eth: Add backend methods.

[JoeGruffins]

This issue is meant to track adding functionality to eth swaps. Currently there is a bare bones implementation. Anyone who would like to work on adding a method, please comment here first so work is not duplicated.

As the dex was originally designed with UTXO based coins in mind, some methods may require far reaching changes.

server

• TxData(coinID []byte) ([]byte, error)
• InitTxSize() uint32
• InitTxSizeBase() uint32
• Contract(coinID []byte, redeemScript []byte) (*asset.Contract, error)
• ValidateSecret(secret, contract []byte) bool
• Redemption(redemptionID, contractID []byte) (asset.Coin, error)

- [ ] FundingCoin(ctx context.Context, coinID []byte, redeemScript []byte) (asset.FundingCoin, error)

• ValidateCoinID(coinID []byte) (string, error)
• ValidateContract(contract []byte) error

- [ ] VerifyUnspentCoin(ctx context.Context, coinID []byte)

• run(ctx context.Context) // fix TODOs and refactor
• ValidateSignature(addr string, pubkey, msg, sig []byte) error

client

• Balance() (*asset.Balance, error) // fix TODO
• MaxOrder(lotSize uint64, feeSuggestion uint64, nfo *dex.Asset) (*asset.SwapEstimate, error)
• PreSwap(req *asset.PreSwapForm) (*asset.PreSwap, error)
• PreRedeem(req *asset.PreRedeemForm) (*asset.PreRedeem, error)
• FundOrder(ord *asset.Order) (asset.Coins, []dex.Bytes, error)
• ReturnCoins(unspents asset.Coins) error
• FundingCoins(ids []dex.Bytes) (asset.Coins, error)
• Swap(swaps *asset.Swaps) ([]asset.Receipt, asset.Coin, uint64, error)
• Redeem(form *asset.RedeemForm) ([]dex.Bytes, asset.Coin, uint64, error)
• SignMessage(coin asset.Coin, msg dex.Bytes) (pubkeys, sigs []dex.Bytes, err error)
• AuditContract(coinID, contract, txData dex.Bytes) (*asset.AuditInfo, error)
• LocktimeExpired(contract dex.Bytes) (bool, time.Time, error)
• FindRedemption(ctx context.Context, coinID dex.Bytes) (redemptionCoin, secret dex.Bytes, err error)
• Refund(coinID, contract dex.Bytes) (dex.Bytes, error) // fix TODOs
• PayFee(address string, regFee uint64) (asset.Coin, error)
• Withdraw(addr string, value uint64) (asset.Coin, error) // fix TODOs

- [ ] Confirmations(ctx context.Context, id dex.Bytes) (confs uint32, spent bool, err error)
- [ ] RefundAddress(contract dex.Bytes) (string, error)

• checkForNewBlocks() // Needs logic to check for redemptions.

changelog

2021
08/06 - issue created
09/02 - check server InitTxSize() uint32 and InitTxSizeBase() uint32
10/05 - check client MaxOrder, PreSwap, and PreRedeem
10/18 - check server Contract and client SignMessage, FundingCoins, ReturnCoins, and FundOrder
10/21 - check server ValidateSecret and Redemption
11/05 - check server ValidateCoinID
11/11 - FundingCoin and VerifyUnspentCoin removed from server list
11/24 - check server TxData and ValidateContract
12/02 - check client Swap and Balance, add fix TODOs to Withdrawal, RefundAddress removed by #1312
12/16 - check server run and client Redeem, AuditContract, LocktimeExpired, FindRedemption, and checkForNewBlocks
12/17 - check server Refund and remove Confirmations, it looks like that was divided into SwapConfs and RegFeeConfs and those are done, add ValidateSignature to server

[JoeGruffins]

Will work on the server's TxData(coinID []byte) ([]byte, error)
That's right, this isn't used yet. Because I don't have a great idea of how it will be used atm, I'll go with the next server one InitTxSize() uint32

[JoeGruffins]

Included InitTxSizeBase() uint32 in the same pr as InitTxSize() uint32

Will do Contract(coinID []byte, redeemScript []byte) (*asset.Contract, error) for the server.

[martonp]

I'll work on the client MaxOrder(lotSize uint64, feeSuggestion uint64, nfo *dex.Asset) (*asset.SwapEstimate, error).

[martonp]

I'll do PreSwap(req *asset.PreSwapForm) (*asset.PreSwap, error) next.

[JoeGruffins]

Contract is in the pipeline so moving to server's ValidateSecret(secret, contract []byte) bool

[JoeGruffins]

#1089 will change/add some client methods

[JoeGruffins]

Will do Redemption(redemptionID, contractID []byte) (asset.Coin, error) for the server.

[JoeGruffins]

Also started on FundingCoin(ctx context.Context, coinID []byte, redeemScript []byte) (asset.FundingCoin, error) because Contract, Redemption, and FundingCoin all use the same asset.Coin interface to some extent.

[martonp]

I'll do PreRedeem(req *asset.PreRedeemForm) (*asset.PreRedeem, error) next.

[martonp]

I'll do FundOrder(ord *asset.Order) (asset.Coins, []dex.Bytes, error) next.

[martonp]

Will do Swap(swaps *asset.Swaps) ([]asset.Receipt, asset.Coin, uint64, error) next.

[JoeGruffins]

Will work on server's ValidateCoinID.

[martonp]

Will do Redeem(form *asset.RedeemForm) ([]dex.Bytes, asset.Coin, uint64, error)

[JoeGruffins]

Actually looks like ValidateCoinID was already done, doing ValidateContract

[buck54321]

I'll do TxData

[buck54321]

@JoeGruffins please remove the FundingCoin and VerifyUnspentCoin methods from the server list. We'll have to handle that a bit differently. I'll offer up something in a minute.

[JoeGruffins]

@buck54321 #1243 exists

[buck54321]

@buck54321 #1243 exists

I'm really sorry about that, @JoeGruffins. I should have taken a wider look at this stuff earlier.

[JoeGruffins]

it's fine. I really didn't want to mess with the server as much as possible, but I'm confident your way is better. I was just going to shoehorn it in there.

[buck54321]

Here's what I'm looking at for required communications.

Message	Required	Currently Sending	Recommended Action	Field assignments
Limit / Market	account address	account address, amount, nonce	drop nonce. 1	Trade.Coins = []Coin{[]byte(accountAddr)}
Init	txid, secret hash	txid, secret hash, contract address	drop contract address. 2	txid = CoinID, secretHash = Contract
Redeem	secret (maker) 3	n / a	we'll send the secret	secret = Secret

¹ Leave amount encoded for internal use, but only send address in the actual Message.

² I'm going to propose something different for contract address validation, but if we do want to validate the contract address, it'll need to be done earlier than this anyway, so let's not plan to send it here.

³ We may want to record the redemption transaction IDs too, but it seems less important for eth.

There's also Cancel, but that' straightforward once we get a signature algo figured out.

[JoeGruffins]

I'll look into the server run and what's up with eth reorgs. Not working in this area are you @buck54321 ?

[buck54321]

Go for it, @JoeGruffins.

I'll claim Confirmations -> SwapConfirmations + RegFeeConfirmations

[chappjc]

@buck54321 If you're working on SwapConfirmations, please consider how we can apply the "redeemable" check in that. If ETH's impl. calls (*rpcclient).isRedeemable in addition to the confirmation checks (perhaps just when >0 confs), the return from SwapConfirmations should reflect its findings. Off the top of my head, a couple options are 1) a new return bool, which would likely just be true for utxo assets, 2) force confs to 0 if isRedeemable says no, or 3) if confs are >0 but isRedeemable says no, maybe return an error since that would be the indicator of an exploit attempt.

Background for why call data + confirmations is not sufficient to determine redeemability: #1274 (comment)

[chappjc]

Or, um, I guess isRedeemable can be used in Redeem just before actual broadcasting the secret key.

[martonp]

Regarding the CoinID to send during the Init request, I agree that we don't really need the Index field of the TxCoinID since we are also sending the secretHash in the Contract field, but I think it would be better to maintain a set of ETH coin IDs and actually use those when sending coin IDs. A coin ID should represent a specific amount of ETH, and without the Index field, the TxCoinID doesn't really do this. Even though it's a bit of extraneous information, it's still worth sending the entire coin ID over. Otherwise we'll have a set of coin ids, but the coin id that we are sending in a message doesn't deserialize to any of them, which is kind of confusing.

[martonp]

I'll do AuditContract next.

[martonp]

I'll do Refund next.

[JoeGruffins]

I guess I'll take a whack at the Withdrawal TODOs since they are still there and probably not related to other's work.

[buck54321]

I'm working on (*Driver).Exists (#1332)

[buck54321]

I'll do LocktimeExpired (#1333)

[buck54321]

I'll work on FindRedemption. (#1334)

[JoeGruffins]

I guess I'll do PayFee for completion.

[JoeGruffins]

I guess I'll do the server's ValidateSignature.