add selector

selector/strategy.go

@@ -0,0 +1,72 @@
+package selector
+
+import (
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/go-gost/core/selector"
+)
+
+type roundRobinStrategy[T selector.Selectable] struct {
+	counter uint64
+}
+
+// RoundRobinStrategy is a strategy for node selector.
+// The node will be selected by round-robin algorithm.
+func RoundRobinStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &roundRobinStrategy[T]{}
+}
+
+func (s *roundRobinStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+
+	n := atomic.AddUint64(&s.counter, 1) - 1
+	return vs[int(n%uint64(len(vs)))]
+}
+
+type randomStrategy[T selector.Selectable] struct {
+	rand *rand.Rand
+	mux  sync.Mutex
+}
+
+// RandomStrategy is a strategy for node selector.
+// The node will be selected randomly.
+func RandomStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &randomStrategy[T]{
+		rand: rand.New(rand.NewSource(time.Now().UnixNano())),
+	}
+}
+
+func (s *randomStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+
+	s.mux.Lock()
+	defer s.mux.Unlock()
+
+	r := s.rand.Int()
+
+	return vs[r%len(vs)]
+}
+
+type fifoStrategy[T selector.Selectable] struct{}
+
+// FIFOStrategy is a strategy for node selector.
+// The node will be selected from first to last,
+// and will stick to the selected node until it is failed.
+func FIFOStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &fifoStrategy[T]{}
+}
+
+// Apply applies the fifo strategy for the nodes.
+func (s *fifoStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+	return vs[0]
+}