this, client,
                  std::placeholders::_1));
  }

  void remove_client(Client* client) {
    if (client->fd_)
      looper_->remove(client->fd_.get());
    if (client->watchdog_)
      looper_->cancel(client->watchdog_);
    auto it = std::find(clients_.begin(), clients_.end(), client);
    if (it != clients_.end()) {
      clients_.erase(it);
    } else {
      assert(false);
    }
    delete client;
  }

  std::shared_ptr<Looper> looper_;
  std::shared_ptr<Logger> logger_;
  std::vector<unique_fd> listen_;
  std::vector<Client*> clients_;
};

}  // namespace

// static
std::unique_ptr<Server> Server::create() {
  return std::make_unique<ServerImpl>();
}