Hylian : Price Oracle SCORE

Introduction

Hylian is a generic price oracle on ICON working with a list of price feeds such as Daedric. In the current version, it simply returns a median value of the whitelisted price feeds.

Prerequisites

• T-Bears should be installed
• T-Bears needs to be launched using the configuration file provided in this repository :

tbears start -c ./config/localhost/tbears_server_config.json

• You also need jq. Install it with sudo apt-get install jq

Installation

• Run the install.sh script located in the root folder of the repository;

• It will generate 3 operator wallets :

  • A first one on the Yeouido network in ./config/yeouido/keystores/operator.icx
  • A second one on the Euljiro network in ./config/euljiro/keystores/operator.icx
  • A last one on the Mainnet network in ./config/mainnet/keystores/operator.icx

• Make sure to send some funds to these wallets before deploying a SCORE (20 ICX should be good enough).

• A wallet for localhost development is already pre-generated.

• If you correctly loaded T-bears using the configuration as described in the prerequisites, tbears balance hxba2e54b54b695085f31ff1a9b33868b5aea44e33 should return some balance.

Deploy Hylian SCORE to localhost, testnet or mainnet

• In the root folder of the project, run the following command:

./scripts/score/deploy_score.sh

• It should display the following usage:

> Usage:
 `-> ./scripts/score/deploy_score.sh [options]

> Options:
 -n <network> : Network to use (localhost, yeouido, euljiro or mainnet)
 -t <ticker name> : The name of the medianizer ticker
 -m <minimum> : The minimum amount of price feeds required for the oracle to run

• Fill the -n option corresponding to the network you want to deploy to: localhost, yeouido, euljiro or mainnet.
• Fill the -t option with the name of the ticker, such as ICXUSD. Note that ticker name needs to be the same than the deployed Medianizer SCORE.
• Fille the -m option with the minimum number of price feeds available for the price oracle to work, otherwise it will raise an error.
• Example :

$ ./scripts/score/deploy_score.sh -n localhost -t ICXUSD -m 5

Update an already deployed Hylian to localhost, testnet or mainnet

• If you modified the Hylian SCORE source code, you may need to update it.

• In the root folder of the project, run the following command:

$ ./scripts/score/update_score.sh

• It should display the following usage:

> Usage:
 `-> ./scripts/score/update_score.sh [options]

> Options:
 -n <network> : Network to use (localhost, yeouido, euljiro or mainnet)

• Fill the -n option corresponding to the network where your SCORE is deployed to: localhost, yeouido, euljiro or mainnet.

• Example :

$ ./scripts/score/update_score.sh -n localhost

Whitelist a price feed SCORE (such as Daedric)

• Your Hyalin SCORE needs price feeds in order to work. For doing so, you need to whitelist some price feed SCOREs.

• In the root folder of the project, run the following command:

$ ./scripts/score/add_feed.sh

• It should display the following usage:

> Usage:
 `-> ./scripts/score/add_feed.sh [options]

> Options:
 -n <network> : Network to use (localhost, yeouido, euljiro or mainnet)
 -a <score address> : SCORE address of the new price feed

• Fill the -n option corresponding to the network where your SCORE is deployed to: localhost, yeouido, euljiro or mainnet.
• Fill the -a option with the address of the price feed SCORE you want to whitelist.
• Example :

$ ./scripts/score/add_feed.sh -n localhost -a cx17fea4a9a01970cc730db9100dee9d1727af11a5

Read the price from the oracle

• Once you have enough price feeds subscribed, you may call the oracle with the value method:

$ ./scripts/score/value.sh

• It should display the following usage:

> Usage:
 `-> ./scripts/score/value.sh [options]

> Options:
 -n <network> : Network to use (localhost, yeouido, euljiro or mainnet)

• Fill the -n option corresponding to the network where your SCORE is deployed to: localhost, yeouido, euljiro or mainnet.

• Example :

$ ./scripts/score/value.sh -n localhost

If not enough feeds fulfill the conditions declared in the Hylian SCORE, it will return the following error:

{
    "jsonrpc": "2.0",
    "error": {
        "code": -32032,
        "message": "NotEnoughFeedsAvailable(0)"
    },
    "id": 1
}

Otherwise, it will return the following result containing the price value:

> Command:
$ tbears call <(python ./scripts/score/dynamic_call/value.py localhost)
            -c ./config/localhost/tbears_cli_config.json
> Result:
$ response : {
    "jsonrpc": "2.0",
    "result": "0x8ac7230489e80000",
    "id": 1
}