import BigNumber from 'bignumber.js';

export interface UTXO {
  readonly txHash: string; // hex string without 0x prefix
  readonly vOut?: number;
  readonly amount: number; // in sats
  readonly scriptPubKey?: string; // hex string without 0x prefix
  readonly confirmations: number;
  readonly block?: number;
}

/**
 * sortUTXOs compares two UTXOs by amount, then confirmations and then hash.
 *
 * @example
 * sortUTXOs({amount: 1, confirmations: 1}, {amount: 2, confirmations: 0});
 * // -1, representing that the first parameter should be ordered first.
 *
 * @returns a negative value to represent that a should come before b or a
 * positive value to represent that b should come before a.
 */
export const sortUTXOs = (a: UTXO, b: UTXO): number => {
  // Sort greater values first
  if (a.amount !== b.amount) {
    return b.amount - a.amount;
  }
  // Sort older UTXOs first
  if (a.confirmations !== b.confirmations) {
    return a.confirmations - b.confirmations;
  }
  return a.txHash <= b.txHash ? -1 : 1;
};

/**
 * fixValue turns a readable value, e.g. `0.0001` BTC, to the value in the smallest
 * unit, e.g. `10000` sats.
 *
 * @example
 * fixValue(0.0001, 8) = 10000;
 *
 * @param value Value in the readable representation, e.g. `0.0001` BTC.
 * @param decimals The number of decimals to shift by, e.g. 8.
 */
export const fixValue = (value: number, decimals: number) =>
  new BigNumber(value)
    .multipliedBy(new BigNumber(10).exponentiatedBy(decimals))
    .decimalPlaces(0)
    .toNumber();

/**
 * fixUTXO calls {{fixValue}} on the value of the UTXO.
 */
export const fixUTXO = (utxo: UTXO, decimals: number): UTXO => ({
  ...utxo,
  amount: fixValue(utxo.amount, decimals),
});

/**
 * fixUTXOs maps over an array of UTXOs and calls {{fixValue}}.
 */
export const fixUTXOs = (utxos: readonly UTXO[], decimals: number) => {
  return utxos.map(utxo => fixUTXO(utxo, decimals));
};