#include "camera.h"

Camera::Camera() {

}

void Camera::updateView() {
    //roll can be removed from here. because is not actually used in FPS camera
    glm::mat4 matRoll  = glm::mat4(1.0f);//identity matrix; 
    glm::mat4 matPitch = glm::mat4(1.0f);//identity matrix
    glm::mat4 matYaw   = glm::mat4(1.0f);//identity matrix
    
    //roll, pitch and yaw are used to store our angles in our class
    matRoll  = glm::rotate(matRoll,  roll,  glm::vec3(0.0f, 0.0f, 1.0f));
    matPitch = glm::rotate(matPitch, pitch, glm::vec3(1.0f, 0.0f, 0.0f));
    matYaw   = glm::rotate(matYaw,   yaw,   glm::vec3(0.0f, 1.0f, 0.0f));
    
    //order matters
    glm::mat4 rotate = matRoll * matPitch * matYaw;
    
    glm::mat4 translate = glm::mat4(1.0f);
    translate = glm::translate(translate, -eyeVector);
    
    viewMatrix = rotate * translate;
}

glm::mat4 Camera::getViewMatrix() {
    return viewMatrix;
}

glm::vec3 Camera::getPos() {
    return eyeVector;
}

void Camera::handleMouse(SDL_Event e) {
    if (e.type != SDL_MOUSEMOTION)
        return;


    float mouseDX = e.motion.xrel;
    float mouseDY = e.motion.yrel;

    glm::vec2 mouseDelta {mouseDX, mouseDY};

    mouseMoved(mouseDelta);
}

void Camera::moveCamera() {
    float dx = 0; //how much we strafe on x
    float dz = 0; //how much we walk on z

    const Uint8* state = SDL_GetKeyboardState(NULL);

    if (state[SDL_SCANCODE_W])
        dz += 2;
    if (state[SDL_SCANCODE_S])
        dz += -2;
    if (state[SDL_SCANCODE_A])
        dx += -2;
    if (state[SDL_SCANCODE_D])
        dx += 2;
    // if (state[SDL_SCANCODE_Z])

    // if (state[SDL_SCANCODE_LSHIFT])
    
    
    //get current view matrix
    glm::mat4 mat = getViewMatrix();
    //row major
    glm::vec3 forward(mat[0][2], mat[1][2], mat[2][2]);
    glm::vec3 strafe (mat[0][0], mat[1][0], mat[2][0]);
        
    //forward vector must be negative to look forward. 
    //read :http://in2gpu.com/2015/05/17/view-matrix/
    eyeVector += (-dz * forward + dx * strafe) * cameraSpeed;
        
    //update the view matrix
    updateView();
}

void Camera::mouseMoved(glm::vec2 mouseDelta) {
    //note that yaw and pitch must be converted to radians.
    //this is done in UpdateView() by glm::rotate
    yaw   += mouseSensitivity * mouseDelta.x;
    pitch += mouseSensitivity * mouseDelta.y;
    
    updateView();
}