http_request_update

[dansteren]

To perform an http request call the canister needs to expose two endpoints: http_request as a query method, and http_request_update as an update method. The http_request method needs to return an upgrade value of Some(true) and all other fields are ignored.

We already have tests for http_request so it is proposed that this canister's http_request method be hardcoded rather than arbitrary.

The generated canister may look like this:

import {
    Canister,
    HttpRequest,
    HttpResponse,
    nat8,
    None,
    Null,
    query,
    Some,
    update
} from 'azle';

const state: number = 0;

export default Canister({
    http_request: query([HttpRequest], HttpResponse(Null), () => {
        return {
            status_code: 204,
            headers: [],
            body: new Uint8Array(),
            streaming_strategy: None,
            upgrade: Some(true)
        };
    }),
    http_request_update: update(
        [HttpRequest],
        HttpResponse(Null),
        (request) => {
            const expectations = {};
            if (request !== expectations) {
                throw new Error('The http request was different than expected');
            }

            return {
                status_code: 201,
                headers: [
                    ['content-type', 'text/plain'],
                    ['content-encoding', 'gzip']
                ],
                body: Uint8Array.from([
                    31, 139, 8, 0, 55, 2, 27, 98, 0, 3, 43, 45, 72, 73, 44, 73,
                    229, 2, 0, 168, 218, 145, 108, 7, 0, 0, 0
                ]),
                streaming_strategy: None,
                upgrade: None
            };
        }
    ),
    get_state: query([], nat8, () => {
        return state;
    })
});

Then we can hit the http_request endpoint with various http requests with different methods, urls, headers, and bodies, and then update can effect state changes...

So we also need a way to get the state changes back out... so we could use http_request and have it return the state... but then we'd have to control how it decides to do a query vs update... I think it's better to just leave http_request alone and instead have a second method for querying state.

So the test will be, when we make an arbitrary http request:

• Does the body request param inside of http_request_update decode correctly?
• Does it return data correctly?
• Does it update the state?

So tests would look like:

• get the state before
• call http_request
• check that the body is good
• verify the returned response
• check the state again

Resources:

• https://internetcomputer.org/docs/current/references/http-gateway-protocol-spec#upgrade-to-update-calls