/* === YOUR WORK HERE ===
 * Fragment shader: you need to edit the code here!
 * First, you need to understand the Java program,
 * mainly understand how the variables in this shader program
 * are associated with buffers and variables defined  in your Java program.
 * Also you need to understand how data are passed from
 * your vertex shader to the fragment shader.
 * The changes you need to do here is
 * (a) use the 'texture0' variable for applying a texture to the die
 * (b) compute the ambient+diffuse shading term for each pixel. This will need
 *     to be multiplied with the texture color
 * (c) use the timer to further modulate the red and green channel of your pixels
*/
#version 330

in vec2 uv_coordinates_raster;
in vec3 normals_raster;
in vec3 light0_vector_raster;

uniform sampler2D texture0;
uniform float timer;

out vec4 glFragColor; // user-defined variable replacing gl_FragColor in latest GLSL versions

void main() {

    const vec3 diffuse_light_color = vec3(0.25, 0.25, 0.5);
    const vec3 ambient_light_color = vec3(0.75, 0.75, 0.75);

    // you need to change the following lines (and use the above variables and constants)
    glFragColor = texture(texture0, uv_coordinates_raster) * vec4(ambient_light_color + (diffuse_light_color * max(dot(normals_raster, light0_vector_raster), 0.0)), 0.0);
    glFragColor += vec4(0.1 * cos(.01*timer), 0.1 * cos(.01*timer), 0.0, 1.0);
}