Anker Info

Checks if Anker is on sale

Checks are performed each Monday at 08:00. The most recent data is available shortly afterwards.

Polling

Visit https://anker.uzwil-to-tokyo.ch/api/promotion for the newest promotion data. The data is formatted as described here

Webhooks

If you URL is listed in the Webhooks data on https://github.com/noahzarro/anker-data/tree/main, then you receive a POST request every time the new promotions are loaded. It has a payload like described here

Payload

{
    "hasPromotion": true,
    "isHalfPrice": true,
    "promotionString": "50% ab jetzt", // (string or null)
    "checkedAt": 1234235654, // seconds since epoch
    "signedData": "srtzw.dhrert.sfgrth" // a jwt as explained in chapter Signature
}

Signature

The signedData contains a JWT, containing all data in the payload, except for (obviously) the signedData. Like this, the response is still human readable, but also secure from attacks from the adversary. He will attempt to send fake POST requests to the registered webhook clients. To prevent replay attacks, the receiver must check check that the checkedAt time stamp is strictly larger than the one of the last received webhook request.

The signature is calculated using the ES512 algorithm. It can easily be checked with a JWT library. An example is provided below:

pip install pyjwt[crypto]

public_key_pem = """
-----BEGIN PUBLIC KEY-----
MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBDLErTusEhI/Dbxw7HwRjugx5A1sg
13CKQXCpdOfPbfN3YyF1sSOlXdeztU6LHVnx+xNVVLKPKbei370laJpxq3EAHEqX
guTVasOeTvBnqMugZUH+SLDx0ZgraMjFE75kNQAHRZvA8inPoDPXJZ30onuYupkO
7gnhEQEkU6qsAvhBiFE=
-----END PUBLIC KEY-----
"""

with open("timestamp.json", "r") as file:
    last_timestamp = json.load(file)["timestamp"]

decoded_data = jwt.decode(signed_data, public_key_pem, algorithms=["ES512"])

if(decoded_data["checkedAt"] > last_timestamp):
    print("payload is valid")
    print(decoded_data)
    with open("timestamp.json", "w") as file:
        json.dump({"timestamp": decoded_data["checkedAt"]}, file)

This code will throw a jwt.exceptions.InvalidSignatureError if the signature is incorrect. The same public key is used as in the example

TODO:

Add Reviews Request: https://www.coop.ch/rest/v2/coopathome/products/3458809/reviews?currentPage=0&pageSize=20&sort=most_helpful&language=en

Deployment

Note to myself: Start Docker Desktop to start the docker container that is also used by WSL Build and publish the docker container like this

docker build -t noahzarro/anker-api:v3 .
docker push noahzarro/anker-api:v3

Create new Container in Portainer and select correct docker image (noahzarro/anker-api:v3) and add a name (anker-api). Create the container and then add it to the npm network. Then add forwarding rule to the reverse proxy manager (anker.uzwil-to-tokyo.ch -> anker-api:5000) only for http. Then add a let's encrypt certificate and save.