# 8. Contract Lottery | Raffle

### One Liner Dependencies Installation

```sh
yarn add --dev @nomiclabs/hardhat-ethers@npm:hardhat-deploy-ethers ethers @nomiclabs/hardhat-etherscan @nomiclabs/hardhat-waffle chai ethereum-waffle hardhat hardhat-contract-sizer hardhat-deploy hardhat-gas-reporter prettier prettier-plugin-solidity solhint solidity-coverage dotenv
```

***

### Contract Details

* Raffle
* Enter the lottery (paying some amount)
* Pick a random winner (verifiably random)
* Winner to be selected every X minutes -> completely automate
* Chainlink Oracle -> Randomness, Automated Execution (Chainlink Keepers)

***

### Events

* Whenever we update a dynamic array or mapping, we should emit an event
* Stored in the logging data structure of the EVM
* Whenever we emit an event, there are two types of parameters
  * **indexed** parameters / **topics**
    * We can have upto **3** of these
    * These are seachable
  * **unindexed** parameters
    * Decoded via their ABIs
    * Costs less gas

***

### Hardhat Shorthand

* Npm package that is installed globally as package `hh`
* Supports shell autocomplete
* `yarn global add shorthand`

***

### Hardhat special testing/debugging methods

<https://hardhat.org/hardhat-network/docs/reference#special-testing/debugging-methods>

#### `evm_increaseTime`

Allows us to increase time of the blockchain

#### `evm_mine`

Allows us to mine(create) new blocks

***

### Final Files

<https://github.com/PatrickAlphaC/hardhat-smartcontract-lottery-fcc>

***


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