lotto.ts

import crypto from 'crypto';
import fs from 'fs';
import path from 'path';

const startingPrize = 30000;
const prizes = [0.7, 0.15, 0.1, 0.05];
const price = 2;

const ranHex = (length: number) => {
  return crypto
    .randomBytes(Math.ceil(length / 2))
    .toString('hex')
    .slice(0, length);
};

const genRand = (max: number) => {
  const hex = ranHex(64);
  return parseInt('0x' + hex.substr(0, 8)) % max;
};

const tryRand = (n: number, max: number, maxPowerBall: number) => {
  const hex = ranHex(64);

  const result: number[] = [(parseInt(`0x` + hex.substr(0, 8)) % max) + 1];
  let i = 1;
  while (result.length < n && i < hex.length - 8) {
    const a = (parseInt(`0x` + hex.substr(i++, 8)) % max) + 1;
    if (!result.includes(a)) {
      result.push(a);
    }
  }

  result.push(parseInt('0x' + hex.substr(n + 1, 8)) % maxPowerBall + 1);

  return result;
};

const rand = (n: number, max: number, maxPowerBall: number) => {
  let r: number[] = [];
  do {
    r = tryRand(n, max, maxPowerBall);
  } while (r.length < n + 1);

  return r;
};

const match = (win: number[], ticket: number[]) => {
  let count = 0;

  const normalWinGroup = win.slice(0, win.length - 1);
  const normalTicketGroup = ticket.slice(0, ticket.length - 1);

  normalWinGroup.forEach((t) => {
    if (normalTicketGroup.includes(t)) {
      count++;
    }
  });

  if (count < 2) {
    return 0
  }

  if (
    count === win.length - 1 &&
    win[win.length - 1] === ticket[ticket.length - 1]
  ) {
    return count + 1;
  }

  return count;
};

const round = (
  n: number,
  range: number,
  powerBallMax: number,
  ticketBought: number,
) => {
  let winCount = prizes.map(_ => 0);
  const winningNumbers = rand(n, range, powerBallMax);
  console.log('Winning numbers', winningNumbers);
  for (let index = 0; index < ticketBought; index++) {
    const ticket = rand(n, range, powerBallMax);
    const matchCount = match(winningNumbers, ticket);
    if (matchCount) {
      if (matchCount === n + 1) {
        winCount[0] += 1
      } else {
        winCount[n + 1 - matchCount] += 1;
      }
    }
  }

  return [winCount, winningNumbers];
};

const main = async () => {
  const n = 4;
  const max = 50;
  const observeRound = 100;
  const powerBallMax = 24;
  const estTicketBought = 1e6

  const file = fs.createWriteStream(
    path.resolve(process.cwd(), `${Date.now()}-result-${n}-${max}-${observeRound}-pb-${powerBallMax}.tsv`),
    {
      flags: 'w',
    },
  );
  const heading =
    [
      '#',
      'Ticket bought',
      'Jackpot',
      `Winning numbers`,
      'champion',
      'runner-up',
      'third place',
      '4th',
      'x',
    ].join('\t') + '\n';
  file.write(heading);
  let totalPrize = startingPrize;

  for (let roundIndex = 0; roundIndex < observeRound; roundIndex++) {
    console.log('Round', roundIndex);
    const ticketBought = genRand(estTicketBought);
    console.log(ticketBought, 'tickets sold');
    let income = ticketBought * price;
    totalPrize += income;
    const jackpot = totalPrize * prizes[0];
    console.log('Total prize', totalPrize);
    console.log('Jackpot', jackpot, prizes[0]);

    const [winCount, winningNumbers] = round(n, max, powerBallMax, ticketBought);
    console.log(winCount);

    let prizePaid = 0;
    winCount.forEach((count, index) => {
      if (count && index === 0) {
        console.log('BINGO!!!');
      }

      if (count > 0) {
        prizePaid += prizes[index] * totalPrize;
      }
    });

    console.log('Paid', prizePaid);
    if (Math.round(Math.abs(totalPrize - prizePaid)) === 0) {
      // sai so cua js
      totalPrize = startingPrize;
    } else {
      totalPrize -= prizePaid;
    }

    const line =
      [
        roundIndex,
        ticketBought,
        jackpot,
        `(${winningNumbers.join('-')})`,
        winCount[0],
        winCount[1],
        winCount[2],
        winCount[3],
        winCount[0] ? 'BINGO!!!' : '',
      ].join('\t') + '\n';

    file.write(line);
  }

  file.end();
};

main().catch(console.error);