From 5050a296fe002bcf8d0eefec1eb957e841a33477 Mon Sep 17 00:00:00 2001
From: Xevion <xevion@xevion.dev>
Date: Tue, 5 Sep 2023 12:36:09 -0500
Subject: [PATCH] Edge case handling, reduce nesting, general refactor of
 location funcs

---
 src/location.ts | 68 +++++++++++++++++++++++++++++++------------------
 1 file changed, 43 insertions(+), 25 deletions(-)

diff --git a/src/location.ts b/src/location.ts
index 815781d..20aa18c 100644
--- a/src/location.ts
+++ b/src/location.ts
@@ -4,10 +4,11 @@ import * as life360 from 'life360-node-api';
 import logger from '@/logger';
 import Result, { err, ok } from 'true-myth/result';
 
-const center = {
+const targetCenter = {
 	longitude: env.CENTER_LONGITUDE,
 	latitude: env.CENTER_LATITUDE
 };
+
 const MILES_PER_NAUTICAL_MILE = 1.15078;
 const KILOMETERS_PER_MILE = 1.60934;
 
@@ -16,39 +17,50 @@ export type Position = {
 	latitude: number;
 };
 
-// K = Kilometers, N = Nautical Miles, M = Miles (default: M)
+/**
+ *
+ * Calculate the distance between two points using the Haversine formula
+ *
+ * K = Kilometers, N = Nautical Miles, M = Miles (default: M)
+ *
+ * @param a
+ * @param b
+ * @param unit
+ */
 export function distance(
 	a: Position,
 	b: Position,
 	unit: 'K' | 'N' | 'M' = 'M'
 ) {
+	// TODO: Handle floating point precision errors
+	// Edge case: same point
 	if (a.latitude == b.latitude && a.longitude == b.longitude) {
 		return 0;
-	} else {
-		const radlat1 = (Math.PI * a.latitude) / 180;
-		const radlat2 = (Math.PI * b.latitude) / 180;
-		const theta = a.longitude - b.longitude;
-		const radtheta = (Math.PI * theta) / 180;
-		let dist =
-			Math.sin(radlat1) * Math.sin(radlat2) +
-			Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
+	}
 
-		if (dist > 1) dist = 1;
+	const radlat1 = (Math.PI * a.latitude) / 180;
+	const radlat2 = (Math.PI * b.latitude) / 180;
+	const theta = a.longitude - b.longitude;
+	const radtheta = (Math.PI * theta) / 180;
+	let dist =
+		Math.sin(radlat1) * Math.sin(radlat2) +
+		Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
 
-		dist = Math.acos(dist);
-		dist = (dist * 180) / Math.PI;
-		dist = dist * 60 * MILES_PER_NAUTICAL_MILE; // Convert to miles
+	if (dist > 1) dist = 1;
 
-		// Convert to the specified unit
-		switch (unit) {
-			case 'K':
-				return dist * KILOMETERS_PER_MILE;
-			case 'N':
-				return dist / MILES_PER_NAUTICAL_MILE;
-			case 'M':
-			default:
-				return dist;
-		}
+	dist = Math.acos(dist);
+	dist = (dist * 180) / Math.PI;
+	dist = dist * 60 * MILES_PER_NAUTICAL_MILE; // Convert to miles
+
+	// Convert to the specified unit
+	switch (unit) {
+		case 'K':
+			return dist * KILOMETERS_PER_MILE;
+		case 'N':
+			return dist / MILES_PER_NAUTICAL_MILE;
+		case 'M':
+		default:
+			return dist;
 	}
 }
 
@@ -67,6 +79,7 @@ export async function getDistance(): Promise<Result<number, string>> {
 			})`
 		);
 	}
+	logger.debug(`Logged in to Life360 (${env.LIFE360_USERNAME}).`);
 
 	// Get my current location
 	let me;
@@ -88,6 +101,11 @@ export async function getDistance(): Promise<Result<number, string>> {
 		);
 	}
 
+	if (me == undefined)
+		return err(
+			`Failed to find member with ID ${env.LIFE360_MEMBER_ID} in Life360`
+		);
+
 	// Parse my latitude and longitude into floats
 	const current = {
 		latitude: parseFloat(me.location.latitude),
@@ -95,5 +113,5 @@ export async function getDistance(): Promise<Result<number, string>> {
 	};
 
 	// Calculate the distance between my location and the center, multiply x1000 for meters
-	return ok(distance(current, center, 'K') * 1000);
+	return ok(distance(current, targetCenter, 'K') * 1000);
 }