#import "Common/ShaderLib/GLSLCompat.glsllib"

uniform vec4      m_Diffuse;
uniform sampler2D m_DiffuseMap;
uniform bool      m_HasDiffuseMap;
uniform sampler2D m_NormalMap;
uniform bool      m_HasNormalMap;
uniform float     m_Wetness;

in vec2  texCoord;
in vec3  vNormal;
in vec3  vTangent;
in float vHandedness;

void main() {
    vec3 baseColor;
    if (m_HasDiffuseMap) {
        vec4 tex = texture2D(m_DiffuseMap, texCoord);
        if (tex.a < 0.5) discard;
        baseColor = tex.rgb * m_Diffuse.rgb;
    } else {
        vec2 uv  = texCoord * 2.0 - 1.0;
        if (dot(uv, uv) > 0.95) discard;
        baseColor = m_Diffuse.rgb;
    }

    vec3 N = normalize(vNormal);
    if (m_HasNormalMap) {
        vec3 T  = normalize(vTangent);
        vec3 B  = normalize(cross(N, T) * vHandedness);
        mat3 TBN = mat3(T, B, N);
        vec3 nm  = texture2D(m_NormalMap, texCoord).rgb * 2.0 - 1.0;
        N = normalize(TBN * nm);
    }

    vec3  sun   = normalize(vec3(0.4, 1.0, 0.3));
    float diff  = max(0.0, dot(N, sun));
    // two-sided: underside receives half brightness
    diff = max(diff, max(0.0, dot(-N, sun)) * 0.5);
    float lit   = 0.45 + diff * 0.55;

    baseColor *= (1.0 - 0.18 * m_Wetness);
    float shine = pow(diff, 12.0) * m_Wetness * 0.25;
    gl_FragColor = vec4(baseColor * lit + vec3(shine), 1.0);
}