refac: rewrite a lil in rust

wasm/betterseqta-wasm/src/time_format.rs

@@ -0,0 +1,83 @@
+//! 12-hour timetable formatting (mirrors TS helpers around `convertTo12HourFormat`).
+
+use wasm_bindgen::prelude::*;
+
+/// Mirrors JavaScript `Number(s.trim())` for a single split segment, including `"" -> 0`.
+fn js_number_from_split_segment(part: Option<&str>) -> f64 {
+    let s = part.unwrap_or("");
+    let trimmed = s.trim();
+    if trimmed.is_empty() {
+        return 0.0;
+    }
+    trimmed.parse::<f64>().unwrap_or(f64::NAN)
+}
+
+/// Mirrors `n.toString()` for timetable paths.
+fn js_number_to_string(n: f64) -> String {
+    if n.is_nan() {
+        return "NaN".to_string();
+    }
+    if n == 0.0 && n.is_sign_negative() {
+        return "0".to_string();
+    }
+    if (n - n.round()).abs() < f64::EPSILON {
+        format!("{}", n as i64)
+    } else {
+        format!("{n}")
+    }
+}
+
+/// 1:1 with `convertTo12HourFormat` in `src/seqta/utils/convertTo12HourFormat.ts`.
+#[wasm_bindgen(js_name = convertTo12HourFormat)]
+pub fn convert_to_12_hour_format(time: &str, no_minutes: bool) -> String {
+    let parts: Vec<&str> = time.split(':').collect();
+    let mut hours = js_number_from_split_segment(parts.first().copied());
+    let minutes = js_number_from_split_segment(parts.get(1).copied());
+
+    let mut period = "am";
+    if hours >= 12.0 {
+        period = "pm";
+        if hours > 12.0 {
+            hours -= 12.0;
+        }
+    } else if hours == 0.0 {
+        hours = 12.0;
+    }
+
+    let mut hours_str = js_number_to_string(hours);
+    if hours_str.len() == 2 && hours_str.starts_with('0') {
+        hours_str = hours_str[1..].to_string();
+    }
+
+    let minute_part = if no_minutes {
+        String::new()
+    } else {
+        let m = js_number_to_string(minutes);
+        let m = if m.len() >= 2 { m } else { format!("0{m}") };
+        format!(":{m}")
+    };
+
+    format!("{hours_str}{minute_part}{period}")
+}
+
+/// `convertTo12HourFormat(...).toLowerCase().replace(" ", "")` from `updateTimetableTimes.ts`.
+#[wasm_bindgen(js_name = formatTimetableTimeLabel)]
+pub fn format_timetable_time_label(time: &str, no_minutes: bool) -> String {
+    convert_to_12_hour_format(time, no_minutes)
+        .to_lowercase()
+        .replace(' ', "")
+}
+
+/// Formats a `start–end` / `start-end` range label for timetable rows.
+#[wasm_bindgen(js_name = formatTimetableTimeRange)]
+pub fn format_timetable_time_range(original: &str) -> Option<String> {
+    let mut parts = original
+        .split(|c| c == '-' || c == '\u{2013}')
+        .map(str::trim)
+        .filter(|p| !p.is_empty());
+    let start = parts.next()?;
+    let end = parts.next()?;
+    let start12 = format_timetable_time_label(start, false);
+    let end12 = format_timetable_time_label(end, false);
+    Some(format!("{start12}\u{2013}{end12}"))
+}