Camera.h

#pragma once

#include <GL/glew.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>

// Defines several possible options for camera movement. Used as abstraction to stay away from window-system specific input methods
enum Camera_Movement {
	FORWARD,
	BACKWARD,
	LEFT,
	RIGHT
};

// Default camera values
const GLfloat YAW = 90.0f;
const GLfloat PITCH = 90.0f;
const GLfloat SPEED = 3.0f;
const GLfloat SENSITIVTY = 0.5f;
const GLfloat ZOOM = 45.0f;


// An abstract camera class that processes input and calculates the corresponding Eular Angles, Vectors and Matrices for use in OpenGL
class Camera
{
public:
	// Camera Attributes
	glm::vec3 Position;
	glm::vec3 Front;
	glm::vec3 Up;
	glm::vec3 Right;
	glm::vec3 WorldUp;
	// Eular Angles
	GLfloat Yaw;
	GLfloat Pitch;
	// Camera options
	GLfloat MovementSpeed;
	GLfloat MouseSensitivity;
	GLfloat Zoom;

	// Constructor with vectors
	Camera(glm::vec3 position = glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3 up = glm::vec3(0.0f, 1.0f, 0.0f), GLfloat yaw = YAW, GLfloat pitch = PITCH) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVTY), Zoom(ZOOM)
	{
		this->Position = position;
		this->WorldUp = up;
		this->Yaw = yaw;
		this->Pitch = pitch;
		this->updateCameraVectors();
	}
	// Constructor with scalar values
	Camera(GLfloat posX, GLfloat posY, GLfloat posZ, GLfloat upX, GLfloat upY, GLfloat upZ, GLfloat yaw, GLfloat pitch) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVTY), Zoom(ZOOM)
	{
		this->Position = glm::vec3(posX, posY, posZ);
		this->WorldUp = glm::vec3(upX, upY, upZ);
		this->Yaw = yaw;
		this->Pitch = pitch;
		this->updateCameraVectors();
	}

	// Returns the view matrix calculated using Eular Angles and the LookAt Matrix
	glm::mat4 GetViewMatrix()
	{
		return glm::lookAt(this->Position, this->Position + this->Front, this->Up);
	}

	// Processes input received from any keyboard-like input system. Accepts input parameter in the form of camera defined ENUM (to abstract it from windowing systems)
	void ProcessKeyboard(Camera_Movement direction, GLfloat deltaTime)
	{
		GLfloat velocity = this->MovementSpeed * deltaTime;
		if (direction == FORWARD)
			this->Position += this->Front * velocity;
		if (direction == BACKWARD)
			this->Position -= this->Front * velocity;
		if (direction == LEFT)
			this->Position -= this->Right * velocity;
		if (direction == RIGHT)
			this->Position += this->Right * velocity;
	}
	

	// Processes input received from a mouse input system. Expects the offset value in both the x and y direction.
	void ProcessMouseMovement(GLfloat xoffset, GLfloat yoffset, GLboolean constrainPitch = true)
	{
		xoffset *= this->MouseSensitivity;
		yoffset *= this->MouseSensitivity;

		this->Yaw -= xoffset;
		this->Pitch -= yoffset;
		
		// Make sure that when pitch is out of bounds, screen doesn't get flipped
		if (constrainPitch)
		{
			if (this->Pitch > 179.0f)
				this->Pitch = 179.0f;
			if (this->Pitch < 1.0f)
				this->Pitch = 1.0f;
		}
		cout << "yaw: " << Yaw << ", pitch: " << Pitch << endl;
		// Update Front, Right and Up Vectors using the updated Eular angles
		this->updateCameraVectors();
	}

	// Processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
	void ProcessMouseScroll(GLfloat yoffset)
	{
		if (this->Zoom >= 1.0f && this->Zoom <= 45.0f)
			this->Zoom -= yoffset;
		if (this->Zoom <= 1.0f)
			this->Zoom = 1.0f;
		if (this->Zoom >= 45.0f)
			this->Zoom = 45.0f;
	}

private:
	// Calculates the front vector from the Camera's (updated) Eular Angles
	void updateCameraVectors()
	{
		// Calculate the new Front vector
		glm::vec3 front;
		front.x = -sin(glm::radians(this->Pitch)) * cos(glm::radians(this->Yaw));
		front.y = -cos(glm::radians(this->Pitch));
		front.z = -sin(glm::radians(this->Pitch)) * sin(glm::radians(this->Yaw));
		this->Front = glm::normalize(front);
		// Also re-calculate the Right and Up vector
		this->Right = glm::normalize(glm::cross(this->Front, glm::vec3(0.0f, 1.0f, 0.0f)));
		this->Up = glm::normalize(glm::cross(this->Right, this->Front));
		this->Position = -1.0f*glm::length(Position)*(this->Front);
		//this->Right = glm::normalize(glm::cross(this->Front, this->WorldUp));  // Normalize the vectors, because their length gets closer to 0 the more you look up or down which results in slower movement.
		//this->Up = glm::normalize(glm::cross(this->Right, this->Front));
	}
};