Create Habit Controller

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>> Speaker 1: So what we want to do is go to our Controllers folder here, make a new controller We'll say HabitController.ts and we'll get to work on this

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We'll say import type Response from Express, so we get that, and we're gonna use our authenticated Request from our middleware instead of Express-like

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You need to get our database in here because we're gonna be doing database things—that's the whole point of the server, or the whole point of the API, I should say

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Then we're going to import the habits table And because of relations, we might have the entries table because you can create entries for a habit

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You might also have habit tags if someone wants to create a tag or associate a habit with a tag We're allowing them to do that through the habit resource; we might also allow that through the tag resource because it's a many-to-many relationship, so it's denormalized

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You can do either on either side: you can create a tag and assign it to these habits, or create a habit and assign these tags, so either way

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And then some helper methods from Drizzle ORM—we'll get the one that we used before, equals, we'll get an ascending order for sorting, we'll get an in-array for checking

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OK, so the first one we want to do is the C part of CRUD, which is create We'll export a function here called createHabit It's going to take a request, but it's going to be an authenticated request

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We'll take a response from Express We're going to do a try-catch block We'll destructure the payload from the body: we'll get the name, description, frequency, target count, and any tag IDs

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If you have some tag IDs, you can send them up, and we'll associate this new habit with these tags We'll get the user ID using req.user.id

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What's new here, if you've never worked with databases, is we're going to make a transaction on the database What is a transaction

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If you have to write to the database more than once for this function, and the first write operation worked, but the second operation failed, now your database is left in a broken state because you needed both of those things to succeed

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Imagine transferring money from a bank account where three database operations are happening Two succeeded—the part where it took money out of your account—but the part where it sent it to the other account failed

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Now what A transaction groups database write operations into one call, and if one fails, it rolls back all the others It's essentially a Git commit, but for the database

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We'll start a transaction by calling transaction and getting a TX object It does the exact same thing as the DB object—you just treat it like DB

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We'll create a new habit using TX.insert on the habits table, passing in the user ID, name, description, frequency, and target count

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If tag IDs were passed, we'll create associations in the habit_tag table We'll map over the tag IDs and create entries linking the new habit ID with each tag ID

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The transaction ensures that if anything breaks, everything is rolled back If everything succeeds, we'll return a 201 status with a "Habit Created" message

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If something fails, it's likely a server-side issue, so we'll return a 500 status We'll then add this to our habit routes, creating a validation schema that matches our database and controller expectations