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package db
import (
"encoding/base64"
"fmt"
"net/http"
"strings"
"time"
)
// CacheControl sets the default cache policy on static asset responses
func CacheControl(next http.Handler) http.HandlerFunc {
return http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
cacheDisabled := ConfigCache("cache_disabled").(bool)
if cacheDisabled {
res.Header().Add("Cache-Control", "no-cache")
next.ServeHTTP(res, req)
} else {
age := int64(ConfigCache("cache_max_age").(float64))
etag := ConfigCache("etag").(string)
if age == 0 {
age = DefaultMaxAge
}
policy := fmt.Sprintf("max-age=%d, public", age)
res.Header().Add("ETag", etag)
res.Header().Add("Cache-Control", policy)
if match := req.Header.Get("If-None-Match"); match != "" {
if strings.Contains(match, etag) {
res.WriteHeader(http.StatusNotModified)
return
}
}
next.ServeHTTP(res, req)
}
})
}
// NewEtag generates a new Etag for response caching
func NewEtag() string {
now := fmt.Sprintf("%d", time.Now().Unix())
etag := base64.StdEncoding.EncodeToString([]byte(now))
return etag
}
// InvalidateCache sets a new Etag for http responses
func InvalidateCache() error {
err := PutConfig("etag", NewEtag())
if err != nil {
return err
}
return nil
}
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