Shader "Kaiju/Julia"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _MaxIterations("Max Iterations", range(0, 555)) = 255
        _Pan("Pan", vector) = (0.5, 0.0, 0.0, 0.0)
        _Zoom("Zoom", range(0, 4)) = 3
        _Aspect("Aspect", range(0, 4)) = 1
        _JuliaSeed("JuliaSeed", vector) = (0.39, -0.2, 0.0, 0.0)
        _Colors("Colors", vector) = (3.0, 3.0, 3.0, 0.0)
    }
    SubShader
    {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            // #pragma enable_d3d11_debug_symbols
            #pragma target 3.0
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            float   _MaxIterations;
            float2  _Pan;
            float   _Zoom;
            float   _Aspect;
            float2  _JuliaSeed;
            float3  _Colors;

            float ComputeValue(float2 v, float2 offset) {
                float vxsquare = 0;
                float vysquare = 0;

                float iteration;
                for (iteration = 0; iteration < _MaxIterations; iter++) {

                }

                // do {
                //     vxsquare = v.x * v.x;
                //     vysquare = v.y * v.y;

                //     v = float2(vxsquare - vysquare, v.x * v.y * 2) + offset;

                //     iteration++;

                //     if ((lastIteration == _MaxIterations) && (vxsquare + vysquare) > 4.0) {
                //         lastIteration = iteration + 1;
                //     }
                // } while (iteration < lastIteration);

                // return (float(iteration) - (log(log(sqrt(vxsquare + vysquare))) / log(2.0))) / float(_MaxIterations);
            }

//         for each pixel (Px, Py) on the screen do
    // x0 := scaled x coordinate of pixel (scaled to lie in the Mandelbrot X scale (-2.5, 1))
    // y0 := scaled y coordinate of pixel (scaled to lie in the Mandelbrot Y scale (-1, 1))
    // x := 0.0
    // y := 0.0
    // iteration := 0
    // max_iteration := 1000
    // // Here N = 2^8 is chosen as a reasonable bailout radius.

    // while x*x + y*y ≤ (1 << 16) and iteration < max_iteration do
    //     xtemp := x*x - y*y + x0
    //     y := 2*x*y + y0
    //     x := xtemp
    //     iteration := iteration + 1

    // // Used to avoid floating point issues with points inside the set.
    // if iteration < max_iteration then
    //     // sqrt of inner term removed using log simplification rules.
    //     log_zn := log(x*x + y*y) / 2
    //     nu := log(log_zn / log(2)) / log(2)
    //     // Rearranging the potential function.
    //     // Dividing log_zn by log(2) instead of log(N = 1<<8)
    //     // because we want the entire palette to range from the
    //     // center to radius 2, NOT our bailout radius.
    //     iteration := iteration + 1 - nu

    // color1 := palette[floor(iteration)]
    // color2 := palette[floor(iteration) + 1]
    // // iteration % 1 = fractional part of iteration.
    // color := linear_interpolate(color1, color2, iteration % 1)
    // plot(Px, Py, color)

            float4 Mandelbrot_PixelShader(float2 texCoord : TEXCOORD0) : COLOR0 {
                float2 v = (texCoord - 0.5) * _Zoom * float2(1, _Aspect) - _Pan;
                float val = ComputeValue(v, v);
                return float4(sin(val * _Colors.x), sin(val * _Colors.y), sin(val * _Colors.z), 1);
            }

            float4 Julia_PixelShader(float2 texCoord : TEXCOORD0) : COLOR0 {
                _JuliaSeed = float2(sin(_Time.y), cos(_Time.y));
                float2 v = (texCoord - 0.5) * _Zoom * float2(1, _Aspect) - _Pan;
                float val = ComputeValue(v, _JuliaSeed);
                return float4(sin(val * _Colors.x), sin(val * _Colors.y), sin(val * _Colors.z), 1);
            }

            float4 frag (v2f i) : SV_Target {
                // return Julia_PixelShader(i.uv);
                return Mandelbrot_PixelShader(i.uv);
            }

            ENDCG
        }
    }
}