vorteil/direktiv

package engine

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

const (
    instanceRuntimeInfoVersion1 = "v1"
)

var ErrInvalidInstanceRuntimeInfo = errors.New("invalid instance runtime info")

// InstanceRuntimeInfo keeps other miscellaneous information useful to the engine.
type InstanceRuntimeInfo struct {
    Version        string // to let us identify and correct outdated versions of this struct
    Controller     string
    Flow           []string // NOTE: now that we keep a copy of the definition we could replace []string with []int
    StateBeginTime time.Time
    Attempts       int
}

func (info *InstanceRuntimeInfo) MarshalJSON() ([]byte, error) {
    if info == nil {
        return json.Marshal(&instanceRuntimeInfoV1{
            Version: instanceRuntimeInfoVersion1,
        })
    }

    return json.Marshal(&instanceRuntimeInfoV1{
        Version:        instanceRuntimeInfoVersion1,
        Controller:     info.Controller,
        Flow:           info.Flow,
        StateBeginTime: info.StateBeginTime,
        Attempts:       info.Attempts,
    })
}

type instanceRuntimeInfoV1 struct {
    Version        string    `json:"version"`
    Controller     string    `json:"controller"`
    Flow           []string  `json:"flow"`
    StateBeginTime time.Time `json:"state_begin_time"`
    Attempts       int       `json:"attempts"`
}

//nolint:dupl
func LoadInstanceRuntimeInfo(data []byte) (*InstanceRuntimeInfo, 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 runtime info: %w: missing version", ErrInvalidInstanceRuntimeInfo)
    }

    var info *InstanceRuntimeInfo

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

    switch version {
    case instanceRuntimeInfoVersion1:
        var v1 instanceRuntimeInfoV1
        err = dec.Decode(&v1)
        if err != nil {
            return nil, fmt.Errorf("failed to load instance runtime info: %w: %w", ErrInvalidInstanceRuntimeInfo, err)
        }

        info = &InstanceRuntimeInfo{
            Version:        v1.Version,
            Controller:     v1.Controller,
            Flow:           v1.Flow,
            StateBeginTime: v1.StateBeginTime,
            Attempts:       v1.Attempts,
        }

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

    return info, nil
}