[[ ":$PATH:" != *":$HOME/.bky:"* ]] && export PATH="$PATH:$HOME/.bky"
ln -sf "$HOME/.bky/bky-as-v0.1.0-beta.13" "$HOME/.bky/bky-as"

## Overview

Blocky AS supports more than just performing basic computations. Our WASM
environment provides mechanisms for logging, making HTTP calls, verifying
attestations, and more. This is done by injecting "host" functions into
our WASM runtime. While you can call these directly, it requires adding
build tags and memory management code to your functions. For convenience, we
have released the
[Blocky Web Assembly (BASM) SDK](https://github.com/blocky/basm-go-sdk/tree/main),
which contains wrappers for importing and calling our WASM host functions.
Below we demonstrate how to use BASM to make an HTTP request.

## Make an HTTP Request

1. Clone the Blocky AS
[examples repository](https://github.com/blocky/attestation-service-examples/tree/release/v0.1.0-beta.13)
and navigate to the `shipment_tracking_with_dhl` directory:
git clone --branch main git@github.com:blocky/attestation-service-examples.git
cd attestation-service-examples/shipment_tracking_with_dhl
2. Start by looking at the main WASM function in
[main.go](https://github.com/blocky/attestation-service-examples/tree/release/v0.1.0-beta.13/shipment_tracking_with_dhl/main.go).
There are four actions taken by our DHL tracking function. First, we use the
BASM SDK to read non-sensitive input (i.e., the tracking number) from the host
Blocky AS server. Next we read in our secret input (i.e., the API key). Then we
use these inputs to make our API call. Finally, we write the response data back
to the host Blocky AS server.

3. Now let's look at the function that makes the API call.
We construct and make an HTTP request with the BASM SDK. We only need to
construct the HTTP request, while BASM handles importing the HTTP host
function and writing our request to the Blocky AS server's host memory.
Similarly, BASM reads and returns the result of the call from the host to us.

4. Lastly, we use BASM to write our output back to the host Blocky AS server,
where it then gets bundled into an attestation and returned to the client.

5. Let's try running the example. The DHL API provides a
[Demo key](https://developer.dhl.com/api-reference/shipment-tracking?language_content_entity=en#get-started/) that returns
mock responses. Compile and invoke `trackingFunc` with the Demo key:
mkdir -p ./tmp
bky-c build . ./tmp/x.wasm
jq '.secret.api_key = "demo-key"' fn-call.json | bky-as attest-fn-call > out.json
6. Verify the Blocky AS attestations and extract the function claims:
jq '{
enclave_attested_application_public_key: .enclave_attested_application_public_key.enclave_attestation,
transitive_attested_function_call: .transitive_attested_function_call.transitive_attestation
}' out.json | bky-as verify-fn-call > verified.json
jq -r ".transitive_attested_function_call.claims" verified.json
7. Verify that the claim values match the function and inputs we specified
in our call:
openssl dgst -sha3-512 ./tmp/x.wasm
jq -rcj '.input' fn-call.json | openssl dgst -sha3-512
jq '.secret.api_key = "demo-key"' fn-call.json 
| jq -rcj '.secret' 
| openssl dgst -sha3-512
8. Finally, extract and decode our output:
jq -r ".transitive_attested_function_call.claims.output | @base64d | fromjson" verified.json


## Next Steps

You can now make HTTP requests from your WASM functions on Blocky AS.
Check out our
[examples repository](https://github.com/blocky/attestation-service-examples/tree/release/v0.1.0-beta.13)
for more HTTP request examples, or read on to learn about bringing your function
output [on-chain](/attestation-service/how-tos/on-chain).

rm -rf attestation-service-examples