storage.go

package main

import (
	"encoding/json"
	"os"
	"path/filepath"
)

type Storage[T any] struct {
	FileName string
}

func NewStorage[T any](fileName string) *Storage[T] {
	exePath, _ := os.Executable()
	dir := filepath.Dir(exePath)
	fullPath := filepath.Join(dir, fileName)

	return &Storage[T]{FileName: fullPath}
}

func (s *Storage[T]) Save(data T) error {
	fileData, err := json.MarshalIndent(data, "", "    ")

	if err != nil {
		return err
	}
	return os.WriteFile(s.FileName, fileData, 0644)
}

func (s *Storage[T]) Load(data *T) error {

	// ✅ Step 1: ensure file exists
	if _, err := os.Stat(s.FileName); os.IsNotExist(err) {
		os.WriteFile(s.FileName, []byte("[]"), 0644)
	}

	// read file
	fileData, err := os.ReadFile(s.FileName)
	if err != nil {
		return err
	}

	return json.Unmarshal(fileData, data)
}