Golang goautoneg.ParseAccept函數代碼示例

// PrefersHTML returns true if the request was made by something that looks like a browser, or can receive HTML
func PrefersHTML(req *http.Request) bool {
	accepts := goautoneg.ParseAccept(req.Header.Get("Accept"))
	acceptsHTML := false
	acceptsJSON := false
	for _, accept := range accepts {
		if accept.Type == "text" && accept.SubType == "html" {
			acceptsHTML = true
		} else if accept.Type == "application" && accept.SubType == "json" {
			acceptsJSON = true
		}
	}

	// If HTML is accepted, return true
	if acceptsHTML {
		return true
	}

	// If JSON was specifically requested, return false
	// This gives browsers a way to make requests and add an "Accept" header to request JSON
	if acceptsJSON {
		return false
	}

	// In Intranet/Compatibility mode, IE sends an Accept header that does not contain "text/html".
	if strings.HasPrefix(req.UserAgent(), "Mozilla") {
		return true
	}

	return false
}

func chooseEncoder(req *http.Request) (encoder, string) {
	accepts := goautoneg.ParseAccept(req.Header.Get(acceptHeader))
	for _, accept := range accepts {
		switch {
		case accept.Type == "application" &&
			accept.SubType == "vnd.google.protobuf" &&
			accept.Params["proto"] == "io.prometheus.client.MetricFamily":
			switch accept.Params["encoding"] {
			case "delimited":
				return text.WriteProtoDelimited, DelimitedTelemetryContentType
			case "text":
				return text.WriteProtoText, ProtoTextTelemetryContentType
			case "compact-text":
				return text.WriteProtoCompactText, ProtoCompactTextTelemetryContentType
			default:
				continue
			}
		case accept.Type == "text" &&
			accept.SubType == "plain" &&
			(accept.Params["version"] == "0.0.4" || accept.Params["version"] == ""):
			return text.MetricFamilyToText, TextTelemetryContentType
		default:
			continue
		}
	}
	return text.MetricFamilyToText, TextTelemetryContentType
}

// If we know the location of the asset server, redirect to it when / is requested
// and the Accept header supports text/html
func assetServerRedirect(handler http.Handler, assetPublicURL string) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		if req.URL.Path == "/" {
			accepts := goautoneg.ParseAccept(req.Header.Get("Accept"))
			for _, accept := range accepts {
				if accept.Type == "text" && accept.SubType == "html" {
					http.Redirect(w, req, assetPublicURL, http.StatusFound)
					return
				}
			}
		}
		// Dispatch to the next handler
		handler.ServeHTTP(w, req)
	})
}

// Negotiate returns the Content-Type based on the given Accept header.
// If no appropriate accepted type is found, FmtText is returned.
func Negotiate(h http.Header) Format {
	for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {
		// Check for protocol buffer
		if ac.Type == ProtoType && ac.SubType == ProtoSubType && ac.Params["proto"] == ProtoProtocol {
			switch ac.Params["encoding"] {
			case "delimited":
				return FmtProtoDelim
			case "text":
				return FmtProtoText
			case "compact-text":
				return FmtProtoCompact
			}
		}
		// Check for text format.
		ver := ac.Params["version"]
		if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {
			return FmtText
		}
	}
	return FmtText
}

// negotiate the most appropriate content type given the accept header and a list of
// alternatives.
func negotiate(header string, alternatives []string) (goautoneg.Accept, bool) {
	alternates := make([][]string, 0, len(alternatives))
	for _, alternate := range alternatives {
		alternates = append(alternates, strings.SplitN(alternate, "/", 2))
	}
	for _, clause := range goautoneg.ParseAccept(header) {
		for _, alternate := range alternates {
			if clause.Type == alternate[0] && clause.SubType == alternate[1] {
				return clause, true
			}
			if clause.Type == alternate[0] && clause.SubType == "*" {
				clause.SubType = alternate[1]
				return clause, true
			}
			if clause.Type == "*" && clause.SubType == "*" {
				clause.Type = alternate[0]
				clause.SubType = alternate[1]
				return clause, true
			}
		}
	}
	return goautoneg.Accept{}, false
}

// negotiateMediaTypeOptions returns the most appropriate content type given the accept header and
// a list of alternatives along with the accepted media type parameters.
func negotiateMediaTypeOptions(header string, accepted []acceptedMediaType, endpoint endpointRestrictions) (mediaTypeOptions, bool) {
	if len(header) == 0 && len(accepted) > 0 {
		return mediaTypeOptions{
			accepted: &accepted[0],
		}, true
	}

	clauses := goautoneg.ParseAccept(header)
	for _, clause := range clauses {
		for i := range accepted {
			accepts := &accepted[i]
			switch {
			case clause.Type == accepts.Type && clause.SubType == accepts.SubType,
				clause.Type == accepts.Type && clause.SubType == "*",
				clause.Type == "*" && clause.SubType == "*":
				// TODO: should we prefer the first type with no unrecognized options?  Do we need to ignore unrecognized
				// parameters.
				return acceptMediaTypeOptions(clause.Params, accepts, endpoint)
			}
		}
	}
	return mediaTypeOptions{}, false
}