ballistics_engine/
adjustment.rs

1//! Turret adjustment-unit conversions and click-value parsing (MBA-1355).
2//!
3//! Shared by the CLI (`main.rs`) and the WASM terminal (`wasm.rs`). This lives in the
4//! library crate — not `main.rs` — so it compiles for `wasm32-unknown-unknown` with no
5//! feature gate. To avoid a circular dependency on `main.rs`'s clap `AdjustmentUnit`
6//! `ValueEnum`, this module defines its own minimal angular base (`ClickBase`) and factor
7//! table; `main.rs` maps its own `AdjustmentUnit` onto `ClickBase`/`adjustment_factor`
8//! locally (see `drop_to_adjustment` in `main.rs`).
9
10/// Angular base unit for a turret click graduation (MBA-1355). A click graduation is
11/// always expressed in mil, (true) MOA, or SMOA/IPHY — never in whole clicks itself.
12#[derive(Debug, Clone, Copy, PartialEq)]
13pub enum ClickBase {
14    Mil,
15    Moa,
16    Smoa,
17}
18
19/// The `(drop_yd / range_yd) * factor` conversion factor for a `ClickBase`:
20/// - `Mil`: 1000.0 (milliradians)
21/// - `Moa`: 3438.0 (true MOA; this crate's locked printed-table constant — see MBA-724 —
22///   deliberately not the exact-angle 3437.7467)
23/// - `Smoa`: 3600.0 ("shooter's MOA" / inches-per-hundred-yards; exact by definition)
24pub fn adjustment_factor(base: ClickBase) -> f64 {
25    match base {
26        ClickBase::Mil => 1000.0,
27        ClickBase::Moa => 3438.0,
28        ClickBase::Smoa => 3600.0,
29    }
30}
31
32/// A turret click graduation, parsed from suffixed CLI/profile syntax
33/// like "0.1mil" / "0.25moa" / "0.125smoa" (MBA-1355).
34#[derive(Debug, Clone, Copy, PartialEq)]
35pub struct ClickValue {
36    pub size: f64,
37    pub base: ClickBase,
38}
39
40/// Parses a suffixed click graduation string. The unit suffix is mandatory — one of
41/// `mil`, `moa`, `smoa`, `iphy` (`iphy` is accepted as an alias for `smoa`, the identical
42/// unit) — and the magnitude must be a positive, finite number.
43pub fn parse_click_value(s: &str) -> Result<ClickValue, String> {
44    let t = s.trim().to_ascii_lowercase();
45    let (num, base) = if let Some(n) = t.strip_suffix("smoa") {
46        (n, ClickBase::Smoa)
47    } else if let Some(n) = t.strip_suffix("iphy") {
48        (n, ClickBase::Smoa)
49    } else if let Some(n) = t.strip_suffix("moa") {
50        (n, ClickBase::Moa)
51    } else if let Some(n) = t.strip_suffix("mil") {
52        (n, ClickBase::Mil)
53    } else {
54        return Err(format!(
55            "click value '{s}' needs a unit suffix: mil, moa, smoa, or iphy (e.g. 0.1mil, 0.25moa)"
56        ));
57    };
58    let size: f64 = num
59        .trim()
60        .parse()
61        .map_err(|_| format!("click value '{s}' has an invalid number '{num}'"))?;
62    if !size.is_finite() || size <= 0.0 {
63        return Err(format!("click value '{s}' must be a positive, finite graduation"));
64    }
65    Ok(ClickValue { size, base })
66}
67
68/// Whole-click adjustment for a drop at a range: the angular value in the graduation's
69/// own base unit divided by the graduation, rounded to the nearest click (ties away from
70/// zero). Sign is preserved. Ranges under 1 yard are defined as zero adjustment, matching
71/// the CLI's `drop_to_adjustment` short-range guard.
72pub fn clicks_for(drop_yd: f64, range_yd: f64, click: &ClickValue) -> i64 {
73    if range_yd < 1.0 {
74        return 0;
75    }
76    let angle = (drop_yd / range_yd) * adjustment_factor(click.base);
77    (angle / click.size).round() as i64
78}
79
80#[cfg(test)]
81mod tests {
82    use super::*;
83
84    #[test]
85    fn parse_click_value_accepts_suffixed_and_rejects_bare() {
86        let c = parse_click_value("0.25moa").unwrap();
87        assert!((c.size - 0.25).abs() < 1e-12);
88        assert!(matches!(c.base, ClickBase::Moa));
89        assert!(matches!(parse_click_value("0.1mil").unwrap().base, ClickBase::Mil));
90        assert!(matches!(parse_click_value("0.125smoa").unwrap().base, ClickBase::Smoa));
91        assert!(matches!(parse_click_value("0.125iphy").unwrap().base, ClickBase::Smoa));
92        for bad in ["0.25", "moa", "-0.1mil", "0mil", "0.1mils", ""] {
93            assert!(parse_click_value(bad).is_err(), "{bad:?} must be rejected");
94        }
95        // error message names the accepted suffixes
96        let e = parse_click_value("0.25").unwrap_err();
97        assert!(e.contains("mil") && e.contains("moa"), "{e}");
98    }
99
100    #[test]
101    fn clicks_round_to_nearest_whole_click() {
102        let quarter_moa = parse_click_value("0.25moa").unwrap();
103        // 2.6 TMOA of drop -> 10.4 clicks -> 10
104        let drop_yd = 2.6 / 3438.0 * 100.0;
105        assert_eq!(clicks_for(drop_yd, 100.0, &quarter_moa), 10);
106        // negative (wind left) rounds symmetrically
107        assert_eq!(clicks_for(-drop_yd, 100.0, &quarter_moa), -10);
108        // 10.5 clicks rounds away from zero
109        let drop_yd = 2.625 / 3438.0 * 100.0;
110        assert_eq!(clicks_for(drop_yd, 100.0, &quarter_moa), 11);
111    }
112}
ballistics_engine/adjustment.rs

ballistics_engine/
adjustment.rs
