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directive.go
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directive.go
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/**
* Copyright 2015 Paul Querna, 2018 Luis Gomez
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package cacheobject
import (
"fmt"
"strings"
"time"
)
var (
defaultMaxAge = time.Hour * 24 * 365
)
// TODO(pquerna): add extensions from here: http://www.iana.org/assignments/http-cache-directives/http-cache-directives.xhtml
// DeltaSeconds specifies a non-negative integer, representing
// time in seconds: http://tools.ietf.org/html/rfc7234#section-1.2.1
//
// When set to -1, this means unset.
//
type DeltaSeconds int32
// Fields present in a header.
type FieldNames map[string]bool
// LOW LEVEL API: Repersentation of possible response directives in a `Cache-Control` header: http://tools.ietf.org/html/rfc7234#section-5.2.2
//
// Note: Many fields will be `nil` in practice.
//
type ResponseCacheDirectives struct {
// must-revalidate(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.1
//
// The "must-revalidate" response directive indicates that once it has
// become stale, a cache MUST NOT use the response to satisfy subsequent
// requests without successful validation on the origin server.
MustRevalidate bool
// no-cache(FieldName): http://tools.ietf.org/html/rfc7234#section-5.2.2.2
//
// The "no-cache" response directive indicates that the response MUST
// NOT be used to satisfy a subsequent request without successful
// validation on the origin server.
//
// If the no-cache response directive specifies one or more field-names,
// then a cache MAY use the response to satisfy a subsequent request,
// subject to any other restrictions on caching. However, any header
// fields in the response that have the field-name(s) listed MUST NOT be
// sent in the response to a subsequent request without successful
// revalidation with the origin server.
NoCache FieldNames
// no-cache(cast-to-bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.2
//
// While the RFC defines optional field-names on a no-cache directive,
// many applications only want to know if any no-cache directives were
// present at all.
NoCachePresent bool
// no-store(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.3
//
// The "no-store" request directive indicates that a cache MUST NOT
// store any part of either this request or any response to it. This
// directive applies to both private and shared caches.
NoStore bool
// no-transform(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.4
//
// The "no-transform" response directive indicates that an intermediary
// (regardless of whether it implements a cache) MUST NOT transform the
// payload, as defined in Section 5.7.2 of RFC7230.
NoTransform bool
// public(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.5
//
// The "public" response directive indicates that any cache MAY store
// the response, even if the response would normally be non-cacheable or
// cacheable only within a private cache.
Public bool
// private(FieldName): http://tools.ietf.org/html/rfc7234#section-5.2.2.6
//
// The "private" response directive indicates that the response message
// is intended for a single user and MUST NOT be stored by a shared
// cache. A private cache MAY store the response and reuse it for later
// requests, even if the response would normally be non-cacheable.
//
// If the private response directive specifies one or more field-names,
// this requirement is limited to the field-values associated with the
// listed response header fields. That is, a shared cache MUST NOT
// store the specified field-names(s), whereas it MAY store the
// remainder of the response message.
Private FieldNames
// private(cast-to-bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.6
//
// While the RFC defines optional field-names on a private directive,
// many applications only want to know if any private directives were
// present at all.
PrivatePresent bool
// proxy-revalidate(bool): http://tools.ietf.org/html/rfc7234#section-5.2.2.7
//
// The "proxy-revalidate" response directive has the same meaning as the
// must-revalidate response directive, except that it does not apply to
// private caches.
ProxyRevalidate bool
// max-age(delta seconds): http://tools.ietf.org/html/rfc7234#section-5.2.2.8
//
// The "max-age" response directive indicates that the response is to be
// considered stale after its age is greater than the specified number
// of seconds.
MaxAge DeltaSeconds
// s-maxage(delta seconds): http://tools.ietf.org/html/rfc7234#section-5.2.2.9
//
// The "s-maxage" response directive indicates that, in shared caches,
// the maximum age specified by this directive overrides the maximum age
// specified by either the max-age directive or the Expires header
// field. The s-maxage directive also implies the semantics of the
// proxy-revalidate response directive.
SMaxAge DeltaSeconds
////
// Experimental features
// - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#Extension_Cache-Control_directives
// - https://www.fastly.com/blog/stale-while-revalidate-stale-if-error-available-today
////
// immutable(cast-to-bool): experimental feature
Immutable bool
// stale-if-error(delta seconds): experimental feature
StaleIfError DeltaSeconds
// stale-while-revalidate(delta seconds): experimental feature
StaleWhileRevalidate DeltaSeconds
// Extensions: http://tools.ietf.org/html/rfc7234#section-5.2.3
//
// The Cache-Control header field can be extended through the use of one
// or more cache-extension tokens, each with an optional value. A cache
// MUST ignore unrecognized cache directives.
Extensions []string
}
func (directive *ResponseCacheDirectives) BuildResponseHeader() string {
headerTokens := make([]string, 0)
if directive.Immutable {
directive.MaxAge = DeltaSeconds(defaultMaxAge.Seconds())
}
if len(directive.Private) > 0 {
headerTokens = append(headerTokens, "private")
}
if len(directive.NoCache) > 0 {
headerTokens = append(headerTokens, "no-cache")
}
if directive.Public {
headerTokens = append(headerTokens, "public")
}
if directive.NoStore {
headerTokens = append(headerTokens, "no-store")
}
if directive.NoTransform {
headerTokens = append(headerTokens, "no-transform")
}
if directive.MustRevalidate {
headerTokens = append(headerTokens, "must-revalidate")
}
if directive.ProxyRevalidate {
headerTokens = append(headerTokens, "proxy-revalidate")
}
if directive.Immutable {
headerTokens = append(headerTokens, "immutable")
}
if directive.MaxAge != 0 {
headerTokens = append(headerTokens, fmt.Sprintf("max-age=%d", directive.MaxAge))
}
if directive.SMaxAge != 0 {
headerTokens = append(headerTokens, fmt.Sprintf("s-maxage=%d", directive.SMaxAge))
}
if directive.StaleIfError != 0 {
headerTokens = append(headerTokens, fmt.Sprintf("stale-if-error=%d", directive.StaleIfError))
}
if directive.StaleWhileRevalidate != 0 {
headerTokens = append(headerTokens, fmt.Sprintf("stale-while-revalidate=%d", directive.StaleWhileRevalidate))
}
headerTokens = append(headerTokens, directive.Extensions...)
return strings.Join(headerTokens, ", ")
}