use itertools::Itertools;
use num_traits::Zero;
use super::Scale;
#[derive(Clone)]
pub struct ScaleBand<T> {
domain: Vec<T>,
range_diff: f32,
avg_width: f32,
padding_inner: f32,
padding_outer: f32,
}
impl<T> ScaleBand<T> {
pub fn new(domain: Vec<T>, range: Vec<f32>) -> Self {
let len = domain.len() as f32;
let range_diff = range
.iter()
.minmax()
.into_option()
.map_or(0., |(min, max)| max - min);
Self {
domain,
range_diff,
avg_width: if len.is_zero() { 0. } else { range_diff / len },
padding_inner: 0.,
padding_outer: 0.,
}
}
pub fn band_width(&self) -> f32 {
(self.avg_width * (1. - self.padding_inner)).min(30.)
}
pub fn padding_inner(mut self, padding_inner: f32) -> Self {
self.padding_inner = padding_inner;
self
}
pub fn padding_outer(mut self, padding_outer: f32) -> Self {
self.padding_outer = padding_outer;
self
}
fn ratio(&self) -> f32 {
1. + self.padding_inner / (self.domain.len() - 1) as f32
}
fn display_avg_width(&self) -> f32 {
let padding_outer_width = self.avg_width * self.padding_outer;
(self.range_diff - padding_outer_width * 2.) / self.domain.len() as f32
}
}
impl<T> Scale<T> for ScaleBand<T>
where
T: PartialEq,
{
fn tick(&self, value: &T) -> Option<f32> {
let index = self.domain.iter().position(|v| v == value)?;
let domain_len = self.domain.len();
if domain_len == 1 {
return Some((self.range_diff - self.band_width()) / 2.);
}
let avg_width = self.display_avg_width();
let padding_outer_width = self.avg_width * self.padding_outer;
Some(index as f32 * avg_width * self.ratio() + padding_outer_width)
}
fn least_index(&self, tick: f32) -> usize {
if self.domain.is_empty() {
return 0;
}
let domain_len = self.domain.len();
if domain_len == 1 {
return 0;
}
let avg_width = self.display_avg_width();
let padding_outer_width = self.avg_width * self.padding_outer;
let adjusted_tick = tick - padding_outer_width;
let index = (adjusted_tick / (avg_width * self.ratio())).round() as i32;
(index.max(0) as usize).min(domain_len.saturating_sub(1))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_scale_band() {
let scale = ScaleBand::new(vec![1, 2, 3], vec![0., 90.]);
assert_eq!(scale.tick(&1), Some(0.));
assert_eq!(scale.tick(&2), Some(30.));
assert_eq!(scale.tick(&3), Some(60.));
assert_eq!(scale.band_width(), 30.);
}
#[test]
fn test_scale_band_zero() {
let scale = ScaleBand::new(vec![], vec![0., 90.]);
assert_eq!(scale.tick(&1), None);
assert_eq!(scale.tick(&2), None);
assert_eq!(scale.tick(&3), None);
assert_eq!(scale.band_width(), 0.);
let scale = ScaleBand::new(vec![1, 2, 3], vec![]);
assert_eq!(scale.tick(&1), Some(0.));
assert_eq!(scale.tick(&2), Some(0.));
assert_eq!(scale.tick(&3), Some(0.));
assert_eq!(scale.band_width(), 0.);
}
}