#include <catch2/catch_test_macros.hpp>

#include "matador/utils/result.hpp"

namespace matador::test {

enum class math_error : int32_t {
  DIVISION_BY_ZERO = 1
};

utils::result<float, math_error>divide(int x, int y) {
  if (y == 0) {
    return utils::error(math_error::DIVISION_BY_ZERO);
  }

  return utils::ok(float(x) / y);
}

utils::result<float, math_error>multiply(int x, int y) {
  return utils::ok(float(x) * y);
}

utils::result<float, math_error>plus(int x, int y) {
  return utils::ok(float(x) + y);
}

utils::result<float, std::string>error_to_string(math_error err) {
  switch (err) {
    case math_error::DIVISION_BY_ZERO:
      return utils::error(std::string("division by zero error"));
    default:
      return utils::error(std::string("unknown error"));
  }
}

}

using namespace matador;

TEST_CASE("Result tests", "[result]") {
  auto res = test::divide(4, 2);
  REQUIRE(res);
  REQUIRE(res.is_ok());
  REQUIRE(!res.is_error());

  REQUIRE((res.value() == 2.0));

  REQUIRE_THROWS(res.err());

  res = test::divide(4, 0);
  REQUIRE(!res);
  REQUIRE(!res.is_ok());
  REQUIRE(res.is_error());

  REQUIRE((res.err() == test::math_error::DIVISION_BY_ZERO));

  res = test::divide(4, 2)
    .and_then([](const auto &val) { return test::multiply(val, 5); })
    .and_then([](const auto &val) { return test::plus(val, 10); });

  REQUIRE(res);
  REQUIRE(res.is_ok());
  REQUIRE(!res.is_error());
  REQUIRE((res.value() == 20.0));

  res = test::divide(4, 0)
    .and_then([](const auto &val) {
      return test::multiply(val, 5);
    });

  REQUIRE(!res);
  REQUIRE(!res.is_ok());
  REQUIRE(res.is_error());
  REQUIRE((res.err() == test::math_error::DIVISION_BY_ZERO));

  auto res2 = test::divide(4, 0)
    .or_else([](const auto &err) {
      return test::error_to_string(err);
    });

  REQUIRE(!res2);
  REQUIRE(!res2.is_ok());
  REQUIRE(res2.is_error());
  REQUIRE((res2.err() == "division by zero error"));

  res = test::divide(4, 2)
    .and_then([](const auto &val) { return test::multiply(val, 5); })
    .transform([](const auto &val) { return val + 10; });

  REQUIRE(res);
  REQUIRE(res.is_ok());
  REQUIRE(!res.is_error());
  REQUIRE((res.value() == 20.0));

}