From bb67c78163bff98652d0812be6062119836a25a2 Mon Sep 17 00:00:00 2001
From: Matthew Oslan <derpthemeus@gmail.com>
Date: Sat, 6 Jun 2020 15:57:16 -0400
Subject: [PATCH] Add geocoder cache

---
 .gitignore                   |  1 +
 routes/geocoders/Geocoder.ts | 40 +++++++++++++++++++++++++++++++++++-
 routes/weather.ts            |  2 +-
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 5952f55..2afc654 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ baselineEToData/*.png
 baselineEToData/*.tif
 baselineEToData/dataPreparer[.exe]
 observations.json
+geocoderCache.json
diff --git a/routes/geocoders/Geocoder.ts b/routes/geocoders/Geocoder.ts
index 44640b0..80e5c6d 100644
--- a/routes/geocoders/Geocoder.ts
+++ b/routes/geocoders/Geocoder.ts
@@ -1,11 +1,49 @@
+import fs = require("fs");
+
 import { GeoCoordinates } from "../../types";
 
 export abstract class Geocoder {
+
+	private static cacheFile: string = __dirname + "/../../../geocoderCache.json";
+
+	private cache: Map<string, GeoCoordinates>;
+
+	public constructor() {
+		// Load the cache from disk.
+		if ( fs.existsSync( Geocoder.cacheFile ) ) {
+			this.cache = new Map( JSON.parse( fs.readFileSync( Geocoder.cacheFile, "utf-8" ) ) );
+		} else {
+			this.cache = new Map();
+		}
+
+		// Write the cache to disk every 5 minutes.
+		setInterval( () => {
+			this.saveCache();
+		}, 5 * 60 * 1000 );
+	}
+
+	private saveCache(): void {
+		fs.writeFileSync( Geocoder.cacheFile, JSON.stringify( Array.from( this.cache.entries() ) ) );
+	}
+
 	/**
 	 * 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>;
+	protected abstract geocodeLocation( location: string ): Promise<GeoCoordinates>;
+
+	/**
+	 * Converts a location name to geographic coordinates, first checking the cache and updating it if necessary.
+	 */
+	public async getLocation( location: string ): Promise<GeoCoordinates> {
+		if ( this.cache.has( location ) ) {
+			return this.cache.get( location );
+		}
+
+		const coords: GeoCoordinates = await this.geocodeLocation( location );
+		this.cache.set( location, coords );
+		return coords;
+	}
 }
diff --git a/routes/weather.ts b/routes/weather.ts
index 591b921..0afe94e 100644
--- a/routes/weather.ts
+++ b/routes/weather.ts
@@ -57,7 +57,7 @@ export async function resolveCoordinates( location: string ): Promise< GeoCoordi
 		const split: string[] = location.split( "," );
 		return [ parseFloat( split[ 0 ] ), parseFloat( split[ 1 ] ) ];
 	} else {
-		return GEOCODER.geocodeLocation( location );
+		return GEOCODER.getLocation( location );
 	}
 }