json-validator/include/jvalidate/compat/curl.h

#pragma once
#include <cstdlib>
#include <sstream>
#include <string>
#include <string_view>

#include <curl/curl.h>

#include <jvalidate/adapter.h>
#include <jvalidate/compat/expected.h>
#include <jvalidate/forward.h>
#include <jvalidate/uri.h>

namespace jvalidate {
inline size_t transfer_to_buffer(char * data, size_t size, size_t nmemb, void * userdata) {
  std::stringstream & ss = *static_cast<std::stringstream *>(userdata);
  size_t const actual_size = size * nmemb;
  ss << std::string_view(data, actual_size);
  return actual_size;
}

template <typename JSON>
auto curl_get(jvalidate::URI const & uri, JSON & out) noexcept
    -> detail::expected<void, std::string> {
  using jvalidate::adapter::load_file;
  using jvalidate::adapter::load_stream;
  if (uri.scheme().starts_with("http")) {
    std::stringstream ss;
    if (CURL * curl = curl_easy_init(); curl) {
      curl_easy_setopt(curl, CURLOPT_URL, uri.c_str());
      curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
      curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ss);
      curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &transfer_to_buffer);

      CURLcode const res = curl_easy_perform(curl);
      curl_easy_cleanup(curl);

      if (res == CURLE_OK) {
        return load_stream(ss, out);
      }
    }
    return detail::unexpected("curl error");
  }
  if (uri.scheme() == "file") {
    return load_file(uri.resource(), out);
  }
  return detail::unexpected("unknown scheme");
}
}