struct Environment {
    ambient: vec4<f32>,
    light: vec4<f32>,
    dir: vec4<f32>,
}

struct Eye {
    // from camera to screen
    proj: mat4x4<f32>,
    // from screen to camera
    inv: mat4x4<f32>,
    // world to camera
    view: mat4x4<f32>,
    // camera transform
    frame: mat4x4<f32>,
}

// Vertex shader
@group(0) @binding(0)
var<uniform> eye: Eye;
@group(0) @binding(1)
var<uniform> environment: Environment;
@group(0) @binding(2)
var sky_sampler: sampler;
@group(0) @binding(3)
var sky_texture: texture_2d<f32>;

struct VertexInput {
    @location(0) position: vec3<f32>,
    @location(1) normal: vec3<f32>,
    @location(2) tex_coords: vec2<f32>,
}

struct InstanceInput {
    @location(4) model_matrix_0: vec4<f32>,
    @location(5) model_matrix_1: vec4<f32>,
    @location(6) model_matrix_2: vec4<f32>,
    @location(7) model_matrix_3: vec4<f32>,
    @location(8) model_color: vec4<f32>,
}


struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,
    @location(0) tex_coords: vec2<f32>,
    @location(1) color: vec4<f32>,
    @location(2) world_normal: vec3<f32>,
    @location(3) world_position: vec3<f32>,
}

@vertex
fn vs_main(
    model: VertexInput,
    instance: InstanceInput,
) -> VertexOutput {
    var out: VertexOutput;
    let model_matrix = mat4x4<f32>(
        instance.model_matrix_0,
        instance.model_matrix_1,
        instance.model_matrix_2,
        instance.model_matrix_3,
    );
    let model_rot_matrix = mat3x3<f32>(
        instance.model_matrix_0.xyz,
        instance.model_matrix_1.xyz,
        instance.model_matrix_2.xyz,
    );
    out.tex_coords = model.tex_coords;
    out.color = instance.model_color;
    out.world_normal = model_rot_matrix * model.normal;
    var world_position: vec4<f32> = model_matrix * vec4<f32>(model.position, 1.0);
    out.world_position = world_position.xyz;
    out.clip_position = eye.proj * eye.view * world_position;
    return out;
}

// Fragment shader

@group(1) @binding(0)
var s_diffuse: sampler;
@group(1) @binding(1)
var t_diffuse: texture_2d<f32>;
@group(1) @binding(2)
var t_normal: texture_2d<f32>;
@group(1) @binding(3)
var t_rough: texture_2d<f32>;

fn sky_aspect(look: vec3<f32>) -> vec4<f32> {
    var pi = 3.14159;
    let u_angle = atan2(look.x,look.z);
    let u = (u_angle/pi) + 0.5; // from -pi/2 -> pi/2 into 0 -> 1
    let v_angle = atan2(-look.y,sqrt(look.x * look.x + look.z * look.z));
    let v = (v_angle/pi) + 0.5;//(v_angle/pi) + 0.5; // from -pi/2 -> pi/2 into 0 -> 1
    let uv = vec2<f32>(u,v); // Get UV on skybox
    return textureSample(sky_texture, sky_sampler, uv);
}

fn rotation(mat: mat4x4<f32>) -> mat3x3<f32> {
    return mat3x3<f32>(
        mat[0].xyz,
        mat[1].xyz,
        mat[2].xyz,
    );
}

fn translation(mat: mat4x4<f32>) -> vec4<f32> {
    //return vec4<f32>(mat[0][3],mat[1][3],mat[2][3],mat[3][3]);
    return mat[3];
}

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let object_color: vec4<f32> = textureSample(t_diffuse, s_diffuse, in.tex_coords);
    let object_normal: vec4<f32> = textureSample(t_normal, s_diffuse, in.tex_coords);

    let diffuse_color = object_color.xyz;
    let specular_color = vec3<f32>(0.0,0.0,0.0);
    let reflection = sky_aspect(reflect(normalize(in.world_position-translation(eye.frame).xyz),normalize(in.world_normal)));

    //let result = (environment.ambient.xyz + diffuse_color + specular_color) * object_color.xyz;

    //let light_dir = normalize(environment.dir.xyz);
    //let view_dir = normalize(eye.frame[3].xyz - in.world_position);
    //let half_dir = normalize(view_dir + light_dir);

    //let diffuse_strength = max(dot(tangent_normal, light_dir), 0.0);
    //let diffuse_color = environment.light.xyz * diffuse_strength;

    //let specular_strength = pow(max(dot(tangent_normal, half_dir), 0.0), 32.0);
    //let specular_color = specular_strength * environment.light.xyz;

    let result = (environment.ambient.xyz + diffuse_color.xyz + specular_color.xyz) * object_color.xyz;

    return vec4<f32>(reflection.xyz,object_color.a);
}

struct SkyOutput {
    @builtin(position) position: vec4<f32>,
    @location(0) pos: vec4<f32> // unadulterated by WGSL
}

const TRI_VERTICES = array(
    vec4(-1.0, -1.0, 1.0, 1.0),
    vec4(-1.0,  1.0, 1.0, 1.0),
    vec4( 1.0, -1.0, 1.0, 1.0),
    vec4( 1.0,  1.0, 1.0, 1.0),
    vec4(-1.0,  1.0, 1.0, 1.0),
    vec4( 1.0, -1.0, 1.0, 1.0),
);

@vertex
fn vs_sky(@builtin(vertex_index) index: u32) -> SkyOutput {
    var out: SkyOutput;
    out.position = TRI_VERTICES[index];
    out.pos = out.position;
    return out;
}

@fragment
fn fs_sky(in: SkyOutput) -> @location(0) vec4<f32> {
    let look = rotation(eye.frame) * in.pos.xyz;
    return sky_aspect(look);
}