refactor: split into packages and add tests

internal/util/util.go

@@ -0,0 +1,54 @@
+package util
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/akedrou/textdiff"
+	"github.com/akedrou/textdiff/myers"
+	apperrors "gitlab.com/technofab/nixtest/internal/errors"
+)
+
+func ComputeDiff(expected, actual string) (string, error) {
+	// FIXME: ComputeEdits deprecated
+	edits := myers.ComputeEdits(expected, actual)
+	diff, err := textdiff.ToUnified("expected", "actual", expected, edits, 3)
+	if err != nil {
+		return "", err
+	}
+	// remove newline hint
+	diff = strings.ReplaceAll(diff, "\\ No newline at end of file\n", "")
+	return diff, nil
+}
+
+// ParseFile reads and decodes a JSON file into the provided type
+func ParseFile[T any](filePath string) (result T, err error) {
+	file, err := os.Open(filePath)
+	if err != nil {
+		return result, &apperrors.FileReadError{Path: filePath, Err: fmt.Errorf("failed to open: %w", err)}
+	}
+	defer file.Close()
+
+	decoder := json.NewDecoder(file)
+	err = decoder.Decode(&result)
+	if err != nil {
+		return result, &apperrors.JSONUnmarshalError{Source: filePath, Err: fmt.Errorf("failed to decode: %w", err)}
+	}
+	return result, nil
+}
+
+// PrefixLines adds a prefix to each line of the input string
+func PrefixLines(input string, prefix string) string {
+	lines := strings.Split(input, "\n")
+	for i := range lines {
+		lines[i] = prefix + lines[i]
+	}
+	return strings.Join(lines, "\n")
+}
+
+func IsString(value any) bool {
+	_, ok := value.(string)
+	return ok
+}