#version 300 es

#define BASE_COLOR vec4(1.0, 1.0, 1.0, 1.0)
#define AMBIENT_LIGHT vec3(0.3, 0.3, 0.3)
#define LIGHT_DIRECTION normalize(vec3(0.85, 0.8, 0.75))
#define LIGHT_COLOR vec3(1.0, 1.0, 1.0)

precision highp float;

layout(location = 0) in vec4 aVertexPosition;
layout(location = 1) in vec3 aVertexNormal;
layout(location = 2) in float aHeight;
flat out vec4 vColor;

uniform mat4 uModelViewMatrix;
uniform mat4 uProjectionMatrix;
uniform mat4 uNormalMatrix;

void main() {
  float instanceX =
      aVertexPosition.x + float(gl_InstanceID) * 2.0 * abs(aVertexPosition.x);
  float vertexY =
      aVertexPosition.y > 0.0 ? aVertexPosition.y * aHeight : aVertexPosition.y;

  gl_Position = uProjectionMatrix * uModelViewMatrix *
                vec4(instanceX, vertexY, aVertexPosition.zw);

  vec4 transformedNormal = uNormalMatrix * vec4(aVertexNormal, 1.0);
  float directionalLight =
      max(dot(transformedNormal.xyz, LIGHT_DIRECTION), 0.0);

  if (aHeight == 0.0) {
    vColor = vec4(0.0, 0.0, 0.0, 0.0);
  } else {
    vec4 transformedNormal = uNormalMatrix * vec4(aVertexNormal, 1.0);
    float directionalLight =
        max(dot(transformedNormal.xyz, LIGHT_DIRECTION), 0.0);
    vColor = vec4(AMBIENT_LIGHT + (directionalLight * LIGHT_COLOR), 1.0);
  }
}