gitea

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