package main import ( "encoding/json" "strconv" "strings" "time" "github.com/pkg/errors" ) type settingExtractor func([]byte) (interface{}, error) var extractors = map[string]settingExtractor{ "devicename": func(p []byte) (interface{}, error) { return extractGenericJSONValue("DeviceName", p) }, "ledstate": func(p []byte) (interface{}, error) { return extractFloatToInt("LedState", p) }, "module": extractModule, "otaurl": func(p []byte) (interface{}, error) { return extractGenericJSONValue("OtaUrl", p) }, "teleperiod": func(p []byte) (interface{}, error) { return extractFloatToInt("TelePeriod", p) }, "timezone": func(p []byte) (interface{}, error) { return extractGenericJSONValue("Timezone", p) }, "topic": func(p []byte) (interface{}, error) { return extractGenericJSONValue("Topic", p) }, } func extractSettingValue(setting string, payloadChan chan []byte) (interface{}, error) { e, ok := extractors[strings.ToLower(setting)] if !ok { // Default extractor: Full value e = func(in []byte) (interface{}, error) { return string(in), nil } } var deadline = time.NewTimer(cfg.MQTTCommandTimeout) for { select { case payload := <-payloadChan: return e(payload) case <-deadline.C: return nil, errors.New("Read timed out") } } } func extractGenericJSONValue(setting string, payload []byte) (interface{}, error) { var data = map[string]interface{}{} if err := json.Unmarshal(payload, &data); err != nil { return nil, errors.Wrap(err, "Unable to map payload into map[string]interface{}") } return data[setting], nil } func extractFloatToInt(setting string, payload []byte) (interface{}, error) { v, err := extractGenericJSONValue(setting, payload) if err != nil { return nil, err } if _, ok := v.(float64); !ok { return nil, errors.Errorf("Expected float value, got %T in %s", v, setting) } return int(v.(float64)), nil } func extractModule(payload []byte) (interface{}, error) { var v = &struct { Module map[string]string `json:"Module"` }{} if err := json.Unmarshal(payload, v); err != nil { return nil, err } var values []string for k := range v.Module { values = append(values, k) } if len(values) != 1 { return nil, errors.New("Unexpected number of module definitions found") } return strconv.Atoi(values[0]) }