From 9dd79fc6205b5217088142af79631ca1b19801a8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Matczuk?= <michal@scylladb.com>
Date: Thu, 3 Dec 2020 11:33:14 +0100
Subject: [PATCH] migrate: Add CallbackRegister

---
 migrate/callback.go | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/migrate/callback.go b/migrate/callback.go
index 1d6921e..0288261 100644
--- a/migrate/callback.go
+++ b/migrate/callback.go
@@ -6,6 +6,7 @@ package migrate
 
 import (
 	"context"
+	"errors"
 
 	"github.com/scylladb/gocqlx/v2"
 )
@@ -31,3 +32,30 @@ type CallbackFunc func(ctx context.Context, session gocqlx.Session, ev CallbackE
 // Use this variable to register a global callback dispatching function.
 // See CallbackFunc for details.
 var Callback CallbackFunc
+
+type nameEvent struct {
+	name  string
+	event CallbackEvent
+}
+
+// CallbackRegister allows to register a handlers for an event type and a name.
+// It dispatches calls to the registered handlers.
+// If there is no handler registered for CallComment an error is returned.
+type CallbackRegister map[nameEvent]CallbackFunc
+
+// Add registers a callback handler.
+func (r CallbackRegister) Add(ev CallbackEvent, name string, f CallbackFunc) {
+	r[nameEvent{name, ev}] = f
+}
+
+// Callback is CallbackFunc.
+func (r CallbackRegister) Callback(ctx context.Context, session gocqlx.Session, ev CallbackEvent, name string) error {
+	f, ok := r[nameEvent{name, ev}]
+	if !ok {
+		if ev == CallComment {
+			return errors.New("missing handler")
+		}
+		return nil
+	}
+	return f(ctx, session, ev, name)
+}