Chaos Farm implements a client for the Chainlink VRF V2 service and keeps record of the VRF call results along with the account the call results belong to. This allows instances of Chaos Farm to manage a Programmatic Subscription to Chainlink for use by other contracts that need to assign and keep track of VRF results to addresses.
Chaos Farm may be deployed to local EVM development blockchains like Anvil, Hardhat Network or Ganache and testnet/mainnet on networks that are compatible with Chainlink VRF.
Start an Anvil instance in a terminal:
anvil
In a new terminal at the project root, run the demo script:
./script/demo.sh
A simple use case is demonstrated on the Polygon Mumbai Testnet.
Add Polygon Testnet Mumbai: https://mumbai.polygonscan.com/
Set up VRF subscription: https://vrf.chain.link/
Test MATIC; get from faucet here: https://faucet.polygon.technology/
Test LINK; get here: https://faucets.chain.link/mumbai
Send LINK to VRF subscription with the token address here: https://docs.chain.link/resources/link-token-contracts/
Set the following environment variables for contract creation:
# Max price for a request; this hash is for max 500 Gwei on Mumbai Testnet.
GAS_LANE_KEY_HASH=0x4b09e658ed251bcafeebbc69400383d49f344ace09b9576fe248bb02c003fe9f
# Put your unique subscription ID here.
SUBSCRIPTION_ID=1234
# The Coordinator address for Mumbai Testnet.
VRF_COORDINATOR=0x7a1BaC17Ccc5b313516C5E16fb24f7659aA5ebed
# CardExample expects an array even though it only uses the first value.
NUM_WORDS=2
# This is the maximum gas limit; it may be reduced from here. Setting it any higher will cause errors.
CALLBACK_GAS_LIMIT=2500000
# How long Chainlink will wait to respond. Longer wait = more secure.
REQUEST_CONFIRMATIONS=3
GAS_LIMIT=1000000
RPC_URL=https://rpc-mumbai.matic.today
Set the wallet values:
WALLET_ADDRESS=<your-wallet-address-goes-here>
PRIVATE_KEY=<private-key-goes-here>
forge create --constructor-args ${GAS_LANE_KEY_HASH} ${SUBSCRIPTION_ID} ${VRF_COORDINATOR} ${NUM_WORDS} ${CALLBACK_GAS_LIMIT} ${REQUEST_CONFIRMATIONS} --private-key ${PRIVATE_KEY} --rpc-url ${RPC_URL} --gas-limit ${GAS_LIMIT} src/Chaos.sol:Chaos
Save the contract address from the terminal output to the CHAOS_FARM_DEMO environment variable:
CHAOS_FARM_DEMO=0x...
Set the contract address as a Consumer in the VRF Dashboard as well.
We'll use the Card Example as the implementation contract.
Deploy the CardExample contract to Mumbai as well (make sure the CHAOS_FARM_DEMO env var is set to your contract address):
forge create --constructor-args ${CHAOS_FARM_DEMO} --private-key ${PRIVATE_KEY} --rpc-url ${RPC_URL} --gas-limit ${GAS_LIMIT} src/examples/CardExample.sol:CardExample
CARD_EXAMPLE_DEMO=0x...
Set CardExample as the authorized caller on the Chaos Farm deployment:
cast send ${CHAOS_FARM_DEMO} "setAllowedCaller(address)" ${CARD_EXAMPLE_DEMO} --private-key ${PRIVATE_KEY} --rpc-url ${RPC_URL} --gas-limit ${GAS_LIMIT}
cast send ${CARD_EXAMPLE_DEMO} "requestNewCard()(uint)" --private-key ${PRIVATE_KEY} --rpc-url ${RPC_URL} --gas-limit ${GAS_LIMIT}
cast send ${CARD_EXAMPLE_DEMO} "completeNewCard()(uint)" --private-key ${PRIVATE_KEY} --rpc-url ${RPC_URL} --gas-limit ${GAS_LIMIT}
See the card that was drawn:
cast call ${CARD_EXAMPLE_DEMO} "lastCard(address)" ${WALLET_ADDRESS} --rpc-url https://rpc-mumbai.matic.today