package chanfunding import ( "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/lightningnetwork/lnd/lnwallet/chainfee" ) // CoinSource is an interface that allows a caller to access a source of UTXOs // to use when attempting to fund a new channel. type CoinSource interface { // ListCoins returns all UTXOs from the source that have between // minConfs and maxConfs number of confirmations. ListCoins(minConfs, maxConfs int32) ([]Coin, error) // CoinFromOutPoint attempts to locate details pertaining to a coin // based on its outpoint. If the coin isn't under the control of the // backing CoinSource, then an error should be returned. CoinFromOutPoint(wire.OutPoint) (*Coin, error) } // CoinSelectionLocker is an interface that allows the caller to perform an // operation, which is synchronized with all coin selection attempts. This can // be used when an operation requires that all coin selection operations cease // forward progress. Think of this as an exclusive lock on coin selection // operations. type CoinSelectionLocker interface { // WithCoinSelectLock will execute the passed function closure in a // synchronized manner preventing any coin selection operations from // proceeding while the closure is executing. This can be seen as the // ability to execute a function closure under an exclusive coin // selection lock. WithCoinSelectLock(func() error) error } // OutpointLocker allows a caller to lock/unlock an outpoint. When locked, the // outpoints shouldn't be used for any sort of channel funding of coin // selection. Locked outpoints are not expected to be persisted between // restarts. type OutpointLocker interface { // LockOutpoint locks a target outpoint, rendering it unusable for coin // selection. LockOutpoint(o wire.OutPoint) // UnlockOutpoint unlocks a target outpoint, allowing it to be used for // coin selection once again. UnlockOutpoint(o wire.OutPoint) } // Request is a new request for funding a channel. The items in the struct // governs how the final channel point will be provisioned by the target // Assembler. type Request struct { // LocalAmt is the amount of coins we're placing into the funding // output. LocalAmt btcutil.Amount // RemoteAmt is the amount of coins the remote party is contributing to // the funding output. RemoteAmt btcutil.Amount // MinConfs controls how many confirmations a coin need to be eligible // to be used as an input to the funding transaction. If this value is // set to zero, then zero conf outputs may be spent. MinConfs int32 // SubtractFees should be set if we intend to spend exactly LocalAmt // when opening the channel, subtracting the fees from the funding // output. This can be used for instance to use all our remaining funds // to open the channel, since it will take fees into // account. SubtractFees bool // FeeRate is the fee rate in sat/kw that the funding transaction // should carry. FeeRate chainfee.SatPerKWeight // ChangeAddr is a closure that will provide the Assembler with a // change address for the funding transaction if needed. ChangeAddr func() (btcutil.Address, error) } // Intent is returned by an Assembler and represents the base functionality the // caller needs to proceed with channel funding on a higher level. If the // Cancel method is called, then all resources assembled to fund the channel // will be released back to the eligible pool. type Intent interface { // FundingOutput returns the witness script, and the output that // creates the funding output. FundingOutput() ([]byte, *wire.TxOut, error) // ChanPoint returns the final outpoint that will create the funding // output described above. ChanPoint() (*wire.OutPoint, error) // RemoteFundingAmt is the amount the remote party put into the // channel. RemoteFundingAmt() btcutil.Amount // LocalFundingAmt is the amount we put into the channel. This may // differ from the local amount requested, as depending on coin // selection, we may bleed from of that LocalAmt into fees to minimize // change. LocalFundingAmt() btcutil.Amount // Cancel allows the caller to cancel a funding Intent at any time. // This will return any resources such as coins back to the eligible // pool to be used in order channel fundings. Cancel() } // Assembler is an abstract object that is capable of assembling everything // needed to create a new funding output. As an example, this assembler may be // our core backing wallet, an interactive PSBT based assembler, an assembler // than can aggregate multiple intents into a single funding transaction, or an // external protocol that creates a funding output out-of-band such as channel // factories. type Assembler interface { // ProvisionChannel returns a populated Intent that can be used to // further the channel funding workflow. Depending on the // implementation of Assembler, additional state machine (Intent) // actions may be required before the FundingOutput and ChanPoint are // made available to the caller. ProvisionChannel(*Request) (Intent, error) } // FundingTxAssembler is a super-set of the regular Assembler interface that's // also able to provide a fully populated funding transaction via the intents // that it produuces. type FundingTxAssembler interface { Assembler // FundingTxAvailable is an empty method that an assembler can // implement to signal to callers that its able to provide the funding // transaction for the channel via the intent it returns. FundingTxAvailable() }