// NegotiateContentEncoding returns the best offered content encoding for the
// request's Accept-Encoding header. If two offers match with equal weight and
// then the offer earlier in the list is preferred. If no offers are
// acceptable, then "" is returned.
func NegotiateContentEncoding(r *http.Request, offers []string) string {
bestOffer := "identity"
bestQ := -1.0
specs := header.ParseAccept(r.Header, "Accept-Encoding")
for _, offer := range offers {
for _, spec := range specs {
if spec.Q > bestQ &&
(spec.Value == "*" || spec.Value == offer) {
bestQ = spec.Q
bestOffer = offer
}
}
}
if bestQ == 0 {
bestOffer = ""
}
return bestOffer
}
// NegotiateContentType returns the best offered content type for the request's
// Accept header. If two offers match with equal weight, then the more specific
// offer is preferred. For example, text/* trumps */*. If two offers match
// with equal weight and specificity, then the offer earlier in the list is
// preferred. If no offers match, then defaultOffer is returned.
func NegotiateContentType(r *http.Request, offers []string, defaultOffer string) string {
bestOffer := defaultOffer
bestQ := -1.0
bestWild := 3
specs := header.ParseAccept(r.Header, "Accept")
for _, offer := range offers {
for _, spec := range specs {
switch {
case spec.Q == 0.0:
// ignore
case spec.Q < bestQ:
// better match found
case spec.Value == "*/*":
if spec.Q > bestQ || bestWild > 2 {
bestQ = spec.Q
bestWild = 2
bestOffer = offer
}
case strings.HasSuffix(spec.Value, "/*"):
if strings.HasPrefix(offer, spec.Value[:len(spec.Value)-1]) &&
(spec.Q > bestQ || bestWild > 1) {
bestQ = spec.Q
bestWild = 1
bestOffer = offer
}
default:
if spec.Value == offer &&
(spec.Q > bestQ || bestWild > 0) {
bestQ = spec.Q
bestWild = 0
bestOffer = offer
}
}
}
}
return bestOffer
}