assets swap deposits [2/N]: extend the loop tapd client with funding, signing, and swap support utilities #980

bhandras · 2025-07-15T13:46:04Z

This commit adds methods to the tapd client for preparing, funding, signing, and publishing virtual PSBTs, managing asset balances, handling proofs, and watching for asset send/receive completion events. Also introduces utility methods for creating OP_TRUE sweep vpackets from asset proofs.

Build on top of: #979

Pull Request Checklist

Update release_notes.md if your PR contains major features, breaking changes or bugfixes

gemini-code-assist

Summary of Changes

Hello @bhandras, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly expands the loop tapd client's capabilities, particularly in the realm of asset swaps and deposits. It introduces a suite of new methods for advanced transaction construction, including funding and signing virtual PSBTs, managing asset proofs, and monitoring asset transfer events. Furthermore, it lays the groundwork for atomic swaps by adding dedicated support for Taproot Asset HTLCs and general utilities for sweeping assets.

Highlights

Extended tapd Client Functionality: The TapdClient has been significantly extended with new methods for funding, signing, and publishing virtual PSBTs, which are crucial for constructing and broadcasting Taproot Asset transactions. This includes FundAndSignVpacket, PrepareAndCommitVirtualPsbts, and LogAndPublish.
Asset Balance Management and Key Derivation: New utilities have been added to query asset balances, specifically GetAssetBalance and GetUnEncumberedAssetBalance, providing detailed insight into spendable assets. The client also gains DeriveNewKeys for generating new internal and script keys for asset management.
Proof Handling and Import: The TapdClient now supports importing and managing asset proofs through ImportProof and ImportProofFile, which is essential for verifying asset ownership and maintaining a complete asset history within the tapd database.
Asset Event Monitoring: Capabilities to subscribe to and monitor asset send and receive events have been introduced with WaitForReceiveComplete and WaitForSendComplete, enabling real-time tracking and automation of asset transfers.
Taproot Asset HTLC Support: New packages (assets/htlc) have been added to provide comprehensive support for constructing and managing Taproot Asset Hash Time-Locked Contracts (HTLCs). This includes generating success/timeout scripts, computing aggregate keys, creating virtual PSBTs for HTLCs, and generating Bitcoin control blocks for HTLC paths.
OP_TRUE Sweep Utilities: A new utility function, CreateOpTrueSweepVpkt, has been introduced to create virtual PSBTs specifically for sweeping assets that are secured by a simple OP_TRUE Tapscript, simplifying certain asset recovery or transfer scenarios.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point in your pull request via creating an issue comment (i.e. comment on the pull request page) using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands.

Feature	Command	Description
Code Review	`/gemini review`	Performs a code review for the current pull request in its current state.
Pull Request Summary	`/gemini summary`	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in issue comments and review comments.
Help	`/gemini help`	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist is currently in preview and may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments to provide feedback.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

gemini-code-assist

Code Review

This pull request adds significant functionality to the tapd client for asset swaps. It introduces methods for funding, signing, and managing virtual PSBTs, handling proofs, and watching for send/receive events. New packages htlc and tapkit provide utilities for creating HTLC scripts and sweeping assets. The changes are extensive and well-structured. My review focuses on improving robustness, maintainability, and consistency. Key areas for improvement include handling of goroutine lifecycle, removing duplicated code, and addressing TODO comments.

gemini-code-assist · 2025-07-15T13:48:30Z

assets/client.go

+			case <-receiveEventsClient.Context().Done():
+				panic(receiveEventsClient.Context().Err())


Panicking within a goroutine will crash the entire application. The context being done is a normal part of the lifecycle (e.g., shutdown) and should be handled gracefully. Instead of panicking, the error should be sent to the errChan and the goroutine should exit.

Suggested change

case <-receiveEventsClient.Context().Done():

panic(receiveEventsClient.Context().Err())

case <-receiveEventsClient.Context().Done():

errChan <- receiveEventsClient.Context().Err()

return

gemini-code-assist · 2025-07-15T13:48:30Z

assets/client.go

+	errChan := make(chan error, 1)
+
+	go func() {
+		for {


This goroutine's loop is missing a check for context cancellation. Unlike WaitForReceiveComplete, it doesn't handle the case where the client context is closed. This could lead to a goroutine leak if the context is cancelled while the Recv() call is blocking.

Please add a select block to check for sendEventsClient.Context().Done() similar to the one in WaitForReceiveComplete to ensure graceful shutdown of the goroutine.

gemini-code-assist · 2025-07-15T13:48:31Z

assets/htlc/swapkit.go

+
+// GenTaprootAssetRootFromProof generates the taproot asset root from the proof
+// of the swap.
+func GenTaprootAssetRootFromProof(proof *proof.Proof) ([]byte, error) {


The function GenTaprootAssetRootFromProof is also defined in assets/tapkit.go. To avoid code duplication and improve maintainability, this function should be defined in a single, shared location (e.g., in assets/tapkit.go or a new utility file) and used from there.

gemini-code-assist · 2025-07-15T13:48:31Z

assets/tapkit.go

+
+// GenTaprootAssetRootFromProof generates the taproot asset root from the proof
+// of the swap.
+func GenTaprootAssetRootFromProof(proof *proof.Proof) ([]byte, error) {


The function GenTaprootAssetRootFromProof is also defined in assets/htlc/swapkit.go. To avoid code duplication and improve maintainability, this function should be defined in a single, shared location and imported where needed.

gemini-code-assist · 2025-07-15T13:48:31Z

assets/tapkit.go

+		// TODO(bhandras): set this to the actual internal key derived
+		// from the sender node, otherwise they'll lose the 1000 sats
+		// of the tombstone output.


This TODO comment indicates that the internal key for the tombstone output is not being set correctly, which could lead to a loss of funds (1000 sats). This is a critical issue that should be addressed before merging.

gemini-code-assist · 2025-07-15T13:48:31Z

assets/client.go

+func handleReceiveEvent(event *taprpc.ReceiveEvent,
+	resChan chan<- TapReceiveEvent) (bool, error) {
+
+	fmt.Printf("!!! Received event: %v\n", event.Status)


This fmt.Printf appears to be a debug statement. It should be removed or replaced with a proper logger call (e.g., using a log package) before merging to avoid polluting production logs.

Suggested change

fmt.Printf("!!! Received event: %v\n", event.Status)

// fmt.Printf("!!! Received event: %v\n", event.Status)

gemini-code-assist · 2025-07-15T13:48:32Z

assets/htlc/script.go

+		asset.NUMSPubKey, rootHash[:],
+	)
+
+	merkleRootHash := tree.RootNode.TapHash()


The variable merkleRootHash is a redundant calculation of rootHash, which is already computed on line 69. This line can be removed. You will need to update line 86 to use rootHash.

gemini-code-assist · 2025-07-15T13:48:32Z

assets/htlc/script.go

+			RawKey: keychain.KeyDescriptor{
+				PubKey: asset.NUMSPubKey,
+			},
+			Tweak: merkleRootHash[:],


To accompany the removal of the redundant merkleRootHash variable, this line should be updated to use rootHash.

Suggested change

Tweak: merkleRootHash[:],

Tweak: rootHash[:],

gemini-code-assist · 2025-07-15T13:48:32Z

assets/htlc/swapkit.go

+		ScriptKey:         asset.NUMSScriptKey,
+	})
+	pkt.Outputs = append(pkt.Outputs, &tappsbt.VOutput{
+		// todo(sputn1ck) assetversion


This todo comment indicates that the asset version is hardcoded. This should be addressed before merging to ensure the correct asset version is used.

gemini-code-assist · 2025-07-15T13:48:32Z

assets/tapkit.go

+	/*
+		addressRecvVpkt, err := tappsbt.FromAddresses([]*address.Tap{addr}, 0)
+		if err != nil {
+			return nil, err
+		}
+
+		sweepVpkt.Outputs = addressRecvVpkt.Outputs
+	*/


This block of code is commented out. If it's no longer needed, it should be removed to improve code clarity and maintainability.

With this commit we add high level helpers along with scripts to create asset HTLCs.

This commit enables package relayed HTLCs by making the CSV check in the success path optional.

This commit adds additional scaffolding to our tapd client, along with new high-level helpers in the assets package, which will be used later for swaps and deposits.

gemini-code-assist bot reviewed Jul 15, 2025

View reviewed changes

bhandras mentioned this pull request Jul 15, 2025

assets swap deposits [3/N]: extend swapserverrpc with asset deposit RPCs #981

Draft

1 task

bhandras force-pushed the asset-swap-deposits-2 branch 2 times, most recently from e9141c9 to d1e742b Compare July 15, 2025 16:16

assets: add asset HTLC helpers

512028b

With this commit we add high level helpers along with scripts to create asset HTLCs.

bhandras force-pushed the asset-swap-deposits-2 branch 2 times, most recently from f3b944d to 8970466 Compare July 17, 2025 12:15

bhandras added 2 commits July 17, 2025 15:03

assets: add no-csv option to the asset HTLC to support package relay

7638d8b

This commit enables package relayed HTLCs by making the CSV check in the success path optional.

assets: extend the tapd client and add high-level TAP helpers

1bfa780

This commit adds additional scaffolding to our tapd client, along with new high-level helpers in the assets package, which will be used later for swaps and deposits.

bhandras force-pushed the asset-swap-deposits-2 branch from 8970466 to 1bfa780 Compare July 17, 2025 13:11

sputn1ck self-requested a review July 21, 2025 11:49

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

assets swap deposits [2/N]: extend the loop tapd client with funding, signing, and swap support utilities #980

assets swap deposits [2/N]: extend the loop tapd client with funding, signing, and swap support utilities #980

Uh oh!

bhandras commented Jul 15, 2025

Uh oh!

gemini-code-assist bot left a comment

Uh oh!

gemini-code-assist bot left a comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

gemini-code-assist bot Jul 15, 2025

Uh oh!

Uh oh!

		case <-receiveEventsClient.Context().Done():
		panic(receiveEventsClient.Context().Err())

	fmt.Printf("!!! Received event: %v\n", event.Status)
	// fmt.Printf("!!! Received event: %v\n", event.Status)

assets swap deposits [2/N]: extend the loop tapd client with funding, signing, and swap support utilities #980

Are you sure you want to change the base?

assets swap deposits [2/N]: extend the loop tapd client with funding, signing, and swap support utilities #980

Uh oh!

Conversation

bhandras commented Jul 15, 2025

Pull Request Checklist

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Summary of Changes

Highlights

Footnotes

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Jul 15, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!