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// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#pragma once

#include <chrono>
#include <cmath>
#include <cstdint>
#include <ios>

#include <libhal/error.hpp>
#include <libhal/timeout.hpp>
#include <libhal/units.hpp>

#include "math.hpp"

namespace hal {
[[nodiscard]] constexpr std::int64_t cycles_per(hertz p_source,
                                                hal::time_duration p_duration)
{
  // Full Equation:
  //                              / ratio_num \_
  //   frequency_hz * |period| * | ----------- |  = cycles
  //                              \ ratio_den /
  //
  // std::chrono::nanoseconds::period::num == 1
  // std::chrono::nanoseconds::period::den == 1,000,000

  const auto denominator = decltype(p_duration)::period::den;
  const auto float_count = static_cast<float>(p_duration.count());
  const auto cycle_count = (float_count * p_source) / denominator;

  return static_cast<std::int64_t>(cycle_count);
}

template<typename Period>
constexpr std::chrono::duration<int64_t, Period> wavelength(hertz p_source)
{
  using duration = std::chrono::duration<int64_t, Period>;

  static_assert(Period::num == 1, "The period ratio numerator must be 1");
  static_assert(Period::den >= 1,
                "The period ratio denominator must be 1 or greater than 1.");

  constexpr auto denominator = static_cast<decltype(p_source)>(Period::den);
  auto period = (1.0f / p_source) * denominator;

  if (std::isinf(period)) {
    return duration(std::numeric_limits<int64_t>::max());
  }

  return duration(static_cast<int64_t>(period));
}

constexpr float wavelength(hertz p_source)
{
  if (equals(p_source, 0.0f)) {
    return 0.0f;
  }
  auto duration = (1.0f / p_source);
  return float(duration);
}

[[nodiscard]] inline result<std::chrono::nanoseconds> duration_from_cycles(
  hertz p_source,
  uint32_t p_cycles)
{
  // Full Equation (based on the equation in cycles_per()):
  //
  //
  //                /    cycles * ratio_den    \_
  //   |period| =  | ---------------------------|
  //                \ frequency_hz * ratio_num /
  //
  constexpr auto ratio_den = std::chrono::nanoseconds::period::den;
  constexpr auto ratio_num = std::chrono::nanoseconds::period::num;
  constexpr auto int_min = std::numeric_limits<std::int64_t>::min();
  constexpr auto int_max = std::numeric_limits<std::int64_t>::max();
  constexpr auto float_int_min = static_cast<float>(int_min);
  constexpr auto float_int_max = static_cast<float>(int_max);

  const auto source = std::abs(p_source);
  const auto float_cycles = static_cast<float>(p_cycles);
  const auto nanoseconds = (float_cycles * ratio_den) / (source * ratio_num);

  if (float_int_min <= nanoseconds && nanoseconds <= float_int_max) {
    return std::chrono::nanoseconds(static_cast<std::int64_t>(nanoseconds));
  }
  return new_error(std::errc::result_out_of_range);
}

template<class CharT, class Traits>
inline std::basic_ostream<CharT, Traits>& operator<<(
  std::basic_ostream<CharT, Traits>& p_ostream,
  const hal::byte& p_byte)
{
  return p_ostream << std::hex << "0x" << unsigned(p_byte);
}
}  // namespace hal