import BN from "bn.js";
import Address from "./address";

export interface TransferUrl {
  address: string;
  amount?: string;
  text?: string;
}

/**
 * @param url {string}
 * @return {{address: string, amount?: string, text?: string}}
 * @throws if invalid url
 */
export function parseTransferUrl(url: string): TransferUrl {
  const PREFIX = "ton://transfer/";

  if (!url.startsWith(PREFIX)) {
    throw new Error("must starts with " + PREFIX);
  }

  const arr = url.substring(PREFIX.length).split("?");
  if (arr.length > 2) {
    throw new Error('multiple "?"');
  }

  const address = arr[0];
  if (!Address.isValid(address)) {
    throw new Error("invalid address format " + address);
  }
  const result: TransferUrl = {
    address: address,
  };

  const rest = arr[1];
  if (rest && rest.length) {
    const pairs = rest.split("&").map((s) => s.split("="));

    for (const pair of pairs) {
      if (pair.length !== 2) throw new Error("invalid url pair");
      const key = pair[0];
      const value = pair[1];

      if (key === "amount") {
        if (result.amount) {
          throw new Error("amount already set");
        }
        const bn = new BN(value);
        if (bn.isNeg()) {
          throw new Error("negative amount");
        }
        result.amount = value;
      } else if (key === "text") {
        if (result.text) {
          throw new Error("text already set");
        }
        result.text = decodeURIComponent(value);
      } else {
        throw new Error("unknown url var " + key);
      }
    }
  }
  return result;
}

/**
 * @param address   {string}
 * @param amount?    {string} in nano
 * @param text?   {string}
 * @return {string}
 */
export function formatTransferUrl(
  address: string,
  amount?: string,
  text?: string
) {
  let url = "ton://transfer/" + address;

  const params = [];

  if (amount) {
    params.push("amount=" + amount);
  }
  if (text) {
    params.push("text=" + encodeURIComponent(text));
  }

  if (params.length === 0) return url;

  return url + "?" + params.join("&");
}