move transactionId generator to CS

charger/ocpp/connector.go

@@ -29,9 +29,8 @@ type Connector struct {
 	meterUpdated time.Time
 	measurements map[types.Measurand]types.SampledValue
 
-	txnCount int // change initial value to the last known global transaction. Needs persistence
-	txnId    int
-	idTag    string
+	txnId int
+	idTag string
 
 	remoteIdTag string
 }

charger/ocpp/connector_core.go

@@ -102,8 +102,7 @@ func (conn *Connector) StartTransaction(request *core.StartTransactionRequest) (
 		return res, nil
 	}
 
-	conn.txnCount++
-	conn.txnId = conn.txnCount
+	conn.txnId = instance.NewTransactionID()
 	conn.idTag = request.IdTag
 
 	res := &core.StartTransactionConfirmation{

charger/ocpp/cs.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"sync"
+	"time"
 
 	"github.com/evcc-io/evcc/util"
 	ocpp16 "github.com/lorenzodonini/ocpp-go/ocpp1.6"
@@ -13,7 +14,8 @@ type CS struct {
 	mu  sync.Mutex
 	log *util.Logger
 	ocpp16.CentralSystem
-	cps map[string]*CP
+	cps   map[string]*CP
+	txnId int
 }
 
 // Register registers a charge point with the central system.
@@ -106,3 +108,16 @@ func (cs *CS) ChargePointDisconnected(chargePoint ocpp16.ChargePointConnection)
 		cp.connect(false)
 	}
 }
+
+// NewTransactionID returns a new unique transaction id
+func (cs *CS) NewTransactionID() int {
+	cs.mu.Lock()
+	defer cs.mu.Unlock()
+
+	if cs.txnId == 0 {
+		cs.txnId = int(time.Now().UTC().Unix())
+	}
+
+	cs.txnId++
+	return cs.txnId
+}