feat: 实现 Go 与 JS/TS SDK 连接收发与其余接口

sdk/go/backoff.go

@@ -0,0 +1,122 @@
+package nixmsg
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// reconnectBackoff 按 DEVELOPMENT 第 9 节：1s 起、加倍、上限 30s、±30% 抖动；
+// 稳定在线 60s 后恢复到 1s。
+type reconnectBackoff struct {
+	mu       sync.Mutex
+	base     time.Duration
+	onlineAt time.Time
+	online   bool
+	stable   bool
+	timer    *time.Timer
+}
+
+func newReconnectBackoff() *reconnectBackoff {
+	return &reconnectBackoff{base: time.Second}
+}
+
+func (b *reconnectBackoff) Func(attempt int) time.Duration {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if attempt <= 0 {
+		return 0
+	}
+	d := b.base
+	for i := 1; i < attempt; i++ {
+		d *= 2
+		if d > 30*time.Second {
+			d = 30 * time.Second
+			break
+		}
+	}
+	return withJitter(d)
+}
+
+func (b *reconnectBackoff) MarkOnline() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.online = true
+	b.onlineAt = time.Now()
+	b.stable = false
+	if b.timer != nil {
+		b.timer.Stop()
+	}
+	b.timer = time.AfterFunc(60*time.Second, func() {
+		b.mu.Lock()
+		defer b.mu.Unlock()
+		if b.online {
+			b.stable = true
+			b.base = time.Second
+		}
+	})
+}
+
+func (b *reconnectBackoff) MarkOffline() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.timer != nil {
+		b.timer.Stop()
+		b.timer = nil
+	}
+	wasOnline := b.online
+	b.online = false
+	if !wasOnline {
+		// 连接尚未成功就失败：在 Func 内已按 attempt 加倍，这里把 base 提到下次周期的起点。
+		next := b.base * 2
+		if next > 30*time.Second {
+			next = 30 * time.Second
+		}
+		if next < time.Second {
+			next = time.Second
+		}
+		b.base = next
+		return
+	}
+	if b.stable || time.Since(b.onlineAt) >= 60*time.Second {
+		b.base = time.Second
+		b.stable = false
+		return
+	}
+	next := b.base * 2
+	if next > 30*time.Second {
+		next = 30 * time.Second
+	}
+	b.base = next
+	b.stable = false
+}
+
+func (b *reconnectBackoff) Base() time.Duration {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.base
+}
+
+func withJitter(d time.Duration) time.Duration {
+	// ±30%
+	f := 0.7 + rand.Float64()*0.6
+	return time.Duration(float64(d) * f)
+}
+
+// computeBackoffDelay 供单测：无 attempt 与 base 计算无抖动前的标称延迟。
+func computeBackoffDelay(base time.Duration, attempt int) time.Duration {
+	if attempt <= 0 {
+		return 0
+	}
+	d := base
+	for i := 1; i < attempt; i++ {
+		d *= 2
+		if d > 30*time.Second {
+			return 30 * time.Second
+		}
+	}
+	if d > 30*time.Second {
+		return 30 * time.Second
+	}
+	return d
+}