/*
 * Copyright 2011-2017 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "stdosl.h"
#include "node_fresnel.h"

shader node_principled_bsdf(
	string distribution = "Multiscatter GGX",
	color BaseColor = color(0.8, 0.8, 0.8),
	float Subsurface = 0.0,
	vector SubsurfaceRadius = vector(1.0, 1.0, 1.0),
	color SubsurfaceColor = color(0.7, 0.1, 0.1),
	float Metallic = 0.0,
	float Specular = 0.5,
	float SpecularTint = 0.0,
	float Roughness = 0.5,
	float Anisotropic = 0.0,
	float AnisotropicRotation = 0.0,
	float Sheen = 0.0,
	float SheenTint = 0.5,
	float Clearcoat = 0.0,
	float ClearcoatRoughness = 0.03,
	float IOR = 1.45,
	float Transmission = 0.0,
	float TransmissionRoughness = 0.0,
	normal Normal = N,
	normal ClearcoatNormal = N,
	normal Tangent = normalize(dPdu),
	output closure color BSDF = 0)
{
	float f = max(IOR, 1e-5);
	float diffuse_weight = (1.0 - clamp(Metallic, 0.0, 1.0)) * (1.0 - clamp(Transmission, 0.0, 1.0));
	float final_transmission = clamp(Transmission, 0.0, 1.0) * (1.0 - clamp(Metallic, 0.0, 1.0));
	float specular_weight = (1.0 - final_transmission);

	vector T = Tangent;

	float m_cdlum = luminance(BaseColor);
	color m_ctint = m_cdlum > 0.0 ? BaseColor / m_cdlum : color(0.0, 0.0, 0.0); // normalize lum. to isolate hue+sat

	/* rotate tangent */
	if (AnisotropicRotation != 0.0)
		T = rotate(T, AnisotropicRotation * M_2PI, point(0.0, 0.0, 0.0), Normal);

	if (diffuse_weight > 1e-5) {
		if (Subsurface > 1e-5) {
			color mixed_ss_base_color = SubsurfaceColor * Subsurface + BaseColor * (1.0 - Subsurface);
			BSDF = mixed_ss_base_color * bssrdf_principled(Normal, Subsurface * SubsurfaceRadius, 0.0, SubsurfaceColor, Roughness);
		} else {
			BSDF = BaseColor * principled_diffuse(Normal, Roughness);
		}

		if (Sheen > 1e-5) {
			color sheen_color = color(1.0, 1.0, 1.0) * (1.0 - SheenTint) + m_ctint * SheenTint;

			BSDF = BSDF + sheen_color * Sheen * principled_sheen(Normal);
		}

		BSDF = BSDF * diffuse_weight;
	}

	if (specular_weight > 1e-5) {
		float aspect = sqrt(1.0 - Anisotropic * 0.9);
		float r2 = Roughness * Roughness;

		float alpha_x = r2 / aspect;
		float alpha_y = r2 * aspect;

		color tmp_col = color(1.0, 1.0, 1.0) * (1.0 - SpecularTint) + m_ctint * SpecularTint;

		color Cspec0 = (Specular * 0.08 * tmp_col) * (1.0 - Metallic) + BaseColor * Metallic;

		if (distribution == "GGX" || Roughness <= 0.075) {
			BSDF = BSDF  + specular_weight * microfacet_ggx_aniso_fresnel(Normal, T, alpha_x, alpha_y, (2.0 / (1.0 - sqrt(0.08 * Specular))) - 1.0, BaseColor, Cspec0);
		} else {
			BSDF = BSDF + specular_weight * microfacet_multi_ggx_aniso_fresnel(Normal, T, alpha_x, alpha_y, (2.0 / (1.0 - sqrt(0.08 * Specular))) - 1.0, BaseColor, Cspec0);
		}
	}

	if (final_transmission > 1e-5) {
		color Cspec0 = BaseColor * SpecularTint + color(1.0, 1.0, 1.0) * (1.0 - SpecularTint);
		float eta = backfacing() ? 1.0 / f : f;

		if (distribution == "GGX" || Roughness <= 5e-2) {
			float cosNO = dot(Normal, I);
			float Fr = fresnel_dielectric_cos(cosNO, eta);

			float refl_roughness = Roughness;
			if (Roughness <= 1e-2)
				refl_roughness = 0.0;

			float transmission_roughness = refl_roughness;
			if (distribution == "GGX")
				transmission_roughness = 1.0 - (1.0 - refl_roughness) * (1.0 - TransmissionRoughness);

			BSDF = BSDF + final_transmission * (Fr * microfacet_ggx_fresnel(Normal, refl_roughness * refl_roughness, eta, BaseColor, Cspec0) +
			       (1.0 - Fr) * BaseColor * microfacet_ggx_refraction(Normal, transmission_roughness * transmission_roughness, eta));
		} else {
			BSDF = BSDF + final_transmission * microfacet_multi_ggx_glass_fresnel(Normal, Roughness * Roughness, eta, BaseColor, Cspec0);
		}
	}

	if (Clearcoat > 1e-5) {
		BSDF = BSDF + principled_clearcoat(ClearcoatNormal, Clearcoat, ClearcoatRoughness * ClearcoatRoughness);
	}
}