gistfile1.txt

I wrote out some solidity as some psuedocode to figure out how to do https://github.com/Synthetixio/synthetix/issues/295

I'll convert this to actual web3 calls instead of solidity once I'm sure I have all the right order of operations.

How does this look?

```solidity
function maximumRewardedArb() public view
    rateNotStale("ETH")
    rateNotStale("SNX")
    notPaused
    returns (uint max_eth_to_convert, uint tokens_bought, uint reward_tokens)
{
    /* Ensure there is enough more sETH than ETH in the Uniswap pool */
    uint seth_in_uniswap = synth.balanceOf(uniswapAddress);
    uint eth_in_uniswap = uniswapAddress.balance;
    require(eth_in_uniswap.divideDecimal(seth_in_uniswap) < uint(divisor-off_peg_min).divideDecimal(divisor), "sETH/ETH ratio is too high");

    /* Get the amount of ETH needed to restore the peg */
    uint max_eth_to_convert = maxConvert(eth_in_uniswap, seth_in_uniswap, divisor, divisor-off_peg_min);

    /* Get the amount of sETH that will be purchased for that max amount of ETH */
    uint tokens_bought = uniswapExchange.getEthToTokenInputPrice(max_eth_to_convert);

    /* Get the amount of SNX that should be rewarded */
    uint snx_rate = exchangeRates.rateForCurrency("SNX");
    uint eth_rate = exchangeRates.rateForCurrency("ETH");
    reward_tokens = eth_rate.multiplyDecimal(tokens_bought).divideDecimal(snx_rate);

    /* Check reward */
    let snx_in_rewarder = synthetix.balance(self);
    if snx_in_rewarder < reward_tokens {
        /* there isn't enough SNX available to pay the full reward. what should we do? Calculate a new tokens_bought based on snx_in_rewarder? */
    }

    (max_eth_to_convert, tokens_bought, reward_tokens)
}
```

While writing this, I noticed a few things:
 * arbSynthRate calls "transfer" without checking the returned value
 * I think arbSynthRate can call "transfer" with too many tokens. If transfer is called with too large of a number, what happens? Does some transfer happen, or does none of it happen?

I think this is better:

function maximumRewardedArb() public view
    rateNotStale("ETH")
    rateNotStale("SNX")
    notPaused
    returns (uint max_eth_to_convert, uint tokens_bought, uint reward_tokens)
{
    /* Ensure there is enough more sETH than ETH in the Uniswap pool */
    uint seth_in_uniswap = synth.balanceOf(uniswapAddress);
    uint eth_in_uniswap = uniswapAddress.balance;
    require(eth_in_uniswap.divideDecimal(seth_in_uniswap) < uint(divisor-off_peg_min).divideDecimal(divisor), "sETH/ETH ratio is too high");

    /* calculate the sETH we have to buy to be rewarded all of the SNX in this contract */
    uint snx_in_rewarder = synthetix.balance(self);
    uint snx_rate = exchangeRates.rateForCurrency("SNX");
    uint eth_rate = exchangeRates.rateForCurrency("ETH");

    uint tokens_to_buy = snx_rate.multiplyDecimal(snx_in_rewarder).divideDecimal(eth_rate);

    /* calculate the ETH we have to send to receive all of the SNX in this contract */
    uint eth_to_convert = uniswapExchange.getEthToTokenOutputPrice(tokens_to_buy);

    /* Get the amount of ETH needed to restore the peg */
    uint eth_to_restore_peg = maxConvert(eth_in_uniswap, seth_in_uniswap, divisor, divisor-off_peg_min);

    /* if buying this much eth would break the peg, reduce eth_to_convert and recalculate */
    if eth_to_convert > eth_to_restore_peg {
        eth_to_convert = eth_to_restore_peg;

        tokens_to_buy = uniswapExchange.getEthToTokenInputPrice(eth_to_convert);
    }

    reward_tokens = eth_rate.multiplyDecimal(tokens_to_buy).divideDecimal(snx_rate);

    (eth_to_convert, tokens_to_buy, reward_tokens)
}