Making HTTP Requests

In this recipe we will create a slashcommand that runs a GET HTTP based on arguments you provide. We will use the App.RocketChat.Tester as the base project for it. All the code for this recipe is in the branch recipes/http-requests.
You can see the complete documentation on HTTP requests in Rocket.Chat Apps at IHttp's docs page.
Moving parts
You'll need to have handy:
A Rocket.Chat server to deploy the app to
Our Tester App or a newly created app (your choice)
Create the slashcommand
Our command will be called get, so when we call it from the chat, we just have to type /get <url>.
First, let's create a slashcommand directory at the root of the project and add a file named HTTPRequestCommand.ts. Then add the following code:
HTTPRequestCommand.ts
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import {
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    IHttp,
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    IModify,
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    IRead,
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} from '@rocket.chat/apps-engine/definition/accessors';
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import {
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    ISlashCommand,
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    SlashCommandContext,
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} from '@rocket.chat/apps-engine/definition/slashcommands';
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​
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export class HTTPRequestCommand implements ISlashCommand {
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    public command = 'get'; // [1]
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    public i18nParamsExample = '';
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    public i18nDescription = '';
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    public providesPreview = false;
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​
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    public async executor(context: SlashCommandContext, read: IRead, modify: IModify, http: IHttp): Promise<void> {
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        const [url] = context.getArguments(); // [2]
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​
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        if (!url) { // [3]
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            throw new Error('Error!');
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        }
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​
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        await http.get(url); // [4]
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    }
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}
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What this code tells us:
[1] The command will be called get.
When it gets executed, [2] it gets the argument the user passed after the command and use it as the url
[3] The argument is mandatory
[4] Make the get request with the provided argument
Learn more about HTTP requests in Rocket.Chat Apps at IHttp's docs page.
Optionally, you can store the GET request in a constant to console.log it when the command gets executed.
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const response = await http.get(url);
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console.log("result: " + response.data);
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Register the slashcommand
After getting the slashcommand's code done, we have to register it at the app's main class, at the project's root.
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import { IAppAccessors, IConfigurationExtend, ILogger } from '@rocket.chat/apps-engine/definition/accessors';
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import { App } from '@rocket.chat/apps-engine/definition/App';
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import { IAppInfo } from '@rocket.chat/apps-engine/definition/metadata';
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import { HTTPRequestCommand } from './slashcommands/HTTPRequestCommand'; // [1]
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​
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export class RocketChatTester extends App {
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    constructor(info: IAppInfo, logger: ILogger, accessors: IAppAccessors) {
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        super(info, logger, accessors);
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    }
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​
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    public async extendConfiguration(configuration: IConfigurationExtend) {
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        configuration.slashCommands.provideSlashCommand(new HTTPRequestCommand()); // [2]
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    }
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}
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Here we [1] import our new slashcommand class and then [2] register it in the app's configuration. Now it is available for us.
Deploy to the server
To deploy the app, run:
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rc-apps deploy --url <server_url><server_port> -u <user> -p <pwd>
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Finally: calling the slashcommand
After deploying the app, you can type in any channel /get <some_url> and the app will make a GET request to the provided url.
In this example we will use JSONPlaceholder to get some fake data to test our app:
Enter /get https://jsonplaceholder.typicode.com/todos/1 in a chat
Your Rocket.Chat instance will print out to the console the following:
result: {"userId":1,"id":1,"title":"delectus aut autem","completed":false}
If you don't see the result, enable info logs in your instance at Administration > Logs > Log Level by selecting "1 - Errors and Information".
Bonus: print the request in the chat
Now, instead of console logging data to the instance's log, let's display the output in the chat.
In the HTTPRequestCommand.ts, add the following private method:
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    private async sendMessage(context: SlashCommandContext, modify: IModify, message: string): Promise<void> {
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        const messageStructure = modify.getCreator().startMessage();
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        const sender = context.getSender(); // [1]
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        const room = context.getRoom(); // [2]
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​
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        messageStructure
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        .setSender(sender)
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        .setRoom(room)
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        .setText(message); // [3]
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​
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        await modify.getCreator().finish(messageStructure); // [4]
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    }
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This function [1] gets the user who called the command (in this case, yours), [2] selects the room in which the command was run, [3] sets the received string as the message and then [4] sends the message in the room.
To know more about messaging, you can go to the IMessageBuilder docs.
After that, append this code at the end of the executor method:
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    const response = await http.get(url); // [1]
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    const message = JSON.stringify(response.data, null, 2); // [2]
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    await this.sendMessage(context, modify, message); // [3]
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Instead of just making the request and not catching the response data, [1] we store the response in a constant, then [2] format its content as a string to [3] send it using our new sendMessage method.
Save the file and redeploy the app by running:
rc-apps deploy --url <server_url><server_port> -u <user> -p <pwd> --update
Now, when you run the slashcommand /get https://jsonplaceholder.typicode.com/todos/1, you'll receive the response in the chat, as your user, like the following:
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{
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    "userId": 1,
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    "id": 1,
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    "title": "delectus aut autem",
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    "completed": false
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}
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Extending Messages

Storing User Input

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Contents

Moving parts

Create the slashcommand

Deploy to the server

Finally: calling the slashcommand

Bonus: print the request in the chat