rpc/server: add notification filters

And check state string correctness on unmarshaling.

pkg/rpc/server/subscription.go

@@ -2,7 +2,10 @@ package server
 
 import (
 	"github.com/gorilla/websocket"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/request"
 	"github.com/nspcc-dev/neo-go/pkg/rpc/response"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/response/result"
 	"go.uber.org/atomic"
 )
 
@@ -16,7 +19,11 @@ type (
 		// cheaper doing it this way rather than creating a map),
 		// pointing to EventID is an obvious overkill at the moment, but
 		// that's not for long.
-		feeds [maxFeeds]response.EventID
+		feeds [maxFeeds]feed
+	}
+	feed struct {
+		event  response.EventID
+		filter interface{}
 	}
 )
 
@@ -34,3 +41,27 @@ const (
 	// a lot in terms of memory used.
 	notificationBufSize = 1024
 )
+
+func (f *feed) Matches(r *response.Notification) bool {
+	if r.Event != f.event {
+		return false
+	}
+	if f.filter == nil {
+		return true
+	}
+	switch f.event {
+	case response.TransactionEventID:
+		filt := f.filter.(request.TxFilter)
+		tx := r.Payload[0].(*transaction.Transaction)
+		return tx.Type == filt.Type
+	case response.NotificationEventID:
+		filt := f.filter.(request.NotificationFilter)
+		notification := r.Payload[0].(result.NotificationEvent)
+		return notification.Contract.Equals(filt.Contract)
+	case response.ExecutionEventID:
+		filt := f.filter.(request.ExecutionFilter)
+		applog := r.Payload[0].(result.ApplicationLog)
+		return len(applog.Executions) != 0 && applog.Executions[0].VMState == filt.State
+	}
+	return false
+}