gtsocial-umbx

assets.go (4507B)

---

 // GoToSocial
 // Copyright (C) GoToSocial Authors admin@gotosocial.org
 // SPDX-License-Identifier: AGPL-3.0-or-later
 //
 // 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"
 	"strings"
 
 	"github.com/gin-gonic/gin"
 	"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
 }
 
 // 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
 //
 // todo: move this middleware out of the 'web' package and into the 'middleware'
 // package along with the other middlewares
 func (m *Module) assetsCacheControlMiddleware(fs http.FileSystem) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		// Acquire context from gin request.
 		ctx := c.Request.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(ctx, "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
 	}
 }