/*
 * Based on code from OpenSubdiv released under this license:
 *
 * Copyright 2013 Pixar
 *
 * Licensed under the Apache License, Version 2.0 (the "Apache License")
 * with the following modification; you may not use this file except in
 * compliance with the Apache License and the following modification to it:
 * Section 6. Trademarks. is deleted and replaced with:
 *
 * 6. Trademarks. This License does not grant permission to use the trade
 *   names, trademarks, service marks, or product names of the Licensor
 *   and its affiliates, except as required to comply with Section 4(c) of
 *   the License and to reproduce the content of the NOTICE file.
 *
 * You may obtain a copy of the Apache License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Apache License with the above modification is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the Apache License for the specific
 * language governing permissions and limitations under the Apache License.
 *
 */

CCL_NAMESPACE_BEGIN

typedef struct PatchHandle {
	int array_index, patch_index, vert_index;
} PatchHandle;

ccl_device_inline int patch_map_resolve_quadrant(float median, float *u, float *v)
{
	int quadrant = -1;

	if(*u < median) {
		if(*v < median) {
			quadrant = 0;
		}
		else {
			quadrant = 1;
			*v -= median;
		}
	}
	else {
		if(*v < median) {
			quadrant = 3;
		}
		else {
			quadrant = 2;
			*v -= median;
		}
		*u -= median;
	}

	return quadrant;
}

/* retrieve PatchHandle from patch coords */

ccl_device_inline PatchHandle patch_map_find_patch(KernelGlobals *kg, int object, int patch, float u, float v)
{
	PatchHandle handle;

	kernel_assert((u >= 0.0f) && (u <= 1.0f) && (v >= 0.0f) && (v <= 1.0f));

	int node = (object_patch_map_offset(kg, object) + patch)/2;
	float median = 0.5f;

	for(int depth = 0; depth < 0xff; depth++) {
		float delta = median * 0.5f;

		int quadrant = patch_map_resolve_quadrant(median, &u, &v);
		kernel_assert(quadrant >= 0);

		uint child = kernel_tex_fetch(__patches, node + quadrant);

		/* is the quadrant a hole? */
		if(!(child & PATCH_MAP_NODE_IS_SET)) {
			handle.array_index = -1;
			return handle;
		}

		uint index = child & PATCH_MAP_NODE_INDEX_MASK;

		if(child & PATCH_MAP_NODE_IS_LEAF) {
			handle.array_index = kernel_tex_fetch(__patches, index + 0);
			handle.patch_index = kernel_tex_fetch(__patches, index + 1);
			handle.vert_index = kernel_tex_fetch(__patches, index + 2);

			return handle;
		} else {
			node = index;
		}

		median = delta;
	}

	/* no leaf found */
	kernel_assert(0);

	handle.array_index = -1;
	return handle;
}

ccl_device_inline void patch_eval_bspline_weights(float t, float *point, float *deriv)
{
	/* The four uniform cubic B-Spline basis functions evaluated at t */
	float inv_6 = 1.0f / 6.0f;

	float t2 = t * t;
	float t3 = t * t2;

	point[0] = inv_6 * (1.0f - 3.0f*(t - t2) - t3);
	point[1] = inv_6 * (4.0f - 6.0f*t2 + 3.0f*t3);
	point[2] = inv_6 * (1.0f + 3.0f*(t + t2 - t3));
	point[3] = inv_6 * t3;

	/* Derivatives of the above four basis functions at t */
	deriv[0] = -0.5f*t2 + t - 0.5f;
	deriv[1] =  1.5f*t2 - 2.0f*t;
	deriv[2] = -1.5f*t2 + t + 0.5f;
	deriv[3] =  0.5f*t2;
}

ccl_device_inline void patch_eval_adjust_boundary_weights(uint bits, float *s, float *t)
{
	int boundary = ((bits >> 8) & 0xf);

	if(boundary & 1) {
		t[2] -= t[0];
		t[1] += 2*t[0];
		t[0] = 0;
	}

	if(boundary & 2) {
		s[1] -= s[3];
		s[2] += 2*s[3];
		s[3] = 0;
	}

	if(boundary & 4) {
		t[1] -= t[3];
		t[2] += 2*t[3];
		t[3] = 0;
	}

	if(boundary & 8) {
		s[2] -= s[0];
		s[1] += 2*s[0];
		s[0] = 0;
	}
}

ccl_device_inline int patch_eval_depth(uint patch_bits)
{
	return (patch_bits & 0xf);
}

ccl_device_inline float patch_eval_param_fraction(uint patch_bits)
{
	bool non_quad_root = (patch_bits >> 4) & 0x1;
	int depth = patch_eval_depth(patch_bits);

	if(non_quad_root) {
		return 1.0f / (float)(1 << (depth-1));
	}
	else {
		return 1.0f / (float)(1 << depth);
	}
}

ccl_device_inline void patch_eval_normalize_coords(uint patch_bits, float *u, float *v)
{
	float frac = patch_eval_param_fraction(patch_bits);

	int iu = (patch_bits >> 22) & 0x3ff;
	int iv = (patch_bits >> 12) & 0x3ff;

	/* top left corner */
	float pu = (float)iu*frac;
	float pv = (float)iv*frac;

	/* normalize uv coordinates */
	*u = (*u - pu) / frac;
	*v = (*v - pv) / frac;
}

/* retrieve patch control indices */

ccl_device_inline int patch_eval_indices(KernelGlobals *kg, const PatchHandle *handle, int channel,
                                         int indices[PATCH_MAX_CONTROL_VERTS])
{
	int index_base = kernel_tex_fetch(__patches, handle->array_index + 2) + handle->vert_index;

	/* XXX: regular patches only */
	for(int i = 0; i < 16; i++) {
		indices[i] = kernel_tex_fetch(__patches, index_base + i);
	}

	return 16;
}

/* evaluate patch basis functions */

ccl_device_inline void patch_eval_basis(KernelGlobals *kg, const PatchHandle *handle, float u, float v,
                                float weights[PATCH_MAX_CONTROL_VERTS],
                                float weights_du[PATCH_MAX_CONTROL_VERTS],
                                float weights_dv[PATCH_MAX_CONTROL_VERTS])
{
	uint patch_bits = kernel_tex_fetch(__patches, handle->patch_index + 1); /* read patch param */
	float d_scale = 1 << patch_eval_depth(patch_bits);

	bool non_quad_root = (patch_bits >> 4) & 0x1;
	if(non_quad_root) {
		d_scale *= 0.5f;
	}

	patch_eval_normalize_coords(patch_bits, &u, &v);

	/* XXX: regular patches only for now. */

	float s[4], t[4], ds[4], dt[4];

	patch_eval_bspline_weights(u, s, ds);
	patch_eval_bspline_weights(v, t, dt);

	patch_eval_adjust_boundary_weights(patch_bits, s, t);
	patch_eval_adjust_boundary_weights(patch_bits, ds, dt);

	for(int k = 0; k < 4; k++) {
		for(int l = 0; l < 4; l++) {
			weights[4*k+l] = s[l] * t[k];
			weights_du[4*k+l] = ds[l] * t[k] * d_scale;
			weights_dv[4*k+l] = s[l] * dt[k] * d_scale;
		}
	}
}

/* generic function for evaluating indices and weights from patch coords */

ccl_device_inline int patch_eval_control_verts(KernelGlobals *kg, int object, int patch, float u, float v, int channel,
                                        int indices[PATCH_MAX_CONTROL_VERTS],
                                        float weights[PATCH_MAX_CONTROL_VERTS],
                                        float weights_du[PATCH_MAX_CONTROL_VERTS],
                                        float weights_dv[PATCH_MAX_CONTROL_VERTS])
{
	PatchHandle handle = patch_map_find_patch(kg, object, patch, u, v);
	kernel_assert(handle.array_index >= 0);

	int num_control = patch_eval_indices(kg, &handle, channel, indices);
	patch_eval_basis(kg, &handle, u, v, weights, weights_du, weights_dv);

	return num_control;
}

/* functions for evaluating attributes on patches */

ccl_device float patch_eval_float(KernelGlobals *kg, const ShaderData *sd, int offset,
                                  int patch, float u, float v, int channel,
                                  float *du, float* dv)
{
	int indices[PATCH_MAX_CONTROL_VERTS];
	float weights[PATCH_MAX_CONTROL_VERTS];
	float weights_du[PATCH_MAX_CONTROL_VERTS];
	float weights_dv[PATCH_MAX_CONTROL_VERTS];

	int num_control = patch_eval_control_verts(kg, sd->object, patch, u, v, channel,
	                                           indices, weights, weights_du, weights_dv);

	float val = 0.0f;
	if(du) *du = 0.0f;
	if(dv) *dv = 0.0f;

	for(int i = 0; i < num_control; i++) {
		float v = kernel_tex_fetch(__attributes_float, offset + indices[i]);

		val += v * weights[i];
		if(du) *du += v * weights_du[i];
		if(dv) *dv += v * weights_dv[i];
	}

	return val;
}

ccl_device float3 patch_eval_float3(KernelGlobals *kg, const ShaderData *sd, int offset,
                                    int patch, float u, float v, int channel,
                                    float3 *du, float3 *dv)
{
	int indices[PATCH_MAX_CONTROL_VERTS];
	float weights[PATCH_MAX_CONTROL_VERTS];
	float weights_du[PATCH_MAX_CONTROL_VERTS];
	float weights_dv[PATCH_MAX_CONTROL_VERTS];

	int num_control = patch_eval_control_verts(kg, sd->object, patch, u, v, channel,
	                                           indices, weights, weights_du, weights_dv);

	float3 val = make_float3(0.0f, 0.0f, 0.0f);
	if(du) *du = make_float3(0.0f, 0.0f, 0.0f);
	if(dv) *dv = make_float3(0.0f, 0.0f, 0.0f);

	for(int i = 0; i < num_control; i++) {
		float3 v = float4_to_float3(kernel_tex_fetch(__attributes_float3, offset + indices[i]));

		val += v * weights[i];
		if(du) *du += v * weights_du[i];
		if(dv) *dv += v * weights_dv[i];
	}

	return val;
}

ccl_device float3 patch_eval_uchar4(KernelGlobals *kg, const ShaderData *sd, int offset,
                                    int patch, float u, float v, int channel,
                                    float3 *du, float3 *dv)
{
	int indices[PATCH_MAX_CONTROL_VERTS];
	float weights[PATCH_MAX_CONTROL_VERTS];
	float weights_du[PATCH_MAX_CONTROL_VERTS];
	float weights_dv[PATCH_MAX_CONTROL_VERTS];

	int num_control = patch_eval_control_verts(kg, sd->object, patch, u, v, channel,
	                                           indices, weights, weights_du, weights_dv);

	float3 val = make_float3(0.0f, 0.0f, 0.0f);
	if(du) *du = make_float3(0.0f, 0.0f, 0.0f);
	if(dv) *dv = make_float3(0.0f, 0.0f, 0.0f);

	for(int i = 0; i < num_control; i++) {
		float3 v = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, offset + indices[i]));

		val += v * weights[i];
		if(du) *du += v * weights_du[i];
		if(dv) *dv += v * weights_dv[i];
	}

	return val;
}

CCL_NAMESPACE_END

