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In this video, we are going to start to developing basket microservices.

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So as you can see, that basket microservices has mainly two task.

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The first task is accommodate incoming HTTP post requests from the API gateway and after that it is

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basically publish check out event into the Amazon event page.

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So let's get start implementation.

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For that purpose.

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I have created separate section and lecture folder in here.

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So this is the common text that we are going to do one by one.

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Basically, we will create a Node.js project for our lecture and this will be publishing to basket lambda

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function.

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So in order to make it Node.js module, I will start the API and why please go to correct folder sector

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and start with the NPM command.

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So we have create package JSON file.

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The first thing we should do that set the type as a module to gain a security six standards.

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Okay.

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If you come back to common text after that, we, we would like to install the required package.

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So which packages we are need to do.

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We basically need to client event bridge.

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If you go to documentation, you can see that we will use one page client, a WS SDK library.

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If you scroll down, you can see the details and how we can install it using API command.

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And here you can see the import statement and if you scroll down, you can see the simple implementation

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or even client object.

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Okay, after installing this package, we will use put event commands in order to publish checkout,

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even to Amazon event page.

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So let's copy this install command, go back to our project and here I'm going to copy paste from in

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here and hit enter.

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So these will install required even package that we can use for our basket microservices.

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Basically we need to incoming payload from API Gateway.

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After that, we need to publish that message to Amazon until each custom event pass.

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So that's why we use this event page.

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Please verify from the node modules and also package JSON file.

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Go to dependencies and make sure that you have installed client event successfully.

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Okay.

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Very good.

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Now it is time to develop our lambda function code.

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We should plan our development for basket microservices.

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Now let's write a PC code for that purpose.

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I have created index file.

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If you open this file, you can see that I have implement minimum minimum method of the lambda function.

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This is the our handler method and the first line of code I have log incoming event.

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After that I put here try cash flow.

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Now I'm going to write down the PC code.

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That means plan our operations in this lambda function.

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So basically the first operation is let me come here and write down one by one.

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So the first step is accommodate the incoming HTTP post request to the correct set.

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So that means if you go back to our architecture, we will accommodate three post operation from API

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Gateway into basket microservices.

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If you come back to our used to do operation, the second step is get the request.

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But.

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Eight requests by the payload, which include event data when it comes to trigger from the API gateway.

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The body information includes the actual payload, so that's why we should get the request by the payload.

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The second second step and the third step.

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After getting the request data, we basically publish message to Amazon event page custom event twice

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using different HDC libraries.

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And the last step.

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Since it is a synchronous invocation, we should return back the synchronous basket payload to the API

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gateway.

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So now let's get started.

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Implement these four step in our lambda function in the try case below.

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For that purpose, I'm going to start with the first step in the trip.

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Look, let me come here and copy paste in here.

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As you can see that in the first step we are validating the incoming acid method.

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The acid method should be post, otherwise we are throwing an exception because we are expecting a HTTP

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post operation for the basket payload for the checkout operation and the payload include should include

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the required event details about the checkout basket.

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Okay, this was the first step.

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And if you go back the second step, which is the gate request, but the payload in order to do that,

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we should check the incoming event.

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You can see in here basically we got the event that body and JSON parse to get basket request and validate

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the basket request should not be null and also detailed type should not be null.

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So you can see the expected payload that we are expecting from the HTTP post operation in here.

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And also I'll copy paste from the command text if you come here.

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We basically expect this kind of payload include item price, detail, type and source.

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You can see the second expected payload example in here.

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We are expecting this payload because if you scroll down, you can remember that in the last video we

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had defined event pattern in Amazon event page.

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So our event pattern including to detail type and source information.

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So that's why we will paste these to information from payload to the event page.

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Okay.

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So after understanding the payload, we basically validate the payload that including the detail type

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also.

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And we got the request basket request from the event, but the information which comes from the Amazon

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API gateway and now I'm going to come to third step.

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In the third step, I don't want to implement now I will implement in the next video, but in the third

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step we will use the event event page client object to publish message to the Amazon event page.

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In the fourth step, basically we will return back to synchronous response.

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So if you come here and we should return 200 success response when it comes to work, everything well.

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And as you can see that when I am facing the body information as a data which will come from the published

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message and we we return the successful message.

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So if you scroll down in the cache block, we will lock the error.

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And after that we should return the 500 error statement to the sync response.

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You can see in here, we basically return 500 such code and error details in this return statement.

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So that means since it is a synchronous invocation, we are response back to synchronous response to

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API gateway.

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If everything goes well, we return success.

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Response is if there is an exception, we will return back the exception details and 500 cells code.

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As you can see that we have write down our code and implement into the cache block of our handle method.

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Now in the next video we will focus on the third step, which is the published message to Amazon event

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page.