package filesystem

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"code.uint32.ru/tiny/storage/internal/errinternal"
)

const (
	fileModeDir  os.FileMode = 0755
	fileModeFile os.FileMode = 0644
)

var (
	ErrInvalidKey = errinternal.ErrInvalidKey
	ErrNotFound   = errinternal.ErrNotFound
)

func New(path string) (*Storage, error) {
	info, err := os.Stat(path)
	if err != nil {
		return nil, err
	}

	if !info.IsDir() {
		return nil, fmt.Errorf("provided path %s is not a directory", path)
	}

	abs, err := filepath.Abs(path)
	if err != nil {
		return nil, fmt.Errorf("could not tarnslate %s to absolute path", path)
	}

	return &Storage{Dir: abs}, nil
}

type Storage struct {
	Dir string
}

func (s *Storage) Save(key string, data []byte) error {
	if err := validateKey(key); err != nil {
		return err
	}

	path := s.getKeyPath(key)
	if err := os.MkdirAll(path, fileModeDir); err != nil {
		return err
	}

	if err := os.WriteFile(filepath.Join(path, key), data, fileModeFile); err != nil {
		return err
	}

	return nil
}

func (s *Storage) Load(key string) ([]byte, error) {
	if err := validateKey(key); err != nil {
		return nil, err
	}

	path := s.getKeyPath(key)

	b, err := os.ReadFile(filepath.Join(path, key))
	if err != nil && errors.Is(err, os.ErrNotExist) {
		return nil, errors.Join(errinternal.ErrNotFound, err)
	} else if err != nil {
		return nil, err
	}

	return b, nil
}

func (s *Storage) Delete(key string) error {
	if err := validateKey(key); err != nil {
		return err
	}

	path := s.getKeyPath(key)

	err := os.Remove(filepath.Join(path, key))
	if err != nil && errors.Is(err, os.ErrNotExist) {
		return nil
	} else if err != nil {
		return err
	}

	// TODO: think of cleaning up path when no files left
	// in /basedir/a/b/ after deleting key abc

	return nil
}

func (s *Storage) getKeyPath(key string) string {
	return filepath.Join(s.Dir, getPrefixPath(key))
}

func validateKey(key string) error {
	if len([]rune(key)) < 3 {
		return errors.Join(ErrInvalidKey, fmt.Errorf("key must be at least 3 characters long"))
	}

	// Of course windoze guys are missing the whole point, but
	// let us use os-specific path separator and not ruin the whole fun
	// for them :)
	if strings.Contains(key, string(os.PathSeparator)) {
		return errors.Join(ErrInvalidKey, fmt.Errorf("key must not contain path separator character: %s", string(os.PathSeparator)))
	}

	return nil
}

func getPrefixPath(key string) string {
	r := []rune(key)
	out := []rune{r[0], os.PathSeparator, r[1]}

	return string(out)
}