97 lines
3.7 KiB
Go
97 lines
3.7 KiB
Go
/*
|
|
GoToSocial
|
|
Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
|
|
|
|
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 api
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
|
|
"github.com/gin-gonic/gin"
|
|
)
|
|
|
|
// Offer represents an offered mime-type.
|
|
type Offer string
|
|
|
|
const (
|
|
AppJSON Offer = `application/json` // AppJSON is the mime type for 'application/json'.
|
|
AppActivityJSON Offer = `application/activity+json` // AppActivityJSON is the mime type for 'application/activity+json'.
|
|
AppActivityLDJSON Offer = `application/ld+json; profile="https://www.w3.org/ns/activitystreams"` // AppActivityLDJSON is the mime type for 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
|
|
TextHTML Offer = `text/html` // TextHTML is the mime type for 'text/html'.
|
|
)
|
|
|
|
// ActivityPubAcceptHeaders represents the Accept headers mentioned here:
|
|
// https://www.w3.org/TR/activitypub/#retrieving-objects
|
|
var ActivityPubAcceptHeaders = []Offer{
|
|
AppActivityJSON,
|
|
AppActivityLDJSON,
|
|
}
|
|
|
|
// JSONAcceptHeaders is a slice of offers that just contains application/json types.
|
|
var JSONAcceptHeaders = []Offer{
|
|
AppJSON,
|
|
}
|
|
|
|
// HTMLAcceptHeaders is a slice of offers that just contains text/html types.
|
|
var HTMLAcceptHeaders = []Offer{
|
|
TextHTML,
|
|
}
|
|
|
|
// NegotiateAccept takes the *gin.Context from an incoming request, and a
|
|
// slice of Offers, and performs content negotiation for the given request
|
|
// with the given content-type offers. It will return a string representation
|
|
// of the first suitable content-type, or an error if something goes wrong or
|
|
// a suiteable content-type cannot be matched.
|
|
//
|
|
// For example, if the request in the *gin.Context has Accept headers of value
|
|
// [application/json, text/html], and the provided offers are of value
|
|
// [application/json, application/xml], then the returned string will be
|
|
// 'application/json', which indicates the content-type that should be returned.
|
|
//
|
|
// If there are no Accept headers in the request, or the length of offers is 0,
|
|
// then an error will be returned, so this function should only be called in places
|
|
// where format negotiation is actually needed and headers are expected to be present
|
|
// on incoming requests.
|
|
//
|
|
// Callers can use the offer slices exported in this package as shortcuts for
|
|
// often-used Accept types.
|
|
//
|
|
// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation#server-driven_content_negotiation
|
|
func NegotiateAccept(c *gin.Context, offers ...Offer) (string, error) {
|
|
if len(offers) == 0 {
|
|
return "", errors.New("no format offered")
|
|
}
|
|
|
|
accepts := c.Request.Header.Values("Accept")
|
|
if len(accepts) == 0 {
|
|
return "", fmt.Errorf("no Accept header(s) set on incoming request; this endpoint offers %s", offers)
|
|
}
|
|
|
|
strings := []string{}
|
|
for _, o := range offers {
|
|
strings = append(strings, string(o))
|
|
}
|
|
|
|
format := c.NegotiateFormat(strings...)
|
|
if format == "" {
|
|
return "", fmt.Errorf("no format can be offered for requested Accept header(s) %s; this endpoint offers %s", accepts, offers)
|
|
}
|
|
|
|
return format, nil
|
|
}
|