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In the last section we spoke about our processing pipeline.

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We're now going to install two different modules that are going to help us implement this entire pipeline

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right here.

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So I'm going to change on over to my terminal.

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I'm going to kill my running server and I'm going to run NPM install dash dash save and we're going

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to grab something called Low dash and something called Path dash parser.

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OK.

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And these are only going to take a second to install.

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So let's just let it do its thing and then we will start our server backup the load ash library something

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that we use a lot for doing any type of iteration.

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It's got a whole bunch of helper methods inside of it.

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And then the path parser library is something that's going to help us extract just the survey ID and

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the choice pieces out of the you are out.

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So after those are done installing will start back up with NPM run death.

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Now let that just do it start up and run in the background.

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And while that's going to flip back over to my code editor and I'm going to find my survey routes file

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inside of the routes directory inside of here.

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We've got our post request handler for API surveys web hooks.

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So right here is where we're going to want to do all this processing logic to look at the incoming array

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of events which remember exists on the body property and do all this processing over that.

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Now before we start to add any logic to this event handler we're assuming this route handler at all

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let's import one or two libraries at the very top of the file.

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So at the very top We're going to import actually in total three different libraries.

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The first one is going to be the load ash library that we just installed convention by convention.

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Whenever we import load ash we assign the library to the underscore character right here.

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So underscore is a valid javascript variable.

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Again it's just convention that we use underscore for loadout library.

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Next we're also going to install or require an I should say the path library that we just installed

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can the path Dasch parser.

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And then finally we're also going to install or require in you r l and we're going to get that from

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the u r l module.

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Now this one right here doesn't look much like anything that we've required in before.

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So yes you're correct we did not just install a library called you r l l is a default or integrated

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module in the no js system.

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So you don't have to install you are l you get it for FREE.

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Whenever you make use of node the your library has a bunch of different helpers on it for helping us

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parse you URLs inside of our application.

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The part of this library that actually helps us deal with this stuff is this.

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You r l capital U R L function right here.

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So this requires in a big a library with a bunch of different helpers.

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The only helper that we care about is this capital-T you are L-1 which is why we are destructuring it

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off of the L library.

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OK.

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So let's get to start inside of our robot handler now.

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So here's our web hooks handler.

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I'm going to remove the stuff that's in here right now and we're going to replace it with a little bit

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of logic.

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So the first thing that we're going to do is we're going to map over let's look at our diagram rather

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than me just say it.

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So we're going to map over our list of events and we're going to attempt to do these extraction steps.

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So let's try that first.

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So inside of here we'll say Konst I don't know is Culdee events and we'll use underscore dot map series

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low dashes map function to iterate over Reyk dot body.

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So that's my list of events.

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Now as the second argument to this function will pop pop in our iterator function.

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So for every element in Wreck-Gar body run this function right here will take in the given event and

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we're going to do a little bit of processing on it where we attempt to extract the path and then the

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actual pieces of data that we really care about.

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Now again this is a two step process.

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The first step where we process the event we're going to make sure that we are extracting just the route

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of the you are out.

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We don't care about the domain.

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We just want the route.

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So to make sure that we only get the route we're going to use that you are el helper that we just imported

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and right here.

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So inside the map function I'm going to say new capital L and then the event or the you are all that

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we want to pass into this is event don't you are.

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Remember that's the u r l that we really care about here is obvious event object.

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So say event Daut you are out like so.

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And now to make sure that we only get the route where the pathname part of the you are l will then say

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Dot pathname like so.

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So this line right here is going to implement step number 1 where we take the entire fully qualified

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you are l and we extract off just this route.

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Now step number two and let's assign this to a temporary variable right now.

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Step number two is going to be where we start to make use of this path parser library.

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So we're going to look at the pathname that we just extracted and we're going to try to pull off just

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the survey ID and the choice to do so.

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We're going to first create a parser object so we'll say Konst P is a new path.

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So remember path right here is the path parser library that we just installed and then we pass in the

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string to kind of give this thing the pattern of the different variables that we're trying to extract

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from this pathname right here.

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So the pattern that we are simply trying to extract is slash API slash surveys.

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So that's going to match up with API slash surveys.

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And then this next little thing that goes between these next two slashes right here.

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That is a variable that we want to somehow extract out of our pathname.

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So to tell the PAF library that we want to extract this next part of the you are all going to say colon

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survey ID and then to also extract the choice will say Colan choice like so.

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Okay I know that I'm going kind of quick here but the thing about all this extraction stuff is that

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once we actually kind of run this code and test it you're going to have a much better sense of what

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is actually going on here.

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So I know we're going kind of quick but again as long as we just kind of like see the result you'll

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have a really good idea of exactly what's happening.

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So again when we created this new path object right here and assigned it to p p is now an object that

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we can use to look at the pathname and somehow extract out a survey ID and a choice.

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So now we will run the dot test pathname.

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And I'm thinking that right now how about we just canceled this thing out to get a better sense of what's

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going on.

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Okay.

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All right.

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So at this point we're looking at the list of events for every event we extract just the path or just

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the route portion of the L..

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We then create this little matchers thing right here.

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We then attempt to use the matcher to extract the survey ID and the choice from the pathname and then

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we cancel it out all out.

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So let's give this thing a little test and see how we're doing.

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So going to flip on over to my e-mail accounts and I'm just going to click on one of the buttons in

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here.

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So that's going to issue a web request over to our application which should hit the post request route

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handler that that we've been working on.

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So if we now flip on over to the terminal remember it always takes a little bit of time to see this

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stuff actually pop up in the terminal.

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So let's take a quick break right now.

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We'll wait for this thing to pop up and it will continue in the next section and say yes it looks like

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we're going down the right path right now.

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So quick break and I'll see you in just a minute.