use std::f64::consts::PI;

use crate::numeric::FloatingPoint;

pub fn get_current_lr<D>(
    base_lr: D,
    lr_adjustment: bool,
    lr_min: D,
    total_timeline: usize,
    global_i: usize,
) -> D
where
    D: FloatingPoint,
{
    let cos_term = ((D::from_f64(PI) * D::from_u32(global_i as u32))
        / D::from_u32(total_timeline as u32))
    .cos();

    let decay_factor = D::from_f64(0.5) * (D::one() + cos_term);
    match lr_adjustment {
        true => lr_min + (base_lr - lr_min) * decay_factor,
        false => base_lr,
    }
}