tlib/synth/voice_allocator.h

#pragma once
#include "audio_buffer.h"
#include "midi_event.h"

#include <algorithm>
#include <cassert>
#include <functional>
#include <memory>
#include <vector>

namespace trnr {

template <typename t_voice, typename t_sample>
class voice_allocator {
public:
	std::vector<std::shared_ptr<t_voice>> voice_ptrs;
	std::vector<midi_event> input_queue;
	int index_to_steal = 0;
	const int internal_block_size = 16;
	size_t active_voice_count;
	bool steal_non_gated = true;

	voice_allocator(size_t num_voices = 1)
	{
		assert(num_voices > 0 && "number of voices must be greater than 0");
		init_voice_ptrs(num_voices);
	}

	void set_voice_count(const int& voice_count)
	{
		active_voice_count = std::min<size_t>(voice_count, voice_ptrs.size());
	}

	void note_on(const midi_event& event)
	{
		auto voice = get_free_voice();

		if (!voice) { voice = steal_voice(); }

		if (voice) { voice->note_on(event.midi_note, event.velocity); }
	}

	void note_off(const midi_event& event)
	{
		for (const auto& v : voice_ptrs) {
			if (v->midi_note == event.midi_note) v->note_off();
		}
	}

	void access(std::function<void(t_voice*)> f)
	{
		std::for_each(voice_ptrs.begin(), voice_ptrs.end(), [&](std::shared_ptr<t_voice> ptr) {
			if (ptr) {
				f(ptr.get()); // Call the function with the raw pointer
			}
		});
	}

	void process_samples(t_sample** _outputs, int _start_index, int _block_size,
						 std::vector<audio_buffer<t_sample>> _modulators = {})
	{
		for (int b = _start_index; b < _start_index + _block_size; b += internal_block_size) {

			// process all events in the block (introduces potential inaccuracy of up to 16 samples)
			process_events(b, internal_block_size);

			for (size_t i = 0; i < active_voice_count; ++i) {
				voice_ptrs[i]->process_samples(_outputs, b, internal_block_size, _modulators);
			}
		}
	}

	void add_event(midi_event event) { input_queue.push_back(event); }

	bool voices_active()
	{
		bool voices_active = false;

		for (const auto& v : voice_ptrs) {
			bool busy = v->is_busy();
			voices_active |= busy;
		}

		return voices_active;
	}

	void set_samplerate(double _samplerate)
	{
		for (const auto& v : voice_ptrs) { v->set_samplerate(_samplerate); }
	}

	void init_voice_ptrs(size_t num_voices)
	{
		voice_ptrs.reserve(num_voices);

		for (size_t i = 0; i < num_voices; ++i) { voice_ptrs.emplace_back(std::make_shared<t_voice>()); }
	}

	std::shared_ptr<t_voice> get_free_voice()
	{
		for (size_t i = 0; i < active_voice_count; ++i) {
			if (!voice_ptrs[i]->is_busy()) { return voice_ptrs[i]; }
		}

		return nullptr;
	}

	std::shared_ptr<t_voice> steal_voice()
	{
		// Try to find a voice that is not gated (not playing a note)
		if (steal_non_gated)
			for (size_t i = 0; i < active_voice_count; ++i) {
				if (!voice_ptrs[i]->gate) { return voice_ptrs[i]; }
			}

		// If all voices are gated, steal one round-robin
		auto voice = voice_ptrs[index_to_steal];
		index_to_steal++;
		if (index_to_steal >= active_voice_count) index_to_steal = 0;
		return voice;
	}

	void process_events(int _start_index, int _block_size)
	{
		for (int s = _start_index; s < _start_index + _block_size; s++) {
			auto iterator = input_queue.begin();
			while (iterator != input_queue.end()) {

				midi_event& event = *iterator;
				if (event.offset == s) {

					switch (event.type) {
					case midi_event_type::note_on:
						note_on(event);
						break;
					case midi_event_type::note_off:
						note_off(event);
						break;
					case midi_event_type::pitch_wheel:
						access([&event](t_voice* voice) { voice->modulate_pitch(event.data); });
						break;
					default:
						break;
					}

					iterator = input_queue.erase(iterator);
				} else {
					iterator++;
				}
			}
		}
	}
};
} // namespace trnr