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In the last section we created a new user instance and saved it to our database.

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Any time a user came back to our application from the Google flow now we tested this out and we were

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able to verify.

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Yes we did it correctly save a user to our database.

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However there's just one little issue right now.

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If I open up a new tab again and go to localhost Colin 5000 slash off slash Google again.

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Yeah the browser still hangs.

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That's totally fine.

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But if I go over to my inland collection again and refresh the page you will now notice that there are

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two user records inside of my user user collection with identical Google IDs.

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Now this really is not ideal for any user who signs into application.

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We want to have just exactly one user account for them or one user record.

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So I think that we need to modify that call back where we are currently creating a new user an ad just

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a little bit more logic to it.

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So here's what we're going to do when the user comes back to us from the Google flow and we get access

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to their profile before we create a new user.

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We will check to see if anyone inside of our users collection already has this given profile I.D. or

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the profile ID that we just got back from the Google flow.

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Now if someone does have that profile ID will then fantastic.

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We do not need to create a new record so do not create a new model instance and do not save it.

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But if no one has used that profile ID before then.

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OK.

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This must be a new person.

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We need to create a new record and save it to that collection.

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So the linchpin here is clearly we have to make sure that we somehow query our existing collection we

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have to do a search and there we have to check to see if anyone has used this profile ID.

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So lets figure out how we do queries using mongoose.

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The first thing I want you to remember is that we currently have access to a model class which represents

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the entire underlying collection of records that exist inside of our database.

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We make use of that model class to search over all the records that exist inside the collection.

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So let's flip back over to our code editor and we're going to add a line of code that's going to use

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our motto class which is the capital you use or right here to initiate a query or initiate a search

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over all the records inside the collection to do so.

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We will write user find one.

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And then we're going to pass some search criteria inside of an object.

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We're going to say attempt to find one record inside the user's collection where there are Google ID

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is equal to profile dot Id like so now again triple check make sure you've got a lowercase d here for

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ID no capitals.

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So again look through the users collection find the first record inside that collection with a google

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id of profile ID.

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So this line of code right here will essentially initiate that query for us.

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But before we try to make use of this query in practice there's one last little thing we have to do

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any time we reach out to our Mongo database in any way shape or form be it to search through a collection

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or to save a new record to it or to edit an existing record or to delete one.

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It doesn't matter.

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No matter what it is.

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Any time we reach out to our database we are initiating an asynchronous action.

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In other words we can't just say like oh yeah this returns our user right here.

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This line of code right here does not return the user directly.

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We can't just put down Konst user and attempt to get access to the results of the query.

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Instead the query returns a promise a promise is a tool that we use with javascript for handling asynchronous

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code.

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Now in this course we are not going to be using promises very heavily because we're going to use an

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advanced feature of javascript that was included in E.S. 2017 for kind of making promises look a little

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bit nicer.

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So I'm going to tell you right now that if you're not familiar with promises that is OK.

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But for this very first query that we're going to do we will use a promise and then later on we will

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come back and refactor it a little bit.

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So if you're not familiar with promises toy fine.

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Just follow along for one second and then we'll come back later and refactor this stuff a little bit

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more.

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OK so find one returns a promise to get some indication or some signal of where when the query has completed

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we will chain on a dot then statement inside of there we will add an arrow function and the arrow function

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will be called with whatever the user was found.

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If one exists we're going to call that the existing user.

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So this will be a model instance in model instance that represents a user who was found.

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Now if a user has a google id of profile ID then the argument existing user right here will be equal

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to null.

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So to figure out whether or not we found a user you want to figure out whether or not existing user

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exists or not we can ask a very simple question will say if existing user exists like so.

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So if that existing user exists that means we already have a record with the given profile ID

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and that means that we do not need to create and save a new record else we want to create a new user

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in which case we don't have a user record with this Id make a new record.

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And so this case down here would be the case in which we had previously created the new model instance

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and saved it to our database.

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So going to take this new user and save statement and then add it down here OK.

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So this gets us at least one step further.

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We are now making sure that we do not attempt to create a new user any time that one already exists

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with a given profile ID.

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Now really quick let's test it inside the browser and then we will move on to the next section and add

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a little bit better logic to this statement right here.

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So inside my browser I'm going to open up a new tab I will navigate to localhost 5000 slash Auth. slash

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Google.

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Now of course it's still going to hang.

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But if we flip back over to in lab and refresh the collection we should still only see two records.

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And there's Arti right there.

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Now of course we still don't even want to records for our test database here so I'm going to delete

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one of these records by clicking the little trash can on the right hand side.

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So now we can go through our flow as many times as we want.

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So I'm going to do it again.

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And no matter how many times we do it we are definitely guaranteed that we will only ever create exactly

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one record inside of our users collection to represent this given user.

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OK.

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So that's pretty much it.

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That gets us one step further.

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But we still have to kind of you know look at the browser.

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I don't mean to tell you what we have to do everything is still kind of just hanging in the browser.

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Clearly we are really not done with this callback function right here.

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So let's take a quick break come back in the next section and add a little bit more logic to kind of

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nudge passport along after we figure out whether or not we need to create a user.

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So I'll see you in the next section.