//
//  Shaders.metal
//  MetalRenderer
//
//  Created by Stuart Carnie on 5/31/18.
//  Copyright © 2018 Stuart Carnie. All rights reserved.
//

// File for Metal kernel and shader functions

#include <metal_stdlib>
#include <simd/simd.h>

// Including header shared between this Metal shader code and Swift/C code executing Metal API commands
#import "ShaderTypes.h"

using namespace metal;

#pragma mark - functions using projected coordinates

vertex ColorInOut basic_vertex_proj_tex(const Vertex in [[ stage_in ]],
                                        const device Uniforms &uniforms [[ buffer(BufferIndexUniforms) ]])
{
    ColorInOut out;
    out.position = uniforms.projectionMatrix * float4(in.position, 1.0);
    out.texCoord = in.texCoord;
    return out;
}

fragment float4 basic_fragment_proj_tex(ColorInOut in [[stage_in]],
                                        constant Uniforms & uniforms [[ buffer(BufferIndexUniforms) ]],
                                        texture2d<half> tex          [[ texture(TextureIndexColor) ]],
                                        sampler samp                 [[ sampler(SamplerIndexDraw) ]])
{
    half4 colorSample = tex.sample(samp, in.texCoord.xy);
    return float4(colorSample);
}

#pragma mark - functions using normalized device coordinates

vertex ColorInOut basic_vertex_ndc_tex(const Vertex in [[ stage_in ]])
{
    ColorInOut out;
    out.position = float4(in.position, 1.0);
    out.texCoord = in.texCoord;
    return out;
}

fragment float4 basic_fragment_ndc_tex(ColorInOut in       [[stage_in]],
                                       texture2d<half> tex [[ texture(TextureIndexColor) ]],
                                       sampler samp        [[ sampler(SamplerIndexDraw) ]])
{
    half4 colorSample = tex.sample(samp, in.texCoord.xy);
    return float4(colorSample);
}

#pragma mark - functions for rendering fonts

vertex FontFragmentIn font_vertex(const FontVertex in [[ stage_in ]], const device Uniforms &uniforms [[ buffer(BufferIndexUniforms) ]])
{
    FontFragmentIn out;
    out.position = uniforms.projectionMatrix * float4(in.position, 0, 1);
    out.texCoord = in.texCoord;
    out.color    = in.color;
    return out;
}

fragment float4 font_fragment(FontFragmentIn  in  [[ stage_in ]],
                              texture2d<half> tex [[ texture(TextureIndexColor) ]],
                              sampler samp        [[ sampler(SamplerIndexDraw) ]])
{
    half4 colorSample = tex.sample(samp, in.texCoord.xy);
    return float4(in.color.rgb, in.color.a * colorSample.r);
}