fsm: add generic fsm

This commit adds a generic fsm which will help with threadsafe
access for fsm values

Author: sputn1ck

fsm/generic_fsm.go

@@ -0,0 +1,72 @@
+package fsm
+
+import "sync"
+
+type GenericFSM[T any] struct {
+	*StateMachine
+
+	Val     *T
+	ValLock sync.RWMutex
+}
+
+// NewGenericFSM creates a new generic FSM with the given initial state and
+// value.
+func NewGenericFSM[T any](fsm *StateMachine, val *T) *GenericFSM[T] {
+	return &GenericFSM[T]{
+		StateMachine: fsm,
+		Val:          val,
+	}
+}
+
+type callOptions struct {
+	withMainMutex bool
+}
+
+// CallOption is a functional option that can be used to modify the runFuncs.
+type CallOption func(*callOptions)
+
+// WithMainMutex is an option that can be used to run the function with the main
+// mutex locked. This requires the FSM to not be currently running an action.
+func WithMainMutex() CallOption {
+	return func(o *callOptions) {
+		o.withMainMutex = true
+	}
+}
+
+// RunFunc runs the given function in the FSM. It locks the FSM value lock
+// before running the function and unlocks it after the function is done.
+func (fsm *GenericFSM[T]) RunFunc(fn func(val *T) error, options ...CallOption,
+) error {
+
+	opts := &callOptions{}
+	for _, option := range options {
+		option(opts)
+	}
+
+	fsm.ValLock.Lock()
+	defer fsm.ValLock.Unlock()
+	if opts.withMainMutex {
+		fsm.mutex.Lock()
+		defer fsm.mutex.Unlock()
+	}
+
+	return fn(fsm.Val)
+}
+
+// GetVal returns the value of the FSM.
+func (fsm *GenericFSM[T]) GetVal(options ...CallOption) *T {
+	opts := &callOptions{}
+	for _, option := range options {
+		option(opts)
+	}
+
+	fsm.ValLock.RLock()
+	defer fsm.ValLock.RUnlock()
+
+	if opts.withMainMutex {
+		fsm.mutex.Lock()
+		defer fsm.mutex.Unlock()
+	}
+
+	return fsm.Val
+}