import BN from "bn.js";
import { assert } from "chai";
import { Fraction } from "./fraction";
const MAX128 = new BN(2).pow(new BN(128)).subn(1);
/**
 * Modifies the price to work with ERC20 units
 * @param price - Amount of buy token in exchange for one sell token
 * @param sellTokenDecimals - Number of decimals of the sell token
 * @param buyTokenDecimals - Number of decimals of the buy token
 * Returns Fraction representing the number of buy tokens in exchange for one unit of sell token
 */
export function getUnitPrice(price, sellTokenDecimals, buyTokenDecimals) {
    assert.isTrue(sellTokenDecimals >= 0, "sell token decimals must be non-negative");
    assert.isTrue(buyTokenDecimals >= 0, "buy token decimals must be non-negative");
    return Fraction.fromNumber(price).mul(new Fraction(new BN(10).pow(new BN(buyTokenDecimals)), new BN(10).pow(new BN(sellTokenDecimals))));
}
/**
 * Computes the amount of output token units from their price and the amount of input token units
 * Note that the price is expressed in terms of tokens, while the amounts are in terms of token units
 * @param price - Amount of buy token in exchange for one sell token
 * @param sellAmount - Amount of sell token units that are exchanged at price
 * @param sellTokenDecimals - Number of decimals of the sell token
 * @param buyTokenDecimals - Number of decimals of the buy token
 * Returns amount of output token units obtained
 */
export function getBuyAmountFromPrice(price, sellAmount, sellTokenDecimals, buyTokenDecimals) {
    const unitPrice = getUnitPrice(price, sellTokenDecimals, buyTokenDecimals);
    const buyAmount = unitPrice.mul(new Fraction(sellAmount, 1));
    return buyAmount.toBN();
}
/**
 * Computes the buy and sell token amounts required for an unlimited order in the exchange
 * @param price - Price of the buyToken relative to one sell token
 * @param sellTokenDecimals - Number of decimals of the sell token
 * @param buyTokenDecimals - Number of decimals of the buy token
 * Returns amounts of sell-buy token for an unlimited order at the input price
 */
export function getUnlimitedOrderAmounts(price, sellTokenDecimals, buyTokenDecimals) {
    let sellAmount = MAX128.clone();
    let buyAmount = getBuyAmountFromPrice(price, sellAmount, sellTokenDecimals, buyTokenDecimals);
    if (buyAmount.gt(sellAmount)) {
        buyAmount = MAX128.clone();
        sellAmount = getBuyAmountFromPrice(1 / price, buyAmount, buyTokenDecimals, sellTokenDecimals);
        assert.isTrue(buyAmount.gte(sellAmount), "Error: unable to create unlimited order");
    }
    return { base: sellAmount, quote: buyAmount };
}
