package backend

import (
	"errors"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
)

// CharacterService serves character images from a single directory.
type CharacterService struct {
	root *os.Root
}

// NewCharacterService opens the characters directory. Files outside it can never be served.
func NewCharacterService(path string) (*CharacterService, error) {
	root, err := os.OpenRoot(path)
	if err != nil {
		return nil, err
	}
	return &CharacterService{root: root}, nil
}

// List returns the file names of all character images.
func (c *CharacterService) List() ([]string, error) {
	entries, err := fs.ReadDir(c.root.FS(), ".")
	if err != nil {
		return nil, err
	}
	characters := []string{}
	for _, entry := range entries {
		if !entry.IsDir() && isImage(entry.Name()) {
			characters = append(characters, entry.Name())
		}
	}
	return characters, nil
}

// Open opens the character image with the given file name.
func (c *CharacterService) Open(name string) (*os.File, error) {
	if name == "" || name != filepath.Base(name) || !isImage(name) {
		return nil, ErrInvalidName
	}
	f, err := c.root.Open(name)
	if errors.Is(err, fs.ErrNotExist) {
		return nil, ErrNotFound
	}
	return f, err
}

// Close releases the characters directory.
func (c *CharacterService) Close() error {
	return c.root.Close()
}

func isImage(name string) bool {
	switch strings.ToLower(filepath.Ext(name)) {
	case ".jpg", ".jpeg", ".png":
		return true
	}
	return false
}