/*
**  DrawWall code generation
**  Copyright (c) 2016 Magnus Norddahl
**
**  This software is provided 'as-is', without any express or implied
**  warranty.  In no event will the authors be held liable for any damages
**  arising from the use of this software.
**
**  Permission is granted to anyone to use this software for any purpose,
**  including commercial applications, and to alter it and redistribute it
**  freely, subject to the following restrictions:
**
**  1. The origin of this software must not be misrepresented; you must not
**     claim that you wrote the original software. If you use this software
**     in a product, an acknowledgment in the product documentation would be
**     appreciated but is not required.
**  2. Altered source versions must be plainly marked as such, and must not be
**     misrepresented as being the original software.
**  3. This notice may not be removed or altered from any source distribution.
**
*/

#include "precomp.h"
#include "timestamp.h"
#include "fixedfunction/drawwallcodegen.h"
#include "ssa/ssa_function.h"
#include "ssa/ssa_scope.h"
#include "ssa/ssa_for_block.h"
#include "ssa/ssa_if_block.h"
#include "ssa/ssa_stack.h"
#include "ssa/ssa_function.h"
#include "ssa/ssa_struct_type.h"
#include "ssa/ssa_value.h"

void DrawWallCodegen::Generate(DrawWallVariant variant, SSAValue args, SSAValue thread_data)
{
	dest = args[0][0].load(true);
	source = args[0][1].load(true);
	source2 = args[0][5].load(true);
	pitch = args[0][9].load(true);
	count = args[0][10].load(true);
	dest_y = args[0][11].load(true);
	texturefrac = args[0][12].load(true);
	texturefracx = args[0][16].load(true);
	iscale = args[0][20].load(true);
	textureheight = args[0][24].load(true);
	light = args[0][28].load(true);
	srcalpha = args[0][32].load(true);
	destalpha = args[0][33].load(true);
	SSAShort light_alpha = args[0][34].load(true);
	SSAShort light_red = args[0][35].load(true);
	SSAShort light_green = args[0][36].load(true);
	SSAShort light_blue = args[0][37].load(true);
	SSAShort fade_alpha = args[0][38].load(true);
	SSAShort fade_red = args[0][39].load(true);
	SSAShort fade_green = args[0][40].load(true);
	SSAShort fade_blue = args[0][41].load(true);
	SSAShort desaturate = args[0][42].load(true);
	SSAInt flags = args[0][43].load(true);
	start_z = args[0][44].load(true);
	step_z = args[0][45].load(true);
	dynlights = args[0][46].load(true);
	num_dynlights = args[0][47].load(true);
	shade_constants.light = SSAVec4i(light_blue.zext_int(), light_green.zext_int(), light_red.zext_int(), light_alpha.zext_int());
	shade_constants.fade = SSAVec4i(fade_blue.zext_int(), fade_green.zext_int(), fade_red.zext_int(), fade_alpha.zext_int());
	shade_constants.desaturate = desaturate.zext_int();

	thread.core = thread_data[0][0].load(true);
	thread.num_cores = thread_data[0][1].load(true);
	thread.pass_start_y = thread_data[0][2].load(true);
	thread.pass_end_y = thread_data[0][3].load(true);

	is_simple_shade = (flags & DrawWallArgs::simple_shade) == SSAInt(DrawWallArgs::simple_shade);
	is_nearest_filter = (flags & DrawWallArgs::nearest_filter) == SSAInt(DrawWallArgs::nearest_filter);

	count = count_for_thread(dest_y, count, thread);
	dest = dest_for_thread(dest_y, pitch, dest, thread);

	pitch = pitch * thread.num_cores;

	stack_frac.store(texturefrac + iscale * skipped_by_thread(dest_y, thread));
	fracstep = iscale * thread.num_cores;
	one = ((0x80000000 + textureheight - 1) / textureheight) * 2 + 1;

	start_z = start_z + step_z * SSAFloat(skipped_by_thread(dest_y, thread));
	step_z = step_z * SSAFloat(thread.num_cores);

	SSAIfBlock branch;
	branch.if_block(is_simple_shade);
	LoopShade(variant, true);
	branch.else_block();
	LoopShade(variant, false);
	branch.end_block();
}

void DrawWallCodegen::LoopShade(DrawWallVariant variant, bool isSimpleShade)
{
	SSAIfBlock branch;
	branch.if_block(is_nearest_filter);
	Loop(variant, isSimpleShade, true);
	branch.else_block();
	stack_frac.store(stack_frac.load() - (one / 2));
	Loop(variant, isSimpleShade, false);
	branch.end_block();
}

void DrawWallCodegen::Loop(DrawWallVariant variant, bool isSimpleShade, bool isNearestFilter)
{
	stack_index.store(SSAInt(0));
	stack_z.store(start_z);
	{
		SSAForBlock loop;
		SSAInt index = stack_index.load();
		z = stack_z.load();
		loop.loop_block(index < count);

		SSAInt frac = stack_frac.load();
		SSAInt offset = index * pitch * 4;

		SSAVec4i bgcolor = dest[offset].load_vec4ub(false);
		SSAVec4i color = Blend(Shade(Sample(frac, isNearestFilter), isSimpleShade), bgcolor, variant);
		dest[offset].store_vec4ub(color);

		stack_z.store(z + step_z);
		stack_index.store(index.add(SSAInt(1), true, true));
		stack_frac.store(frac + fracstep);
		loop.end_block();
	}
}

SSAVec4i DrawWallCodegen::Sample(SSAInt frac, bool isNearestFilter)
{
	if (isNearestFilter)
	{
		SSAInt sample_index = ((frac >> FRACBITS) * textureheight) >> FRACBITS;
		return source[sample_index * 4].load_vec4ub(false);
	}
	else
	{
		return SampleLinear(source, source2, texturefracx, frac, one, textureheight);
	}
}

SSAVec4i DrawWallCodegen::SampleLinear(SSAUBytePtr col0, SSAUBytePtr col1, SSAInt texturefracx, SSAInt texturefracy, SSAInt one, SSAInt height)
{
	SSAInt frac_y0 = (texturefracy >> FRACBITS) * height;
	SSAInt frac_y1 = ((texturefracy + one) >> FRACBITS) * height;
	SSAInt y0 = frac_y0 >> FRACBITS;
	SSAInt y1 = frac_y1 >> FRACBITS;

	SSAVec4i p00 = col0[y0 * 4].load_vec4ub(true);
	SSAVec4i p01 = col0[y1 * 4].load_vec4ub(true);
	SSAVec4i p10 = col1[y0 * 4].load_vec4ub(true);
	SSAVec4i p11 = col1[y1 * 4].load_vec4ub(true);

	SSAInt inv_b = texturefracx;
	SSAInt a = (frac_y1 >> (FRACBITS - 4)) & 15;
	SSAInt inv_a = 16 - a;
	SSAInt b = 16 - inv_b;

	return (p00 * (a * b) + p01 * (inv_a * b) + p10 * (a * inv_b) + p11 * (inv_a * inv_b) + 127) >> 8;
}

SSAVec4i DrawWallCodegen::Shade(SSAVec4i fg, bool isSimpleShade)
{
	SSAVec4i c;
	if (isSimpleShade)
		c = shade_bgra_simple(fg, light);
	else
		c = shade_bgra_advanced(fg, light, shade_constants);

	stack_lit_color.store(SSAVec4i(0));
	stack_light_index.store(SSAInt(0));

	SSAForBlock block;
	SSAInt light_index = stack_light_index.load();
	SSAVec4i lit_color = stack_lit_color.load();
	block.loop_block(light_index < num_dynlights);
	{
		SSAVec4i light_color = SSAUBytePtr(SSAValue(dynlights[light_index][0]).v).load_vec4ub(true);
		SSAFloat light_x = dynlights[light_index][1].load(true);
		SSAFloat light_y = dynlights[light_index][2].load(true);
		SSAFloat light_z = dynlights[light_index][3].load(true);
		SSAFloat light_rcp_radius = dynlights[light_index][4].load(true);

		// L = light-pos
		// dist = sqrt(dot(L, L))
		// attenuation = 1 - MIN(dist * (1/radius), 1)
		SSAFloat Lxy2 = light_x; // L.x*L.x + L.y*L.y
		SSAFloat Lz = light_z - z;
		SSAFloat dist2 = Lxy2 + Lz * Lz;
		SSAFloat rcp_dist = SSAFloat::rsqrt(dist2);
		SSAFloat dist = dist2 * rcp_dist;
		SSAFloat distance_attenuation = SSAFloat(256.0f) - SSAFloat::MIN(dist * light_rcp_radius, SSAFloat(256.0f));

		// The simple light type
		SSAFloat simple_attenuation = distance_attenuation;

		// The point light type
		// diffuse = dot(N,L) * attenuation
		SSAFloat point_attenuation = light_y * rcp_dist * distance_attenuation;

		SSAInt attenuation = SSAInt((light_y == SSAFloat(0.0f)).select(simple_attenuation, point_attenuation), true);
		SSAVec4i contribution = (light_color * attenuation) >> 8;

		stack_lit_color.store(lit_color + contribution);
		stack_light_index.store(light_index + 1);
	}
	block.end_block();

	return c + ((stack_lit_color.load() * fg) >> 8);
}

SSAVec4i DrawWallCodegen::Blend(SSAVec4i fg, SSAVec4i bg, DrawWallVariant variant)
{
	switch (variant)
	{
	default:
	case DrawWallVariant::Opaque:
		return blend_copy(fg);
	case DrawWallVariant::Masked:
		return blend_alpha_blend(fg, bg);
	case DrawWallVariant::Add:
	case DrawWallVariant::AddClamp:
		return blend_add(fg, bg, srcalpha, calc_blend_bgalpha(fg, destalpha));
	case DrawWallVariant::SubClamp:
		return blend_sub(fg, bg, srcalpha, calc_blend_bgalpha(fg, destalpha));
	case DrawWallVariant::RevSubClamp:
		return blend_revsub(fg, bg, srcalpha, calc_blend_bgalpha(fg, destalpha));
	}
}
