Graph fixes

server/src/forecast.mjs

@@ -2,10 +2,17 @@ import {queryHourly, getCoords, queryCurrent} from './influx.mjs';
 import {getCelestialCurrent} from './celestial.mjs';
 import {getWeatherCondition} from './openweather.mjs';
 import {localDateStr} from './config.mjs';
+import {uvLabel} from './openmeteo.mjs';
 
 export let lastForecast = { ts: 0, slots: [], summary: null }
 export const forecastTTL = 5 * 60 * 60_000
 
+function estimateUV(sunElevation, cloudFraction) {
+	if (sunElevation <= 0) return 0;
+	const clearSkyUV = Math.sin((sunElevation * Math.PI) / 180) * 12;
+	return Math.round(clearSkyUV * (1 - cloudFraction * 0.75) * 10) / 10;
+}
+
 function linearTrend(values) {
 	const n = values.length;
 	if (n < 2) return 0;
@@ -117,6 +124,7 @@ export async function get24HourForecast(currentSensors) {
 		const temperature = Math.round(bgTemp * 10) / 10;
 		const humidity   = forecastHumidity(seedAbsHum, temperature);
 		const wind_speed = forecastWind(seedWind, pressureTrend);
+		const uv_index = estimateUV(celestial.sun_elevation ?? 0, clouds);
 
 		const celestial = getCelestialCurrent(coords.latitude, coords.longitude, time);
 		const snapshot = {
@@ -131,6 +139,8 @@ export async function get24HourForecast(currentSensors) {
 			wind_speed,
 			clouds,
 			precipitation_chance:   Math.round(weather.precipChance * (1 - i * 0.02) * 100),
+			uv_index,
+			uv_index_label: uvLabel(uv_index),
 			...celestial
 		};