Add unit preferences to user settings

src/lib/units.ts

@@ -0,0 +1,56 @@
+export type MeasurementSystem = 'metric' | 'imperial';
+
+export interface UnitPreferences {
+  measurement_system: MeasurementSystem;
+  temperature: 'celsius' | 'fahrenheit';
+  auto_detect: boolean;
+}
+
+// Speed conversions
+export function convertSpeed(kmh: number, system: MeasurementSystem): number {
+  if (system === 'imperial') {
+    return Math.round(kmh * 0.621371);
+  }
+  return Math.round(kmh);
+}
+
+// Distance conversions (meters to feet)
+export function convertDistance(meters: number, system: MeasurementSystem): number {
+  if (system === 'imperial') {
+    return Math.round(meters * 3.28084);
+  }
+  return Math.round(meters);
+}
+
+// Height conversions (cm to inches)
+export function convertHeight(cm: number, system: MeasurementSystem): number {
+  if (system === 'imperial') {
+    return Math.round(cm * 0.393701);
+  }
+  return Math.round(cm);
+}
+
+// Get unit labels
+export function getSpeedUnit(system: MeasurementSystem): string {
+  return system === 'imperial' ? 'mph' : 'km/h';
+}
+
+export function getDistanceUnit(system: MeasurementSystem): string {
+  return system === 'imperial' ? 'ft' : 'm';
+}
+
+export function getHeightUnit(system: MeasurementSystem): string {
+  return system === 'imperial' ? 'in' : 'cm';
+}
+
+export function getShortDistanceUnit(system: MeasurementSystem): string {
+  return system === 'imperial' ? 'ft' : 'm';
+}
+
+// Countries that primarily use imperial system
+export const IMPERIAL_COUNTRIES = ['US', 'LR', 'MM'];
+
+// Detect measurement system from country code
+export function getMeasurementSystemFromCountry(countryCode: string): MeasurementSystem {
+  return IMPERIAL_COUNTRIES.includes(countryCode.toUpperCase()) ? 'imperial' : 'metric';
+}