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]

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

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

_{(expires Fri, 20 Sep 2024 05:05:46 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 79d73546692f99aad8468c28e36db434e2c190ac}

[dterceroparker]

** 🦋 praise:** I tested two separate lists and six items, and not only is dateLastPurchased no longer null, but dateNextPurchased is accurately updating based on dateLastPurchased and purchaseInterval. The added documentation in the PR was very helpful.

Well done 🎊! Your work on this feature would make a great LinkedIn post 😉

[shuveksha-tuladhar]

@NickRoccodev11 and @stacy-tech Great work! I am approving this code.

But, I have a question about how the purchaseInterval is being updated. I added a new item with a purchaseInterval of 14 and then I purchased that item from the List page.

When I checked data on the Firebase for that particular item, the purchaseInterval was reset to 0.

Is this the expected behavior for the purchaseInterval, or should it retain the previous value of 14 for that item?

Here is the workflow of how I tested it:

updated-screen.mov

[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

[jtkabenni]

Looks good and the behavior is working as expected! See the notes I added. Nothing is a blocker though.

[jtkabenni]

i would consider what to name this function - if i wanted to get the days between dates, i would expect this function to accept two values, date1 and date 2. Since you are only passing in one date and compare it to today, i would name this function something to reflect that.

This is so when this util function is needed for something else in the future it's easy to tell what it can do.

[jtkabenni]

I would also reconsider making this function name more specific

[jtkabenni]

I think your logic makes sense here, however it is a little bit hard to follow (in nature due to the calculation itself being tricky. I would consider adding comments to each line to make sure it is clear what each line is doing.

This also feels like quite a big block of code. I would consider trying to separate out anything that is not the purpose of the updateItem function (to update the database with the item's updated data), and seeing where else I could put this calculating dates logic - maybe in the list component itself, or another util function? You will then need to change the arguments for this function. This way we can keep this main function less noisy.

[stacy-tech]

Hi Jenny,
Thank you for your feedback! I appreciate your suggestion about adding comments to clarify the code. I’ve added comments to each line to explain what’s happening. This should make the logic more transparent.