factory-hole-core/include/Components/Chute.hpp

#pragma once

#include <deque>
#include <cmath>
#include <algorithm>
#include <vector>

#include "flecs.h"

#include "Types/Item.hpp"
#include "Components/Misc.hpp"
#include "Components/Inventory.hpp"
#include "Util/SharedBuffer.h"

struct ChuteConfig
{
	float Gravity{ 1.0f };
	float MinSpeed{ 0.5f };
};

struct ChuteInventoryInput : public Inventory {};
struct ChuteInventoryOutput : public Inventory {};

struct Chute
{
	struct ChuteLink
	{
		int8_t RelativeX{};
		int8_t RelativeY{};
		uint16_t Tick{};
	};
	struct ChuteItem
	{
		Item ItemInfo{};
		uint16_t ChuteEntered{}; // use TickCounter - ChuteEntered to get the time it has been in the chute
	};
	struct ChuteData
	{
		std::deque<ChuteItem> ItemsInChute{};
		uint16_t TicksToReachEnd{};
		uint16_t TickCounter{};
	};

public:
	Chute() = default;
	Chute(const std::vector<Vector2>& positions, const ChuteConfig& config = {})
		: Data{static_cast<int>(positions.size() - 1), ChuteData{}}
	{
		float velocity = 0.0f;
		float totalTicks = 0.0f;

		for (size_t i = 1; i < positions.size(); ++i)
		{
			int dx = positions[i].X - positions[i - 1].X;
			int dy = positions[i].Y - positions[i - 1].Y;

			// accumulate velocity from vertical drop (dy <= 0, so -dy >= 0)
			velocity += config.Gravity * static_cast<float>(std::abs(dy));
			velocity = std::max(velocity, config.MinSpeed);

			float distance = std::max(1.0f, std::sqrt(static_cast<float>(dx * dx + dy * dy)));
			float linkTicks = distance / velocity;

			Data[i - 1].RelativeX = static_cast<int8_t>(dx);
			Data[i - 1].RelativeY = static_cast<int8_t>(dy);
			Data[i - 1].Tick = static_cast<uint16_t>(std::ceil(linkTicks));

			totalTicks += linkTicks;
		}

		Data.GetMetaData()->TicksToReachEnd = static_cast<uint16_t>(std::ceil(totalTicks));
	}

	void PushItem(Item item)
	{
		auto* meta = Data.GetMetaData();
		meta->ItemsInChute.push_back(ChuteItem{ .ItemInfo = item, .ChuteEntered = meta->TickCounter });
	}

public:
	SharedBuffer<ChuteLink, ChuteData> Data{};
};

inline void Flecs_Chute(flecs::world& world)
{
	world.component<ChuteInventoryInput>().is_a<Inventory>();
	world.component<ChuteInventoryOutput>().is_a<Inventory>();

	world.component<ChuteConfig>()
		.member<float>("Gravity")
		.member<float>("MinSpeed");

	world.component<Chute>();

	// tick the chute counter
	world.system<Chute>("Chute Tick")
		.kind(flecs::PreUpdate)
		.each([](Chute& chute) {
			chute.Data.GetMetaData()->TickCounter++;
		});

	// pull items from input inventory into chute
	world.system<Chute, ChuteInventoryInput>("Chute Input")
		.kind(flecs::OnUpdate)
		.each([](Chute& chute, ChuteInventoryInput& input) {
			for (uint16_t i = 0; i < input.Slots.GetSize(); ++i)
			{
				while (input.Slots[i] > 0)
				{
					input.Slots[i]--;
					chute.PushItem(Item{ i });
				}
			}
		});

	// pop items that have reached the end and deposit into output inventory
	world.system<Chute, ChuteInventoryOutput, WorldInventory>("Chute Output")
		.kind(flecs::OnUpdate)
		.each([](Chute& chute, ChuteInventoryOutput& output, WorldInventory& worldInv) {
			auto* meta = chute.Data.GetMetaData();
			while (!meta->ItemsInChute.empty())
			{
				auto& front = meta->ItemsInChute.front();
				uint16_t elapsed = meta->TickCounter - front.ChuteEntered;
				if (elapsed < meta->TicksToReachEnd)
					break;

				uint16_t itemID = front.ItemInfo.ItemID;
				meta->ItemsInChute.pop_front();

				if (!output.IsFull(itemID))
					output.AddItems(itemID, 1);
				else
					worldInv.AddItems(itemID, 1);
			}
		});
}

inline void Chute_Helper(const flecs::entity& entity,
	const std::vector<Vector2>& positions,
	const Inventory& sourceInventory,
	const Inventory& destInventory,
	const ChuteConfig& config = {})
{
	entity.set<Chute>(Chute{positions, config});
	entity.set<ChuteInventoryInput>(ChuteInventoryInput{sourceInventory});
	entity.set<ChuteInventoryOutput>(ChuteInventoryOutput{destInventory});
}