#include <sonus/sequence.hpp>

#include <algorithm>
#include <cmath>
#include <limits>
#include <utility>

#include <sonus/detail/errors.hpp>
#include "detail/sequence_player.hpp"


sonus::playback_session::playback_session(std::shared_ptr<std::atomic<sonus::playback_status>> status)
    : status_{std::move(status)} {}

auto sonus::playback_session::status() const -> sonus::playback_status {
  return status_ ? status_->load(std::memory_order_acquire) : sonus::playback_status::STOPPED;
}

auto sonus::playback_session::stop() const -> void {
  if (status_) {
    auto expected = sonus::playback_status::PLAYING;
    status_->compare_exchange_strong(expected, sonus::playback_status::STOPPED, std::memory_order_acq_rel);
  }
}

sonus::prepared_sequence::prepared_sequence(std::unique_ptr<sonus::detail::sequence_state> state)
    : state_{std::move(state)} {}

sonus::prepared_sequence::prepared_sequence(prepared_sequence &&) noexcept = default;

auto sonus::prepared_sequence::operator=(prepared_sequence &&) noexcept -> prepared_sequence & = default;

sonus::prepared_sequence::~prepared_sequence() = default;

auto sonus::prepared_sequence::create(sonus::sample_sequence sequence, std::uint32_t sample_rate) -> std::expected<sonus::prepared_sequence, modulus::error> {
  auto fail = [](std::string message) -> std::expected<sonus::prepared_sequence, modulus::error> {
    return sonus::detail::fail<sonus::prepared_sequence>(sonus::detail::error_invalid_argument, std::move(message));
  };
  if (sample_rate < 8000U || sample_rate > 384000U || sequence.max_voices == 0U || sequence.max_voices > 256U || sequence.events.size() > 1000000U || sequence.samples.size() > 4096U || sequence.duration_frames == 0U || sequence.duration_frames > static_cast<std::uint64_t>(sample_rate) * 86400U || !std::isfinite(sequence.gain) || sequence.gain < 0.0F || sequence.gain > 1.0F) {
    return fail("invalid sequence limits or gain");
  }
  if (sequence.release_envelope.empty() || sequence.release_envelope.size() > sample_rate / 2U || sequence.release_envelope.front() != 1.0F || sequence.release_envelope.back() != 0.0F || std::any_of(sequence.release_envelope.begin(), sequence.release_envelope.end(), [](auto value) { return !std::isfinite(value) || value < 0.0F || value > 1.0F; })) {
    return fail("release envelope must run from one to zero within 500 milliseconds");
  }
  auto sample_count = std::uint64_t{};
  for (auto const &sample : sequence.samples) {
    sample_count += sample.frames.size();
    if (sample_count > 16U * 1024U * 1024U || sample.sample_rate != sample_rate || sample.loop_start >= sample.loop_end || sample.loop_end > sample.frames.size() || std::any_of(sample.frames.begin(), sample.frames.end(), [](auto value) { return !std::isfinite(value) || std::abs(value) > 1.0F; })) {
      return fail("invalid sample rate, loop, PCM data or sample memory limit");
    }
  }
  auto endpoints = std::vector<std::pair<std::uint64_t, std::int32_t>>{};
  endpoints.reserve(sequence.events.size() * 2U);
  auto end = sequence.duration_frames;
  auto previous_start = std::uint64_t{};
  for (auto const &event : sequence.events) {
    if (event.sample >= sequence.samples.size() || event.duration_frames == 0U || event.start_frame < previous_start || event.start_frame >= sequence.duration_frames || event.duration_frames > sequence.duration_frames - event.start_frame || !std::isfinite(event.gain) || event.gain < 0.0F || event.gain > 1.0F) {
      return fail("invalid or unsorted sample event");
    }
    auto release_end = event.start_frame + event.duration_frames + sequence.release_envelope.size();
    endpoints.emplace_back(event.start_frame, 1);
    endpoints.emplace_back(release_end, -1);
    end = std::max(end, release_end);
    previous_start = event.start_frame;
  }
  std::sort(endpoints.begin(), endpoints.end());
  auto voices = std::int32_t{};
  auto peak = std::int32_t{};
  for (auto const &[frame, change] : endpoints) {
    voices += change;
    peak = std::max(peak, voices);
    if (voices > static_cast<std::int32_t>(sequence.max_voices)) {
      return fail("sequence exceeds simultaneous voice capacity including releases");
    }
  }
  auto next = std::make_unique<sonus::detail::sequence_state>();
  next->voices.resize(static_cast<std::size_t>(peak));
  next->sequence = std::move(sequence);
  next->status = std::make_shared<std::atomic<sonus::playback_status>>(sonus::playback_status::PLAYING);
  next->end_frame = end;
  next->sample_rate = sample_rate;
  return sonus::prepared_sequence{std::move(next)};
}

auto sonus::detail::sequence_player::play(sonus::prepared_sequence sequence, std::uint32_t sample_rate) -> std::expected<sonus::playback_session, modulus::error> {
  if (!sequence.state_ || sequence.state_->sample_rate != sample_rate) {
    return sonus::detail::fail<sonus::playback_session>(sonus::detail::error_invalid_argument, "empty sequence or incompatible sample rate");
  }
  auto next = std::move(sequence.state_);
  auto result = sonus::playback_session{next->status};
  auto lock = std::scoped_lock{mutex_};
  if (auto current = snapshots_.current()) {
    sonus::playback_session{current->status}.stop();
  }
  snapshots_.publish(std::move(next));
  return result;
}

auto sonus::detail::sequence_player::stop() -> void {
  auto lock = std::scoped_lock{mutex_};
  if (auto current = snapshots_.current()) {
    sonus::playback_session{current->status}.stop();
  }
  snapshots_.publish(nullptr);
}

auto sonus::detail::sequence_player::collect() -> void {
  auto lock = std::scoped_lock{mutex_};
  if (auto current = snapshots_.current(); current && current->status->load(std::memory_order_acquire) != sonus::playback_status::PLAYING) {
    snapshots_.publish(nullptr);
  }
  snapshots_.collect();
}

auto sonus::detail::sequence_player::fail() -> void {
  auto guard = snapshots_.read();
  if (auto current = guard.get()) {
    auto expected = sonus::playback_status::PLAYING;
    current->status->compare_exchange_strong(expected, sonus::playback_status::FAILED, std::memory_order_release);
  }
}

auto sonus::detail::sequence_player::render(std::float32_t *output, std::uint64_t frames, std::uint32_t channels, std::float32_t gain) -> void {
  auto guard = snapshots_.read();
  auto current = guard.get();
  if (!current || current->status->load(std::memory_order_acquire) != sonus::playback_status::PLAYING) {
    return;
  }
  auto const &sequence = current->sequence;
  for (auto frame = std::uint64_t{}; frame < frames && current->frame < current->end_frame; ++frame, ++current->frame) {
    for (auto &voice : current->voices) {
      if (voice.active) {
        auto const &event = sequence.events[voice.event];
        if (current->frame >= event.start_frame + event.duration_frames + sequence.release_envelope.size()) {
          voice.active = false;
        }
      }
    }
    while (current->next_event < sequence.events.size() && sequence.events[current->next_event].start_frame == current->frame) {
      auto slot = std::find_if(current->voices.begin(), current->voices.end(), [](auto const &voice) { return !voice.active; });
      if (slot == current->voices.end()) {
        auto expected = sonus::playback_status::PLAYING;
        current->status->compare_exchange_strong(expected, sonus::playback_status::FAILED, std::memory_order_release);
        return;
      }
      *slot = {.event = current->next_event++, .active = true};
    }
    auto mixed = std::float32_t{};
    for (auto const &voice : current->voices) {
      if (!voice.active) {
        continue;
      }
      auto const &event = sequence.events[voice.event];
      auto const &sample = sequence.samples[event.sample];
      auto age = current->frame - event.start_frame;
      auto index = age < sample.loop_end ? age : sample.loop_start + (age - sample.loop_start) % (sample.loop_end - sample.loop_start);
      auto release = age < event.duration_frames ? 1.0F : sequence.release_envelope[age - event.duration_frames];
      mixed += sample.frames[index] * event.gain * release;
    }
    for (auto channel = std::uint32_t{}; channel < channels; ++channel) {
      auto &destination = output[frame * channels + channel];
      destination = std::clamp(destination + mixed * sequence.gain * gain, -1.0F, 1.0F);
    }
  }
  if (current->frame == current->end_frame) {
    auto expected = sonus::playback_status::PLAYING;
    current->status->compare_exchange_strong(expected, sonus::playback_status::COMPLETED, std::memory_order_release);
  }
}