vorteil/direktiv

package engine

import (
    "bytes"
    "encoding/json"
    "errors"
    "fmt"
)

const (
    telemetryInfoVersion1 = "v1"
)

var ErrInvalidInstanceTelemetryInfo = errors.New("invalid instance telemetry info")

// InstanceTelemetryInfo keeps information useful to our telemetry logic.
type InstanceTelemetryInfo struct {
    Version  string // to let us identify and correct outdated versions of this struct
    TraceID  string
    SpanID   string
    CallPath string

    NamespaceName string
}

func (info *InstanceTelemetryInfo) MarshalJSON() ([]byte, error) {
    if info == nil {
        return json.Marshal(&instanceTelemetryInfoV1{
            Version: telemetryInfoVersion1,
        })
    }

    return json.Marshal(&instanceTelemetryInfoV1{
        Version:  telemetryInfoVersion1,
        TraceID:  info.TraceID,
        SpanID:   info.SpanID,
        CallPath: info.CallPath,

        NamespaceName: info.NamespaceName,
    })
}

type instanceTelemetryInfoV1 struct {
    Version  string `json:"version"`
    TraceID  string `json:"trace_id"`
    SpanID   string `json:"span_id"`
    CallPath string `json:"call_path"`

    NamespaceName string
}

//nolint:dupl
func LoadInstanceTelemetryInfo(data []byte) (*InstanceTelemetryInfo, error) {
    m := make(map[string]interface{})

    err := json.Unmarshal(data, &m)
    if err != nil {
        return nil, err
    }

    version, defined := m["version"]
    if !defined {
        return nil, fmt.Errorf("failed to load instance telemetry info: %w: missing version", ErrInvalidInstanceTelemetryInfo)
    }

    var info *InstanceTelemetryInfo

    dec := json.NewDecoder(bytes.NewReader(data))
    dec.DisallowUnknownFields()

    switch version {
    case telemetryInfoVersion1:
        var v1 instanceTelemetryInfoV1
        err = dec.Decode(&v1)
        if err != nil {
            return nil, fmt.Errorf("failed to load instance telemetry info: %w: %w", ErrInvalidInstanceTelemetryInfo, err)
        }

        info = &InstanceTelemetryInfo{
            Version:  v1.Version,
            TraceID:  v1.TraceID,
            SpanID:   v1.SpanID,
            CallPath: v1.CallPath,

            NamespaceName: v1.NamespaceName,
        }

    default:
        return nil, fmt.Errorf("failed to load instance telemetry info: %w: unknown version", ErrInvalidInstanceTelemetryInfo)
    }

    return info, nil
}