feat: add block timestamp to substrate events (#40)

chains/substrate/connection/connection.go

@@ -4,13 +4,17 @@
 package connection
 
 import (
+	"bytes"
 	"math/big"
 	"sync"
+	"time"
 
 	"github.com/centrifuge/go-substrate-rpc-client/v4/client"
+	"github.com/centrifuge/go-substrate-rpc-client/v4/registry"
 	"github.com/centrifuge/go-substrate-rpc-client/v4/registry/parser"
 	"github.com/centrifuge/go-substrate-rpc-client/v4/registry/retriever"
 	"github.com/centrifuge/go-substrate-rpc-client/v4/registry/state"
+	"github.com/vedhavyas/go-subkey/scale"
 
 	"github.com/centrifuge/go-substrate-rpc-client/v4/rpc"
 	"github.com/centrifuge/go-substrate-rpc-client/v4/rpc/chain"
@@ -85,9 +89,48 @@ func (c *Connection) GetBlockEvents(hash types.Hash) ([]*parser.Event, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	timestamp, err := c.GetBlockTimestamp(hash)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, e := range evts {
+		e.Fields = append(e.Fields, &registry.DecodedField{
+			Value: timestamp,
+			Name:  "block_timestamp",
+		})
+	}
 	return evts, nil
 }
 
+func (c *Connection) GetBlockTimestamp(hash types.Hash) (time.Time, error) {
+	callIndex, err := c.meta.FindCallIndex("Timestamp.set")
+	if err != nil {
+		return time.Now(), err
+	}
+
+	block, err := c.GetBlock(hash)
+	if err != nil {
+		return time.Now(), err
+	}
+
+	timestamp := new(big.Int)
+	for _, extrinsic := range block.Block.Extrinsics {
+		if extrinsic.Method.CallIndex != callIndex {
+			continue
+		}
+		timeDecoder := scale.NewDecoder(bytes.NewReader(extrinsic.Method.Args))
+		timestamp, err = timeDecoder.DecodeUintCompact()
+		if err != nil {
+			return time.Now(), err
+		}
+		break
+	}
+	msec := timestamp.Int64()
+	return time.Unix(msec/1e3, (msec%1e3)*1e6), nil
+}
+
 func (c *Connection) FetchEvents(startBlock, endBlock *big.Int) ([]*parser.Event, error) {
 	evts := make([]*parser.Event, 0)
 	for i := new(big.Int).Set(startBlock); i.Cmp(endBlock) <= 0; i.Add(i, big.NewInt(1)) {

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/rs/zerolog v1.25.0
 	github.com/stretchr/testify v1.8.3
 	github.com/syndtr/goleveldb v1.0.1-0.20220614013038-64ee5596c38a
+	github.com/vedhavyas/go-subkey v1.0.4
 	go.opentelemetry.io/otel v1.16.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp v0.39.0
 	go.opentelemetry.io/otel/metric v1.16.0
@@ -45,7 +46,6 @@ require (
 	github.com/rs/cors v1.8.2 // indirect
 	github.com/stretchr/objx v0.5.0 // indirect
 	github.com/supranational/blst v0.3.11 // indirect
-	github.com/vedhavyas/go-subkey v1.0.4 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.16.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric v0.39.0 // indirect
 	golang.org/x/crypto v0.12.0 // indirect