package mock import ( "encoding/binary" "math" "math/rand" "net" "unsafe" "github.com/spf13/viper" ) const ( randomIPStrategyName = "random" incrementalIPStrategyName = "incremental" startIPConfigKey = "startIP" ) var ( fallbackStrategies map[string]ResolverFactory ) type ResolverFactory func(conf *viper.Viper) ResolverFallback func init() { fallbackStrategies = make(map[string]ResolverFactory) fallbackStrategies[incrementalIPStrategyName] = func(conf *viper.Viper) ResolverFallback { return &incrementalIPFallback{ latestIp: ipToInt32(net.ParseIP(conf.GetString(startIPConfigKey))), } } fallbackStrategies[randomIPStrategyName] = func(conf *viper.Viper) ResolverFallback { return &randomIPFallback{} } } func CreateResolverFallback(name string, config *viper.Viper) ResolverFallback { if factory, ok := fallbackStrategies[name]; ok { return factory(config) } else { return fallbackStrategies[randomIPStrategyName](config) } } type ResolverFallback interface { GetIP() net.IP } type incrementalIPFallback struct { latestIp uint32 } func (i *incrementalIPFallback) GetIP() net.IP { if i.latestIp < math.MaxInt32 { i.latestIp += 1 } return uint32ToIP(i.latestIp) } type randomIPFallback struct { } func (randomIPFallback) GetIP() net.IP { return uint32ToIP(uint32(rand.Int31())) } func uint32ToIP(i uint32) net.IP { bytes := (*[4]byte)(unsafe.Pointer(&i))[:] return net.IPv4(bytes[3], bytes[2], bytes[1], bytes[0]) } func ipToInt32(ip net.IP) uint32 { v4 := ip.To4() result := binary.BigEndian.Uint32(v4) return result }