exerr [WIP]

(cherry picked from commit c0443af63b)

exerr/listener.go

@@ -0,0 +1,37 @@
+package exerr
+
+import (
+	"sync"
+)
+
+type Method string
+
+const (
+	MethodOutput Method = "OUTPUT"
+	MethodPrint  Method = "PRINT"
+	MethodBuild  Method = "BUILD"
+	MethodFatal  Method = "FATAL"
+)
+
+type Listener = func(method Method, v ExErr)
+
+var listenerLock = sync.Mutex{}
+var listener = make([]Listener, 0)
+
+func RegisterListener(l Listener) {
+	listenerLock.Lock()
+	defer listenerLock.Unlock()
+
+	listener = append(listener, l)
+}
+
+func (b *Builder) CallListener(m Method) {
+	valErr := b.toBMError()
+
+	listenerLock.Lock()
+	defer listenerLock.Unlock()
+
+	for _, v := range listener {
+		v(m, valErr)
+	}
+}