refactor(app): extract sweeps and band-selection submodules

src/app/band_select.rs

@@ -0,0 +1,162 @@
+//! Band-selection parsing, labelling, and listing views.
+//!
+//! User-facing band token/range parsing and the band-listing view model,
+//! extracted from `app/mod.rs`.
+
+use super::*;
+
+pub fn parse_band_selection(selection: &str, region: ITURegion) -> Result<Vec<usize>, AppError> {
+    let mut parsed = Vec::new();
+    let mut seen = HashSet::new();
+
+    for token in selection.split(',') {
+        let token = token.trim();
+        if token.is_empty() {
+            continue;
+        }
+
+        if let Some((start, end)) = token.split_once('-') {
+            let start_idx = parse_single_band_token(start.trim(), region)?;
+            let end_idx = parse_single_band_token(end.trim(), region)?;
+
+            let ordered = ordered_band_indices_for_region(region);
+            let start_pos = ordered
+                .iter()
+                .position(|idx| *idx == start_idx)
+                .ok_or_else(|| {
+                    AppError::InvalidBandSelection(format!(
+                        "unknown range start '{}'.",
+                        start.trim()
+                    ))
+                })?;
+            let end_pos = ordered
+                .iter()
+                .position(|idx| *idx == end_idx)
+                .ok_or_else(|| {
+                    AppError::InvalidBandSelection(format!("unknown range end '{}'.", end.trim()))
+                })?;
+
+            if start_pos <= end_pos {
+                for idx in &ordered[start_pos..=end_pos] {
+                    if seen.insert(*idx) {
+                        parsed.push(*idx);
+                    }
+                }
+            } else {
+                for idx in ordered[end_pos..=start_pos].iter().rev() {
+                    if seen.insert(*idx) {
+                        parsed.push(*idx);
+                    }
+                }
+            }
+
+            continue;
+        }
+
+        let idx = parse_single_band_token(token, region)?;
+        if seen.insert(idx) {
+            parsed.push(idx);
+        }
+    }
+
+    if parsed.is_empty() {
+        return Err(AppError::EmptyBandSelection);
+    }
+
+    Ok(parsed)
+}
+
+pub fn parse_single_band_token(token: &str, region: ITURegion) -> Result<usize, AppError> {
+    let token = token.trim();
+    if token.is_empty() {
+        return Err(AppError::InvalidBandSelection(
+            "empty band token".to_string(),
+        ));
+    }
+
+    let aliases = band_alias_to_index(region);
+    let key = token.to_ascii_lowercase();
+    aliases
+        .get(&key)
+        .copied()
+        .ok_or_else(|| AppError::InvalidBandSelection(format!("unknown band '{token}'.")))
+}
+
+pub fn band_label_for_index(index: usize, region: ITURegion) -> String {
+    let zero_based = match index.checked_sub(1) {
+        Some(v) => v,
+        None => return index.to_string(),
+    };
+
+    for (idx, band) in crate::bands::get_bands_for_region(region) {
+        if idx == zero_based {
+            return band
+                .name
+                .split_whitespace()
+                .next()
+                .unwrap_or(band.name)
+                .to_string();
+        }
+    }
+
+    index.to_string()
+}
+
+fn ordered_band_indices_for_region(region: ITURegion) -> Vec<usize> {
+    crate::bands::get_bands_for_region(region)
+        .into_iter()
+        .map(|(idx, _)| idx + 1)
+        .collect()
+}
+
+fn band_alias_to_index(region: ITURegion) -> HashMap<String, usize> {
+    let mut aliases = HashMap::new();
+
+    for (idx, band) in crate::bands::get_bands_for_region(region) {
+        let one_based = idx + 1;
+        let full_name = band.name.to_ascii_lowercase();
+        aliases.insert(full_name.clone(), one_based);
+
+        if let Some(short_name) = full_name.split_whitespace().next() {
+            aliases.insert(short_name.to_string(), one_based);
+        }
+    }
+
+    aliases
+}
+
+/// Build a pure view model for the band listing of a given ITU region.
+///
+/// Pure function; performs no I/O.
+pub fn band_listing_view(region: ITURegion) -> BandListingView {
+    let rows = crate::bands::get_bands_for_region(region)
+        .into_iter()
+        .map(|(idx, band)| BandListingRow {
+            index: idx + 1,
+            display: format!("{band}"),
+        })
+        .collect();
+    BandListingView {
+        region_short_name: region.short_name().to_string(),
+        region_long_name: region.long_name().to_string(),
+        rows,
+    }
+}
+
+/// Render a `BandListingView` to display lines (no I/O).
+pub fn band_listing_display_lines(view: &BandListingView) -> Vec<String> {
+    let mut lines = Vec::new();
+    lines.push(String::new());
+    lines.push(format!(
+        "Available bands in Region {} ({} total):",
+        view.region_short_name,
+        view.rows.len()
+    ));
+    lines.push(format!("  ({})", view.region_long_name));
+    lines.push("------------------------------------------------------------".to_string());
+    for row in &view.rows {
+        lines.push(format!("{:2}. {}", row.index, row.display));
+    }
+    lines.push(String::new());
+    lines
+}