#include <array>
#include <chrono>
#include <cstdint>
#include <cstring>
#include <errno.h>
#include <fstream>
#include <print>
#include <random>
#include <string>
#include <string_view>
#include <vector>

#include <boost/sqlite.hpp>

void parse_int(std::string_view arg, std::uint64_t &i) {
  auto [_, ec] = std::from_chars(arg.data(), arg.data() + arg.size(), i);

  if (ec == std::errc{}) {
    return;
  } else {
    throw std::runtime_error(std::format("failed to parse {} as u64", arg));
  }
}

std::uint64_t random_u64() {
  std::ifstream ifstream{"/dev/random", std::ios::binary};

  if (!ifstream.is_open()) {
    throw std::runtime_error(
        std::format("failed to open /dev/random: {}", std::strerror(errno)));
  }

  std::array<char, 8> buff;

  ifstream.read(buff.data(), 8);

  std::uint64_t i;

  std::memcpy(&i, buff.data(), 8);

  return i;
}

int main(int argc, char **argv) {
  if (argc < 3) {
    std::println(stderr, "usage: bench <database> <limit> [seed]");
    return 1;
  }

  auto *path = argv[1];
  auto *limit = argv[2];

  std::println(stderr, "starting benchmark");

  std::uint64_t seed;
  if (argc > 3) {
    try {
      parse_int(argv[3], seed);
    } catch (std::exception &e) {
      std::println(stderr, "{}", e.what());
      return 1;
    }
  } else {
    try {
      seed = random_u64();
    } catch (std::exception &e) {
      std::println(stderr, "{}", e.what());
      return 1;
    }
  }

  std::println(stderr, "using random seed: {}", seed);

  boost::sqlite::connection connection{path};

  std::vector<std::string> keys;

  auto st = connection.prepare("select kv.key from kv limit ?");

  for (const auto row : st.execute({limit})) {
    auto key = row.at(0).get_text();
    keys.push_back(key);
  }

  std::default_random_engine rng{seed};
  std::shuffle(keys.begin(), keys.end(), rng);

  std::println(stderr, "slurped {} keys into memory", keys.size());

  auto start = std::chrono::system_clock::now();

  st = connection.prepare("select kv.value from kv where kv.key=?");

  for (const auto &key : keys) {
    auto row = st.execute({key});

    if (row.done()) {
      std::println(stderr, "found no value for key: {}", key);
    } else {
      continue;
    }
  }

  auto end = std::chrono::system_clock::now();

  std::chrono::duration<double> d = end - start;

  std::println(stderr, "selected {} keys in {} ({})", keys.size(), d,
               keys.size() / d.count());

  return 0;
}