rouggy
9a21c936b1
Everything is computed in kilometres and converted once at display time, in lib/units — storing miles anywhere would give the same number two sources of truth and a rounding error that grows with every hop. The grids capture the unit inside their column definitions, header and formatter both, so a change is published to them the way the date format already is; without that a toggle would only appear after a language change or a restart. The preference is portable, like the other display ones.
50 lines
1.9 KiB
TypeScript
50 lines
1.9 KiB
TypeScript
// Distance units.
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//
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// Everything is COMPUTED in kilometres — the great-circle maths, the backend's
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// distance_km on a spot, the map's path lengths — and converted once, here, at
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// display time. Storing miles anywhere would mean two sources of truth for the
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// same number and a rounding error that grows with every hop.
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//
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// The preference is portable (see lib/uiPref): an operator who works in miles
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// works in miles on every machine they copy their folder to.
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import { writeUiPref } from '@/lib/uiPref';
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export const KEY_MILES = 'opslog.distanceMiles';
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const KM_PER_MILE = 1.609344; // statute miles, the ones a US licence is used in
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export function useMiles(): boolean {
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try { return localStorage.getItem(KEY_MILES) === '1'; } catch { return false; }
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}
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export function setUseMiles(on: boolean): void {
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writeUiPref(KEY_MILES, on ? '1' : '0');
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listeners.forEach((l) => l());
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}
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// subscribeDistanceUnit notifies on a change. The grids capture the unit inside
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// their column definitions (header text and formatter both), so without this a
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// toggle would only show up on the next language change or restart.
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const listeners = new Set<() => void>();
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export function subscribeDistanceUnit(fn: () => void): () => void {
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listeners.add(fn);
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return () => { listeners.delete(fn); };
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}
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// distanceValue converts a distance in km to the operator's unit, rounded to a
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// whole unit — the precision the inputs actually justify (a 4-character grid is
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// a square tens of kilometres wide).
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export function distanceValue(km: number): number {
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if (!isFinite(km)) return 0;
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return Math.round(useMiles() ? km / KM_PER_MILE : km);
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}
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// distanceUnit is the short label: "km" or "mi".
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export function distanceUnit(): string {
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return useMiles() ? 'mi' : 'km';
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}
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// formatDistance is value + unit, thousands-separated: "12 345 km".
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export function formatDistance(km: number): string {
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return `${distanceValue(km).toLocaleString()} ${distanceUnit()}`;
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}
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