Create Geocoder abstraction

routes/geocoders/Geocoder.ts

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+import { GeoCoordinates } from "../../types";
+
+export abstract class Geocoder {
+	/**
+	 * Converts a location name to geographic coordinates.
+	 * @param location A location name.
+	 * @return A Promise that will be resolved with the GeoCoordinates of the specified location, or rejected with a
+	 * CodedError.
+	 */
+	public abstract geocodeLocation( location: string ): Promise<GeoCoordinates>;
+}

routes/geocoders/WUnderground.ts

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+import { GeoCoordinates } from "../../types";
+import { CodedError, ErrorCode } from "../../errors";
+import { httpJSONRequest } from "../weather";
+import { Geocoder } from "./Geocoder";
+
+export default class WUnderground extends Geocoder {
+	public async geocodeLocation( location: string ): Promise<GeoCoordinates> {
+		// Generate URL for autocomplete request
+		const url = "http://autocomplete.wunderground.com/aq?h=0&query=" +
+			encodeURIComponent( location );
+
+		let data;
+		try {
+			data = await httpJSONRequest( url );
+		} catch ( err ) {
+			// If the request fails, indicate no data was found.
+			throw new CodedError( ErrorCode.LocationServiceApiError );
+		}
+
+		// Check if the data is valid
+		if ( typeof data.RESULTS === "object" && data.RESULTS.length && data.RESULTS[ 0 ].tz !== "MISSING" ) {
+
+			// If it is, reply with an array containing the GPS coordinates
+			return [ parseFloat( data.RESULTS[ 0 ].lat ), parseFloat( data.RESULTS[ 0 ].lon ) ];
+		} else {
+
+			// Otherwise, indicate no data was found
+			throw new CodedError( ErrorCode.NoLocationFound );
+		}
+	}
+}