#pragma once

#include <glm/glm.hpp>

namespace engine {

// -----------------------------------------------------------------------
// Camera
//
// A custom orbital ("arcball") camera. It orbits a focus point at a
// controllable yaw/pitch/distance, with all parameters critically-damped
// toward their target values every frame so camera moves - including
// "focus on selected planet" - feel like smooth, cinematic transitions
// rather than instant snaps.
// -----------------------------------------------------------------------
class Camera {
public:
    Camera();

    // Input handlers - called directly from Engine's GLFW callbacks.
    void onMouseDrag(float deltaX, float deltaY);
    void onMousePan(float deltaX, float deltaY);
    void onScroll(float deltaY);
    void reset();

    // Smoothly re-targets the orbit focus to a world-space point (e.g. a
    // selected planet's position) and optionally suggests a nice viewing
    // distance for that object's scale.
    void focusOn(const glm::vec3& worldPoint, float suggestedDistance);

    // Advances the smoothing/interpolation. Must be called once per frame
    // with the frame's delta time in seconds.
    void update(float deltaTime);

    glm::mat4 viewMatrix() const;
    glm::vec3 position() const { return currentPosition_; }
    glm::vec3 focusPoint() const { return currentFocus_; }

    float distance() const { return currentDistance_; }

private:
    // Target (goal) state, set instantly by input; current state chases
    // it every update() call using exponential smoothing.
    float targetYaw_ = -0.6f;
    float targetPitch_ = 0.45f;
    float targetDistance_ = 18.0f;
    glm::vec3 targetFocus_{0.0f};

    float currentYaw_ = -0.6f;
    float currentPitch_ = 0.45f;
    float currentDistance_ = 18.0f;
    glm::vec3 currentFocus_{0.0f};
    glm::vec3 currentPosition_{0.0f};

    static constexpr float kMinPitch = -1.45f;
    static constexpr float kMaxPitch = 1.45f;
    static constexpr float kMinDistance = 2.0f;
    static constexpr float kMaxDistance = 400.0f;
    static constexpr float kSmoothingSpeed = 6.0f;
};

}  // namespace engine