Add runing task dedup lock

transcoder/src/runlock.go

@@ -0,0 +1,63 @@
+package src
+
+import (
+	"errors"
+	"sync"
+)
+
+type RunLock[K comparable, V any] struct {
+	running map[K]*Task[V]
+	lock    sync.Mutex
+}
+
+type Task[V any] struct {
+	ready     sync.WaitGroup
+	listeners []chan Result[V]
+}
+
+type Result[V any] struct {
+	ok  V
+	err error
+}
+
+func NewRunLock[K comparable, V any]() RunLock[K, V] {
+	return RunLock[K, V]{
+		running: make(map[K]*Task[V]),
+	}
+}
+
+func (r *RunLock[K, V]) Start(key K) (func() (V, error), func(val V, err error) (V, error)) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	task, ok := r.running[key]
+
+	if ok {
+		ret := make(chan Result[V])
+		task.listeners = append(task.listeners, ret)
+		return func() (V, error) {
+			res := <-ret
+			return res.ok, res.err
+		}, nil
+	}
+
+	r.running[key] = &Task[V]{
+		listeners: make([]chan Result[V], 0),
+	}
+
+	return nil, func(val V, err error) (V, error) {
+		r.lock.Lock()
+		defer r.lock.Unlock()
+
+		task, ok = r.running[key]
+		if !ok {
+			return val, errors.New("invalid run lock state. aborting.")
+		}
+
+		for _, listener := range task.listeners {
+			listener <- Result[V]{ok: val, err: err}
+			close(listener)
+		}
+		delete(r.running, key)
+		return val, err
+	}
+}