#version 450 core
layout(std430) buffer;

layout(set=0, binding=0) writeonly buffer destBuffer{
    float data[];
}uOutput;

layout(set=0, binding=1) readonly buffer sourceBuffer0{
    float data[];
} uInput;

layout(set=0, binding=2) readonly buffer sourceBuffer1{
    float data[];
} uGrid;

layout(set=0, binding=3) uniform gridSampleBuffer{
	ivec4 inShape;  // inW, inH
	ivec4 outShape; // outW, outH
	bool alignCorners;
}uGridSampleParam;

layout(local_size_x = 256, local_size_y = 1, local_size_z = 1) in;

float LoadSample(int positionX, int positionY, int c, int n) {
	float value;
	int width = uGridSampleParam.inShape.x;
	int height = uGridSampleParam.inShape.y;
#ifdef PAD_MODE_ZEROS
	if (positionX < 0 || positionX >= width || positionY < 0 || positionY >= height) {
		value = 0.0;
	} else {
		value = uInput.data[0
			+ positionX * uGridSampleParam.inShape.z
			+ positionY * width * uGridSampleParam.inShape.z
			+ n * width * height * uGridSampleParam.inShape.z
			+ c
		];
	}
#else
	positionX = clamp(positionX, 0, width - 1);
	positionY = clamp(positionY, 0, height - 1);
	value = uInput.data[0
		+ positionX * uGridSampleParam.inShape.z
		+ positionY * width * uGridSampleParam.inShape.z
		+ n * width * height * uGridSampleParam.inShape.z
		+ c
	];

#endif
	return value;
}

void main()
{
	int pos = int(gl_GlobalInvocationID.x);
	// input output grid layout is NC4HW4

	ivec4 inputShape = uGridSampleParam.inShape;
	ivec4 outputShape = uGridSampleParam.outShape;
	int total = outputShape.x * outputShape.y * outputShape.z * outputShape.w;

	if(pos < total)
	{
		// get nchw num of output 
		int x = pos % outputShape.x;
		int tmp = pos / outputShape.x;
		int y = tmp % outputShape.y;
		tmp = tmp / outputShape.y;
		int z = tmp % outputShape.z;
		int n = tmp / outputShape.z;

		// get position in grid
		int gridPosition = n * outputShape.x * outputShape.y + y * outputShape.x + x;
		float gridX = uGrid.data[inputShape.w * gridPosition + 0];
		float gridY = uGrid.data[inputShape.w * gridPosition + 1];

		// compute position of input
#ifdef NEAREST
		float cordH = (gridY) * (inputShape.y);
		float cordW = (gridX) * (inputShape.x);
		int positionX = int(floor(cordW));
		int positionY = int(floor(cordH));

		float value = LoadSample(positionX, positionY, z, n);
#else
		float cordH = (gridY) * (inputShape.y) - 0.5;
		float cordW = (gridX) * (inputShape.x) - 0.5;
		int w0_h = int(floor(cordH));
		int w0_w = int(floor(cordW));
		int w1_h = w0_h + 1;
		int w1_w = w0_w + 1;
		float oneV = float(1.0);

		float i00 = LoadSample(w0_w, w0_h, z, n);
		float i01 = LoadSample(w1_w, w0_h, z, n);
		float i10 = LoadSample(w0_w, w1_h, z, n);
		float i11 = LoadSample(w1_w, w1_h, z, n);

		float f0 = float(float(w1_w) - cordW);
		float f1 = oneV - f0;
		float h0 = float(float(w1_h) - cordH);
		float h1 = oneV - h0;
		
		float i0 = i00 * f0 + i01 * f1;
		float i1 = i10 * f0 + i11 * f1;

		float value = i0 * h0 + i1 * h1;
#endif
		uOutput.data[0
			+ x * outputShape.z
			+ y * outputShape.x * outputShape.z
			+ z
			+ n * outputShape.x * outputShape.y * outputShape.z
		] = value;
	}
}