/*
 * Copyright 2011-2017 Blender Foundation
 *
 * 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.
 */

CCL_NAMESPACE_BEGIN

ccl_device_inline void kernel_filter_construct_gramian(int x, int y,
                                                       int storage_stride,
                                                       int dx, int dy,
                                                       int w, int h,
                                                       int pass_stride,
                                                       const ccl_global float *ccl_restrict buffer,
                                                       const ccl_global float *ccl_restrict transform,
                                                       ccl_global int *rank,
                                                       float weight,
                                                       ccl_global float *XtWX,
                                                       ccl_global float3 *XtWY,
                                                       int localIdx)
{
	if(weight < 1e-3f) {
		return;
	}

	int p_offset =  y    *w +  x;
	int q_offset = (y+dy)*w + (x+dx);

#ifdef __KERNEL_GPU__
	const int stride = storage_stride;
#else
	const int stride = 1;
	(void) storage_stride;
#endif

#ifdef __KERNEL_CUDA__
	ccl_local float shared_design_row[(DENOISE_FEATURES+1)*CCL_MAX_LOCAL_SIZE];
	ccl_local_param float *design_row = shared_design_row + localIdx*(DENOISE_FEATURES+1);
#else
	float design_row[DENOISE_FEATURES+1];
#endif

	float3 q_color = filter_get_color(buffer + q_offset, pass_stride);

	/* If the pixel was flagged as an outlier during prefiltering, skip it. */
	if(ccl_get_feature(buffer + q_offset, 0) < 0.0f) {
		return;
	}

	filter_get_design_row_transform(make_int2(x, y),       buffer + p_offset,
	                                make_int2(x+dx, y+dy), buffer + q_offset,
	                                pass_stride, *rank, design_row, transform, stride);

	math_trimatrix_add_gramian_strided(XtWX, (*rank)+1, design_row, weight, stride);
	math_vec3_add_strided(XtWY, (*rank)+1, design_row, weight * q_color, stride);
}

ccl_device_inline void kernel_filter_finalize(int x, int y, int w, int h,
                                              ccl_global float *buffer,
                                              ccl_global int *rank,
                                              int storage_stride,
                                              ccl_global float *XtWX,
                                              ccl_global float3 *XtWY,
                                              int4 buffer_params,
                                              int sample)
{
#ifdef __KERNEL_GPU__
	const int stride = storage_stride;
#else
	const int stride = 1;
	(void) storage_stride;
#endif

	if(XtWX[0] < 1e-3f) {
		/* There is not enough information to determine a denoised result.
		 * As a fallback, keep the original value of the pixel. */
		 return;
	}

	/* The weighted average of pixel colors (essentially, the NLM-filtered image).
	 * In case the solution of the linear model fails due to numerical issues,
	 * fall back to this value. */
	float3 mean_color = XtWY[0]/XtWX[0];

	math_trimatrix_vec3_solve(XtWX, XtWY, (*rank)+1, stride);

	float3 final_color = XtWY[0];
	if(!isfinite3_safe(final_color)) {
		final_color = mean_color;
	}

	/* Clamp pixel value to positive values. */
	final_color = max(final_color, make_float3(0.0f, 0.0f, 0.0f));

	ccl_global float *combined_buffer = buffer + (y*buffer_params.y + x + buffer_params.x)*buffer_params.z;
	final_color *= sample;
	if(buffer_params.w) {
		final_color.x += combined_buffer[buffer_params.w+0];
		final_color.y += combined_buffer[buffer_params.w+1];
		final_color.z += combined_buffer[buffer_params.w+2];
	}
	combined_buffer[0] = final_color.x;
	combined_buffer[1] = final_color.y;
	combined_buffer[2] = final_color.z;
}

CCL_NAMESPACE_END