package storage

import (
	"crypto/rand"
	"errors"
	"math/big"
	"strings"
)

var ErrNoSuchFile = errors.New("no such file")

type Storage struct {
	files map[string]File
}

func NewStorage() *Storage {
	return &Storage{
		files: make(map[string]File),
	}
}

func generateKey(length uint) (string, error) {
	key := make([]string, 0, 0)
	alphabet := "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789abcdefghkmnpqrstuvwxyz"

	for i := uint(0); i < length; i++ {
		n, err := rand.Int(rand.Reader, big.NewInt(int64(len(alphabet))))

		if err != nil {
			return "", err
		}

		key = append(key, string(alphabet[n.Int64()]))
	}

	return strings.Join(key, ""), nil
}

func (s *Storage) Get(key string) (*File, error) {
	if file, ok := s.files[key]; ok {
		return &file, nil
	} else {
		return nil, ErrNoSuchFile
	}
}

func (s *Storage) Put(file File) (string, error) {
	key, err := generateKey(8)

	if err != nil {
		return "", err
	}

	s.files[key] = file

	return key, nil
}