VRF Consumer

Consumer smart contract that utilizes VRF functionality from Orakl Network.

Internally, the scripts access following smart contracts:

Baobab

• Prepayment (0x8d3A1663d10eEb0bC9C9e537e1BBeA69383194e7)
• VRFCoordinator (0xDA8c0A00A372503aa6EC80f9b29Cc97C454bE499)

Cypress

• Prepayment (0xc2C88492Cf7e5240C3EB49353539E75336960600)
• VRFCoordinator (0x3F247f70DC083A2907B8E76635986fd09AA80EFb)

If you want to access different deployments of Prepayment or VRFCoordinator, you can change it inside hardhat.config.ts in namedAccounts property.

Prerequisites

Create a copy of .env.example file and fill in values for PROVIDER, and MNEMONIC or PRIV_KEY (the difference is explained below) environment variables. These variables will be used for connection to JSON-RPC endpoint, deployment and use of your VRFConsumer smart contract.

cp .env.example .env

PROVIDER can be set to any JSON-RPC endpoint. The list of free available JSON-RPC endpoint can be found in official Klaytn documentation.

This repository supports connection to wallet either through mnemonic or private key.

Mnemonic

MNEMONIC can be generated using npm mnemonics package.

npx mnemonics

After mnemonic is generated, you need to convert it to public address and fund it with KLAY. If you do not have any KLAY in your account, you cannot deploy smart contracts or make any transactions.

You can convert your newly generated mnemonic with following hardhat task. Please replace the [MENONIC] with your mnemonic.

npx hardhat address --mnemonic [MNEMONIC]

The script will print out a public address corresponding to your mnemonic. Then, you can use this address to receive free KLAY using Baobab's faucet.

Private key

If you already have a wallet, you can reuse its private key, and connect to JSON-RPC endpoint with it. In case you use Metamask, read how to export an account's private key.. After you extract private key, store it in PRIV_KEY variable inside of .env file.

Installation

yarn install

Compilation

yarn compile

Deploy

npx hardhat deploy --network baobab

Get Estimated Service Fee

Prior to creating an account, you have the option to retrieve the estimated service fee for a single VRF request. To do this, you can run the provided script using the following command:

npx hardhat run scripts/get-estimated-service-fee.ts --network baobab

Executing the script will provide you with the cost associated with a single VRF request. This information will help you determine the amount you need to fund your account accordingly to meet your specific requirements.

Create and fund account

There are two types of payments supported by Orakle Network VRF: Prepayment and Direct Payment.

Prepayment requires user to create account and fund it with KLAY before being able to use it. The script below will create a new account and deposit 2.5 KLAY from address corresponding to your mnemonic or private key from .env file.

If you prefer to use Orakl Network VRF without having a long-lasting account, you can use Direct Payment method. In such case, you can skip the following command and go directly to Request VRF with Direct Payment.

npx hardhat run scripts/create-and-fund-account.ts --network baobab

After successfully executing the command above, set the value of environment variable ACC_ID inside of .env file to account ID that was generated using the script above. If you do not do it, the request for VRF using Prepayment won't be working properly. After setting the ACC_ID in .env file, you can move to the next step Request VRF with Prepayment.

If you'd like to use your existing prepayment account, set your account id in the .env file and add your deployed consumer to your account by executing the hardhat addConsumer task (described in more detail below). Note that providing account-id parameter is optional if your account id is already in the .env file and consumer parameter is also optional if you've deployed your consumer using hardhat under this repository.

Request & Read VRF

Before running following scripts, one must deploy VRFConsumer smart contract. To deploy VRFConsumer, run npx hardhat deploy --network baobab.

Request VRF with Prepayment

npx hardhat run scripts/request-vrf.ts --network baobab

Request VRF with Direct Payment

npx hardhat run scripts/request-vrf-direct.ts --network baobab

Read VRF response

npx hardhat run scripts/read-vrf.ts --network baobab

Hardhat tasks

The following tasks allow for more finer control over experimentation with the example code in this repository.

Create a new account

npx hardhat createAccount --network baobab

Deposit to an account

After you have created an account, you can deposit $KLAY to it anytime using the command below.

npx hardhat deposit \
    --account-id $ACCOUNT \
    --amount $AMOUNT \
    --network $NETWORK

Withdraw from an account

To withdraw the remaining balance from an account, you can use the command below.

npx hardhat withdraw \
    --account-id $ACCOUNT \
    --amount $AMOUNT \
    --network $NETWORK

Add a consumer

Add consumer contract to account. Then, the consumer contract will be able to request for VRF service.

npx hardhat addConsumer \
    --consumer $CONSUMERADDRESS \
    --account-id $ACCOUNT \
    --network $NETWORK

Remove a consumer

Remove a consumer contract from an account. Then, the consumer contract will not be able to request for VRF service anymore.

npx hardhat removeConsumer \
    --consumer ${CONSUMERADDRESS} \
    --account-id ${ACCOUNT} \
    --network ${NETWORK}