Enabling trading

Once our condition is ready, any participant can start trading on the market.

In the MarketMakerRepo.ts file it is defined the function that calls the contract to make trade:

trade = async (tradeAmounts: number[], collateralLimit: number, from: string) => {
  return this.lmsrMarketMaker.trade(tradeAmounts, collateralLimit, { from })
}

The function trade is defined in the MarketMaker contract and it has two parameters:

function trade(int[] memory outcomeTokenAmounts, int collateralLimit) public atStage(Stage.Running) onlyWhitelisted returns (int netCost)

• outcomeTokenAmounts: Amounts of each atomic outcome token to buy or sell. If positive, will buy this amount of outcome token from the market. If negative, will sell this amount back to the market instead.
• collateralLimit: If positive, this is the limit for the amount of collateral tokens which will be sent to the market to conduct the trade. If negative, this is the minimum amount of collateral tokens which will be received from the market for the trade. If zero, there is no limit.

If the function succeeds, the following event will be emitted:

event AMMOutcomeTokenTrade(
  address indexed transactor,
  int[] outcomeTokenAmounts,
  int outcomeTokenNetCost,
  uint marketFees
);

Buying outcome tokens

The function to buy outcome tokens is defined in Market.ts:

const buy = async () => {
  const collateral = await marketMakersRepo.getCollateralToken()
  const formatedAmount = new BigNumber(selectedAmount).multipliedBy(
    new BigNumber(Math.pow(10, collateral.decimals)),
  )

  const outcomeTokenAmounts = Array.from(
    { length: marketInfo.outcomes.length },
    (value: any, index: number) =>
      index === selectedOutcomeToken ? formatedAmount : new BigNumber(0),
  )

  const cost = await marketMakersRepo.calcNetCost(outcomeTokenAmounts)

  const collateralBalance = await collateral.contract.balanceOf(account)
  if (cost.gt(collateralBalance)) {
    await collateral.contract.deposit({ value: formatedAmount.toString(), from: account })
    await collateral.contract.approve(marketInfo.lmsrAddress, formatedAmount.toString(), {
      from: account,
    })
  }

  const tx = await marketMakersRepo.trade(outcomeTokenAmounts, cost, account)
}

Selling outcome tokens

The function to sell outcome tokens is defined in Market.ts:

const sell = async () => {
  const collateral = await marketMakersRepo.getCollateralToken()
  const formatedAmount = new BigNumber(selectedAmount).multipliedBy(
    new BigNumber(Math.pow(10, collateral.decimals)),
  )

  const isApproved = await conditionalTokensRepo.isApprovedForAll(account, marketInfo.lmsrAddress)
  if (!isApproved) {
    await conditionalTokensRepo.setApprovalForAll(marketInfo.lmsrAddress, true, account)
  }

  const outcomeTokenAmounts = Array.from({ length: marketInfo.outcomes.length }, (v, i) =>
    i === selectedOutcomeToken ? formatedAmount.negated() : new BigNumber(0),
  )
  const profit = (await marketMakersRepo.calcNetCost(outcomeTokenAmounts)).neg()

  const tx = await marketMakersRepo.trade(outcomeTokenAmounts, profit, account)
}