https://github.com/carmhack/solidity-lottery-dapp
https://github.com/carmhack/solidity-lottery-dapp
Last synced: 12 months ago
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- Host: GitHub
- URL: https://github.com/carmhack/solidity-lottery-dapp
- Owner: carmhack
- Created: 2022-06-14T08:55:48.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2022-06-20T12:41:13.000Z (over 3 years ago)
- Last Synced: 2025-01-12T19:14:15.495Z (about 1 year ago)
- Language: JavaScript
- Size: 1.09 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Lottery Game
This repo contains an example project of a **lottery dApp**. The project was developed for Cadena's Ethereum 101 course and is for educational purposes only.
#### Frontend Stack
- React
- Milligram CSS
- ethers.js
#### Backend Stack
- Solidity
- hardhat
## Smart contract
The smart contract store different data
```js
uint256 private currentId;
mapping(uint256 => Game) private games;
mapping(uint256 => mapping(address => bool)) private uniquePlayers;
address private owner;
```
- **currentId**: id of the latest created games
- **games**: list of all games (ref. to Game struct, below)
- **uniquePlayers**: address list of unique player for a single game
- **owner**: address of the owner
There is one struct called **Game** that describe a single lottery data.
```js
struct Game {
uint256 id;
address[] players;
uint256 price;
uint256 total;
address winner;
bool hasWinner;
uint256 endDate;
}
```
#### Create Game
```js
function createGame(uint256 _price, uint256 _seconds) payable public onlyOwner {
require(_price > 0, "Ticket price must be greater than zero");
require(_seconds > 0, "Game time must be greater than zero");
Game memory newGame = Game({
id: currentId,
players: new address[](0),
total: 0,
price: _price,
winner: address(0),
hasWinner: false,
endDate: block.timestamp + _seconds * 1 seconds
});
games[currentId] = newGame;
currentId++;
}
```
The function receives the ticket price and duration (in seconds) as input and creates the new game. Function is marked as `payable` and has the modifier `onlyOwner`.
#### Take Part
```js
function takePart(uint256 _gameId) public payable {
Game storage game = games[_gameId];
require(block.timestamp < game.endDate, "Game is already complete");
require(game.price == msg.value, "Value must be equal to ticket price");
game.players.push(msg.sender);
game.total += msg.value;
bool alreadyTakePart = uniquePlayers[_gameId][msg.sender];
// Player can only take part 1 time
if (alreadyTakePart == false) {
uniquePlayers[_gameId][msg.sender] = true;
}
}
```
The function receives the id of the game you want to participate in. Check that the game has not already finished and that the `msg.value` is equal to the ticket price. If this is the first time the address has participated, it is set to `true` in the `uniquePlayers` structure. Function is marked as `payable`.
#### Pick Winner
```js
function pickWinner(uint256 _gameId) public onlyOwner {
Game storage game = games[_gameId];
require(block.timestamp < game.endDate, "Game is already complete");
require(!game.hasWinner, "Game has already a winner");
if (game.players.length == 1) {
require(game.players[0] != address(0), "There are no players in this game");
game.winner = game.players[0];
game.hasWinner = true;
(bool success, ) = game.winner.call{value: game.total}("");
require(success, "Transfer failed");
} else {
uint256 winner = random(game.players) % game.players.length;
game.winner = game.players[winner];
game.hasWinner = true;
(bool success, ) = game.winner.call{value: game.total }("");
require(success, "Transfer failed");
}
}
```
The function receives the id of the game whose winner you want to choose. If there was only one participant, the lottery `total` is turned over to his address. If there are more than 1 participants, a winner is chosen randomly. Function has the modifier `onlyOwner`.
#### About randomness
The generated number is pseudo-random and, in a real context, it should be done using an oracle (e.g. chainlink VRF).