#include "/Lib/Settings.glsl"
#include "/Lib/Utilities.glsl"
// MinecraftPT — RTWSM SampleWarp
// Samples the warp map to redistribute shadow map coordinates.

#ifndef SAMPLE_WARP_GLSL
uniform sampler2D rtwWarp1D;
#define SAMPLE_WARP_GLSL

// Warp curve sampling: rtwWarp1D is a RG16 texture, RTW_RESOLUTION x 2
// Row 0: warp curve (cumulative importance), Row 1: inverse warp curve
vec2 SampleWarp(float value){
	vec2 coord = vec2(value * (RTW_RESOLUTION - 1.0) + 0.5, 0.5) / vec2(RTW_RESOLUTION, 2.0);
	return textureLod(rtwWarp1D, coord, 0.0).rg;
}

// Smooth warp sampling with lerp
vec2 SampleRTWWarpSmooth(vec2 shadowScreenPos){
	// The warp is 1D along the shadow map's X axis (sun direction)
	float u = saturate(shadowScreenPos.x);

	// Sample warp curve
	vec2 warp = SampleWarp(u);

	// Apply warp: remap x based on cumulative importance
	float warpedX = warp.x;

	// Also apply to y for 2D warping (using second channel)
	float warpedY = warp.y;

	return vec2(warpedX - u, warpedY - shadowScreenPos.y);
}

// Full warp application for shadow map sampling
vec2 WarpShadowCoord(vec2 shadowScreenPos){
	float u = saturate(shadowScreenPos.x);
	vec2 warp = SampleWarp(u);

	vec2 warped = vec2(warp.x, warp.y);

	// The warp curve maps [0,1] -> [0,1] cumulative
	// Inverse: sample with the inverse curve
	return warped;
}

// Unwarp (for reconstructing world positions)
vec2 UnwarpShadowCoord(vec2 warpedCoord){
	// Binary search on the warp curve (forward map)
	float low = 0.0;
	float high = 1.0;

	for (int i = 0; i < 8; i++){
		float mid = (low + high) * 0.5;
		vec2 sample = SampleWarp(mid);
		if (sample.x < warpedCoord.x){
			low = mid;
		}else{
			high = mid;
		}
	}

	return vec2((low + high) * 0.5, warpedCoord.y);
}

#endif