backrest/internal/config/jsonstore.go

package config

import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sync"

	v1 "github.com/garethgeorge/backrest/gen/go/v1"
	"github.com/natefinch/atomic"
	"google.golang.org/protobuf/encoding/protojson"
)

type JsonFileStore struct {
	Path string
	mu   sync.Mutex
}

var _ ConfigStore = &JsonFileStore{}

func (f *JsonFileStore) Get() (*v1.Config, error) {
	f.mu.Lock()
	defer f.mu.Unlock()

	data, err := os.ReadFile(f.Path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, ErrConfigNotFound
		}
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	var config v1.Config
	if err = (protojson.UnmarshalOptions{DiscardUnknown: true}).Unmarshal(data, &config); err != nil {
		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
	}

	return &config, nil
}

func (f *JsonFileStore) Update(config *v1.Config) error {
	f.mu.Lock()
	defer f.mu.Unlock()

	data, err := protojson.MarshalOptions{
		Indent:    "  ",
		Multiline: true,
	}.Marshal(config)
	if err != nil {
		return fmt.Errorf("failed to marshal config: %w", err)
	}

	err = os.MkdirAll(filepath.Dir(f.Path), 0755)
	if err != nil {
		return fmt.Errorf("failed to create config directory: %w", err)
	}

	err = atomic.WriteFile(f.Path, bytes.NewReader(data))
	if err != nil {
		return fmt.Errorf("failed to write config file: %w", err)
	}

	// only the user running backrest should be able to read the config.
	if err := os.Chmod(f.Path, 0600); err != nil {
		return fmt.Errorf("chmod(0600) config file: %w", err)
	}

	return nil
}