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Now we're going to write the code for our rest API endpoints also call these routes we are going to

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do this inside the app store.

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Jay S-5 said that's in start AWOS STK with save flag will also install some utility modules like moment

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underscore and you ID will need this more use for some operations.

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And then we reference the ADA vs SDK and instantiate an object of dynamically read document client class

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as usual

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the Express router has various methods available like get post patch delete that we can use to process

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incoming UDP requests with the same name like SCDP.

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Get to the post patch delayed and so on.

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So for a moment let's think about what API requests are no taking and are is likely to make on behalf

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of its users

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we might need a way for users to create a new node.

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So we would need a Strout to insert a node item and animo the table when users log into the app.

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They should see all the notes that they previously created.

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So we also need to get route to get all the notes created by the user who has logged in a user might

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want to view or edit an existing node.

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So we need to get around to return a single note and then patch route to a date that node or to save

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changes and finally user might also want to remove it if they dont need it anymore.

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So we also need a delete route to delete the selected No.

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So let's go ahead and create these API endpoints.

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All right let's begin with post-draft to add a new note.

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So we're out door post and then we specify the end point.

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You are a let's say slash API slash node and then a function that takes a request response and next

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object's request is an incoming request object response is the object that we send out as SATB response

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and next is a function that can pass control to the next request response processing block.

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If there is any sense this function of ours will return the final response back to the calling application.

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We don't have the makings of the next function here as there is no processing block after this.

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So inside this function we are simply going to populate the parents object required by dynamically put

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item operation and call the put.

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I am using the document client object.

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Let's declare a new variable item to hold item data received from the calling application and this will

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be a rebel in the request dot body object.

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Since this is a post request so request dot and body dot item for example.

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Now we are going to have the Colling application send us only the node title content and category and

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will populate the rest of the attributes ourselves.

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We don't want to give the end user or the application the ability to alter user id attribute.

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This way we allow the users to add notes against their own User ID and prevent them from adding theirs

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with the user IDs of other users.

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This is not a foolproof access control though and will fix it with fine grained access control later

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when we implement Federated access server inside the item variable.

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We now have data for our title content and get Taggerty let's populate the remaining variables as well.

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I'm going to hard code the user id as test underscore user and user name as Test User

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later on when we implement user authentication in our app will pause the actual data here.

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Then to populate node ID I'm going to use the UI you are the module Lysa.

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This will generate random you you are.

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They are universally unique identifier.

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In other words this will generate a fairly unique random string every time so it will always have a

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new note for every new note that we create.

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I'm also going to prefix this random string with the user id like user id concatenated with the union

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ID and separated by a colon character.

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I'm doing this so when we query the items from the secondary index and the secondary indexes on their

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ID attribute in this case.

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So when we query the items from the secondary index we should have a way to identify the user from the

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next key and this is going to allow us to set up fine grained access control on this secondary index

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and will do this later when we set up the Federated access using cognito time Stan Williams moment dog

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you're next as usual

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and for the expires attribute I'm going to use that time stamp 90 days in the future just as an example.

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Then we simply call the put method to insert the item into the dining table table the table name is

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TV.

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Note that we are recreated and I'm going to declare it as a constant.

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We can reuse it across all our route definitions.

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If there is an error we console on the error object and return back the responses when the corresponding

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status code and message

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else really.

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UDP 200 to denote a successful operation

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and that's it.

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Let's test this out using postman.

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I'm going to use as GTP post request and our API endpoint as local host column 3000 followed by a slash

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API slash note.

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And in the request by the way RS Jason's ring with item attribute containing title content and category

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just like that

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I'm going to save this

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and then hit send to maybe post request card.

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We see 200 OK response.

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This means the operation was successful and we should see a new item inserted in the alimony.

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And we do.

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Let's create a few more such items by fighting this API call a few more times.

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All right the next round is SATB patch operation to allow users to date existing notes for this we could

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use the same root operation but this time we want the users to tell us the node ID and the time stamp

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of the original node that they wish to update timestep will allow us to locate their existing node using

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the combination of user ID and time span as the primary key.

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And then we can replace it with the new data.

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We do not want to change the node ID this time so we asked the end users to parse the original node

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ID as well in the rest.

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So I'm simply going to copy all the code from the previous route and it just it slightly

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we get the item from request body then populate the user id username and the expires attribute just

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as we did the previous route.

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I'm going to remove the code that populates node ID and times that as now we are going to receive it

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from the end user.

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And then we simply call the document client port operation.

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At this time we need to perform a conditional write operation.

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We should first check if the item with the given sarky exists and updated only if it does exist.

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We do not want to create a new item if the users sensing a wrong time stamp.

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So it's a good idea to check if the if the time stamp exists or not.

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So I'm going to use the conditional expression hash t equal to Colon T.

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And then define these variables using expression attribute names an expression attribute ralliers

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the time stamp value will be available in the item variable.

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And rest of the page should remain the same just like the previous book operation.

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Let's test this out.

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I'm going to create a patsy request like so.

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And then let's copy the times tab and note Id from an existing item from our Dynamo the table

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changed the title and current and slightly saved this

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and send the request

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and it returned 200.

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OK.

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And if we look at the dynamo D-B console we do see that the change is reflecting here as well.

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Now let's see what happens if we pass and non-existent time stamp.

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So let's change the time stamp here and find another regressed and we see 400 bad request with an error

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message saying conditional request failed.

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So we can only update existing items.

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Awesome.

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Let's continue building the API in the next media.