/*
 * Copyright 2011-2013 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 path_state_init(KernelGlobals *kg,
                                       ShaderData *stack_sd,
                                       ccl_addr_space PathState *state,
                                       uint rng_hash,
                                       int sample,
                                       ccl_addr_space Ray *ray)
{
	state->flag = PATH_RAY_CAMERA|PATH_RAY_MIS_SKIP|PATH_RAY_TRANSPARENT_BACKGROUND;

	state->rng_hash = rng_hash;
	state->rng_offset = PRNG_BASE_NUM;
	state->sample = sample;
	state->num_samples = kernel_data.integrator.aa_samples;
	state->branch_factor = 1.0f;

	state->bounce = 0;
	state->diffuse_bounce = 0;
	state->glossy_bounce = 0;
	state->transmission_bounce = 0;
	state->transparent_bounce = 0;

#ifdef __DENOISING_FEATURES__
	if(kernel_data.film.pass_denoising_data) {
		state->flag |= PATH_RAY_STORE_SHADOW_INFO;
		state->denoising_feature_weight = 1.0f;
	}
	else {
		state->denoising_feature_weight = 0.0f;
	}
#endif  /* __DENOISING_FEATURES__ */

	state->min_ray_pdf = FLT_MAX;
	state->ray_pdf = 0.0f;
#ifdef __LAMP_MIS__
	state->ray_t = 0.0f;
#endif

#ifdef __VOLUME__
	state->volume_bounce = 0;
	state->volume_bounds_bounce = 0;

	if(kernel_data.integrator.use_volumes) {
		/* Initialize volume stack with volume we are inside of. */
		kernel_volume_stack_init(kg, stack_sd, state, ray, state->volume_stack);
	}
	else {
		state->volume_stack[0].shader = SHADER_NONE;
	}
#endif
}

ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathState *state, int label)
{
	/* ray through transparent keeps same flags from previous ray and is
	 * not counted as a regular bounce, transparent has separate max */
	if(label & LABEL_TRANSPARENT) {
		state->flag |= PATH_RAY_TRANSPARENT;
		state->transparent_bounce++;
		if(state->transparent_bounce >= kernel_data.integrator.transparent_max_bounce) {
			state->flag |= PATH_RAY_TERMINATE_IMMEDIATE;
		}

		if(!kernel_data.integrator.transparent_shadows)
			state->flag |= PATH_RAY_MIS_SKIP;

		/* random number generator next bounce */
		state->rng_offset += PRNG_BOUNCE_NUM;

		return;
	}

	state->bounce++;
	if(state->bounce >= kernel_data.integrator.max_bounce) {
		state->flag |= PATH_RAY_TERMINATE_AFTER_TRANSPARENT;
	}

	state->flag &= ~(PATH_RAY_ALL_VISIBILITY|PATH_RAY_MIS_SKIP);

#ifdef __VOLUME__
	if(label & LABEL_VOLUME_SCATTER) {
		/* volume scatter */
		state->flag |= PATH_RAY_VOLUME_SCATTER;
		state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;

		state->volume_bounce++;
		if(state->volume_bounce >= kernel_data.integrator.max_volume_bounce) {
			state->flag |= PATH_RAY_TERMINATE_AFTER_TRANSPARENT;
		}
	}
	else
#endif
	{
		/* surface reflection/transmission */
		if(label & LABEL_REFLECT) {
			state->flag |= PATH_RAY_REFLECT;
			state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;

			if(label & LABEL_DIFFUSE) {
				state->diffuse_bounce++;
				if(state->diffuse_bounce >= kernel_data.integrator.max_diffuse_bounce) {
					state->flag |= PATH_RAY_TERMINATE_AFTER_TRANSPARENT;
				}
			}
			else {
				state->glossy_bounce++;
				if(state->glossy_bounce >= kernel_data.integrator.max_glossy_bounce) {
					state->flag |= PATH_RAY_TERMINATE_AFTER_TRANSPARENT;
				}
			}
		}
		else {
			kernel_assert(label & LABEL_TRANSMIT);

			state->flag |= PATH_RAY_TRANSMIT;

			if(!(label & LABEL_TRANSMIT_TRANSPARENT)) {
				state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;
			}

			state->transmission_bounce++;
			if(state->transmission_bounce >= kernel_data.integrator.max_transmission_bounce) {
				state->flag |= PATH_RAY_TERMINATE_AFTER_TRANSPARENT;
			}
		}

		/* diffuse/glossy/singular */
		if(label & LABEL_DIFFUSE) {
			state->flag |= PATH_RAY_DIFFUSE|PATH_RAY_DIFFUSE_ANCESTOR;
		}
		else if(label & LABEL_GLOSSY) {
			state->flag |= PATH_RAY_GLOSSY;
		}
		else {
			kernel_assert(label & LABEL_SINGULAR);
			state->flag |= PATH_RAY_GLOSSY|PATH_RAY_SINGULAR|PATH_RAY_MIS_SKIP;
		}
	}

	/* random number generator next bounce */
	state->rng_offset += PRNG_BOUNCE_NUM;

#ifdef __DENOISING_FEATURES__
	if((state->denoising_feature_weight == 0.0f) && !(state->flag & PATH_RAY_SHADOW_CATCHER)) {
		state->flag &= ~PATH_RAY_STORE_SHADOW_INFO;
	}
#endif
}

#ifdef __VOLUME__
ccl_device_inline bool path_state_volume_next(KernelGlobals *kg, ccl_addr_space PathState *state)
{
	/* For volume bounding meshes we pass through without counting transparent
	 * bounces, only sanity check in case self intersection gets us stuck. */
	state->volume_bounds_bounce++;
	if (state->volume_bounds_bounce > VOLUME_BOUNDS_MAX) {
		return false;
	}

	/* Random number generator next bounce. */
	if(state->volume_bounds_bounce > 1) {
		state->rng_offset += PRNG_BOUNCE_NUM;
	}

	return true;
}
#endif

ccl_device_inline uint path_state_ray_visibility(KernelGlobals *kg, ccl_addr_space PathState *state)
{
	uint flag = state->flag & PATH_RAY_ALL_VISIBILITY;

	/* for visibility, diffuse/glossy are for reflection only */
	if(flag & PATH_RAY_TRANSMIT)
		flag &= ~(PATH_RAY_DIFFUSE|PATH_RAY_GLOSSY);
	/* todo: this is not supported as its own ray visibility yet */
	if(state->flag & PATH_RAY_VOLUME_SCATTER)
		flag |= PATH_RAY_DIFFUSE;

	return flag;
}

ccl_device_inline float path_state_continuation_probability(KernelGlobals *kg,
                                                            ccl_addr_space PathState *state,
                                                            const float3 throughput)
{
	if(state->flag & PATH_RAY_TERMINATE_IMMEDIATE) {
		/* Ray is to be terminated immediately. */
		return 0.0f;
	}
	else if(state->flag & PATH_RAY_TRANSPARENT) {
		/* Do at least one bounce without RR. */
		if(state->transparent_bounce <= 1) {
			return 1.0f;
		}
#ifdef __SHADOW_TRICKS__
		/* Exception for shadow catcher not working correctly with RR. */
		else if((state->flag & PATH_RAY_SHADOW_CATCHER) && (state->transparent_bounce <= 8)) {
			return 1.0f;
		}
#endif
	}
	else {
		/* Do at least one bounce without RR. */
		if(state->bounce <= 1) {
			return 1.0f;
		}
#ifdef __SHADOW_TRICKS__
		/* Exception for shadow catcher not working correctly with RR. */
		else if((state->flag & PATH_RAY_SHADOW_CATCHER) && (state->bounce <= 3)) {
			return 1.0f;
		}
#endif
	}

	/* Probabilistic termination: use sqrt() to roughly match typical view
	 * transform and do path termination a bit later on average. */
	return min(sqrtf(max3(fabs(throughput)) * state->branch_factor), 1.0f);
}

/* TODO(DingTo): Find more meaningful name for this */
ccl_device_inline void path_state_modify_bounce(ccl_addr_space PathState *state, bool increase)
{
	/* Modify bounce temporarily for shader eval */
	if(increase)
		state->bounce += 1;
	else
		state->bounce -= 1;
}

ccl_device_inline bool path_state_ao_bounce(KernelGlobals *kg, ccl_addr_space PathState *state)
{
    if(state->bounce <= kernel_data.integrator.ao_bounces) {
        return false;
    }

    int bounce = state->bounce - state->transmission_bounce - (state->glossy_bounce > 0);
    return (bounce > kernel_data.integrator.ao_bounces);
}

ccl_device_inline void path_state_branch(ccl_addr_space PathState *state,
                                         int branch,
                                         int num_branches)
{
	if(num_branches > 1) {
		/* Path is splitting into a branch, adjust so that each branch
		 * still gets a unique sample from the same sequence. */
		state->sample = state->sample*num_branches + branch;
		state->num_samples = state->num_samples*num_branches;
		state->branch_factor *= num_branches;
	}
}

CCL_NAMESPACE_END