#include "math/sdf_shapes"
#include "math/sdf_utils"

struct BVHNode {
    min: vec3<f32>,
    left_idx: i32,
    max: vec3<f32>,
    obj_idx_or_right: i32,
};

@group(0) @binding(2) var<storage, read> bvh_nodes: array<BVHNode>;

fn get_dist(p: vec3<f32>, obj_params: vec4<f32>) -> f32 {
    let obj_type = obj_params.x;
    if (obj_type == 1.0) { return length(p) - 1.0; } // Unit Sphere
    if (obj_type == 2.0) { return sdBox(p, vec3<f32>(1.0)); } // Unit Box
    if (obj_type == 3.0) { return sdTorus(p, vec2<f32>(1.0, 0.4)); } // Unit Torus
    if (obj_type == 4.0) { return sdPlane(p, vec3<f32>(0.0, 1.0, 0.0), 0.0); }
    if (obj_type == 5.0) { return sdBox(p, obj_params.yzw); } // MESH AABB
    return 100.0;
}

fn map_scene(p: vec3<f32>, skip_idx: u32) -> f32 {
    var d = 1000.0;
    var stack: array<i32, 32>;
    var stack_ptr = 0;
    
    if (arrayLength(&bvh_nodes) > 0u) {
        stack[stack_ptr] = 0;
        stack_ptr++;
    }

    while (stack_ptr > 0) {
        stack_ptr--;
        let node_idx = stack[stack_ptr];
        let node = bvh_nodes[node_idx];

        if (aabb_sdf(p, node.min, node.max) < d) {
            if (node.left_idx < 0) { // Leaf
                let obj_idx = u32(node.obj_idx_or_right);
                if (obj_idx == skip_idx) { continue; }
                let obj = object_data.objects[obj_idx];
                let q = (obj.inv_model * vec4<f32>(p, 1.0)).xyz;
                let s = min(length(obj.model[0].xyz), min(length(obj.model[1].xyz), length(obj.model[2].xyz)));
                // IMPORTANT: Plane (type 4.0) and Mesh (type 5.0) should not be scaled by 's'.
                // The 's' factor is meant for unit primitives (sphere, box, torus) that are
                // scaled by the model matrix. Meshes already have correct local-space extents.
                if (obj.params.x != 4.0 && obj.params.x != 5.0) { // Not plane, not mesh
                    d = min(d, get_dist(q, obj.params) * s);
                } else {
                    d = min(d, get_dist(q, obj.params));
                }
            } else { // Internal
                if (stack_ptr < 31) {
                    stack[stack_ptr] = node.left_idx;
                    stack_ptr++;
                    stack[stack_ptr] = node.obj_idx_or_right;
                    stack_ptr++;
                }
            }
        }
    }
    return d;
}