// Copyright 2015 The Prometheus Authors// 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 expfmt import (	"fmt"	"io"	"net/http" 	"github.com/golang/protobuf/proto"	"github.com/matttproud/golang_protobuf_extensions/pbutil"	"github.com/prometheus/common/internal/bitbucket.org/ww/goautoneg" 	dto "github.com/prometheus/client_model/go") // Encoder types encode metric families into an underlying wire protocol.type Encoder interface {	Encode(*dto.MetricFamily) error} // Closer is implemented by Encoders that need to be closed to finalize// encoding. (For example, OpenMetrics needs a final `# EOF` line.)//// Note that all Encoder implementations returned from this package implement// Closer, too, even if the Close call is a no-op. This happens in preparation// for adding a Close method to the Encoder interface directly in a (mildly// breaking) release in the future.type Closer interface {	Close() error} type encoderCloser struct {	encode func(*dto.MetricFamily) error	close  func() error} func (ec encoderCloser) Encode(v *dto.MetricFamily) error {	return ec.encode(v)} func (ec encoderCloser) Close() error {	return ec.close()} // Negotiate returns the Content-Type based on the given Accept header. If no// appropriate accepted type is found, FmtText is returned (which is the// Prometheus text format). This function will never negotiate FmtOpenMetrics,// as the support is still experimental. To include the option to negotiate// FmtOpenMetrics, use NegotiateOpenMetrics.func Negotiate(h http.Header) Format {	for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {		ver := ac.Params["version"]		if ac.Type+"/"+ac.SubType == ProtoType && ac.Params["proto"] == ProtoProtocol {			switch ac.Params["encoding"] {			case "delimited":				return FmtProtoDelim			case "text":				return FmtProtoText			case "compact-text":				return FmtProtoCompact			}		}		if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {			return FmtText		}	}	return FmtText} // NegotiateIncludingOpenMetrics works like Negotiate but includes// FmtOpenMetrics as an option for the result. Note that this function is// temporary and will disappear once FmtOpenMetrics is fully supported and as// such may be negotiated by the normal Negotiate function.func NegotiateIncludingOpenMetrics(h http.Header) Format {	for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {		ver := ac.Params["version"]		if ac.Type+"/"+ac.SubType == ProtoType && ac.Params["proto"] == ProtoProtocol {			switch ac.Params["encoding"] {			case "delimited":				return FmtProtoDelim			case "text":				return FmtProtoText			case "compact-text":				return FmtProtoCompact			}		}		if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {			return FmtText		}		if ac.Type+"/"+ac.SubType == OpenMetricsType && (ver == OpenMetricsVersion || ver == "") {			return FmtOpenMetrics		}	}	return FmtText} // NewEncoder returns a new encoder based on content type negotiation. All// Encoder implementations returned by NewEncoder also implement Closer, and// callers should always call the Close method. It is currently only required// for FmtOpenMetrics, but a future (breaking) release will add the Close method// to the Encoder interface directly. The current version of the Encoder// interface is kept for backwards compatibility.func NewEncoder(w io.Writer, format Format) Encoder {	switch format {	case FmtProtoDelim:		return encoderCloser{			encode: func(v *dto.MetricFamily) error {				_, err := pbutil.WriteDelimited(w, v)				return err			},			close: func() error { return nil },		}	case FmtProtoCompact:		return encoderCloser{			encode: func(v *dto.MetricFamily) error {				_, err := fmt.Fprintln(w, v.String())				return err			},			close: func() error { return nil },		}	case FmtProtoText:		return encoderCloser{			encode: func(v *dto.MetricFamily) error {				_, err := fmt.Fprintln(w, proto.MarshalTextString(v))				return err			},			close: func() error { return nil },		}	case FmtText:		return encoderCloser{			encode: func(v *dto.MetricFamily) error {				_, err := MetricFamilyToText(w, v)				return err			},			close: func() error { return nil },		}	case FmtOpenMetrics:		return encoderCloser{			encode: func(v *dto.MetricFamily) error {				_, err := MetricFamilyToOpenMetrics(w, v)				return err			},			close: func() error {				_, err := FinalizeOpenMetrics(w)				return err			},		}	}	panic(fmt.Errorf("expfmt.NewEncoder: unknown format %q", format))}