SUSE/saptune

package app

import (
    "encoding/json"
    "fmt"
    "github.com/SUSE/saptune/sap/note"
    "os"
    "path"
)

// SaptuneStateDir defines saptunes saved state directory
const SaptuneStateDir = "/run/saptune/saved_state"

// State stores and manages serialised note states.
type State struct {
    StateDirPrefix string
}

// GetPathToNote returns path to the serialised note state file.
func (state *State) GetPathToNote(noteID string) string {
    return path.Join(state.StateDirPrefix, SaptuneStateDir, noteID)
}

// Store creates a file under state directory with the object serialised
// into JSON. Overwrite existing file if there is any.
func (state *State) Store(noteID string, obj note.Note, overwriteExisting bool) error {
    content, err := json.Marshal(obj)
    if err != nil {
        return err
    }
    if err = os.MkdirAll(path.Join(state.StateDirPrefix, SaptuneStateDir), 0755); err != nil {
        return err
    }
    if _, err := os.Stat(state.GetPathToNote(noteID)); os.IsNotExist(err) || overwriteExisting {
        return os.WriteFile(state.GetPathToNote(noteID), content, 0644)
    }
    return nil
}

// List all stored note states. Return note numbers.
func (state *State) List() (ret []string, err error) {
    if err = os.MkdirAll(path.Join(state.StateDirPrefix, SaptuneStateDir), 0755); err != nil {
        return
    }
    // List SaptuneStateDir and collect number from file names
    dirContent, err := os.ReadDir(path.Join(state.StateDirPrefix, SaptuneStateDir))
    if os.IsNotExist(err) {
        return []string{}, nil
    } else if err != nil {
        return
    }
    ret = make([]string, 0, len(dirContent))
    for _, info := range dirContent {
        ret = append(ret, info.Name())
    }
    return
}

// Retrieve deserialises a SAP note into the destination pointer.
// The destination must be a pointer.
func (state *State) Retrieve(noteID string, dest interface{}) error {
    content, err := os.ReadFile(state.GetPathToNote(noteID))
    if err != nil {
        return err
    }
    if len(content) == 0 {
        return fmt.Errorf("empty state file")
    }
    return json.Unmarshal(content, dest)
}

// Remove a serialised state file.
func (state *State) Remove(noteID string) error {
    _, err := os.Stat(state.GetPathToNote(noteID))
    if os.IsNotExist(err) {
        return nil
    } else if err == nil {
        return os.Remove(state.GetPathToNote(noteID))
    } else {
        return err
    }
}