#include "common.slang"

struct VertexShaderInput {
    // Per Vertex
    uint vertex_id : SV_VertexID;
    float3 pos;

    // Per Instance
    uint instance_id : SV_InstanceID;
};

struct VertexShaderOutput {
    float4 pos : SV_POSITION;
    uint selected;
};

struct PixelShaderOutput {
    float4 color : SV_TARGET;
};

[shader("vertex")]
VertexShaderOutput main_vertex(VertexShaderInput input) {
    VertexShaderOutput output;
    float2 tile_pos = float2(input.instance_id % map_width, float(input.instance_id / map_width));
    tile_pos -= float2(0.5, 0.5);

    output.pos = mul(view_projection_matrix, float4(tile_pos + input.pos.xy, 0, 1));
    
    uint2 pos = uint2(input.instance_id % map_width, uint(input.instance_id / map_width));
    uint2 selection_min = min(drag_start, mouse);
    uint2 selection_max = max(drag_start, mouse);
    output.selected = select(all(pos >= selection_min) && all(pos <= selection_max), 1, 0);

    return output;
}

[[vk::binding(0, 3)]]
cbuffer fragment_constants {
    float4 tint;
    float4 selected_tint;
}

[shader("fragment")]
PixelShaderOutput main_fragment(VertexShaderOutput input) {
    PixelShaderOutput output;

    output.color = select(input.selected != 0, selected_tint, tint);
    
    return output;
}