#pragma once
#include "hd2d/GL.h"

#include <glm/glm.hpp>
#include <random>
#include <vector>

namespace hd2d {

struct PointLight;

// High-resolution (non pixel-art) particles: ambient fields (fireflies, dust),
// fire emitters (flames, embers, smoke, glow + flickering light) and bursts.
class ParticleSystem {
public:
    // Must match the kind ids in particles.vert / particles.frag.
    enum class Kind : int {
        Firefly = 0,  // blinking emissive glow, wanders near the ground
        Mote = 1,     // dust speck only visible where sunlight hits it (god rays)
        Spark = 2,    // ballistic burst particle (footstep dust, rain splashes, ...)
        Flame = 3,    // additive tongue of fire, eroded by noise as it ages
        Ember = 4,    // tiny hot spark drifting up on turbulent air
        Smoke = 5,    // alpha-blended puff rising above a fire
        Glow = 6,     // large soft halo around a fire (one per emitter per frame)
    };

    struct Field {  // region that keeps a constant population of ambient particles
        Kind kind;
        glm::vec3 min, max;
        int count;
    };

    struct Fire {
        glm::vec3 pos;      // base of the flames
        float scale = 1.0f; // overall size / intensity
        float flameAccum = 0.0f, emberAccum = 0.0f, smokeAccum = 0.0f;
        float flicker = 1.0f;  // current light flicker multiplier
        float phase = 0.0f;
    };

    ~ParticleSystem();
    void addField(Kind kind, glm::vec3 min, glm::vec3 max, int count);
    int addFire(glm::vec3 pos, float scale = 1.0f);
    void burst(glm::vec3 pos, int count, glm::vec3 color, float speed, float size, float life);
    void update(float dt, float time);
    void draw() const;
    // Appends fire lights first, then up to `maxFireflies` firefly lights.
    void collectLights(std::vector<PointLight>& out, int maxFireflies) const;
    const std::vector<Fire>& fires() const { return fires_; }

    glm::vec3 fireflyColor{2.6f, 3.2f, 0.9f};
    glm::vec3 moteColor{1.0f, 0.95f, 0.8f};
    float fireflyLightRadius = 2.2f;
    glm::vec3 fireLightColor{4.0f, 1.75f, 0.55f};
    float fireLightRadius = 7.0f;
    glm::vec3 wind{0.0f};       // world-space drift applied to smoke and embers
    float ambientFade = 1.0f;   // scales fireflies + motes (Weather lowers it in rain / mist)
    float fireflyGlow = 1.0f;   // firefly brightness + light (WeatherLook::fireflyGlow, raised at night)

private:
    struct Particle {
        glm::vec3 pos, vel;
        glm::vec3 color;
        float size, age, life, phase;
        Kind kind;
        int field;  // ambient field index, or -1
        int fire;   // owning fire, or -1
    };
    struct GpuParticle {
        glm::vec4 posSize;
        glm::vec4 color;   // rgb, a = alpha
        glm::vec4 params;  // x = kind, y = age / life, z = random seed
    };
    void spawnInField(Particle& p, int fieldIndex, bool randomAge);
    void spawnFire(const Fire& f, int fireIndex, Kind kind);

    std::vector<Field> fields_;
    std::vector<Fire> fires_;
    std::vector<Particle> particles_;
    std::vector<GpuParticle> gpu_;
    std::mt19937 rng_{1337};
    GLuint vao_ = 0, vbo_ = 0;
    size_t capacity_ = 0;
};

}  // namespace hd2d