package main

import (
	"context"
	"errors"
	"os"
	"path"
	"strings"

	"golang.org/x/net/webdav"
)

// errImagesOnly is returned when upload is rejected by image-only filter.
var errImagesOnly = errors.New("webdav: only image and SVG files allowed (.svg, .png, .jpg, .jpeg, .gif, .webp, .ico, .bmp, .avif)")

// allowedImageExtensions are the only extensions permitted for upload when images-only mode is on.
var allowedImageExtensions = map[string]bool{
	".svg": true, ".png": true, ".jpg": true, ".jpeg": true,
	".gif": true, ".webp": true, ".ico": true, ".bmp": true, ".avif": true,
}

// imageOnlyFS wraps a webdav.FileSystem and rejects PUT/copy of files that are not images or SVG.
type imageOnlyFS struct {
	webdav.FileSystem
}

func (f *imageOnlyFS) OpenFile(ctx context.Context, name string, flags int, perm os.FileMode) (webdav.File, error) {
	if flags&(os.O_CREATE|os.O_WRONLY|os.O_RDWR) != 0 {
		ext := strings.ToLower(path.Ext(path.Clean(name)))
		if ext == "" || !allowedImageExtensions[ext] {
			return nil, errImagesOnly
		}
	}
	return f.FileSystem.OpenFile(ctx, name, flags, perm)
}