#include "shaders/common.hlsl"

struct vs_instance {
    struct xform xf;
    float2 uv0;
    float2 uv1;
    uint tint_srgb;
};

struct ps_input {
    DESV(float4, screen_pos, SV_POSITION);
    DECL(float2, uv);
    DECL(float4, tint_lin);
};

/* ========================== *
 * Globals
 * ========================== */

SamplerState G_sampler : register(s0);

Texture2D G_Texture : register(t0); 

StructuredBuffer<vs_instance> G_instance_buffer : register(t1);

cbuffer constants : register(b0)
{
    float4x4 G_projection;
    uint G_instance_offset;
};

/* ========================== *
 * Vertex shader
 * ========================== */

ps_input vs_main(uint instance_id : SV_InstanceID, uint vertex_id : SV_VertexID)
{
    // static float2 quad[4] = {
    //     float2(-0.5f, -0.5f),
    //     float2( 0.5f, -0.5f),
    //     float2( 0.5f,  0.5f),
    //     float2(-0.5f,  0.5f)
    // };

    static const uint indices[6] = { 0, 1, 2, 2, 3, 0 };
    static const float2 vertices[4] = {
        float2(-0.5f, -0.5f),
        float2( 0.5f, -0.5f),
        float2( 0.5f,  0.5f),
        float2(-0.5f,  0.5f)
    };

    vs_instance instance = G_instance_buffer[instance_id + G_instance_offset];
    int index = indices[vertex_id];

    int top = index == 0 || index == 1;
    int right = index == 1 || index == 2;
    int bottom = index == 2 || index == 3;
    int left = index == 3 || index == 0;
    //int top = vertex_id == 0 || vertex_id == 2;
    //int left = vertex_id == 0 || vertex_id == 1;
    //int bottom = vertex_id == 1 || vertex_id == 3;
    //int right = vertex_id == 2 || vertex_id == 3;

    float2 vert = vertices[index];
    float2 world_pos = xform_mul(instance.xf, vert);
    float4 screen_pos = mul(G_projection, float4(world_pos, 0, 1));

    float uv_x = instance.uv0.x * left;
    uv_x += instance.uv1.x * right;
    float uv_y = instance.uv0.y * top;
    uv_y += instance.uv1.y * bottom;


    ps_input output;
    output.screen_pos = screen_pos;
    output.uv = float2(uv_x, uv_y);
    output.tint_lin = linear_from_srgb32(instance.tint_srgb);

    return output;
}

/* ========================== *
 * Pixel shader
 * ========================== */

float4 ps_main(ps_input input) : SV_TARGET
{
    float4 color = G_Texture.Sample(G_sampler, input.uv) * input.tint_lin;
    return color;
}