assets+loopd: add scaffolding for the asset deposit manager

This commit extends the deposit package with the `Deposit` type and
a bare-bones `Manager`, along with the structural definition of the
`SQLStore` which together implement the basic structure, run loop and
storage for the deposit manager. It is not yet functional and serves
as a foundation for future commits that will gradually extend its
functionality.

Author: bhandras

assets/deposit/deposit.go

@@ -0,0 +1,202 @@
+package deposit
+
+import (
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"github.com/btcsuite/btcd/wire"
+	"github.com/btcsuite/btcwallet/wtxmgr"
+	"github.com/lightninglabs/taproot-assets/proof"
+)
+
+// State is the enum used for deposit states.
+type State uint8
+
+const (
+	// StateInitiated indicates that the deposit has been initiated by the
+	// client.
+	StateInitiated State = 0
+
+	// StatePending indicates that the deposit is pending confirmation on
+	// the blockchain.
+	StatePending State = 1
+
+	// StateConfirmed indicates that the deposit has been confirmed on the
+	// blockchain.
+	StateConfirmed State = 2
+
+	// StateExpired indicates that the deposit has expired.
+	StateExpired State = 3
+
+	// StateTimeoutSweepPublished indicates that the timeout sweep has been
+	// published.
+	StateTimeoutSweepPublished State = 4
+
+	// StateWithdrawn indicates that the deposit has been withdrawn.
+	StateWithdrawn State = 5
+
+	// StateCooperativeSweepPublished indicates that the cooperative sweep
+	// withdrawing the deposit has been published.
+	StateCooperativeSweepPublished State = 6
+
+	// StateKeyRevealed indicates that the client has revealed a valid key
+	// for the deposit which is now ready to be swept.
+	StateKeyRevealed State = 7
+
+	// StateSpent indicates that the deposit has been spent.
+	StateSpent State = 8
+
+	// StateSwept indicates that the deposit has been swept, either by a
+	// timeout sweep or a cooperative (ie withdrawal) sweep.
+	StateSwept State = 9
+)
+
+// String coverts a deposit state to human readable string.
+func (s State) String() string {
+	switch s {
+	case StateInitiated:
+		return "Initiated"
+
+	case StatePending:
+		return "Pending"
+
+	case StateConfirmed:
+		return "Confirmed"
+
+	case StateExpired:
+		return "Expired"
+
+	case StateTimeoutSweepPublished:
+		return "TimeoutSweepPublished"
+
+	case StateWithdrawn:
+		return "Withdrawn"
+
+	case StateCooperativeSweepPublished:
+		return "CooperativeSweepPublished"
+
+	case StateKeyRevealed:
+		return "KeyRevealed"
+
+	case StateSpent:
+		return "Spent"
+
+	case StateSwept:
+		return "Swept"
+
+	default:
+		return "Unknown"
+	}
+}
+
+// IsFinal returns true if the deposit state is final, meaning that no further
+// actions can be taken on the deposit.
+func (s State) IsFinal() bool {
+	return s == StateSpent || s == StateSwept
+}
+
+// DepositInfo holds publicly available information about an asset deposit.
+// It is used to communicate deposit details to clients of the deposit Manager.
+type DepositInfo struct {
+	// ID is the unique identifier for this deposit which will also be used
+	// to store the deposit in both the server and client databases.
+	ID string
+
+	// Verison is the protocol version of the deposit.
+	Version AssetDepositProtocolVersion
+
+	// CreatedAt is the time when the deposit was created (on the client).
+	CreatedAt time.Time
+
+	// Amount is the amount of asset to be deposited.
+	Amount uint64
+
+	// Addr is the TAP deposit address where the asset will be sent.
+	Addr string
+
+	// State is the deposit state.
+	State State
+
+	// ConfirmationHeight is the block height at which the deposit was
+	// confirmed.
+	ConfirmationHeight uint32
+
+	// Outpoint is the anchor outpoint of the deposit. It is only set if the
+	// deposit has been confirmed.
+	Outpoint *wire.OutPoint
+
+	// Expiry is the block height at which the deposit will expire. It is
+	// only set if the deposit has been confirmed.
+	Expiry uint32
+
+	// SweepAddr is the address we'll use to sweep the deposit back after
+	// timeout or if cooperatively withdrawing.
+	SweepAddr string
+}
+
+// Copy creates a copy of the DepositInfo struct.
+func (d *DepositInfo) Copy() *DepositInfo {
+	info := &DepositInfo{
+		ID:                 d.ID,
+		Version:            d.Version,
+		CreatedAt:          d.CreatedAt,
+		Amount:             d.Amount,
+		Addr:               d.Addr,
+		State:              d.State,
+		ConfirmationHeight: d.ConfirmationHeight,
+		Expiry:             d.Expiry,
+		SweepAddr:          d.SweepAddr,
+	}
+
+	if d.Outpoint != nil {
+		info.Outpoint = &wire.OutPoint{
+			Hash:  d.Outpoint.Hash,
+			Index: d.Outpoint.Index,
+		}
+	}
+
+	return info
+}
+
+// Deposit is the struct that holds all the information about an asset deposit.
+type Deposit struct {
+	*Kit
+
+	*DepositInfo
+
+	// PkScript is the pkscript of the deposit anchor output.
+	PkScript []byte
+
+	// Proof is the proof of the deposit transfer.
+	Proof *proof.Proof
+
+	// AnchorRootHash is the root hash of the deposit anchor output.
+	AnchorRootHash []byte
+}
+
+// label returns a string label that we can use for marking a transfer funding
+// the deposit. This is useful if we need to filter deposits.
+func (d *Deposit) label() string {
+	return fmt.Sprintf("deposit %v", d.ID)
+}
+
+// lockID converts a deposit ID to a lock ID. The lock ID is used to lock inputs
+// used for the deposit sweep transaction. Note that we assume that the deposit
+// ID is a hex-encoded string of the same length as the lock ID.
+func (d *Deposit) lockID() (wtxmgr.LockID, error) {
+	var lockID wtxmgr.LockID
+	depositIDBytes, err := hex.DecodeString(d.ID)
+	if err != nil {
+		return wtxmgr.LockID{}, err
+	}
+
+	if len(depositIDBytes) != len(lockID) {
+		return wtxmgr.LockID{}, fmt.Errorf("invalid deposit ID "+
+			"length: %d", len(depositIDBytes))
+	}
+
+	copy(lockID[:], depositIDBytes)
+
+	return lockID, nil
+}