/*
    pal-singlepass.slang

    svo's PAL single pass shader, ported to libretro
    ------------------------------------------------
    "Software composite video modulation/demodulation experiments

    The idea is to reproduce in GLSL shaders realistic composite-like
    artifacting by applying PAL modulation and demodulation.

    Digital texture, passed through the model of an analog channel,
    should suffer same effects as its analog counterpart and exhibit properties,
    such as dot crawl and colour bleeding, that may be desirable for faithful
    reproduction of look and feel of old computer games."

    https://github.com/svofski/CRT

    Copyright (c) 2016, Viacheslav Slavinsky
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
    this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright notice,
    this list of conditions and the following disclaimer in the documentation
    and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED.
    IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "ReShade.fxh"

uniform float texture_sizeX <
	ui_type = "drag";
	ui_min = 1.0;
	ui_max = BUFFER_WIDTH;
	ui_label = "Screen Width [PAL]";
> = 320.0;

uniform float texture_sizeY <
	ui_type = "drag";
	ui_min = 1.0;
	ui_max = BUFFER_HEIGHT;
	ui_label = "Screen Height [PAL]";
> = 240.0;

uniform float FIR_GAIN <
	ui_type = "drag";
	ui_min = 0.0;
	ui_max = 5.0;
	ui_step = 0.1;
	ui_label = "FIR lowpass gain [PAL]";
> = 1.5;

uniform float FIR_INVGAIN <
	ui_type = "drag";
	ui_min = 0.0;
	ui_max = 5.0;
	ui_step = 0.1;
	ui_label = "Inverse gain for luma recovery [PAL]";
> = 1.1;

uniform float PHASE_NOISE <
	ui_type = "drag";
	ui_min = 0.0;
	ui_max = 5.0;
	ui_step = 0.1;
	ui_label = "Phase noise [PAL]";
> = 1.0;

uniform int FrameCount < source = "framecount"; >;

/* Subcarrier frequency */
#define FSC          4433618.75

/* Line frequency */
#define FLINE        15625.

#define VISIBLELINES 312.

#define PI           3.14159265358

#define RGB_to_YIQ  float3x3( 0.299,    0.595716,  0.211456,\
                            0.587,   -0.274453, -0.522591,\
                            0.114,   -0.321263,  0.311135)

#define YIQ_to_RGB  float3x3( 1.0   ,   1.0,       1.0,\
                            0.9563,  -0.2721,   -1.1070,\
                            0.6210,  -0.6474,    1.7046)

#define RGB_to_YUV  float3x3( 0.299,   -0.14713,   0.615,\
                            0.587,   -0.28886,  -0.514991,\
                            0.114,    0.436,    -0.10001)

#define YUV_to_RGB  float3x3( 1.0,      1.0,       1.0,\
                            0.0,     -0.39465,   2.03211,\
                            1.13983, -0.58060,   0.0)

#define texture_size float2(texture_sizeX, texture_sizeY)
#define SourceSize float4(texture_size, 1.0 / texture_size) //either TextureSize or InputSize

#define FIRTAPS 20

/* subcarrier counts per scan line = FSC/FLINE = 283.7516 */
/* We save the reciprocal of this only to optimize it */
float counts_per_scanline_reciprocal = 1.0 / (FSC/FLINE);

float width_ratio;
float height_ratio;
float altv;
float invx;

float mod(float x, float y)
{
  return x - y * floor(x/y);
}

float rand(float2 co)
{
    float a  = 12.9898;
    float b  = 78.233;
    float c  = 43758.5453;
    float dt = dot(co.xy, float2(a, b));
    float sn = mod(dt,3.14);

    return frac(sin(sn) * c);
}

float modulated(float2 xy, float sinwt, float coswt)
{
    float3 rgb = tex2D(ReShade::BackBuffer, float2((0.0) * (invx) + xy.x, xy.y)).xyz;
    float3 yuv = RGB_to_YUV * rgb;

    return clamp(yuv.x + yuv.y * sinwt + yuv.z * coswt, 0.0, 1.0);
}

float2 modem_uv(float2 xy, float ofs) {
    float t  = (xy.x + ofs * invx) * SourceSize.x;
    float wt = t * 2. * PI / width_ratio;

    float sinwt = sin(wt);
    float coswt = cos(wt + altv);

    float3 rgb = tex2D(ReShade::BackBuffer, float2((ofs) * (invx) + xy.x, xy.y)).xyz;
    float3 yuv = RGB_to_YUV * rgb;
    float signal = clamp(yuv.x + yuv.y * sinwt + yuv.z * coswt, 0.0, 1.0);

    if (PHASE_NOISE != 0.)
    {
        /* .yy is horizontal noise, .xx looks bad, .xy is classic noise */
        float2 seed = xy.yy * float(FrameCount);
        wt        = wt + PHASE_NOISE * (rand(seed) - 0.5);
        sinwt     = sin(wt);
        coswt     = cos(wt + altv);
    }

    return float2(signal * sinwt, signal * coswt);
}

void PS_PAL(float4 pos : SV_POSITION, float2 coords : TEXCOORD0, out float4 col : COLOR)
{
    float2 xy    = coords;
    width_ratio  = SourceSize.x * (counts_per_scanline_reciprocal);
    height_ratio = SourceSize.y / VISIBLELINES;
    altv         = mod(floor(xy.y * VISIBLELINES + 0.5), 2.0) * PI;
    invx         = 0.25 * (counts_per_scanline_reciprocal); // equals 4 samples per Fsc period

	float2 uv;
	float2 filtered = float2(0.0,0.0);
	float FIR1 = -0.008030271;
	float FIR2 = 0.003107906;
	float FIR3 = 0.016841352;
	float FIR4 = 0.032545161;
	float FIR5 = 0.049360136;
	float FIR6 = 0.066256720;
	float FIR7 = 0.082120150;
	float FIR8 = 0.095848433;
	float FIR9 = 0.106453014;
	float FIR10 = 0.113151423;
	float FIR11 = 0.115441842;
	float FIR12 = 0.113151423;
	float FIR13 = 0.106453014;
	float FIR14 = 0.095848433;
	float FIR15 = 0.082120150;
	float FIR16 = 0.066256720;
	float FIR17 = 0.049360136;
	float FIR18 = 0.032545161;
	float FIR19 = 0.016841352;
	float FIR20 = 0.003107906;

	#define macro_loopz(c)	uv = modem_uv(xy, float(c) - FIRTAPS*0.5); \
        filtered += FIR_GAIN * uv * FIR##c;

	float FIR[20] = {
	   -0.008030271,
		0.003107906,
		0.016841352,
		0.032545161,
		0.049360136,
		0.066256720,
		0.082120150,
		0.095848433,
		0.106453014,
		0.113151423,
		0.115441842,
		0.113151423,
		0.106453014,
		0.095848433,
		0.082120150,
		0.066256720,
		0.049360136,
		0.032545161,
		0.016841352,
		0.003107906
	};

	if(__RENDERER__ == 0x09300 || __RENDERER__ >= 0x10000){
		macro_loopz(1)
		macro_loopz(2)
		macro_loopz(3)
		macro_loopz(4)
		macro_loopz(5)
		macro_loopz(6)
		macro_loopz(7)
		macro_loopz(8)
		macro_loopz(9)
		macro_loopz(10)
		macro_loopz(11)
		macro_loopz(12)
		macro_loopz(13)
		macro_loopz(14)
		macro_loopz(15)
		macro_loopz(16)
		macro_loopz(17)
		macro_loopz(18)
		macro_loopz(19)
		macro_loopz(20)
	} else {
		for (int i = 0; i < FIRTAPS; i++) {
			float2 uv   = modem_uv(xy, i - FIRTAPS*0.5);
			filtered += FIR_GAIN * uv * FIR[i];
		}
	}

    float t  = xy.x * SourceSize.x;
    float wt = t * 2. * PI / width_ratio;

    float sinwt = sin(wt);
    float coswt = cos(wt + altv);

    float luma = modulated(xy, sinwt, coswt) - FIR_INVGAIN * (filtered.x * sinwt + filtered.y * coswt);
    float3 yuv_result = float3(luma, filtered.x, filtered.y);

	col = float4(YUV_to_RGB * yuv_result, 1.0);
}

technique PAL
{
	pass PAL
	{
		VertexShader = PostProcessVS;
		PixelShader = PS_PAL;
	}
}