ingest: Move SAC event parsing to its own package, add more events. (#…

…4802)

* Move contract event parsing to its own package
* Add helper to parse ScAddresses
* Add mint test cases, contract address parsing
* Add fuzzing to parser to ensure no panics
* Add clawback event parsing, abstract to generic parser
* Add burn event support
* Add helper to parse i128 amounts

support/contractevents/burn.go

@@ -0,0 +1,54 @@
+package contractevents
+
+import (
+	"github.com/stellar/go/support/errors"
+	"github.com/stellar/go/xdr"
+)
+
+var ErrNotBurnEvent = errors.New("event is not a valid 'burn' event")
+
+type BurnEvent struct {
+	sacEvent
+
+	From   string
+	Amount xdr.Int128Parts
+}
+
+// parseBurnEvent tries to parse the given topics and value as a SAC "burn"
+// event.
+//
+// Internally, it assumes that the `topics` array has already validated both the
+// function name AND the asset <--> contract ID relationship. It will return a
+// best-effort parsing even in error cases.
+func (event *BurnEvent) parse(topics xdr.ScVec, value xdr.ScVal) error {
+	//
+	// The burn event format is:
+	//
+	// 	"burn"  	Symbol
+	//  <from>		Address
+	// 	<asset>		Bytes
+	//
+	// 	<amount> 	i128
+	//
+	// Reference: https://github.com/stellar/rs-soroban-env/blob/main/soroban-env-host/src/native_contract/token/event.rs#L102-L109
+	//
+	if len(topics) != 3 {
+		return ErrNotBurnEvent
+	}
+
+	rawFrom := topics[1]
+	from := parseAddress(&rawFrom)
+	if from == nil {
+		return ErrNotBurnEvent
+	}
+
+	event.From = MustScAddressToString(from)
+
+	amount := parseAmount(&value)
+	if amount == nil {
+		return ErrNotBurnEvent
+	}
+
+	event.Amount = *amount
+	return nil
+}

support/contractevents/clawback.go

@@ -0,0 +1,41 @@
+package contractevents
+
+import (
+	"github.com/stellar/go/support/errors"
+	"github.com/stellar/go/xdr"
+)
+
+var ErrNotClawbackEvent = errors.New("event is not a valid 'clawback' event")
+
+type ClawbackEvent struct {
+	sacEvent
+
+	Admin  string
+	From   string
+	Amount xdr.Int128Parts
+}
+
+// parseClawbackEvent tries to parse the given topics and value as a SAC
+// "clawback" event.
+//
+// Internally, it assumes that the `topics` array has already validated both the
+// function name AND the asset <--> contract ID relationship. It will return a
+// best-effort parsing even in error cases.
+func (event *ClawbackEvent) parse(topics xdr.ScVec, value xdr.ScVal) error {
+	//
+	// The clawback event format is:
+	//
+	// 	"clawback" 	Symbol
+	//  <admin>		Address
+	//  <from> 		Address
+	// 	<asset>		Bytes
+	//
+	// 	<amount> 	i128
+	//
+	var err error
+	event.Admin, event.From, event.Amount, err = parseBalanceChangeEvent(topics, value)
+	if err != nil {
+		return ErrNotClawbackEvent
+	}
+	return nil
+}