Updating dateNextPurchased with smart calculation of new date (#33)

* created getDaysBetweenDates function

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* getting the last updated date of the item

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* update getDaysBetweenDates to only return whole numbers

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* update updateItem function to calculate a new dateNextPurchased and save to DB

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* added clarification comment for previousEstimate variable

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* removing accidental import of random last func

* put testing console.log in for showing the changes

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

* removed console.logs

* switch to Math.floor to make sure focus is on full days passed

---------

Co-authored-by: Ross Clettenberg <RossaMania@users.noreply.github.com>

package.json

@@ -7,6 +7,7 @@
 		"npm": ">=8.19.0"
 	},
 	"dependencies": {
+		"@the-collab-lab/shopping-list-utils": "^2.2.0",
 		"firebase": "^10.12.5",
 		"fp-ts": "^2.16.9",
 		"io-ts": "^2.2.21",

src/api/firebase.ts

@@ -11,7 +11,8 @@ import {
 } from "firebase/firestore";
 import { useEffect, useState } from "react";
 import { db } from "./config";
-import { getFutureDate } from "../utils";
+import { getFutureDate, getDaysBetweenDates } from "../utils";
+import { calculateEstimate } from "@the-collab-lab/shopping-list-utils";
 
 import * as t from "io-ts";
 import { isLeft } from "fp-ts/lib/Either";
@@ -253,9 +254,36 @@ export async function addItem(
 export async function updateItem(listPath: string, item: ListItem) {
 	const itemDocRef = doc(db, listPath, "items", item.id);
 
-	const updates: Pick<ListItem, "totalPurchases" | "dateLastPurchased"> = {
+	const lastUpdatedDate = item.dateLastPurchased
+		? item.dateLastPurchased
+		: item.dateCreated;
+
+	// Last estimated date of next purchase, or previous dateNextPurchased in whole number
+	const previousEstimate = getDaysBetweenDates(
+		lastUpdatedDate.toDate(),
+		item.dateNextPurchased.toDate(),
+	);
+
+	const daysSinceLastPurchased = getDaysBetweenDates(
+		new Date(),
+		lastUpdatedDate.toDate(),
+	);
+
+	const newDateNextPurchased = getFutureDate(
+		calculateEstimate(
+			previousEstimate,
+			daysSinceLastPurchased,
+			item.totalPurchases,
+		),
+	);
+
+	const updates: Pick<
+		ListItem,
+		"totalPurchases" | "dateLastPurchased" | "dateNextPurchased"
+	> = {
 		totalPurchases: item.totalPurchases + 1,
 		dateLastPurchased: Timestamp.fromDate(new Date()),
+		dateNextPurchased: Timestamp.fromDate(newDateNextPurchased),
 	};
 
 	try {

src/utils/dates.ts

@@ -1,4 +1,4 @@
-const ONE_DAY_IN_MILLISECONDS = 86400000;
+export const ONE_DAY_IN_MILLISECONDS = 86400000;
 
 /**
  * Get a new JavaScript Date that is `offset` days in the future.
@@ -19,3 +19,14 @@ export function moreThan24HoursPassed(purchaseDate: Date): boolean {
 
 	return timeElapsedInMilliseconds >= ONE_DAY_IN_MILLISECONDS;
 }
+
+export function getDaysBetweenDates(date1: Date, date2: Date): number {
+	const numberOfDaysBetween =
+		Math.abs(date1.getTime() - date2.getTime()) / ONE_DAY_IN_MILLISECONDS;
+
+	if (numberOfDaysBetween < 1) {
+		return 0;
+	}
+
+	return Math.floor(numberOfDaysBetween);
+}