// Common utility functions for WGSL shaders.
// Reduces duplication across renderer_3d, mesh_render, etc.

// Constants
const PI: f32 = 3.14159265359;
const TAU: f32 = 6.28318530718;

// Transform normal from local to world space using inverse model matrix
fn transform_normal(inv_model: mat4x4<f32>, normal_local: vec3f) -> vec3f {
    let normal_matrix = mat3x3<f32>(inv_model[0].xyz, inv_model[1].xyz, inv_model[2].xyz);
    return normalize(normal_matrix * normal_local);
}

// Spherical UV mapping (sphere or any radial surface)
// Returns UV in [0,1] range
fn spherical_uv(p: vec3f) -> vec2<f32> {
    let u = atan2(p.x, p.z) / TAU + 0.5;
    let v = acos(clamp(p.y / length(p), -1.0, 1.0)) / PI;
    return vec2<f32>(u, v);
}

// Spherical UV from direction vector (for skybox, etc.)
fn spherical_uv_from_dir(dir: vec3f) -> vec2<f32> {
    let u = atan2(dir.z, dir.x) / TAU + 0.5;
    let v = asin(clamp(dir.y, -1.0, 1.0)) / PI + 0.5;
    return vec2<f32>(u, v);
}

// Grid pattern for procedural texturing (checkerboard-like)
fn grid_pattern(uv: vec2<f32>) -> f32 {
    let grid = 0.5 + 0.5 * sin(uv.x * PI) * sin(uv.y * PI);
    return smoothstep(0.45, 0.55, grid);
}

// NOTE: calc_sdf_normal_bumped() removed - too specialized, depends on get_dist()
// from scene_query snippets. Keep bump mapping code inline in shaders that use it.

// Calculates normalized screen coordinates from fragment position and resolution.
// Input `p` is the fragment's @builtin(position), `resolution` is the screen resolution.
// Returns a vec2<f32> in NDC space, with X adjusted for aspect ratio.
fn getScreenCoord(p: vec4<f32>, resolution: vec2<f32>) -> vec2<f32> {
    let q = p.xy / resolution;
    var coord = -1.0 + 2.0 * q;
    coord.x *= resolution.x / resolution.y;
    return coord;
}