usingnamespace @import("xrvk.zig");
const glm = @import("glm");
const math = @import("std").math;

pub fn vec2vec(v: xr.Vector3f) glm.Vec3 {
    return glm.Vec3.init([_]f32{ v.x, v.y, v.z });
}

pub fn quat2mat(q: xr.Quaternionf) glm.Mat4 {
    const x = -q.x;
    const y = -q.y;
    const z = -q.z;
    const w = q.w;
    const x2 = q.x * q.x;
    const y2 = q.y * q.y;
    const z2 = q.z * q.z;

    // zig fmt: off
    return glm.Mat4.init([_][4]f32{
        [_]f32{ 1 - 2 * y2 - 2 * z2, 2 * x * y - 2 * z * w, 2 * x * z + 2 * y * w, 0 },
        [_]f32{ 2 * x * y + 2 * z * w, 1 - 2 * x2 - 2 * z2, 2 * y * z - 2 * x * w, 0 },
        [_]f32{ 2 * x * z - 2 * y * w, 2 * y * z + 2 * x * w, 1 - 2 * x2 - 2 * y2, 0 },
        [_]f32{ 0, 0, 0, 1 },
    });
    // zig fmt: on
}

pub fn pose2mat(pose: xr.Posef) glm.Mat4 {
    return glm.translation(vec2vec(pose.position)).mul(quat2mat(pose.orientation));
}

pub fn pose2matInverse(pose: xr.Posef) glm.Mat4 {
    var inverse = pose;
    inverse.orientation.x *= -1;
    inverse.orientation.y *= -1;
    inverse.orientation.z *= -1;
    inverse.position.x *= -1;
    inverse.position.y *= -1;
    inverse.position.z *= -1;
    return quat2mat(inverse.orientation).mul(glm.translation(vec2vec(inverse.position)));
}


pub fn projection(fov: xr.Fovf, near: f32, far: f32) glm.Mat4 {
    const tanUp = math.tan(fov.angle_up);
    const tanDown = math.tan(fov.angle_down);
    const tanLeft = math.tan(fov.angle_left);
    const tanRight = math.tan(fov.angle_right);
    const tanW  = tanRight - tanLeft;
    const tanH  = tanUp - tanDown ;

    return glm.Mat4.init([_][4]f32{
        [_]f32{ 2 / tanW, 0, 0, 0 },
        [_]f32{ 0, 2 / tanH, 0, 0 },
        [_]f32{ (tanRight + tanLeft) / tanW, (tanUp + tanDown) / tanH, -far / (far - near), -1 },
        [_]f32{ 0, 0, -far * near / (far - near), 0 },
    });
}