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/*
GoToSocial
Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package web
import (
"fmt"
"net/http"
"path"
"path/filepath"
"strings"
"github.com/gin-gonic/gin"
"github.com/superseriousbusiness/gotosocial/internal/config"
"github.com/superseriousbusiness/gotosocial/internal/log"
)
type fileSystem struct {
fs http.FileSystem
}
// FileSystem server that only accepts directory listings when an index.html is available
// from https://gist.github.com/hauxe/f2ea1901216177ccf9550a1b8bd59178
func (fs fileSystem) Open(path string) (http.File, error) {
f, err := fs.fs.Open(path)
if err != nil {
return nil, err
}
s, _ := f.Stat()
if s.IsDir() {
index := strings.TrimSuffix(path, "/") + "/index.html"
if _, err := fs.fs.Open(index); err != nil {
return nil, err
}
}
return f, nil
}
func (m *Module) mountAssetsFilesystem(group *gin.RouterGroup) {
webAssetsAbsFilePath, err := filepath.Abs(config.GetWebAssetBaseDir())
if err != nil {
log.Panicf("mountAssetsFilesystem: error getting absolute path of assets dir: %s", err)
}
fs := fileSystem{http.Dir(webAssetsAbsFilePath)}
// use the cache middleware on all handlers in this group
group.Use(m.assetsCacheControlMiddleware(fs))
// serve static file system in the root of this group,
// will end up being something like "/assets/"
group.StaticFS("/", fs)
}
// getAssetFileInfo tries to fetch the ETag for the given filePath from the module's
// assetsETagCache. If it can't be found there, it uses the provided http.FileSystem
// to generate a new ETag to go in the cache, which it then returns.
func (m *Module) getAssetETag(filePath string, fs http.FileSystem) (string, error) {
file, err := fs.Open(filePath)
if err != nil {
return "", fmt.Errorf("error opening %s: %s", filePath, err)
}
defer file.Close()
fileInfo, err := file.Stat()
if err != nil {
return "", fmt.Errorf("error statting %s: %s", filePath, err)
}
fileLastModified := fileInfo.ModTime()
if cachedETag, ok := m.eTagCache.Get(filePath); ok && !fileLastModified.After(cachedETag.lastModified) {
// only return our cached etag if the file wasn't
// modified since last time, otherwise generate a
// new one; eat fresh!
return cachedETag.eTag, nil
}
eTag, err := generateEtag(file)
if err != nil {
return "", fmt.Errorf("error generating etag: %s", err)
}
// put new entry in cache before we return
m.eTagCache.Set(filePath, eTagCacheEntry{
eTag: eTag,
lastModified: fileLastModified,
})
return eTag, nil
}
// assetsCacheControlMiddleware implements Cache-Control header setting, and checks
// for files inside the given http.FileSystem.
//
// The middleware checks if the file has been modified using If-None-Match etag,
// if present. If the file hasn't been modified, the middleware returns 304.
//
// See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-None-Match
// and: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
func (m *Module) assetsCacheControlMiddleware(fs http.FileSystem) gin.HandlerFunc {
return func(c *gin.Context) {
// set this Cache-Control header to instruct clients to validate the response with us
// before each reuse (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control)
c.Header(cacheControlHeader, cacheControlNoCache)
ifNoneMatch := c.Request.Header.Get(ifNoneMatchHeader)
// derive the path of the requested asset inside the provided filesystem
upath := c.Request.URL.Path
if !strings.HasPrefix(upath, "/") {
upath = "/" + upath
}
assetFilePath := strings.TrimPrefix(path.Clean(upath), assetsPathPrefix)
// either fetch etag from ttlcache or generate it
eTag, err := m.getAssetETag(assetFilePath, fs)
if err != nil {
log.Errorf("error getting ETag for %s: %s", assetFilePath, err)
return
}
// Regardless of what happens further down, set the etag header
// so that the client has the up-to-date version.
c.Header(eTagHeader, eTag)
// If client already has latest version of the asset, 304 + bail.
if ifNoneMatch == eTag {
c.AbortWithStatus(http.StatusNotModified)
return
}
// else let the rest of the request be processed normally
}
}
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