/* Copyright (c) 2024, Sascha Willems
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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.
 */

struct VSOutput
{
    float4 Pos : SV_POSITION;
	float3 Normal : NORMAL0;
	float4 Color : TEXCOORD0;
	float3 LightVec : TEXCOORD1;
	float3 LightColor[2] : TEXCOORD2;
	float3 ViewVec : TEXCOORD3;
	float LightIntensity : TEXCOORD4;
};

float4 main(VSOutput input) : SV_TARGET0
{
	float attenuation = 1.0 / dot(input.LightVec, input.LightVec);

	float3 N = normalize(input.Normal);
	float3 L = normalize(input.LightVec);
	float3 V = normalize(input.ViewVec);
	float3 R = reflect(-L, N);

	float3 diffuse  = input.LightColor[0] * attenuation * max(dot(N, L), 0) * input.LightIntensity;
	float3 ambient  = input.LightColor[1];
	float3 specular = pow(max(dot(R, V), 0.0), 16.0) * float3(0.65, 0.65, 0.65);
	
	return float4((ambient + diffuse) * input.Color.rgb + (specular * input.LightIntensity / 50), input.Color.a);
}