import { BigNumber, constants } from "ethers";

import { CoinTransferMap, TokenIndexedCoinTransferMap } from "./free-balance";

const { Zero } = constants;

// makes all values that are decremental incremental. Example:
// fb.sub(balanceDecrement) === fb.add(flib(balanceDecrement))
export function flipTokenIndexedBalances(
  tokenIndexedBalances: TokenIndexedCoinTransferMap,
): TokenIndexedCoinTransferMap {
  return Object.entries(tokenIndexedBalances).reduce(
    (returnValueAccumulator, [tokenAddress, balances]) => ({
      ...returnValueAccumulator,
      [tokenAddress]: flip(balances),
    }),
    {},
  );
}

/**
 * Returns a mapping with all values negated
 */
export function flip(coinTransferMap: CoinTransferMap): CoinTransferMap {
  return Object.entries(coinTransferMap).reduce(
    (returnValueAccumulator, [to, amount]) => ({
      ...returnValueAccumulator,
      [to]: Zero.sub(amount),
    }),
    {},
  );
}

/**
 * Returns the first base mapping, but incremented by values specified in the
 * second increment. Passing increments whose keys are not present in the base
 * sets them to the increment. Keys in the base mapping which are not explicitly
 * incremented are returned unchanged.
 */
export function merge(base: { [s: string]: BigNumber }, increments: CoinTransferMap) {
  const ret = {} as { [s: string]: BigNumber };

  const s1 = new Set(Object.keys(base));
  const s2 = new Set(Object.keys(increments));

  for (const key of new Set([...s1, ...s2])) {
    ret[key] = (base[key] || Zero).add(increments[key] || Zero);
  }
  return ret;
}