Add support for fallback WeatherProviders

routes/weather.ts

@@ -7,7 +7,11 @@ import * as geoTZ from "geo-tz";
 
 import * as local from "./local";
 import { AdjustmentOptions, GeoCoordinates, TimeData, WateringData, WeatherData, WeatherProvider } from "../types";
-const weatherProvider: WeatherProvider = require("./weatherProviders/" + ( process.env.WEATHER_PROVIDER || "OWM" ) ).default;
+import CompositeWeatherProvider from "./weatherProviders/CompositeWeatherProvider";
+
+const weatherProvider: WeatherProvider = new CompositeWeatherProvider(
+	( process.env.WEATHER_PROVIDER || "OWM" ).split( "," ).map( ( id ) => require( "./weatherProviders/" + id ).default )
+);
 
 // Define regex filters to match against location
 const filters = {

routes/weatherProviders/CompositeWeatherProvider.ts

@@ -0,0 +1,45 @@
+import { GeoCoordinates, WateringData, WeatherData, WeatherProvider } from "../../types";
+
+/**
+ * A WeatherProvider calls other WeatherProviders until one successfully returns a value.
+ * This is a special utility WeatherProvider, and should NOT be selected with the WEATHER_PROVIDER environment variable.
+ */
+export default class CompositeWeatherProvider implements WeatherProvider {
+
+	private readonly weatherProviders: WeatherProvider[];
+
+	public constructor( weatherProviders: WeatherProvider[] ) {
+		this.weatherProviders = weatherProviders;
+	}
+
+	public async getWateringData( coordinates : GeoCoordinates ): Promise< WateringData > {
+		return await this.callMethod( "getWateringData", coordinates ) as WateringData;
+	}
+
+	public async getWeatherData( coordinates : GeoCoordinates ): Promise< WeatherData > {
+		return await this.callMethod( "getWeatherData", coordinates ) as WeatherData;
+	}
+
+	/**
+	 * Calls a specified function in each WeatherProvider until one returns a non-undefined value. If the function is
+	 * not defined for a WeatherProvider, it will be skipped.
+	 * @param func The name of the function to call.
+	 * @param args The arguments to pass to the function.
+	 * @return A promise that will be resolved with the first non-undefined value returned by a WeatherProvider, or
+	 * resolved with undefined if none of the WeatherProviders returned a value.
+	 */
+	private async callMethod( func: "getWateringData" | "getWeatherData", ...args: any ): Promise< unknown > {
+		for ( const weatherProvider of this.weatherProviders ) {
+			if ( !weatherProvider[ func ] ) {
+				continue;
+			}
+
+			// @ts-ignore
+			const result = await weatherProvider[ func ]( ...args );
+			if ( result ) {
+				return result;
+			}
+		}
+		return undefined;
+	}
+}