card-drop/src/helpers/CardDropHelper.ts

import { CardRarity } from "../constants/CardRarity";
import Card from "../database/entities/card/Card";

export default class CardDropHelper {
    public static async GetRandomCard(): Promise<Card> {
        const randomRarity = Math.random() * 100;

        let cardRarity: CardRarity;

        const bronzeChance = 62;
        const silverChance = bronzeChance + 31;
        const goldChance = silverChance + 6.4;

        if (randomRarity < bronzeChance) cardRarity = CardRarity.Bronze;
        else if (randomRarity < silverChance) cardRarity = CardRarity.Silver;
        else if (randomRarity < goldChance) cardRarity = CardRarity.Gold;
        else cardRarity = CardRarity.Legendary;

        const randomCard = await this.GetRandomCardByRarity(cardRarity);

        return randomCard;
    }

    public static async GetRandomCardByRarity(rarity: CardRarity): Promise<Card> {
        const allCards = await Card.FetchAllByRarity(rarity, [ "Series" ]);

        const randomCardIndex = Math.floor(Math.random() * allCards.length);

        const card = allCards[randomCardIndex];

        return card;
    }
}