Issue 11 Estimate next purchase date

[NickRoccodev11]

Description

This ticket creates an estimate for the next purchase date of an item.

• It bases the estimate on the users purchasing history, comparing the intervals between purchase dates while considering the number of total purchases.
• Working on this ticket helped improve our logic for calculating future dates.
• We ran into issues regarding copying Dates, as they are references.

Related Issue

closes #11

Acceptance Criteria

• [ ] When the user purchases an item, the item’s dateNextPurchased property is calculated using the calculateEstimate function and saved to the Firestore database

• [ ] dateNextPurchased is saved as a date, not a number

• [ ] A getDaysBetweenDates function is exported from utils/dates.js and imported into api/firebase.js

  • [ ] This function takes two JavaScript Dates and return the number of days that have passed between them

Updates

Before

After

Testing Steps / QA Criteria

• Open the Firestore database.
• Locate an item in your list that you want to purchase, and make note of dateNextPurchased date.
• Sign In to app using email account.
• Click on a list and navigate to List view.
• Purchase the item you previously observed in Firestore.
• After successful purchase, return to Firestore to view the item.
• Confirm that dateNextPurchased has changed to a future date.
• If you are interested in seeing how the estimate is calculated given various conditions, refer to this documentation: https://github.com/the-collab-lab/shopping-list-utils/blob/main/src/calculateEstimate/calculateEstimate.ts

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 3a52628):

https://tcl-74-smart-shopping-list--pr29-sd-nr-11-c1v1e3jx.web.app

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[NickRoccodev11]

@shuveksha-tuladhar Thanks for the video explanation! so yes, for now that is the expected behavior. the calculateEstimate function first checks the total number of purchases an item has. if it has been purchased less than twice, the function returns daysSinceLastPurchase . (or "daysSinceLastTransaction" as it's labeled in the documentation linked above) What this means is, if you create an item and buy it on the same day, 0 days have passed since the item was last interacted with, so it sets the interval to 0. This might not be the behavior we ultimately want (considering adding an item to the list isn't technically purchasing it) but it is what we expect at this point