//    wearechat - generic multiplayer game with voip
//    Copyright (C) 2025 metamuffin
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License as published by
//    the Free Software Foundation, version 3 of the License only.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program.  If not, see <https://www.gnu.org/licenses/>.

struct VertexOut {
    @builtin(position) clip: vec4<f32>,
    @location(0) normal: vec3<f32>,
    @location(1) tangent: vec3<f32>,
    @location(2) texcoord: vec2<f32>,
}

struct Material {
    roughness: f32,
    metallic: f32,
    albedo_alpha: vec4<f32>,
    emission: vec3<f32>,
}

@group(0) @binding(0) var tex_albedo: texture_2d<f32>;
@group(0) @binding(1) var tex_albedo_sampler: sampler;
@group(1) @binding(0) var tex_normal: texture_2d<f32>;
@group(1) @binding(1) var tex_normal_sampler: sampler;
@group(2) @binding(0) var<uniform> material: Material;

const LIGHT: vec3<f32> = vec3(0.64, 0.64, 0.64);

@fragment
fn main(vo: VertexOut) -> @location(0) vec4<f32> {
    let t_albedo = textureSample(tex_albedo, tex_albedo_sampler, vo.texcoord);
    let t_normal = textureSample(tex_normal, tex_normal_sampler, vo.texcoord);

    let tangent_basis = mat3x3(vo.tangent, cross(vo.tangent, vo.normal), vo.normal);
    let normal = tangent_basis * (t_normal.rgb * 2. - 1.);

    let alpha = t_albedo.a;
    let lighting = mix(1., saturate(dot(LIGHT, normal)), 0.9);

    let color = t_albedo.rgb * lighting;

    // TODO better (and faster?) randomness for alpha dither
    if fract(dot(sin(vo.clip * 123.) * 1213., vec4(3., 2., 1., 4.))) > alpha {
        discard;
    }
    return vec4(color, 1.);
}