// Copyright 2020 The Gitea Authors. All rights reserved.// SPDX-License-Identifier: MIT package httpcache import (	"io"	"net/http"	"strconv"	"strings"	"time" 	"code.gitea.io/gitea/modules/setting") // SetCacheControlInHeader sets suitable cache-control headers in the responsefunc SetCacheControlInHeader(h http.Header, maxAge time.Duration, additionalDirectives ...string) {	directives := make([]string, 0, 2+len(additionalDirectives)) 	// "max-age=0 + must-revalidate" (aka "no-cache") is preferred instead of "no-store"	// because browsers may restore some input fields after navigate-back / reload a page.	if setting.IsProd {		if maxAge == 0 {			directives = append(directives, "max-age=0", "private", "must-revalidate")		} else {			directives = append(directives, "private", "max-age="+strconv.Itoa(int(maxAge.Seconds())))		}	} else {		directives = append(directives, "max-age=0", "private", "must-revalidate") 		// to remind users they are using non-prod setting.		h.Set("X-Gitea-Debug", "RUN_MODE="+setting.RunMode)		h.Set("X-Forgejo-Debug", "RUN_MODE="+setting.RunMode)	} 	h.Set("Cache-Control", strings.Join(append(directives, additionalDirectives...), ", "))} func ServeContentWithCacheControl(w http.ResponseWriter, req *http.Request, name string, modTime time.Time, content io.ReadSeeker) {	SetCacheControlInHeader(w.Header(), setting.StaticCacheTime)	http.ServeContent(w, req, name, modTime, content)} // HandleGenericETagCache handles ETag-based caching for a HTTP request.// It returns true if the request was handled.func HandleGenericETagCache(req *http.Request, w http.ResponseWriter, etag string) (handled bool) {	if len(etag) > 0 {		w.Header().Set("Etag", etag)		if checkIfNoneMatchIsValid(req, etag) {			w.WriteHeader(http.StatusNotModified)			return true		}	}	SetCacheControlInHeader(w.Header(), setting.StaticCacheTime)	return false} // checkIfNoneMatchIsValid tests if the header If-None-Match matches the ETagfunc checkIfNoneMatchIsValid(req *http.Request, etag string) bool {	ifNoneMatch := req.Header.Get("If-None-Match")	if len(ifNoneMatch) > 0 {		for _, item := range strings.Split(ifNoneMatch, ",") {			item = strings.TrimPrefix(strings.TrimSpace(item), "W/") // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag#directives			if item == etag {				return true			}		}	}	return false} // HandleGenericETagTimeCache handles ETag-based caching with Last-Modified caching for a HTTP request.// It returns true if the request was handled.func HandleGenericETagTimeCache(req *http.Request, w http.ResponseWriter, etag string, lastModified *time.Time) (handled bool) {	if len(etag) > 0 {		w.Header().Set("Etag", etag)	}	if lastModified != nil && !lastModified.IsZero() {		// http.TimeFormat required a UTC time, refer to https://pkg.go.dev/net/http#TimeFormat		w.Header().Set("Last-Modified", lastModified.UTC().Format(http.TimeFormat))	} 	if len(etag) > 0 {		if checkIfNoneMatchIsValid(req, etag) {			w.WriteHeader(http.StatusNotModified)			return true		}	}	if lastModified != nil && !lastModified.IsZero() {		ifModifiedSince := req.Header.Get("If-Modified-Since")		if ifModifiedSince != "" {			t, err := time.Parse(http.TimeFormat, ifModifiedSince)			if err == nil && lastModified.Unix() <= t.Unix() {				w.WriteHeader(http.StatusNotModified)				return true			}		}	}	SetCacheControlInHeader(w.Header(), setting.StaticCacheTime)	return false}