staticaddr: fractional swap amount #887

hieblmi · 2025-02-20T14:47:14Z

This PR adds an amount flag to static loop-in swaps that allows the caller to only swap a fraction of the value of the selected deposits. If only amount is selected, the client selects deposits automatically to cover for the swaps amount.

To ensure backwards UX compatibility, omitting the new flag (--amount=0) selects the total deposit amount for swapping.

TODO

Sign sweepless sweep with change output if needed
integration test

Copilot

Pull Request Overview

This PR introduces support for fractional swap amounts in static loop‐in swaps by adding a new amount flag. Key changes include:

Logic updates in the loop-in store, manager, and swap creation to use a user-specified amount if provided.
Additions to the deposit and SQL layers to support lookup by outpoint and store the selected amount.
Updates to the RPC protos and CLI to expose and handle the new amount flag.

Reviewed Changes

Copilot reviewed 19 out of 23 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
staticaddr/loopin/sql_store.go	Adjusts swap creation logic to set AmountRequested based on flag.
staticaddr/loopin/manager.go	Updates loop-in initiation and sweep handling to use selected amount.
staticaddr/loopin/loopin.go	Uses the selected amount for calculating swap and change outputs.
staticaddr/loopin/interface.go	Adds DepositsForOutpoints signature to retrieve deposits by outpoints.
staticaddr/loopin/actions.go	Adapts invoice and fee calculations based on the selected amount.
staticaddr/deposit/*	Introduces functions to retrieve deposits by outpoint.
looprpc/client.proto	Adds a new field for the swap amount in the loop-in request.
loopdb/sqlc/*	Updates SQL queries and models to include selected_amount.
loopd/swapclient_server.go	Updates quote requests and swap reporting to use the selected amount.
interface.go	Exposes a new SelectedAmount field in the loop-in request interface.
cmd/loop/staticaddr.go	Adds a new CLI flag and coin-selection logic for the swap amount.

Files not reviewed (4)

loopdb/sqlc/migrations/000014_static_selected_amount.down.sql: Language not supported
loopdb/sqlc/migrations/000014_static_selected_amount.up.sql: Language not supported
loopdb/sqlc/queries/static_address_deposits.sql: Language not supported
loopdb/sqlc/queries/static_address_loopin.sql: Language not supported

Comments suppressed due to low confidence (2)

staticaddr/deposit/interface.go:30

[nitpick] Consider revising the comment for clarity. For example, change it to 'Returns all deposits associated with the given outpoints.'

// DepositsForOutpoints returns all deposits that behind the given

cmd/loop/staticaddr.go:639

Review the dust limit check to ensure it correctly handles edge cases when the available deposit sum exactly equals the swap amount plus the dust limit. Clarifying the condition could prevent unexpected behavior in deposit selection.

if depositSum-int64(dustLimit) < amount {

hieblmi · 2025-04-30T10:51:28Z

Rebased

hieblmi · 2025-05-28T09:51:20Z

Rebased

lightninglabs-deploy · 2025-06-04T10:22:52Z

@starius: review reminder
@bhandras: review reminder
@sputn1ck: review reminder
@hieblmi, remember to re-request review from reviewers when ready

bhandras

Just a few comments, otherwise look pretty good!

loopdb/sqlc/migrations/000015_static_selected_amount.down.sql

loopdb/sqlc/migrations/000015_static_selected_amount.up.sql

staticaddr/deposit/manager.go

loopd/swapclient_server.go

cmd/loop/staticaddr.go

bhandras

Looks good, just a few final comments.

bhandras · 2025-06-13T07:12:30Z

staticaddr/loopin/manager.go

@@ -562,8 +606,33 @@ func (m *Manager) initiateLoopIn(ctx context.Context,
 	}
 	totalDepositAmount := tmp.TotalDepositAmount()

+	// If the selected amount would leave a dust change output or exceeds
+	// the total deposits value, we return an error.
+	dustLimit := lnwallet.DustLimitForSize(input.P2TRSize)


nit: why not use SwapAmountFromSelectedAmount?

Sorry, what do you mean by SwapAmountFromSelectedAmount? I can't follow.

bhandras · 2025-06-13T07:21:55Z

cmd/loop/staticaddr.go

+// are needed to cover the amount requested without leaving a dust change. It
+// returns an error if the sum of deposits minus dust is less than the requested
+// amount.
+func selectDeposits(deposits []*looprpc.Deposit, targetAmount int64) ([]string,


(see my next comment too)

Ideally this should be solved with a knapsack algorithm, but since that's a bit difficult, maybe we can use a variance of this heuristic to first try to find a covering deposit?

The current implementation sorts values descending and then fills the sack until the target is met. This might be a good enough approximation of a knapsack solver, see here: https://en.wikipedia.org/wiki/Knapsack_problem#Greedy_approximation_algorithm

bhandras · 2025-06-13T07:29:46Z

staticaddr/loopin/selected_amount_migration.go

+	updateAmounts := make(map[lntypes.Hash]btcutil.Amount)
+	for _, swap := range swaps {
+		for _, outpoint := range swap.DepositOutpoints {
+			op := strings.Split(outpoint, ":")


nit: use wire.NewOutPointFromString.

bhandras · 2025-06-13T07:30:40Z

staticaddr/loopin/selected_amount_migration.go

+func MigrateSelectedSwapAmount(ctx context.Context, db loopdb.SwapStore,
+	depositStore *deposit.SqlStore, swapStore *SqlStore) error {
+
+	migrationDone, err := db.HasMigration(ctx, selectedAmountMigrationID)


Imo the whole migration should be done in a single transaction.

The actual migration is done in a single batch in BatchUpdateSelectedSwapAmounts. Is that what you mean?

hieblmi added the static-loop-in label Feb 20, 2025

hieblmi self-assigned this Feb 20, 2025

hieblmi marked this pull request as draft February 20, 2025 14:47

hieblmi force-pushed the static-arb-amount-swap branch 3 times, most recently from fd6cc75 to f54115f Compare February 21, 2025 15:23

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hieblmi requested a review from Copilot April 2, 2025 13:52

hieblmi marked this pull request as ready for review April 2, 2025 13:52

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hieblmi mentioned this pull request Jun 17, 2025

staticaddr: method to fetch deposits by outpoints #959

Open

hieblmi force-pushed the static-arb-amount-swap branch 3 times, most recently from ac36581 to 677d91c Compare June 17, 2025 17:59

hieblmi added 3 commits June 17, 2025 20:00

swapserverrpc: arbitrary static swap amount

947d08b

staticaddr: method to fetch deposits by outpoints

1cc4bbb

sqlc: selected amount migration for static address swaps

0c6ef86

hieblmi force-pushed the static-arb-amount-swap branch from 677d91c to cdf41b4 Compare June 17, 2025 18:02

hieblmi added 5 commits June 17, 2025 20:05

looprpc: fractional amount for static address loop-ins

da90873

staticaddr: fractional loop-in amount

5f83d05

loopd: fractional static address swap amount

d91a75f

staticaddr: show swap amount in listswaps command

25b79bd

staticaddr: selected swap amount migration

541a118

hieblmi force-pushed the static-arb-amount-swap branch from cdf41b4 to 541a118 Compare June 17, 2025 18:05

hieblmi added medium size and removed medium size labels Jun 17, 2025

staticaddr: fractional swap amount #887

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staticaddr: fractional swap amount #887

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Pull Request Overview

Reviewed Changes

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hieblmi commented Apr 30, 2025

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hieblmi commented Feb 20, 2025 •

edited

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