/**
 * @ Version: SCREEN SPACE SHADERS - UPDATE 18
 * @ Description: SSR implementation
 * @ Modified time: 2024-02-09 06:27
 * @ Author: https://www.moddb.com/members/ascii1457
 * @ Mod: https://www.moddb.com/mods/stalker-anomaly/addons/screen-space-shaders
 */

#ifndef SSFX_SSR_QUALITY
	#define SSFX_SSR_QUALITY 0
#endif

#include "screenspace_common.h"
#include "settings_screenspace_SSR.h"

uniform float4 ssr_setup; // x: SSR Resolution | y: Blur Intensity | z: Temporal Intensity
uniform float4 ssfx_ssr_2; // x: Intensity | y: Sky Intensity | z: Weapon Intensity | w: Max Weapon Intensity
uniform float4 ssfx_is_underground;

Texture2D blue_noise;

static const int2 q_ssr_steps[6] =
{
	int2(8,72),
	int2(16,36),
	int2(24,18),
	int2(32,5),
	int2(48,1),
	int2(64,1),
};

/*static const float q_ssr_noise[6] =
{
	float(0.04f),
	float(0.04f),
	float(0.04f),
	float(0.06f),
	float(0.08f),
	float(0.08f),
};*/

float4 SSFX_ssr_fast_ray(float3 ray_start_vs, float3 ray_dir_vs, float2 tc, uint iSample : SV_SAMPLEINDEX)
{
	float2 sky_tc = 0;
	float2 behind_hit = 0;

	// Noise to "improve" consistency between steps
	float2 uv_noise = tc + timers.x * (ssr_setup.w > 0);
	uv_noise.x *= screen_res.x / screen_res.y;
	float noise = blue_noise.Sample(smp_linear, uv_noise).x * ssr_setup.w * 0.1f;

	// Initialize Ray
	RayTrace ssr_ray = SSFX_ray_init(ray_start_vs, ray_dir_vs, 150, q_ssr_steps[SSFX_SSR_QUALITY].x, 1.0f);

	// Save the original step.x
	float ori_x = ssr_ray.r_step.x;

	// Depth from the start of the ray
	float ray_depthstart = SSFX_get_depth(ssr_ray.r_start, iSample);
	
	float2 ray_check = 0;

	// Ray-march
	[unroll (q_ssr_steps[SSFX_SSR_QUALITY].x)]
	for (int i = 0; i < q_ssr_steps[SSFX_SSR_QUALITY].x; i++)
	{
		// Ray out of screen...
		if (ssr_ray.r_pos.y < 0.0f || ssr_ray.r_pos.y > 1.0f)
			return 0;

		// Trick for the horizontal out of bounds. Mirror border of the screen.
		if (ssr_ray.r_pos.x < 0.0f || ssr_ray.r_pos.x > 1.0f)
		{
			ssr_ray.r_pos -= ssr_ray.r_step; // Step back
			ssr_ray.r_step.x = -ssr_ray.r_step.x; // Invert Horizontal
			ssr_ray.r_pos += ssr_ray.r_step; // Step
		}

		// Ray intersect check
		ray_check = SSFX_ray_intersect(ssr_ray, iSample);

		// Sampled depth is not weapon or sky ( SKY_EPS float(0.001) )
		bool NoWpnSky = ray_check.y > 1.3f;

		// Disable weapon and sky
		ray_check.x *= NoWpnSky;

		// Return if ray is not reflecting backward
		if (ray_check.x > 0)
		{
			if (ray_check.x <= q_ssr_steps[SSFX_SSR_QUALITY].y)
				return float4(ssr_ray.r_pos, ray_check.y, 0);

#if SSFX_SSR_QUALITY > 2 // 1 Binary Search step in higher quality settigns ( Quality 4 & 5 )
			
			// Current ray pos & step to restore later...
			float4 prev_step = 0;
			prev_step.xy = ssr_ray.r_pos;
			prev_step.zw = ssr_ray.r_step;

			// Half and flip
			ssr_ray.r_step *= -0.5f;

			// Step ray
			ssr_ray.r_pos += ssr_ray.r_step;

			// Ray intersect check
			ray_check = SSFX_ray_intersect(ssr_ray, iSample);

			// Depth test... Conditions to use as reflections...
			if (abs(ray_check.x) <= 1.25f)
				return float4(ssr_ray.r_pos, ray_check.y, 0);

			// Restore previous ray position & step
			ssr_ray.r_pos = prev_step.xy;
			ssr_ray.r_step = prev_step.zw;

#endif

		}
		else
		{
			// TexCoor for sky ( Used to fade "SSFX_calc_SSR_fade" )
			if (ray_check.y <= SKY_EPS)
				sky_tc = ssr_ray.r_pos;
			
			behind_hit = ssr_ray.r_pos;

			// Reset or keep depending on... ( > 1.3f = no interaction with weapons and sky )
			behind_hit *= (ray_depthstart - 2.0f < ray_check.y) && NoWpnSky;
		}

		// Step the ray
		ssr_ray.r_pos += ssr_ray.r_step * (1.0f + noise.x * (1.0f - smoothstep(0, q_ssr_steps[SSFX_SSR_QUALITY].x * 0.33f, i)));
		//ssr_ray.r_pos += ssr_ray.r_step * (1.0f + (1.0f - smoothstep(0, q_ssr_steps[SSFX_SSR_QUALITY].x * 0.33f, i)));
	}

	return float4(behind_hit, ray_check.y, sky_tc.y);
}


void SSFX_ScreenSpaceReflections(float2 tc, float4 P, float3 N, float gloss, inout float4 color, uint iSample : SV_SAMPLEINDEX)
{
	// Note: Distance falloff on "rain_patch_normal.ps"
	
	// Material conditions ( MAT_FLORA and Terrain for now... )
	bool m_terrain = abs(P.w - 0.95f) <= 0.02f;
	bool m_flora = abs(P.w - MAT_FLORA) <= 0.04f;

	// Let's start with pure gloss.
	float refl_power = gloss;

	// Calc reflection bounce
	float3 inVec = normalize(P.xyz); // Incident
	float3 reVec = reflect(inVec , N); // Reflected

	// Transform space and calc reflection vector ( Skybox & Fresnel )
	float3 nw		 = mul(m_inv_V, N);
	float3 v2point	 = mul(m_inv_V, inVec);
	float3 v2reflect = reflect(v2point, nw);

	// Fresnel
	float fresnel = saturate (dot(v2reflect, v2point));
	float fresnel_amount = pow(fresnel, 3);
	refl_power *= fresnel_amount;

	float4 hit_uv = 0;

	// Calc SSR ray. Discard low reflective pixels
	if (refl_power > 0.02f)
		hit_uv = SSFX_ssr_fast_ray(P.xyz, reVec, tc, iSample);

	float3 refl_ray;
	float3 reflection = 0;
	float2 uvcoor = 0;

	// Sky is the reflection base...
#ifdef G_SSR_CHEAP_SKYBOX
	reflection = SSFX_calc_env(v2reflect) * ssfx_ssr_2.y * !ssfx_is_underground.x;
#else
	reflection = SSFX_calc_sky(v2reflect) * ssfx_ssr_2.y * !ssfx_is_underground.x;
#endif

	// Valid UV coor? SSFX_trace_ssr_ray return 0.0f if uv is out of bounds or sky.
	if (all(hit_uv.xy))
	{
		// Get scene reflection
		refl_ray = SSFX_get_image(hit_uv.xy, iSample);//SSFX_get_scene(hit_uv.xy, iSample);

		// Set reflection UV
		uvcoor = hit_uv.xy;

		// Reflection fog fadeout
		float refl_fog = 1.0 - saturate(( length(float3(inVec.x,inVec.y,hit_uv.z)) * fog_params.w + fog_params.x));

		// Let's fade the reflection based on ray XY coor to avoid abrupt changes and glitches
		float HitFade = saturate(hit_uv.y * refl_fog * refl_fog * G_SSR_VERTICAL_SCREENFADE);

		// Mix base reflection ( skybox ) with ray reflection
		reflection = lerp(reflection, refl_ray, HitFade);
	}
	else
	{
		// Reset gloss.
		refl_power = gloss * fresnel_amount;

		// Set reflection UV
		uvcoor = float2(0, hit_uv.w);//hit_uv.zw;
	}

	// Fade sky if !m_terrain ( Terrain MAT )
	float ray_fade = saturate(saturate(uvcoor.y * G_SSR_VERTICAL_SCREENFADE) + 1.0f * m_terrain);

	// Adjust the intensity of MAT_FLORA
	refl_power *= m_flora ? G_SSR_FLORA_INTENSITY : 1.0f;

	// Weapon Attenuation factor.
	float WeaponFactor = smoothstep(G_SSR_WEAPON_MAX_LENGTH - 0.2f, G_SSR_WEAPON_MAX_LENGTH, length(P.xyz));

	// Terrain MAT overwrite WeaponFactor.
	WeaponFactor = saturate(WeaponFactor + 1.0f * m_terrain);
	
	// Global intensity and limit max value.
	float main_clamp = clamp(refl_power * ssfx_ssr_2.x, 0, G_SSR_MAX_INTENSITY);
	
	// Raise reflection intensity and max limit when raining. ( NOTE: Reverted to rain intensity, but improvements are on the way... )
	float rain_extra = G_SSR_WEAPON_RAIN_FACTOR * rain_params.x;

	// Weapon intensity and limit max value.
	float wpn_clamp = clamp((refl_power + rain_extra) * ssfx_ssr_2.z, 0, ssfx_ssr_2.w + rain_extra);

	#ifdef G_SSR_WEAPON_REFLECT_ONLY_WITH_RAIN
		wpn_clamp *= rain_params.x;
	#endif

	// Lerp between general reflections and weapon reflections.
	refl_power = lerp(wpn_clamp, main_clamp, WeaponFactor);

	// Apply SSR fade to reflection.
	refl_power *= ray_fade;

	// 'Beefs Shader Based NVGs' optional intensity adjustment
#ifdef G_SSR_BEEFS_NVGs_ADJUSTMENT
	refl_power *= saturate(1.0f - (1.0f - G_SSR_BEEFS_NVGs_ADJUSTMENT) * (shader_param_8.x > 0.0f));
#endif

	// Fog Fix ( Render order problem... )
	float fog = 1.0 - saturate(( length(P.xyz) * fog_params.w + fog_params.x));

	// Add the reflection to the scene.
	color = float4(reflection, refl_power * fog * fog);//lerp(color, reflection, refl_power);
}