feat(core): add event service

core/event/service.go

@@ -0,0 +1,38 @@
+// Package event provides a basic API for app modules to emit events.
+package event
+
+import (
+	"context"
+
+	"google.golang.org/protobuf/runtime/protoiface"
+)
+
+// Service represents an event service which can retrieve and set an event manager in a context.
+// event.Service is a core API type that should be provided by the runtime module being used to
+// build an app via depinject.
+type Service interface {
+	// EmitProtoEvent emits events represented as a protobuf message (as described in ADR 032).
+	//
+	// Callers SHOULD assume that these events may be included in consensus. These events
+	// MUST be emitted deterministically and adding, removing or changing these events SHOULD
+	// be considered state-machine breaking.
+	EmitProtoEvent(ctx context.Context, event protoiface.MessageV1) error
+
+	// EmitKVEvent emits an event based on an event and kv-pair attributes.
+	//
+	// These events will not be part of consensus and adding, removing or changing these events is
+	// not a state-machine breaking change.
+	EmitKVEvent(ctx context.Context, eventType string, attrs ...KVEventAttribute) error
+
+	// EmitProtoEventNonConsensus emits events represented as a protobuf message (as described in ADR 032), without
+	// including it in blockchain consensus.
+	//
+	// These events will not be part of consensus and adding, removing or changing events is
+	// not a state-machine breaking change.
+	EmitProtoEventNonConsensus(ctx context.Context, event protoiface.MessageV1) error
+}
+
+// KVEventAttribute is a kv-pair event attribute.
+type KVEventAttribute struct {
+	Key, Value string
+}