# Use Solidity Development Tools

A DApp or Web3 game developer can also interact with the Adapter contract directly. While you can do this in many ways, such as via [Remix](https://remix.ethereum.org/), [Etherscan](https://etherscan.io/address/0xbd57b868bb3374faa88722d2ee7ba3023c744e05), or programmatically, we recommend using [Cast ](https://book.getfoundry.sh/cast/)from the [Foundry](https://github.com/foundry-rs/foundry) framework.

### Prerequisites 

* Smart Contract development experience in Solidity 
* Experience with [Foundry](https://github.com/foundry-rs/foundry) Solidity development toolkit

### Installation

* Install [Foundry](https://book.getfoundry.sh/getting-started/installation)

### Steps

The instructions below outline the steps a user needs to take in order to request randomness from ARPA Randcast.

***

#### Export your Environment Variables

You can export several environment variables to streamline the execution of the subsequent commands. 

Note: the adapter contract address for the chain you are using can be found on the [Supported Networks & Parameters](https://docs.arpanetwork.io/randcast/supported-networks-and-parameters).

```bash
export ADAPTER_CONTRACT=0xbd57b868bb3374faa88722d2ee7ba3023c744e05 # mainnet adapter contract
export RPC_URL= # Mainnet Alchemy / Infura RPC URL Here
export USER_PUBLIC_KEY= # Eth User You are using to deploy consumer / user contract
export USER_PRIVATE_KEY= # Corresponding Private Key
```

***

#### Create a Subscription

In this step, a subscription is created on the ADAPTER\_CONTRACT using the `createSubscription` method. Save this subscription ID as it will be used later on. The `cast send` command broadcasts a transaction to the Ethereum network.

*(Reference:* [*cast send*](https://book.getfoundry.sh/reference/cast/cast-send)*)*

```bash
cast block-number --rpc-url $RPC_URL # This will be useful for step 3
cast send $ADAPTER_CONTRACT "createSubscription()(uint64)" --private-key $USER_PRIVATE_KEY --rpc-url $RPC_URL  # returns subid
```

***

#### Gather Subscription Details

The subscription id can be retrieved from the contract event logs for subsequent steps.

You can provide the block number from Step 2 to speed up the event search.

*(Reference:* [*cast logs*](https://book.getfoundry.sh/reference/cast/cast-logs)*)*

```bash
cast logs --from-block 174270 --to-block latest 'SubscriptionCreated(uint64 indexed subId, address indexed owner)' "" $USER_PUBLIC_KEY --address $ADAPTER_CONTRACT --rpc-url $RPC_URL

#   topics: [ . # Sample response topics
#       0x464722b4166576d3dcbba877b999bc35cf911f4eaf434b7eba68fa113951d0bf # event sig
#       0x0000000000000000000000000000000000000000000000000000000000000001 # subId
#       0x00000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8 # user public key
#   ]
export SUB_ID= # export subid for your newly created subscription
```

***

#### Fund the Subscription

Next, fund your subscription with Ethereum. These funds will be used to pay for your subsequent randomness requests. 

Note: Recommended eth amounts:

* OP Goerli / Mainnet: 0.01 ETH
* Sepolia: 0.1 ETH

If needed, you can use the [Randcast CLI dryrun](https://docs.arpanetwork.io/randcast/use-randcast-cli#estimate-gas-cost-for-the-fulfillment-of-the-first-request) to estimate how much ETH each randomness request will cost. 

```bash
cast send $ADAPTER_CONTRACT "fundSubscription(uint64)" $SUB_ID --value 1ether --private-key $USER_PRIVATE_KEY --rpc-url $RPC_URL
```

***

#### Deploy the Consumer Contract

The user needs to deploy a contract that will consume the randomness provided by Randcast. "forge create" is used to compile and deploy the contract.

*(Reference:* [*forge create*](https://book.getfoundry.sh/forge/deploying)*)*

```bash
git clone https://github.com/ARPA-Network/Randcast-User-Contract
cd Randcast-User-Contract
forge create --rpc-url $RPC_URL --private-key $USER_PRIVATE_KEY contracts/user/examples/GetRandomNumberExample.sol:GetRandomNumberExample --constructor-args $ADAPTER_CONTRACT

export USER_CONTRACT= # export address for your newly deployed user contract
```

***

#### Add Consumer to Adapter

In this step, the created consumer contract is added to the adapter contract and linked to your existing subscription via the adapter's `addConsumer` method.

```bash
cast send $ADAPTER_CONTRACT "addConsumer(uint64, address)" $SUB_ID $USER_CONTRACT --private-key $USER_PRIVATE_KEY --rpc-url $RPC_URL
```

***

#### Request Randomness

We can now request randomness via the user contract with the method `getRandomNumber`.

```bash
cast send $USER_CONTRACT "getRandomNumber()" --private-key $USER_PRIVATE_KEY --rpc-url $RPC_URL
```

***

#### Check the Last Randomness

Finally, retrieve the last random number generated with the `getLastRandomness` method.

```bash
cast call $ADAPTER_CONTRACT "getLastRandomness()(uint256)" --rpc-url $RPC_URL
```

After completing the entire process, you should have a user contract capable of requesting randomness from the Randcast adapter contract.