ParticleSystem.h

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// SPDX-FileCopyrightText: 2026 Valentin Eloy
// SPDX-License-Identifier: GPL-3.0-or-later
 
#pragma once
 
#include <cstdint>
#include <vector>
 
#include "Core/Ecs/Components/Particle.h"
#include "Core/Ecs/Entity.h"
#include "Core/Math/Vector2.h"

 
namespace core {
 
class World;

inline constexpr std::uint64_t DEFAULT_PARTICLE_SEED = 0x504152544943454CULL;

inline constexpr int MAX_PARTICLES = 256;

inline constexpr float LANDING_MIN_IMPACT_SPEED = 4.0f;
inline constexpr float LANDING_MAX_IMPACT_SPEED = 14.0f;
inline constexpr int LANDING_DUST_MIN_COUNT = 3;
inline constexpr int LANDING_DUST_MAX_COUNT = 10;

struct ParticleEffect {
    int count = 0;
    float speedMin = 0.0f;
    float speedMax = 0.0f;
    float lifeMin = 0.0f;
    float lifeMax = 0.0f;
    float spreadRadians = 0.0f;
};

class ParticleSystem {
public:
    explicit ParticleSystem(std::uint64_t seed = DEFAULT_PARTICLE_SEED) noexcept;

    void update(World& world, float fixedDelta);

    void spawn(World& world, const ParticleEffect& effect, Vector2 origin, Vector2 direction,
               ParticleKind kind);

    void emitDashTrail(World& world, Vector2 position, float facing);

    void emitLanding(World& world, Vector2 position, float impactSpeed);

    void emitDeath(World& world, Vector2 position);

    void clear(World& world);

    [[nodiscard]] int aliveCount() const noexcept {
        return static_cast<int>(_order.size());
    }
 
private:
    [[nodiscard]] Entity reserveSlot(World& world);
 
    std::uint64_t _baseSeed;
    std::uint64_t _stepIndex = 0;
    std::vector<Entity> _order;
};
 
}  // namespace core