Lottery

App.js

import React, { Component } from 'react';
import './App.css';
import web3 from './web3.js';
import lottery from './lottery.js';

class App extends Component {
  state = {
    manager : '',
    players : [],
    balance : '',
    value : '',
    message : ''
  };

  async componentDidMount() {
    const manager = await lottery.methods.manager().call();
    const players = await lottery.methods.getPlayers().call();
    const balance = await web3.eth.getBalance(lottery.options.address);

    this.setState({ manager, players, balance });
  }

  onSubmit = async event => {
    event.preventDefault();

    const accounts = await web3.eth.getAccounts();

    this.setState({ message: 'Waiting on transaction success...' });

    await lottery.methods.enter().send({
      from: accounts[0],
      value: web3.utils.toWei(this.state.value, 'ether')
    });

    this.setState({ message: 'You have been placed to the hat!' });
  };

  onClick = async () => {
    const accounts = await web3.eth.getAccounts();

    this.setState({ message: 'Waiting on transaction success...'});

    await lottery.methods.pickwinner().send({
      from: accounts[0]
    });

    this.setState({ message: 'The one has been picked!'})
  }

  render() {
    return (
      <div>
        <h2>Lottery contract</h2>
        <p>This contract is managed by {this.state.manager}.</p>
        <p>There are currently {this.state.players.length} people entered,
        competing to win {web3.utils.fromWei(this.state.balance, 'ether')} ether!</p>

        <hr/>

        <form onSubmit={this.onSubmit}>
          <h4>Want to check our luck here?</h4>
          <div>
            <label>Amount of Ether to put in:   </label>
            <input
              value={this.state.value}
              onChange={event => this.setState({ value: event.target.value })}
            />
          </div>
          <button>Enter</button>
          </form>

          <hr/>

          <h4>Ready to pick a winner?</h4>
          <button onClick={this.onClick}>Pick winner!</button>

          <hr/>

          <h1>{this.state.message}</h1>
      </div>
    );
  }
}

export default App;

lottery.sol

pragma solidity ^0.4.18;

contract Lottery {
  address public manager;
  address[] public players; //creates dynamic array of addresess

  modifier onlyManager() {
    require(msg.sender == manager);
    _;
  }

  function Lottery() public {
    manager = msg.sender;  //msg - global variable used to describe who just sender
  }

  // function het's the rigth to participate in the Lottery
  function participate() public payable {   //payable for sending ether
    require(msg.value >= .01 ether);
    players.push(msg.sender); //push participants to the array
  }

  function random() private view returns (uint) {
    return uint(keccak256(block.difficulty, now, players));   //the same as sha3 it's class of algo and sha3 is particular instance of it
    //block - global var, difficulty number that indictes numbers of block, now - it's time of now, players just players
  }

  function randomWinner() public onlyManager {
    uint index = random() % players.length;
    players[index].transfer(this.balance); // 0xsome hush
    players = new address[](0);
  }

  function getPlayers() public view returns (address[]) {
    return players;
  }

  function balanceOfLotteryIs() public view returns (uint256) {
    return this.balance;
  }

}