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We finished up our post service.

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So now we're going to put together an initial implementation of our comments service as well just as

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we did before.

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It's gonna be very much be worth our time to really hash out exactly what we want our comments service

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to do so I took a quick stab at how we might want to implement this comment service.

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I think that we're going to have two different root handlers.

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Once again we're going to have one row handler that's going to allow us to create a new comment that

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is associated with some very particular post.

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So you'll notice that inside the path right here we're going to make a request to post slash and then

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the I.D. of the post that we're going to associate this comment with when we make a post request.

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We're going to have a body that has a content that is some string so content is going to be the actual

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text of the comment itself.

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We're then going to have a second row handler that's went to give us all of the different comments that

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are associated with some very particular post I.D. so make a get request to that route.

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That will give us all the comments associate with some given post I.D..

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So pretty straightforward but we are going to have just a little bit more complexity on the service.

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I'll tell you why in just a moment right now.

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Let's open up our code editor and start to put this thing together it's going to look backward my terminal.

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I'm gonna open up my code editor inside of my comments directory

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inside of here right away.

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I'll make an index dot j ust file and at the very top we'll write out a little bit of boilerplate very

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similar to what we ended up with inside of our postal service.

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Just a moment ago it's all get Express.

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I'll get a body parser

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and I'll get that random bytes function that we're using to just generate random ideas.

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Next up going to create my express application I'll associate the body parser middleware with its and

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I'll put together are two root handlers.

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So we want to have a root handler that will deal with a get request to posts i.e. comments

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and of course make sure that you've got that colon right before I.D..

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Right there

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and we could do something very similar.

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Daniel Post requests as well.

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So we're gonna look for a post request to post a line I.D. comments.

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Very good.

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And then finally let's make sure that our Express application listens on some court so say Abdul listen

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and remember we already have another service listening on Port 4000 on our computer.

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So we have to put in another unique port right here in my case I got to put in four thousand and one

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like so once I start listening on there I'll do a console log of listening on four thousand one okay.

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So good start now the next we need to do is that in some actual implementation or getting all the post

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with some given I.D. and all the to me all the comments associated with some post I.D. and creating

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a new common as well.

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Let's first begin with creating a new comment just as we had back on our post micros service.

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We're gonna store all of our comments instead of an in-memory data structure so just like we had previously

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I'm going to create a new object right here called comments by post I.D. and I'll make that an object.

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You'll notice I'm calling the thing by post I.D..

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The reason for that is that we really want this data structure to be optimized for looking up all of

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the different comments associated with a given post so we can have a slightly more complicated data

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structure right here than what we had back on our post service.

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Let me show you a diagram to help you understand what this object is going to really look like.

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All right.

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So here's the idea.

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Here's what we're going to do that.

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Comments by post I.D. is going to look like this diagram right here.

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It's going to have some keys.

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Of course because it is an object.

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And those keys are going to be the I.D. of a post that has been created inside of application then for

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each of those keys.

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We're going to have an array of comments so here's comment number one comment number two and so on.

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So this is going to make it really really easy and straightforward to look up all the comments associated

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with some given post by the Post I.D..

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All we have to do is reach into the comments by post I.D. object look up the given idea of the post

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and that will give us back an array of all the comments that are associated with that post.

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Pretty straightforward to do that look at OK so now we have a better idea of what this object right

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here is going to look like.

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Let's start making use of it inside of our poster request handler inside of here.

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The first thing I'm going to do is generate a new comment I.D. This is going to be just a random I.D.

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so we can identify this comment at some point in the future if we need to.

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So I'll say comment I.D. is going to be that random bytes function we're gonna call it and get a or

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random bytes generated and then convert that to a string.

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That is a hexadecimal string.

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So again just a randomly generated ideas next up will pull out the content property that is provided

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by the user inside of our incoming request.

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Because remember we had said that anytime soon makes a post request we're going gonna have a body that

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is a content that has some string so I'll get content from wreck dot body now.

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Next up we're going to take a look at our comments by I.D. by post idea object right here.

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We're gonna check to see if we've already got some array inside there or the given post I.D. so I'll

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say const comments is going to be comments by post I.D. and we'll look up the post I.D. that was provided

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inside the URL.

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We'll do.

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Rick brands dot I.D. and that will give us either in array or undefined.

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It will give us undefined if we've never had a comment as created that is associate with this post before

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this might be undefined right here.

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So to guard against that I'll say if this results in undefined then just give me by default an empty

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array.

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So now we're going to push in the new comment that we're trying to create into this comments array will

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say comments that push and I want to push in an idea of common I.D. and the content that the user just

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provided and I'll make sure that I assign this comments array back to the given post inside of our comments

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by post I.D. object.

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So we'll say comments by post I.D. at Rick brands I.D. equals comments and that should be it nonetheless

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thing that we can do right here.

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We'll send back just the entire array of comments we could send back just the comment that was created.

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But what the heck let's just send back the entire array of comments.

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I'll do a rez that status to a one and I'll send back the entire array of comments get.

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So there's our post request handler.

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Now we'll put together our get request handler which is going to be a way easier.

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So up here we'll do a rez that sent.

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We're going to look inside of our comments by post I.D. object.

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I'm going to look up inside there.

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The idea that was provided inside the path so we'll do a wreck per Rams I.D. and then once again if

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that results in undefined let's guard against that was put in and or empty array like so so that no

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matter what we always send back an array to whoever is making this request OK.

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So it looks good.

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It's going to say this file.

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The last thing I'm going to do is open up my package not just on file.

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We're going to find a script inside of there as well for starting up our project with Node 1.

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So here's my package that Chase on file and then replace the START script or create a start script.

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I should say and we'll do a node on index dot J.S. Well that should be it for our common service.

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So once again let's take a quick pause right here.

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We'll come back the next video and just do a very quick little manual test with postman post ask me

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post man not node 1 post man to make sure that this is all working as expected.