From 5dd6a5323c530e135aec907493f89e7687157879 Mon Sep 17 00:00:00 2001
From: Knut Ahlers <knut@ahlers.me>
Date: Wed, 1 May 2024 22:39:18 +0200
Subject: [PATCH] [core] Add locking to prevent concurrent rule executions

refs #59

ensures counter actions are not triggered concurrently by two persons

Signed-off-by: Knut Ahlers <knut@ahlers.me>
---
 actions.go                |  5 ++++
 internal/locker/locker.go | 50 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 internal/locker/locker.go

diff --git a/actions.go b/actions.go
index e28d9d3..3c5632f 100644
--- a/actions.go
+++ b/actions.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"path"
 	"sync"
 
 	"github.com/pkg/errors"
@@ -8,6 +9,7 @@ import (
 	"gopkg.in/irc.v4"
 
 	"github.com/Luzifer/go_helpers/v2/fieldcollection"
+	"github.com/Luzifer/twitch-bot/v3/internal/locker"
 	"github.com/Luzifer/twitch-bot/v3/plugins"
 )
 
@@ -79,6 +81,9 @@ func handleMessage(c *irc.Client, m *irc.Message, event *string, eventData *fiel
 }
 
 func handleMessageRuleExecution(c *irc.Client, m *irc.Message, r *plugins.Rule, eventData *fieldcollection.FieldCollection) {
+	locker.LockByKey(path.Join("rule-execution", r.MatcherID()))
+	defer locker.UnlockByKey(path.Join("rule-execution", r.MatcherID()))
+
 	var (
 		ruleEventData   = fieldcollection.NewFieldCollection()
 		preventCooldown bool
diff --git a/internal/locker/locker.go b/internal/locker/locker.go
new file mode 100644
index 0000000..644e9a8
--- /dev/null
+++ b/internal/locker/locker.go
@@ -0,0 +1,50 @@
+// Package locker contains a way to interact with arbitrary locks
+package locker
+
+import "sync"
+
+var (
+	locks       = map[string]*sync.RWMutex{}
+	locksOLocks sync.RWMutex
+)
+
+// LockByKey takes a key to lock and locks the corresponding RWMutex
+func LockByKey(key string) { getLockByKey(key).Lock() }
+
+// RLockByKey takes a key to lock and read-locks the corresponding RWMutex
+func RLockByKey(key string) { getLockByKey(key).RLock() }
+
+// RUnlockByKey takes a key to lock and read-unlocks the corresponding RWMutex
+func RUnlockByKey(key string) { getLockByKey(key).RUnlock() }
+
+// UnlockByKey takes a key to lock and unlocks the corresponding RWMutex
+func UnlockByKey(key string) { getLockByKey(key).Unlock() }
+
+// WithLock takes a key to lock and a function to execute during the
+// lock of this key
+func WithLock(key string, fn func()) {
+	LockByKey(key)
+	defer UnlockByKey(key)
+
+	fn()
+}
+
+// WithRLock takes a key to lock and a function to execute during the
+// read-lock of this key
+func WithRLock(key string, fn func()) {
+	RLockByKey(key)
+	defer RUnlockByKey(key)
+
+	fn()
+}
+
+func getLockByKey(key string) *sync.RWMutex {
+	locksOLocks.Lock()
+	defer locksOLocks.Unlock()
+
+	if locks[key] == nil {
+		locks[key] = new(sync.RWMutex)
+	}
+
+	return locks[key]
+}