screen space position in material graph I have a GLSL vertex shader which computes cameraspace normal and screen space position and then it uses them to compute other values. 

vec3 n = (modelView * vec4(vertexNormal, 0.0)).xyz;
vec3 p = (mvp * vec4(vertexPosition, 0.0f)).xyz;
vec3 w = n+p; (for example)


I am trying to replicate this shader in an eevee material graph but I'm not sure  how can I get screen space and camera space data. Is this posible?
You can get camera space coordinates from the Input > Texture Coordinates node using the Camera or Window socket, depending on what you are looking for.

The same node provides local position for vertex using the Object socket, you can convert to world coordinates using a Vector Transform node.

Using the Vector Math node you can do the required matrix calculations.

If I interpreted your code right you should need something along the lines of the node tree below.