feat: support adaptive traffic units and precise quotas

go-backend/internal/http/handler/traffic_limit.go

@@ -0,0 +1,28 @@
+package handler
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+)
+
+// flowMiB is optional so older clients can keep sending the GB-based flow field.
+// A positive value takes precedence and preserves sub-GB limits exactly.
+func parseTrafficLimit(req map[string]interface{}, defaultGB int64) (flowGB, flowMiB int64, err error) {
+	flowGB = asInt64(req["flow"], defaultGB)
+	if flowGB < 0 {
+		return 0, 0, fmt.Errorf("流量限制不能小于0")
+	}
+	raw, present := req["flowMiB"]
+	if !present {
+		return flowGB, 0, nil
+	}
+	flowMiB, err = strconv.ParseInt(asString(raw), 10, 64)
+	if err != nil || flowMiB < 0 || flowMiB > math.MaxInt64/bytesPerMiB {
+		return 0, 0, fmt.Errorf("流量限制超出范围")
+	}
+	if flowMiB > 0 {
+		flowGB = (flowMiB-1)/1024 + 1
+	}
+	return flowGB, flowMiB, nil
+}