use std::f32::MAX as f32_max;

/// `graph` generates a string representation of the values as a sparkline.
///
/// # Arguments
///
/// * `values` - The values to graph.
///
/// # Example
///
/// ```rust
/// let sparkline = spark::graph(&[1.0, 5.0, 22.0, 13.0, 53.0]);
/// assert_eq!(sparkline, "▁▁▃▂█");
/// ```
pub struct Graph {
    pub min: Option<f32>,
    pub max: Option<f32>,
}

impl Graph {
    pub fn render(&self, values: &[f32]) -> String {
        let ticks = "▁▂▃▄▅▆▇█";

        /* XXX: This doesn't feel like idiomatic Rust */
        let mut min: f32 = self.min.unwrap_or(f32_max);
        let mut max: f32 = self.max.unwrap_or(0.);

        for &i in values.iter() {
            if i > max {
                max = i;
            }
            if i < min {
                min = i;
            }
        }

        let ratio = if max == min {
            1.0
        } else {
            (ticks.chars().count() - 1) as f32 / (max - min)
        };

        values
            .iter()
            .cloned()
            .map(|n| (n - min) * ratio)
            .map(|n| n.floor() as usize)
            .filter_map(|n| ticks.chars().nth(n))
            .collect()
    }
}