core: change notify implementation to save notifications

Fixes #453 and makes it possible to refer to these notifications later.

pkg/core/blockchain.go

@@ -473,7 +473,7 @@ func (bc *Blockchain) storeBlock(block *Block) error {
 			vm.LoadScript(t.Script)
 			err := vm.Run()
 			if !vm.HasFailed() {
-				_, err := systemInterop.mem.Persist()
+				_, err = systemInterop.mem.Persist()
 				if err != nil {
 					return errors.Wrap(err, "failed to persist invocation results")
 				}
@@ -484,6 +484,18 @@ func (bc *Blockchain) storeBlock(block *Block) error {
 					"err":   err,
 				}).Warn("contract invocation failed")
 			}
+			aer := &AppExecResult{
+				TxHash:      tx.Hash(),
+				Trigger:     0x10,
+				VMState:     vm.State(),
+				GasConsumed: util.Fixed8(0),
+				Stack:       vm.Stack("estack"),
+				Events:      systemInterop.notifications,
+			}
+			err = putAppExecResultIntoStore(tmpStore, aer)
+			if err != nil {
+				return errors.Wrap(err, "failed to store notifications")
+			}
 		}
 	}
 

pkg/core/interop_system.go

@@ -343,8 +343,10 @@ func (ic *interopContext) runtimeCheckWitness(v *vm.VM) error {
 // runtimeNotify should pass stack item to the notify plugin to handle it, but
 // in neo-go the only meaningful thing to do here is to log.
 func (ic *interopContext) runtimeNotify(v *vm.VM) error {
-	msg := fmt.Sprintf("%q", v.Estack().Pop().Bytes())
-	log.Infof("script %s notifies: %s", getContextScriptHash(v, 0), msg)
+	// It can be just about anything.
+	e := v.Estack().Pop()
+	ne := NotificationEvent{getContextScriptHash(v, 0), e.Item()}
+	ic.notifications = append(ic.notifications, ne)
 	return nil
 }
 

pkg/core/interops.go

@@ -14,16 +14,18 @@ import (
 )
 
 type interopContext struct {
-	bc      Blockchainer
-	trigger byte
-	block   *Block
-	tx      *transaction.Transaction
-	mem     *storage.MemCachedStore
+	bc            Blockchainer
+	trigger       byte
+	block         *Block
+	tx            *transaction.Transaction
+	mem           *storage.MemCachedStore
+	notifications []NotificationEvent
 }
 
 func newInteropContext(trigger byte, bc Blockchainer, s storage.Store, block *Block, tx *transaction.Transaction) *interopContext {
 	mem := storage.NewMemCachedStore(s)
-	return &interopContext{bc, trigger, block, tx, mem}
+	nes := make([]NotificationEvent, 0)
+	return &interopContext{bc, trigger, block, tx, mem, nes}
 }
 
 // All lists are sorted, keep 'em this way, please.

pkg/core/notification_event.go

@@ -0,0 +1,80 @@
+package core
+
+import (
+	"github.com/CityOfZion/neo-go/pkg/core/storage"
+	"github.com/CityOfZion/neo-go/pkg/io"
+	"github.com/CityOfZion/neo-go/pkg/util"
+	"github.com/CityOfZion/neo-go/pkg/vm"
+	"github.com/pkg/errors"
+)
+
+// NotificationEvent is a tuple of scripthash that emitted the StackItem as a
+// notification and that item itself.
+type NotificationEvent struct {
+	ScriptHash util.Uint160
+	Item       vm.StackItem
+}
+
+// AppExecResult represent the result of the script execution, gathering together
+// all resulting notifications, state, stack and other metadata.
+type AppExecResult struct {
+	TxHash      util.Uint256
+	Trigger     byte
+	VMState     string
+	GasConsumed util.Fixed8
+	Stack       string // JSON
+	Events      []NotificationEvent
+}
+
+// putAppExecResultIntoStore puts given application execution result into the
+// given store.
+func putAppExecResultIntoStore(s storage.Store, aer *AppExecResult) error {
+	buf := io.NewBufBinWriter()
+	aer.EncodeBinary(buf.BinWriter)
+	if buf.Err != nil {
+		return buf.Err
+	}
+	key := storage.AppendPrefix(storage.STNotification, aer.TxHash.Bytes())
+	return s.Put(key, buf.Bytes())
+}
+
+// getAppExecResultFromStore gets application execution result from the
+// given store.
+func getAppExecResultFromStore(s storage.Store, hash util.Uint256) (*AppExecResult, error) {
+	aer := &AppExecResult{}
+	key := storage.AppendPrefix(storage.STNotification, hash.Bytes())
+	if b, err := s.Get(key); err == nil {
+		r := io.NewBinReaderFromBuf(b)
+		aer.DecodeBinary(r)
+		if r.Err != nil {
+			return nil, errors.Wrap(r.Err, "decoding failure:")
+		}
+	} else {
+		return nil, err
+	}
+	return aer, nil
+}
+
+// EncodeBinary implements the Serializable interface.
+func (ne *NotificationEvent) EncodeBinary(w *io.BinWriter) {
+	w.WriteLE(ne.ScriptHash)
+	vm.EncodeBinaryStackItem(ne.Item, w)
+}
+
+// DecodeBinary implements the Serializable interface.
+func (ne *NotificationEvent) DecodeBinary(r *io.BinReader) {
+	r.ReadLE(&ne.ScriptHash)
+	ne.Item = vm.DecodeBinaryStackItem(r)
+}
+
+// EncodeBinary implements the Serializable interface.
+func (aer *AppExecResult) EncodeBinary(w *io.BinWriter) {
+	w.WriteLE(aer.TxHash)
+	w.WriteArray(aer.Events)
+}
+
+// DecodeBinary implements the Serializable interface.
+func (aer *AppExecResult) DecodeBinary(r *io.BinReader) {
+	r.ReadLE(&aer.TxHash)
+	r.ReadArray(&aer.Events)
+}

pkg/core/storage/store.go

@@ -14,6 +14,7 @@ const (
 	STSpentCoin       KeyPrefix = 0x45
 	STValidator       KeyPrefix = 0x48
 	STAsset           KeyPrefix = 0x4c
+	STNotification    KeyPrefix = 0x4d
 	STContract        KeyPrefix = 0x50
 	STStorage         KeyPrefix = 0x70
 	IXHeaderHashList  KeyPrefix = 0x80

pkg/vm/serialization.go

@@ -21,13 +21,20 @@ const (
 
 func serializeItem(item StackItem) ([]byte, error) {
 	w := io.NewBufBinWriter()
-	serializeItemTo(item, w.BinWriter, make(map[StackItem]bool))
+	EncodeBinaryStackItem(item, w.BinWriter)
 	if w.Err != nil {
 		return nil, w.Err
 	}
 	return w.Bytes(), nil
 }
 
+// EncodeBinaryStackItem encodes given StackItem into the given BinWriter. It's
+// similar to io.Serializable's EncodeBinary, but works with StackItem
+// interface.
+func EncodeBinaryStackItem(item StackItem, w *io.BinWriter) {
+	serializeItemTo(item, w, make(map[StackItem]bool))
+}
+
 func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 	if seen[item] {
 		w.Err = errors.New("recursive structures are not supported")
@@ -75,14 +82,18 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 
 func deserializeItem(data []byte) (StackItem, error) {
 	r := io.NewBinReaderFromBuf(data)
-	item := deserializeItemFrom(r)
+	item := DecodeBinaryStackItem(r)
 	if r.Err != nil {
 		return nil, r.Err
 	}
 	return item, nil
 }
 
-func deserializeItemFrom(r *io.BinReader) StackItem {
+// DecodeBinaryStackItem decodes previously serialized StackItem from the given
+// reader. It's similar to the io.Serializable's DecodeBinary(), but implemented
+// as a function because StackItem itself is an interface. Caveat: always check
+// reader's error value before using the returned StackItem.
+func DecodeBinaryStackItem(r *io.BinReader) StackItem {
 	var t byte
 	r.ReadLE(&t)
 	if r.Err != nil {
@@ -107,7 +118,7 @@ func deserializeItemFrom(r *io.BinReader) StackItem {
 		size := int(r.ReadVarUint())
 		arr := make([]StackItem, size)
 		for i := 0; i < size; i++ {
-			arr[i] = deserializeItemFrom(r)
+			arr[i] = DecodeBinaryStackItem(r)
 		}
 
 		if stackItemType(t) == arrayT {
@@ -118,8 +129,8 @@ func deserializeItemFrom(r *io.BinReader) StackItem {
 		size := int(r.ReadVarUint())
 		m := NewMapItem()
 		for i := 0; i < size; i++ {
-			value := deserializeItemFrom(r)
-			key := deserializeItemFrom(r)
+			value := DecodeBinaryStackItem(r)
+			key := DecodeBinaryStackItem(r)
 			if r.Err != nil {
 				break
 			}

pkg/vm/stack.go

@@ -59,6 +59,11 @@ func (e *Element) Prev() *Element {
 	return nil
 }
 
+// Item returns StackItem contained in the element.
+func (e *Element) Item() StackItem {
+	return e.value
+}
+
 // Value returns value of the StackItem contained in the element.
 func (e *Element) Value() interface{} {
 	return e.value.Value()