#version 330 core
#extension GL_ARB_shading_language_420pack : enable

const int MAX_MAPS = 4;

out vec3 FragColor;

in vec2 TexCoords;

layout(binding = 0) uniform isampler2D gPosition;
layout(binding = 1) uniform sampler2D gNormal;
layout(binding = 2) uniform sampler2DArray shadowMap;

uniform vec3 lightDirection;
uniform vec3 lightColour;
uniform ivec3 lightPoint;
uniform mat4 lightViewProjection[MAX_MAPS];
uniform uint lightViewProjectionCount;

const vec3 e1 = vec3(0, 0, 0), e2 = vec3(1, 1, 1);

float
insideShadowCube(vec3 v)
{
	const vec3 s = step(e1, v) - step(e2, v);
	return s.x * s.y * s.z;
}

float
isShaded(vec4 Position)
{
	for (uint m = 0u; m < lightViewProjectionCount; m++) {
		const vec3 PositionInLightSpace = (lightViewProjection[m] * Position).xyz;
		const float inside = insideShadowCube(PositionInLightSpace);
		if (inside > 0) {
			const float lightSpaceDepth = texture(shadowMap, vec3(PositionInLightSpace.xy, m)).r;
			return step(PositionInLightSpace.z, lightSpaceDepth + 0.001);
		}
	}
	return 1;
}

void
main()
{
	const vec4 Position = vec4(texture(gPosition, TexCoords).xyz - lightPoint, 1);
	const vec3 Normal = texture(gNormal, TexCoords).rgb;
	const float shaded = isShaded(Position);
	FragColor = shaded * max(dot(-lightDirection, Normal) * lightColour, 0);
}