import BN from "bn.js";
import { BatchExchangeInstance } from "../types/truffle-typings";

export interface TokenInfo {
  id: number;
  address: string;
  symbol?: string;
  decimals?: number;
}

const MAXU32 = new BN(2).pow(new BN(32)).sub(new BN(1));

/**
 * Used to recover relevant {@link TokenInfo | TokenInfo} by ID from the exchange such as number of decimals or name.
 * @param exchange - An instance of deployed Batch Exchange Contract
 * @param tokenIds - An array of token ids as listed on the Batch Exchange.
 * @param artifacts - A context-like object providing a gateway to Truffle contract ABIs.
 * @returns A mapping of TokenInfo objects fetched from the exchange.
 *   Note that nullish TokenInfo objects are returned in places where the requested token ID failed to fetch.
 */
export async function fetchTokenInfoFromExchange(
  exchange: BatchExchangeInstance,
  tokenIds: number[],
  artifacts: Truffle.Artifacts,
): Promise<Map<number, TokenInfo>> {
  const ERC20 = artifacts.require("ERC20Detailed");
  // Fetching token data from EVM
  const tokenObjects: Map<number, TokenInfo> = new Map();
  await Promise.all(
    tokenIds.map(async (id) => {
      const tokenAddress = await exchange.tokenIdToAddressMap(id);
      let tokenInfo;
      try {
        const tokenInstance = await ERC20.at(tokenAddress);
        const [symbol, decimals] = await Promise.all([
          tokenInstance.symbol(),
          tokenInstance.decimals(),
        ]);
        tokenInfo = {
          id: id,
          symbol: symbol,
          decimals: decimals.toNumber(),
          address: tokenAddress,
        };
      } catch (err) {
        // This generic try-catch is essentially a TokenNotFoundError
        // Could occur when the given ID slot is not occupied by a registered token on the exhchange
        // or if the code registered at address occupied by a token slot is not that of and ERC20 token
        tokenInfo = {
          id: id,
          address: tokenAddress,
        };
      }
      tokenObjects.set(id, tokenInfo);
    }),
  );
  return tokenObjects;
}

/**
 * A handy function providing fee token liquidity by placing orders selling the fee token
 * at the specified provision price for each specified token.
 * @param exchange - BatchExchange Smart Contract
 * @param tokenIds - An array of token indices as represented on the exchange
 * @param provisionPrice - Price at which liquidity is to be provided
 * @param sellAmountOwl - Amount of feeToken to be sold
 * @param artifacts - A context-like object providing a gateway to Truffle contract ABIs.
 * @returns Void Promise
 */
export async function placeFeeTokenLiquidityOrders(
  exchange: BatchExchangeInstance,
  tokenIds: number[],
  provisionPrice: BN,
  sellAmountOwl: BN,
  artifacts: Truffle.Artifacts,
): Promise<number[]> {
  const minBuyAmounts = [];
  const validTokenIds: number[] = [];
  const feeToken = await fetchTokenInfoFromExchange(exchange, [0], artifacts);
  // This is expected to always be OWL which has 18 digits.
  const feeDigits = feeToken.get(0)?.decimals || 18;
  const tokenInfo = await fetchTokenInfoFromExchange(
    exchange,
    tokenIds,
    artifacts,
  );
  for (const tokenId of tokenIds) {
    const numDigits = tokenInfo.get(tokenId)?.decimals;
    if (numDigits) {
      validTokenIds.push(tokenId);
      if (numDigits < feeDigits) {
        minBuyAmounts.push(
          sellAmountOwl
            .mul(provisionPrice)
            .div(new BN(10).pow(new BN(feeDigits - numDigits))),
        );
      } else {
        minBuyAmounts.push(
          sellAmountOwl
            .mul(provisionPrice)
            .mul(new BN(10).pow(new BN(numDigits - feeDigits))),
        );
      }
    }
  }
  const numOrders = validTokenIds.length;
  const batchId = (await exchange.getCurrentBatchId()).toNumber();
  if (numOrders == 0) {
    return [];
  }
  await exchange.placeValidFromOrders(
    validTokenIds, // buyTokens
    Array(numOrders).fill(0), // sellTokens
    Array(numOrders).fill(batchId + 2), // validFroms (all to begin 2 batches from now)
    Array(numOrders).fill(MAXU32), // validTos
    minBuyAmounts, // buyAmounts
    Array(numOrders).fill(sellAmountOwl), // sellAmount
  );

  return validTokenIds;
}