use core::f64;

use vecmath::{vec3_cross, vec3_dot, vec3_sub};

use crate::primitives::{Box3, Triangle};

/// Determine whether two shapes interesect using the separating axis theorem
pub fn tri_aabb_intersect(bx: &Box3, tri: &Triangle) -> bool {
    // Get edge vectors for triangle
    let e1 = vec3_sub(tri.v2, tri.v1);
    let e2 = vec3_sub(tri.v3, tri.v2);
    let e3 = vec3_sub(tri.v1, tri.v3);

    // Get face and edge normals
    let tri_face = vec3_cross(e1, e2);
    let n1 = vec3_cross(e1, e1);
    let n2 = vec3_cross(e2, e1);
    let n3 = vec3_cross(e3, e1);

    // Face normals AABB
    let u0 = [1.0, 0.0, 0.0];
    let u1 = [0.0, 1.0, 0.0];
    let u2 = [0.0, 0.0, 1.0];

    // Now check all of the axes
    let box_vertices = bx.get_vertices();
    for axis in [u0, u1, u2, tri_face, n1, n2, n3] {
        let box_projection = project_pnts(&box_vertices, axis);
        let tri_projection = project_pnts(&[tri.v1, tri.v2, tri.v3], axis);

        let start = f64::max(box_projection.0, tri_projection.0);
        let end = f64::min(box_projection.1, tri_projection.1);
        if start < end {
            return false;
        }
    }
    return true;
}

/// Project points unto an Axis and return the max and min
fn project_pnts(pnts: &[[f64; 3]], axis: [f64; 3]) -> (f64, f64) {
    let mut min_proj = f64::INFINITY;
    let mut max_proj = f64::NEG_INFINITY;
    for pnt in pnts {
        let projection = vec3_dot(axis, *pnt);
        min_proj = min_proj.min(projection);
        max_proj = max_proj.max(projection);
    }
    (min_proj, max_proj)
}