attribute highp vec4 a_Vertex;
attribute highp vec4 a_Color;
attribute highp vec3 a_Normal;
attribute highp vec2 a_TexCoord;

uniform bool u_LightingEnabled;
uniform bool u_ColorArrayEnabled;
uniform highp mat4 u_MvpMatrix;
uniform highp mat3 u_NormalMatrix;
uniform highp vec3 u_LightDirection;
uniform highp vec3 u_HalfPlaneVector;
uniform highp vec4 u_AmbientAndDiffuseColor;
uniform highp float u_AmbientLightBrightness;
uniform highp vec4 u_SpecularColor;
uniform highp float u_Shininess;
uniform int u_PointSize;

varying highp vec2 v_TexCoord;
varying highp vec4 v_AmbientAndDiffuseColor;
varying highp vec4 v_SpecularColor;
varying highp float v_AmbientLightBrightness;
varying highp float v_DiffuseBrightness;
varying highp float v_SpecularBrightness;

const highp float c_Zero = 0.0;
highp vec3 eyeSpaceNormal;

highp float calculateDiffuseBrightness()
{
    if(u_LightingEnabled)
       return max(c_Zero, dot(eyeSpaceNormal, u_LightDirection));
    else return 1.0;
}

highp float calculateSpecularBrightness()
{
    highp float nDotHp = max(c_Zero, dot(eyeSpaceNormal, u_HalfPlaneVector));
    if(u_LightingEnabled && nDotHp > c_Zero)
       return pow(nDotHp, u_Shininess);
    else return 0.0;
}

void main(void)
{
    gl_Position = u_MvpMatrix * a_Vertex;
    if(u_LightingEnabled)
      eyeSpaceNormal = normalize(u_NormalMatrix * a_Normal);
    v_TexCoord = a_TexCoord;
    if(u_ColorArrayEnabled)
       v_AmbientAndDiffuseColor = a_Color;
    else v_AmbientAndDiffuseColor = u_AmbientAndDiffuseColor;
    v_AmbientLightBrightness = u_AmbientLightBrightness;
    v_DiffuseBrightness = calculateDiffuseBrightness();
    v_SpecularColor = u_SpecularColor;
    v_SpecularBrightness = calculateSpecularBrightness();
}