path: root/src/http.cc

#include "http.hh"

#include "buffer.hh"
#include "cfg.hh"
#include "logger.hh"
#include "looper.hh"
#include "str.hh"
#include "unique_fd.hh"

#include <algorithm>
#include <cassert>
#include <cerrno>
#include <charconv>
#include <chrono>
#include <cstdint>
#include <cstring>
#include <fcntl.h>
#include <format>
#include <map>
#include <memory>
#include <netdb.h>
#include <optional>
#include <span>
#include <string>
#include <string_view>
#include <sys/socket.h>
#include <sys/types.h>
#include <system_error>
#include <unistd.h>
#include <utility>
#include <vector>

namespace http {

namespace {

std::string_view ascii_lowercase(std::string_view input, std::string& tmp) {
  auto it = input.begin();
  for (; it != input.end(); ++it) {
    if (*it >= 'A' && *it <= 'Z') {
      tmp.resize(input.size());
      auto out = std::copy(input.begin(), it, tmp.begin());
      // NOLINTNEXTLINE(bugprone-narrowing-conversions)
      *out++ = *it++ | 0x20;
      for (; it != input.end(); ++it) {
        if (*it >= 'A' && *it <= 'Z') {
          // NOLINTNEXTLINE(bugprone-narrowing-conversions)
          *out++ = *it | 0x20;
        } else {
          *out++ = *it;
        }
      }
      return tmp;
    }
  }
  return input;
}

bool eq_lowercase(std::string_view input, std::string_view cmp) {
  if (input.size() != cmp.size())
    return false;

  auto a = input.begin();
  auto b = cmp.begin();
  for (; a != input.end(); ++a, ++b) {
    if (*a >= 'A' && *a <= 'Z') {
      // NOLINTNEXTLINE(bugprone-narrowing-conversions)
      if ((*a | 0x20) != *b)
        return false;
    } else {
      if (*a != *b)
        return false;
    }
  }
  return true;
}

std::string standard_header(std::string_view input) {
  bool capitalize = true;
  std::string ret;
  for (auto c : input) {
    if (c >= 'A' && c <= 'Z') {
      if (capitalize) {
        ret.push_back(c);
        capitalize = false;
      } else {
        // NOLINTNEXTLINE(bugprone-narrowing-conversions)
        ret.push_back(c | 0x20);
      }
    } else if (c >= 'a' && c <= 'z') {
      if (capitalize) {
        // NOLINTNEXTLINE(bugprone-narrowing-conversions)
        ret.push_back(c & 0x20);
        capitalize = false;
      } else {
        ret.push_back(c);
      }
    } else if (c == '-') {
      ret.push_back(c);
      capitalize = true;
    } else {
      ret.push_back(c);
    }
  }
  return ret;
}

void make_nonblock(int fd) {
  int flags = fcntl(fd, F_GETFL);
  if (flags & O_NONBLOCK)
    return;
  fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

void clear(Buffer& buffer) {
  if (buffer.empty())
    return;
  while (true) {
    size_t avail;
    buffer.rptr(avail);
    if (avail == 0)
      break;
    buffer.consume(avail);
  }
}

class MimeTypeImpl : public MimeType {
 public:
  MimeTypeImpl(std::string str, size_t slash, size_t subtype_len,
               std::map<std::string_view, std::string_view> params = {})
      : str_(std::move(str)),
        slash_(slash),
        subtype_len_(subtype_len),
        params_(std::move(params)) {
    assert(slash_ < str_.size());
    assert(slash_ + 1 + subtype_len_ <= str_.size());
  }

  [[nodiscard]]
  std::string_view type() const override {
    return std::string_view(str_).substr(0, slash_);
  }

  [[nodiscard]]
  std::string_view subtype() const override {
    return std::string_view(str_).substr(slash_ + 1, subtype_len_);
  }

  [[nodiscard]]
  std::optional<std::string_view> parameter(
      std::string_view name) const override {
    std::optional<std::string_view> ret;
    std::string tmp;
    auto it = params_.find(ascii_lowercase(name, tmp));
    if (it != params_.end())
      ret = it->second;
    return ret;
  }

  [[nodiscard]]
  std::string const& string() const override {
    return str_;
  }

 private:
  std::string const str_;
  size_t const slash_;
  size_t const subtype_len_;
  std::map<std::string_view, std::string_view> const params_;
};

class MimeTypeBuilderImpl : public MimeType::Builder {
 public:
  MimeTypeBuilderImpl(std::string_view type, std::string_view subtype)
      : slash_(type.size()), subtype_len_(subtype.size()) {
    str_.reserve(type.size() + 1 + subtype.size());
    str_.append(type);
    str_.push_back('/');
    str_.append(subtype);
  }

  MimeType::Builder& parameter(std::string_view name,
                               std::string_view value) override {
    // TODO: make value a quoted string if it contains ;
    std::string tmp;
    auto ret = params_.emplace(ascii_lowercase(name, tmp), value);
    if (!ret.second) {
      ret.first->second = value;
    }
    return *this;
  }

  [[nodiscard]]
  std::unique_ptr<MimeType> build() const override {
    if (params_.empty()) {
      return std::make_unique<MimeTypeImpl>(str_, slash_, subtype_len_);
    }

    std::string tmp(str_);
    std::map<std::pair<size_t, size_t>, size_t> params1;
    for (auto const& pair : params_) {
      tmp.append("; ");
      params1.emplace(std::make_pair(tmp.size(), pair.first.size()),
                      pair.second.size());
      tmp.append(pair.first);
      tmp.push_back('=');
      tmp.append(pair.second);
    }
    std::map<std::string_view, std::string_view> params2;
    std::string_view tmp_view(tmp);
    for (auto const& pair : params1) {
      params2.emplace(tmp_view.substr(pair.first.first, pair.first.second),
                      tmp_view.substr(pair.first.first + pair.first.second + 1,
                                      pair.second));
    }
    return std::make_unique<MimeTypeImpl>(std::move(tmp), slash_, subtype_len_,
                                          std::move(params2));
  }

 private:
  std::string str_;
  size_t const slash_;
  size_t const subtype_len_;
  std::map<std::string, std::string> params_;
};

class OpenPortImpl : public OpenPort {
 public:
  explicit OpenPortImpl(std::vector<unique_fd> fd) : fd_(std::move(fd)) {}

  std::vector<unique_fd> release() { return std::move(fd_); }

 private:
  std::vector<unique_fd> fd_;
};

class ResponseImpl : public Response {
 public:
  ResponseImpl(std::string data, SocketReceiver* socket_receiver)
      : data_(std::move(data)), socket_receiver_(socket_receiver) {}

  bool write(Buffer& buffer) override {
    if (offset_ >= data_.size())
      return false;

    size_t avail;
    auto* ptr = buffer.wptr(avail);
    if (avail == 0)
      return true;

    avail = std::min(data_.size() - offset_, avail);

    std::copy_n(data_.data() + offset_, avail, reinterpret_cast<char*>(ptr));
    offset_ += avail;
    buffer.commit(avail);

    return offset_ < data_.size();
  }

  [[nodiscard]]
  SocketReceiver* socket_receiver() const override {
    return socket_receiver_;
  }

 private:
  std::string const data_;
  size_t offset_{0};
  SocketReceiver* socket_receiver_;
};

class ResponseBuilderImpl : public Response::Builder {
 public:
  explicit ResponseBuilderImpl(StatusCode status) : status_(status) {}

  Response::Builder& content(std::string_view content) override {
    content_ = content;
    return *this;
  }

  Response::Builder& add_header(std::string_view name,
                                std::string_view value) override {
    // TODO: Make sure name or value doesn't contain invalid chars
    headers_.emplace_back(standard_header(name), value);
    return *this;
  }

  Builder& take_over(SocketReceiver& receiver) override {
    socket_receiver_ = &receiver;
    return *this;
  }

  [[nodiscard]]
  std::unique_ptr<Response> build() const override {
    std::string ret;
    ret.reserve(100 + content_.size());
    ret.append("HTTP/1.1 ");
    {
      char tmp[4];
      auto [ptr, ec] =
          std::to_chars(tmp, tmp + sizeof(tmp), std::to_underlying(status_));
      ret.append(tmp, ptr - tmp);
    }
    ret.append(" ");
    switch (status_) {
      case StatusCode::kSwitchingProtocols:
        ret.append("Switching Protocols");
        break;
      case StatusCode::kOK:
        ret.append("OK");
        break;
      case StatusCode::kNoContent:
        ret.append("No Content");
        break;
      case StatusCode::kBadRequest:
        ret.append("Bad Request");
        break;
      case StatusCode::kNotFound:
        ret.append("Not Found");
        break;
      case StatusCode::kMethodNotAllowed:
        ret.append("Method Not Allowed");
        break;
    }
    ret.append("\r\n");
    bool have_content_len = false;
    for (auto const& pair : headers_) {
      if (!have_content_len && pair.first == "Content-Length")
        have_content_len = true;
      ret.append(pair.first);
      ret.append(": ");
      ret.append(pair.second);
      ret.append("\r\n");
    }
    bool need_content_len;
    switch (status_) {
      case StatusCode::kSwitchingProtocols:
      case StatusCode::kNoContent:
        need_content_len = false;
        break;
      case StatusCode::kOK:
      case StatusCode::kBadRequest:
      case StatusCode::kNotFound:
      case StatusCode::kMethodNotAllowed:
        need_content_len = true;
        break;
    }
    if (!have_content_len && need_content_len) {
      char tmp[20];
      auto [ptr, ec] = std::to_chars(tmp, tmp + sizeof(tmp), content_.size());
      ret.append("Content-Length");
      ret.append(": ");
      ret.append(tmp, ptr - tmp);
      ret.append("\r\n");
    }
    ret.append("\r\n");
    if (status_ != StatusCode::kNoContent)
      ret.append(content_);
    return std::make_unique<ResponseImpl>(std::move(ret), socket_receiver_);
  }

 private:
  StatusCode const status_;
  std::string content_;
  std::vector<std::pair<std::string, std::string>> headers_;
  SocketReceiver* socket_receiver_{nullptr};
};

class HeaderIterator {
 public:
  explicit HeaderIterator(std::span<std::string_view> headers)
      : headers_(headers) {
    next();
  }

  [[nodiscard]]
  bool has_name() const {
    return offset_ < headers_.size();
  }

  [[nodiscard]]
  bool has_value() const {
    return has_name() && continue_value_;
  }

  bool next_name() {
    do {
      next();
    } while (has_value());
    return has_name();
  }

  bool next_value() {
    next();
    return has_value();
  }

  [[nodiscard]]
  std::string_view name() const {
    return name_;
  }

  [[nodiscard]]
  std::string_view value() const {
    return value_;
  }

 private:
  void next() {
    if (offset_ >= headers_.size())
      return;

    auto line = headers_[offset_];
    if (offset_ > 0 &&
        (line.empty() || line.front() == ' ' || line.front() == '\t')) {
      continue_value_ = true;
      value_ = str::ltrim(line);
      ++offset_;
      return;
    }
    auto colon = line.find(':');
    if (colon == std::string::npos) {
      assert(false);
      ++offset_;
      next();
      return;
    }
    continue_value_ = false;
    name_ = str::trim(line.substr(0, colon));
    value_ = str::ltrim(line.substr(colon + 1));
    ++offset_;
  }

  std::span<std::string_view> headers_;
  size_t offset_{0};
  bool continue_value_{false};
  std::string_view name_;
  std::string_view value_;
};

class RequestImpl : public Request {
 public:
  RequestImpl(std::string_view method, std::string_view path,
              std::span<std::string_view> headers)
      : method_(method), path_(path), headers_(headers) {}

  [[nodiscard]]
  std::string_view method() const override {
    return method_;
  }

  [[nodiscard]]
  std::string_view path() const override {
    return path_;
  }

  [[nodiscard]]
  std::string_view body() const override {
    return body_;
  }

  void set_body(std::string_view body) { body_ = body; }

  [[nodiscard]]
  bool header_contains(std::string_view name,
                       std::string_view value) const override {
    for (HeaderIterator it{headers_}; it.has_name(); it.next_name()) {
      if (eq_lowercase(it.name(), name)) {
        std::string_view tmp = get_value(it);
        auto values = str::split(tmp, ',', /* keep_empty */ true);
        for (auto v : values) {
          if (eq_lowercase(str::trim(v), value)) {
            return true;
          }
        }
      }
    }
    return false;
  }

  [[nodiscard]]
  std::optional<std::string_view> header_value(
      std::string_view name) const override {
    for (HeaderIterator it{headers_}; it.has_name(); it.next_name()) {
      if (eq_lowercase(it.name(), name)) {
        // Do not look for more entries of the header, this method is used for header
        // values that cannot be combined.
        return get_value(it);
      }
    }
    return std::nullopt;
  }

 private:
  std::string_view get_value(HeaderIterator& it) const {
    std::string_view ret = it.value();
    if (it.next_value()) {
      tmp_.clear();
      tmp_.append(ret);
      do {
        tmp_.append(it.value());
      } while (it.next_value());
      return tmp_;
    }
    return ret;
  }

  std::string_view method_;
  std::string_view path_;
  std::string_view body_;
  std::span<std::string_view> headers_;
  mutable std::string tmp_;
};

// TODO: What is a good value?
const int kListenBacklog = 10;

class ServerImpl : public Server {
 public:
  ServerImpl(logger::Logger& logger, cfg::Config const& cfg,
             looper::Looper& looper, std::unique_ptr<OpenPort> open_port,
             Server::Delegate& delegate)
      : logger_(logger::prefix(logger, "http")),
        cfg_(cfg),
        looper_(looper),
        delegate_(delegate),
        listens_(static_cast<OpenPortImpl*>(open_port.get())->release()) {
    client_timeout_ = std::chrono::duration<double>(
        cfg_.get_uint64("http.client.timeout.seconds").value_or(60));
    client_.resize(cfg_.get_uint64("http.max.clients").value_or(100));
    start_to_listen();
  }

 private:
  static const size_t kInputMinSize = 1024;
  static const size_t kInputMaxSize = static_cast<size_t>(1) * 1024 * 1024;
  static const size_t kOutputSize = static_cast<size_t>(512) * 1024;

  struct Client {
    unique_fd fd;
    std::unique_ptr<Buffer> in{Buffer::dynamic(kInputMinSize, kInputMaxSize)};
    std::unique_ptr<Buffer> out{Buffer::fixed(kOutputSize)};
    std::unique_ptr<Response> resp;
    std::chrono::steady_clock::time_point last;
    uint32_t timeout{0};
    bool read_closed_{false};
    SocketReceiver* take_over_{nullptr};
  };

  void start_to_listen() {
    auto it = listens_.begin();
    while (it != listens_.end()) {
      if (listen(it->get(),
                 static_cast<int>(cfg_.get_uint64("http.listen.backlog")
                                      .value_or(kListenBacklog)))) {
        logger_->warn(
            std::format("Error listening to socket: {}", strerror(errno)));
        it = listens_.erase(it);
      } else {
        make_nonblock(it->get());

        looper_.add(
            it->get(), looper::EVENT_READ,
            [this, fd = it->get()](auto events) { accept_client(fd, events); });
        ++it;
      }
    }

    if (listens_.empty()) {
      logger_->err("No ports left to listen to, exit.");
      looper_.quit();
    }
  }

  void accept_client(int fd, uint8_t event) {
    if (event & looper::EVENT_ERROR) {
      logger_->warn("Listening port returned error, closing.");
      looper_.remove(fd);
      auto it = std::ranges::find_if(
          listens_, [&fd](auto& ufd) { return ufd.get() == fd; });
      if (it != listens_.end()) {
        listens_.erase(it);
        if (listens_.empty()) {
          logger_->err("No ports left to listen to, exit.");
          looper_.quit();
        }
      }
      return;
    }

    unique_fd client_fd(accept4(fd, nullptr, nullptr, SOCK_NONBLOCK));
    if (!client_fd) {
      logger_->info(std::format("Accept returned error: {}", strerror(errno)));
      return;
    }

    if (active_clients_ == client_.size()) {
      logger_->warn("Max number of clients already.");
      return;
    }

    for (; client_[next_client_].fd; next_client_++) {
      if (next_client_ == client_.size())
        next_client_ = 0;
    }

    logger_->dbg(std::format("New client: {}", next_client_));

    auto& client = client_[next_client_];
    client.fd = std::move(client_fd);
    client.last = std::chrono::steady_clock::now();

    looper_.add(
        client.fd.get(), looper::EVENT_READ,
        [this, id = next_client_](auto events) { client_event(id, events); });
    client.timeout = looper_.schedule(
        client_timeout_.count(),
        [this, id = next_client_](auto handle) { client_timeout(id, handle); });

    ++active_clients_;
    ++next_client_;
    // TODO: Stopping listening if active_clients_ == client_.size()
  }

  void client_event(size_t client_id, uint8_t event) {
    if (event & looper::EVENT_ERROR) {
      logger_->info(std::format("Client socket error: {}", client_id));
      close_client(client_id);
      return;
    }

    auto& client = client_[client_id];
    if (event & looper::EVENT_READ) {
      size_t avail;
      auto* ptr = client.in->wptr(avail);
      if (avail == 0) {
        logger_->info(std::format("Client too large request: {}", client_id));
        close_client(client_id);
        return;
      }

      ssize_t got;
      while (true) {
        got = read(client.fd.get(), ptr, avail);
        if (got < 0 && errno == EINTR)
          continue;
        break;
      }
      if (got < 0) {
        if (errno != EWOULDBLOCK && errno != EAGAIN) {
          logger_->info(std::format("Client read error: {}: {}", client_id,
                                    strerror(errno)));
          close_client(client_id);
          return;
        }
      } else if (got == 0) {
        client.read_closed_ = true;
      } else {
        client.in->commit(got);

        if (!client_read(client_id))
          return;
      }
    }

    while (true) {
      size_t avail;
      auto* ptr = client.out->rptr(avail);
      if (avail == 0) {
        if (client.resp) {
          if (!client.resp->write(*client.out)) {
            client.take_over_ = client.resp->socket_receiver();
            client.resp.reset();

            if (client.take_over_) {
              client.read_closed_ = true;
            } else {
              if (!client_read(client_id))
                return;
            }
          }
          continue;
        }
        break;
      }
      ssize_t got;
      while (true) {
        got = write(client.fd.get(), ptr, avail);
        if (got < 0 && errno == EINTR)
          continue;
        break;
      }
      if (got < 0) {
        if (errno != EWOULDBLOCK && errno != EAGAIN) {
          logger_->info(std::format("Client write error: {}: {}", client_id,
                                    strerror(errno)));
          close_client(client_id);
          return;
        }
        break;
      }
      client.out->consume(got);

      if (std::cmp_less(got, avail))
        break;
    }

    if (client.read_closed_ && client.in->empty() && client.out->empty() &&
        !client.resp) {
      if (client.take_over_) {
        looper_.remove(client.fd.get());
        client.take_over_->receive(std::move(client.fd));
        reset_client(client_id);
      } else {
        close_client(client_id);
      }
      return;
    }

    bool want_read = !client.read_closed_ && !client.resp;
    bool want_write = !client.out->empty();

    looper_.update(client.fd.get(), (want_read ? looper::EVENT_READ : 0) |
                                        (want_write ? looper::EVENT_WRITE : 0));
  }

  bool client_read(size_t client_id) {
    auto& client = client_[client_id];
    size_t avail;
    auto* ptr = client.in->rptr(avail);
    if (avail == 0)
      return true;
    std::string_view data(reinterpret_cast<char const*>(ptr), avail);
    // TODO: Cache last search to not have to restart all the time
    auto end = data.find("\r\n\r\n");
    if (end == std::string_view::npos)
      return true;

    auto lines = str::split(data.substr(0, end), "\r\n", /* keep_empty */ true);
    std::string_view method;
    std::string_view path;
    {
      auto parts = str::split(lines[0], ' ', false);
      if (parts.size() != 3) {
        logger_->info(std::format("Client invalid request: {}", client_id));
        close_client(client_id);
        return false;
      }
      method = parts[0];
      path = parts[1];
      if (!parts[2].starts_with("HTTP/")) {
        logger_->info(std::format("Client invalid request: {}", client_id));
        close_client(client_id);
        return false;
      }
      size_t query = path.find('?');
      if (query != std::string_view::npos)
        path = path.substr(0, query);
    }
    for (size_t i = 1; i < lines.size(); ++i) {
      auto colon = lines[i].find(':');
      if (colon == std::string::npos &&
          // Only continue header value lines are allowed to not have a colon.
          (i == 1 || lines[i].empty() ||
           (lines[i].front() != ' ' && lines[i].front() != '\t'))) {
        logger_->info(std::format("Client invalid request: {}", client_id));
        close_client(client_id);
        return false;
      }
    }
    RequestImpl request(method, path, std::span{lines}.subspan(1));
    auto maybe_content_length = request.header_value("content-length");
    if (maybe_content_length.has_value()) {
      uint64_t content_length;
      auto [ptr, ec] = std::from_chars(
          maybe_content_length->data(),
          maybe_content_length->data() + maybe_content_length->size(),
          content_length);
      if (ec != std::errc() ||
          ptr != maybe_content_length->data() + maybe_content_length->size()) {
        logger_->info(std::format(
            "Client invalid request, bad content-length: {}", client_id));
        close_client(client_id);
        return false;
      }
      if (avail - end < content_length) {
        // Need more data.
        if (client.in->full()) {
          logger_->info(std::format("Client invalid request, too much data: {}",
                                    client_id));
          close_client(client_id);
          return false;
        }
        return true;
      }
      request.set_body(data.substr(end + 4, content_length));
      end += content_length;
    }
    client.resp = delegate_.handle(request);
    client.in->consume(end + 4);
    // If client requests close, do so.
    if (request.header_contains("connection", "close")) {
      if (shutdown(client.fd.get(), SHUT_RD) == 0) {
        client.read_closed_ = true;
      }
    }
    return true;
  }

  void client_timeout(size_t client_id, uint32_t id) {
    auto now = std::chrono::steady_clock::now();
    auto& client = client_[client_id];
    assert(client.timeout == id);
    if (now - client.last <
        std::chrono::duration_cast<std::chrono::steady_clock::duration>(
            client_timeout_)) {
      // TODO: Reschedule for delay left, not the full one
      client.timeout = looper_.schedule(client_timeout_.count(),
                                        [this, client_id](auto handle) {
                                          client_timeout(client_id, handle);
                                        });
      return;
    }

    logger_->dbg(std::format("Client timeout: {}", client_id));

    client.timeout = 0;
    close_client(client_id);
  }

  void close_client(size_t client_id) {
    auto& client = client_[client_id];
    if (!client.fd) {
      assert(false);
      return;
    }

    logger_->dbg(std::format("Drop client: {}", client_id));

    looper_.remove(client.fd.get());
    client.fd.reset();

    reset_client(client_id);
  }

  void reset_client(size_t client_id) {
    auto& client = client_[client_id];

    if (client.timeout)
      looper_.cancel(client.timeout);
    clear(*client.in);
    clear(*client.out);
    client.resp.reset();
    client.read_closed_ = false;
    client.take_over_ = nullptr;
    assert(active_clients_ > 0);
    --active_clients_;
    if (next_client_ == client_id + 1)
      next_client_ = client_id;
  }

  std::unique_ptr<logger::Logger> logger_;
  cfg::Config const& cfg_;
  looper::Looper& looper_;
  Server::Delegate& delegate_;
  std::chrono::duration<double> client_timeout_;
  std::vector<unique_fd> listens_;
  std::vector<Client> client_;
  size_t next_client_{0};
  size_t active_clients_{0};
};

}  // namespace

std::unique_ptr<MimeType> MimeType::create(std::string_view type,
                                           std::string_view subtype) {
  std::string tmp;
  tmp.reserve(type.size() + 1 + subtype.size());
  tmp.append(type);
  tmp.push_back('/');
  tmp.append(subtype);
  return std::make_unique<MimeTypeImpl>(std::move(tmp), type.size(),
                                        subtype.size());
}

std::unique_ptr<MimeType::Builder> MimeType::Builder::create(
    std::string_view type, std::string_view subtype) {
  return std::make_unique<MimeTypeBuilderImpl>(type, subtype);
}

std::unique_ptr<OpenPort> open_port(std::string_view host_port,
                                    logger::Logger& logger) {
  auto colon = host_port.find(':');
  std::string host;
  std::string port;
  if (colon == std::string_view::npos) {
    host = "localhost";
    port = host_port;
  } else {
    host = host_port.substr(0, colon);
    port = host_port.substr(colon + 1);
  }

  if (host == "*")
    host = "";

  struct addrinfo hints = {};
  hints.ai_flags =
      AI_PASSIVE  // Use wildcard if host is nullptr
      |
      AI_ADDRCONFIG;  // Only use IPv4 or IPv6 if there is at least one interface of that type
  hints.ai_family = AF_UNSPEC;      // Allow IPv4 or IPv6
  hints.ai_socktype = SOCK_STREAM;  // TCP
  struct addrinfo* res;
  auto ret = getaddrinfo(host.empty() ? nullptr : host.c_str(), port.c_str(),
                         &hints, &res);
  if (ret) {
    logger.err(
        std::format("Unable to bind to {}: {}", host_port, gai_strerror(ret)));
    return nullptr;
  }

  struct addrinfo* addr;
  std::vector<unique_fd> fds;
  for (addr = res; addr != nullptr; addr = addr->ai_next) {
    unique_fd fd{socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol)};
    if (!fd)
      continue;
    if (bind(fd.get(), addr->ai_addr, addr->ai_addrlen) == 0) {
      fds.push_back(std::move(fd));
    }
  }
  freeaddrinfo(res);

  if (fds.empty()) {
    // Assume that the last errno will be bind or socket failing
    logger.err(
        std::format("Unable to bind to {}: {}", host_port, strerror(errno)));
    return nullptr;
  }

  return std::make_unique<OpenPortImpl>(std::move(fds));
}

std::unique_ptr<Response::Builder> Response::Builder::create(
    StatusCode status_code) {
  return std::make_unique<ResponseBuilderImpl>(status_code);
}

std::unique_ptr<Response> Response::status(StatusCode status_code) {
  return Response::Builder::create(status_code)->build();
}

std::unique_ptr<Response> Response::content(std::string_view content,
                                            MimeType const& mime_type) {
  return Response::Builder::create(StatusCode::kOK)
      ->content(content)
      .add_header("Content-Type", mime_type.string())
      .build();
}

std::unique_ptr<Server> create_server(logger::Logger& logger,
                                      cfg::Config const& cfg,
                                      looper::Looper& looper,
                                      std::unique_ptr<OpenPort> open_port,
                                      Server::Delegate& delegate) {
  return std::make_unique<ServerImpl>(logger, cfg, looper, std::move(open_port),
                                      delegate);
}

}  // namespace http