refactor: split into packages and add tests

internal/snapshot/service.go

@@ -0,0 +1,70 @@
+package snapshot
+
+import (
+	"encoding/json"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	apperrors "gitlab.com/technofab/nixtest/internal/errors"
+	"gitlab.com/technofab/nixtest/internal/util"
+)
+
+// Service defines operations related to test snapshots
+type Service interface {
+	GetPath(snapshotDir string, testName string) string
+	CreateFile(filePath string, data any) error
+	LoadFile(filePath string) (any, error)
+	Stat(name string) (os.FileInfo, error)
+}
+
+type DefaultService struct{}
+
+func NewDefaultService() *DefaultService {
+	return &DefaultService{}
+}
+
+// GetPath generates the canonical path for a snapshot file
+func (s *DefaultService) GetPath(snapshotDir string, testName string) string {
+	fileName := filepath.ToSlash(
+		strings.ToLower(strings.ReplaceAll(testName, " ", "_")) + ".snap.json",
+	)
+	return path.Join(snapshotDir, fileName)
+}
+
+// CreateFile creates or updates a snapshot file with the given data
+func (s *DefaultService) CreateFile(filePath string, data any) error {
+	jsonData, err := json.MarshalIndent(data, "", "  ")
+	if err != nil {
+		return &apperrors.SnapshotCreateError{
+			FilePath: filePath,
+			Err:      &apperrors.JSONUnmarshalError{Source: "snapshot data for " + filePath, Err: err},
+		}
+	}
+
+	err = os.MkdirAll(path.Dir(filePath), 0777)
+	if err != nil {
+		return &apperrors.SnapshotCreateError{FilePath: filePath, Err: err}
+	}
+
+	err = os.WriteFile(filePath, jsonData, 0644)
+	if err != nil {
+		return &apperrors.SnapshotCreateError{FilePath: filePath, Err: err}
+	}
+	return nil
+}
+
+// LoadFile loads a snapshot file.
+func (s *DefaultService) LoadFile(filePath string) (any, error) {
+	result, err := util.ParseFile[any](filePath)
+	if err != nil {
+		return nil, &apperrors.SnapshotLoadError{FilePath: filePath, Err: err}
+	}
+	return result, nil
+}
+
+// Stat just wraps os.Stat
+func (s *DefaultService) Stat(name string) (os.FileInfo, error) {
+	return os.Stat(name)
+}