// 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 config

import (
	"errors"
	"fmt"
	"log/slog"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/alecthomas/units"
	"github.com/grafana/regexp"
	"github.com/prometheus/common/config"
	"github.com/prometheus/common/model"
	"github.com/prometheus/common/sigv4"
	"gopkg.in/yaml.v2"

	"github.com/prometheus/prometheus/discovery"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/model/relabel"
	"github.com/prometheus/prometheus/storage/remote/azuread"
	"github.com/prometheus/prometheus/storage/remote/googleiam"
)

var (
	patRulePath     = regexp.MustCompile(`^[^*]*(\*[^/]*)?$`)
	reservedHeaders = map[string]struct{}{
		// NOTE: authorization is checked specially,
		// see RemoteWriteConfig.UnmarshalYAML.
		// "authorization":                  {},
		"host":                              {},
		"content-encoding":                  {},
		"content-length":                    {},
		"content-type":                      {},
		"user-agent":                        {},
		"connection":                        {},
		"keep-alive":                        {},
		"proxy-authenticate":                {},
		"proxy-authorization":               {},
		"www-authenticate":                  {},
		"accept-encoding":                   {},
		"x-prometheus-remote-write-version": {},
		"x-prometheus-remote-read-version":  {},

		// Added by SigV4.
		"x-amz-date":           {},
		"x-amz-security-token": {},
		"x-amz-content-sha256": {},
	}
)

const (
	LegacyValidationConfig = "legacy"
	UTF8ValidationConfig   = "utf8"
)

// Load parses the YAML input s into a Config.
func Load(s string, expandExternalLabels bool, logger *slog.Logger) (*Config, error) {
	cfg := &Config{}
	// If the entire config body is empty the UnmarshalYAML method is
	// never called. We thus have to set the DefaultConfig at the entry
	// point as well.
	*cfg = DefaultConfig

	err := yaml.UnmarshalStrict([]byte(s), cfg)
	if err != nil {
		return nil, err
	}

	if !expandExternalLabels {
		return cfg, nil
	}

	b := labels.NewScratchBuilder(0)
	cfg.GlobalConfig.ExternalLabels.Range(func(v labels.Label) {
		newV := os.Expand(v.Value, func(s string) string {
			if s == "$" {
				return "$"
			}
			if v := os.Getenv(s); v != "" {
				return v
			}
			logger.Warn("Empty environment variable", "name", s)
			return ""
		})
		if newV != v.Value {
			logger.Debug("External label replaced", "label", v.Name, "input", v.Value, "output", newV)
		}
		// Note newV can be blank. https://github.com/prometheus/prometheus/issues/11024
		b.Add(v.Name, newV)
	})
	cfg.GlobalConfig.ExternalLabels = b.Labels()
	return cfg, nil
}

// LoadFile parses the given YAML file into a Config.
func LoadFile(filename string, agentMode, expandExternalLabels bool, logger *slog.Logger) (*Config, error) {
	content, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	cfg, err := Load(string(content), expandExternalLabels, logger)
	if err != nil {
		return nil, fmt.Errorf("parsing YAML file %s: %w", filename, err)
	}

	if agentMode {
		if len(cfg.AlertingConfig.AlertmanagerConfigs) > 0 || len(cfg.AlertingConfig.AlertRelabelConfigs) > 0 {
			return nil, errors.New("field alerting is not allowed in agent mode")
		}

		if len(cfg.RuleFiles) > 0 {
			return nil, errors.New("field rule_files is not allowed in agent mode")
		}

		if len(cfg.RemoteReadConfigs) > 0 {
			return nil, errors.New("field remote_read is not allowed in agent mode")
		}
	}

	cfg.SetDirectory(filepath.Dir(filename))
	return cfg, nil
}

// The defaults applied before parsing the respective config sections.
var (
	// DefaultConfig is the default top-level configuration.
	DefaultConfig = Config{
		GlobalConfig: DefaultGlobalConfig,
	}

	// DefaultGlobalConfig is the default global configuration.
	DefaultGlobalConfig = GlobalConfig{
		ScrapeInterval:     model.Duration(1 * time.Minute),
		ScrapeTimeout:      model.Duration(10 * time.Second),
		EvaluationInterval: model.Duration(1 * time.Minute),
		RuleQueryOffset:    model.Duration(0 * time.Minute),
		// When native histogram feature flag is enabled, ScrapeProtocols default
		// changes to DefaultNativeHistogramScrapeProtocols.
		ScrapeProtocols: DefaultScrapeProtocols,
	}

	DefaultRuntimeConfig = RuntimeConfig{
		// Go runtime tuning.
		GoGC: 75,
	}

	// DefaultScrapeConfig is the default scrape configuration.
	DefaultScrapeConfig = ScrapeConfig{
		// ScrapeTimeout, ScrapeInterval and ScrapeProtocols default to the configured globals.
		ScrapeClassicHistograms: false,
		MetricsPath:             "/metrics",
		Scheme:                  "http",
		HonorLabels:             false,
		HonorTimestamps:         true,
		HTTPClientConfig:        config.DefaultHTTPClientConfig,
		EnableCompression:       true,
	}

	// DefaultAlertmanagerConfig is the default alertmanager configuration.
	DefaultAlertmanagerConfig = AlertmanagerConfig{
		Scheme:           "http",
		Timeout:          model.Duration(10 * time.Second),
		APIVersion:       AlertmanagerAPIVersionV2,
		HTTPClientConfig: config.DefaultHTTPClientConfig,
	}

	// DefaultRemoteWriteConfig is the default remote write configuration.
	DefaultRemoteWriteConfig = RemoteWriteConfig{
		RemoteTimeout:    model.Duration(30 * time.Second),
		ProtobufMessage:  RemoteWriteProtoMsgV1,
		QueueConfig:      DefaultQueueConfig,
		MetadataConfig:   DefaultMetadataConfig,
		HTTPClientConfig: config.DefaultHTTPClientConfig,
	}

	// DefaultQueueConfig is the default remote queue configuration.
	DefaultQueueConfig = QueueConfig{
		// With a maximum of 50 shards, assuming an average of 100ms remote write
		// time and 2000 samples per batch, we will be able to push 1M samples/s.
		MaxShards:         50,
		MinShards:         1,
		MaxSamplesPerSend: 2000,

		// Each shard will have a max of 10,000 samples pending in its channel, plus the pending
		// samples that have been enqueued. Theoretically we should only ever have about 12,000 samples
		// per shard pending. At 50 shards that's 600k.
		Capacity:          10000,
		BatchSendDeadline: model.Duration(5 * time.Second),

		// Backoff times for retrying a batch of samples on recoverable errors.
		MinBackoff: model.Duration(30 * time.Millisecond),
		MaxBackoff: model.Duration(5 * time.Second),
	}

	// DefaultMetadataConfig is the default metadata configuration for a remote write endpoint.
	DefaultMetadataConfig = MetadataConfig{
		Send:              true,
		SendInterval:      model.Duration(1 * time.Minute),
		MaxSamplesPerSend: 2000,
	}

	// DefaultRemoteReadConfig is the default remote read configuration.
	DefaultRemoteReadConfig = RemoteReadConfig{
		RemoteTimeout:        model.Duration(1 * time.Minute),
		ChunkedReadLimit:     DefaultChunkedReadLimit,
		HTTPClientConfig:     config.DefaultHTTPClientConfig,
		FilterExternalLabels: true,
	}

	// DefaultStorageConfig is the default TSDB/Exemplar storage configuration.
	DefaultStorageConfig = StorageConfig{
		ExemplarsConfig: &DefaultExemplarsConfig,
	}

	DefaultExemplarsConfig = ExemplarsConfig{
		MaxExemplars: 100000,
	}

	// DefaultOTLPConfig is the default OTLP configuration.
	DefaultOTLPConfig = OTLPConfig{}
)

// Config is the top-level configuration for Prometheus's config files.
type Config struct {
	GlobalConfig      GlobalConfig    `yaml:"global"`
	Runtime           RuntimeConfig   `yaml:"runtime,omitempty"`
	AlertingConfig    AlertingConfig  `yaml:"alerting,omitempty"`
	RuleFiles         []string        `yaml:"rule_files,omitempty"`
	ScrapeConfigFiles []string        `yaml:"scrape_config_files,omitempty"`
	ScrapeConfigs     []*ScrapeConfig `yaml:"scrape_configs,omitempty"`
	StorageConfig     StorageConfig   `yaml:"storage,omitempty"`
	TracingConfig     TracingConfig   `yaml:"tracing,omitempty"`

	RemoteWriteConfigs []*RemoteWriteConfig `yaml:"remote_write,omitempty"`
	RemoteReadConfigs  []*RemoteReadConfig  `yaml:"remote_read,omitempty"`
	OTLPConfig         OTLPConfig           `yaml:"otlp,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *Config) SetDirectory(dir string) {
	c.GlobalConfig.SetDirectory(dir)
	c.AlertingConfig.SetDirectory(dir)
	c.TracingConfig.SetDirectory(dir)
	for i, file := range c.RuleFiles {
		c.RuleFiles[i] = config.JoinDir(dir, file)
	}
	for i, file := range c.ScrapeConfigFiles {
		c.ScrapeConfigFiles[i] = config.JoinDir(dir, file)
	}
	for _, c := range c.ScrapeConfigs {
		c.SetDirectory(dir)
	}
	for _, c := range c.RemoteWriteConfigs {
		c.SetDirectory(dir)
	}
	for _, c := range c.RemoteReadConfigs {
		c.SetDirectory(dir)
	}
}

func (c Config) String() string {
	b, err := yaml.Marshal(c)
	if err != nil {
		return fmt.Sprintf("<error creating config string: %s>", err)
	}
	return string(b)
}

// GetScrapeConfigs returns the scrape configurations.
func (c *Config) GetScrapeConfigs() ([]*ScrapeConfig, error) {
	scfgs := make([]*ScrapeConfig, len(c.ScrapeConfigs))

	jobNames := map[string]string{}
	for i, scfg := range c.ScrapeConfigs {
		// We do these checks for library users that would not call validate in
		// Unmarshal.
		if err := scfg.Validate(c.GlobalConfig); err != nil {
			return nil, err
		}

		if _, ok := jobNames[scfg.JobName]; ok {
			return nil, fmt.Errorf("found multiple scrape configs with job name %q", scfg.JobName)
		}
		jobNames[scfg.JobName] = "main config file"
		scfgs[i] = scfg
	}
	for _, pat := range c.ScrapeConfigFiles {
		fs, err := filepath.Glob(pat)
		if err != nil {
			// The only error can be a bad pattern.
			return nil, fmt.Errorf("error retrieving scrape config files for %q: %w", pat, err)
		}
		for _, filename := range fs {
			cfg := ScrapeConfigs{}
			content, err := os.ReadFile(filename)
			if err != nil {
				return nil, fileErr(filename, err)
			}
			err = yaml.UnmarshalStrict(content, &cfg)
			if err != nil {
				return nil, fileErr(filename, err)
			}
			for _, scfg := range cfg.ScrapeConfigs {
				if err := scfg.Validate(c.GlobalConfig); err != nil {
					return nil, fileErr(filename, err)
				}

				if f, ok := jobNames[scfg.JobName]; ok {
					return nil, fileErr(filename, fmt.Errorf("found multiple scrape configs with job name %q, first found in %s", scfg.JobName, f))
				}
				jobNames[scfg.JobName] = fmt.Sprintf("%q", filePath(filename))

				scfg.SetDirectory(filepath.Dir(filename))
				scfgs = append(scfgs, scfg)
			}
		}
	}
	return scfgs, nil
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultConfig
	// We want to set c to the defaults and then overwrite it with the input.
	// To make unmarshal fill the plain data struct rather than calling UnmarshalYAML
	// again, we have to hide it using a type indirection.
	type plain Config
	if err := unmarshal((*plain)(c)); err != nil {
		return err
	}

	// If a global block was open but empty the default global config is overwritten.
	// We have to restore it here.
	if c.GlobalConfig.isZero() {
		c.GlobalConfig = DefaultGlobalConfig
	}

	// If a runtime block was open but empty the default runtime config is overwritten.
	// We have to restore it here.
	if c.Runtime.isZero() {
		c.Runtime = DefaultRuntimeConfig
		// Use the GOGC env var value if the runtime section is empty.
		c.Runtime.GoGC = getGoGCEnv()
	}

	for _, rf := range c.RuleFiles {
		if !patRulePath.MatchString(rf) {
			return fmt.Errorf("invalid rule file path %q", rf)
		}
	}

	for _, sf := range c.ScrapeConfigFiles {
		if !patRulePath.MatchString(sf) {
			return fmt.Errorf("invalid scrape config file path %q", sf)
		}
	}

	// Do global overrides and validate unique names.
	jobNames := map[string]struct{}{}
	for _, scfg := range c.ScrapeConfigs {
		if err := scfg.Validate(c.GlobalConfig); err != nil {
			return err
		}

		if _, ok := jobNames[scfg.JobName]; ok {
			return fmt.Errorf("found multiple scrape configs with job name %q", scfg.JobName)
		}
		jobNames[scfg.JobName] = struct{}{}
	}
	rwNames := map[string]struct{}{}
	for _, rwcfg := range c.RemoteWriteConfigs {
		if rwcfg == nil {
			return errors.New("empty or null remote write config section")
		}
		// Skip empty names, we fill their name with their config hash in remote write code.
		if _, ok := rwNames[rwcfg.Name]; ok && rwcfg.Name != "" {
			return fmt.Errorf("found multiple remote write configs with job name %q", rwcfg.Name)
		}
		rwNames[rwcfg.Name] = struct{}{}
	}
	rrNames := map[string]struct{}{}
	for _, rrcfg := range c.RemoteReadConfigs {
		if rrcfg == nil {
			return errors.New("empty or null remote read config section")
		}
		// Skip empty names, we fill their name with their config hash in remote read code.
		if _, ok := rrNames[rrcfg.Name]; ok && rrcfg.Name != "" {
			return fmt.Errorf("found multiple remote read configs with job name %q", rrcfg.Name)
		}
		rrNames[rrcfg.Name] = struct{}{}
	}
	return nil
}

// GlobalConfig configures values that are used across other configuration
// objects.
type GlobalConfig struct {
	// How frequently to scrape targets by default.
	ScrapeInterval model.Duration `yaml:"scrape_interval,omitempty"`
	// The default timeout when scraping targets.
	ScrapeTimeout model.Duration `yaml:"scrape_timeout,omitempty"`
	// The protocols to negotiate during a scrape. It tells clients what
	// protocol are accepted by Prometheus and with what weight (most wanted is first).
	// Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
	// OpenMetricsText1.0.0, PrometheusText0.0.4.
	ScrapeProtocols []ScrapeProtocol `yaml:"scrape_protocols,omitempty"`
	// How frequently to evaluate rules by default.
	EvaluationInterval model.Duration `yaml:"evaluation_interval,omitempty"`
	// Offset the rule evaluation timestamp of this particular group by the specified duration into the past to ensure the underlying metrics have been received.
	RuleQueryOffset model.Duration `yaml:"rule_query_offset,omitempty"`
	// File to which PromQL queries are logged.
	QueryLogFile string `yaml:"query_log_file,omitempty"`
	// File to which scrape failures are logged.
	ScrapeFailureLogFile string `yaml:"scrape_failure_log_file,omitempty"`
	// The labels to add to any timeseries that this Prometheus instance scrapes.
	ExternalLabels labels.Labels `yaml:"external_labels,omitempty"`
	// An uncompressed response body larger than this many bytes will cause the
	// scrape to fail. 0 means no limit.
	BodySizeLimit units.Base2Bytes `yaml:"body_size_limit,omitempty"`
	// More than this many samples post metric-relabeling will cause the scrape to
	// fail. 0 means no limit.
	SampleLimit uint `yaml:"sample_limit,omitempty"`
	// More than this many targets after the target relabeling will cause the
	// scrapes to fail. 0 means no limit.
	TargetLimit uint `yaml:"target_limit,omitempty"`
	// More than this many labels post metric-relabeling will cause the scrape to
	// fail. 0 means no limit.
	LabelLimit uint `yaml:"label_limit,omitempty"`
	// More than this label name length post metric-relabeling will cause the
	// scrape to fail. 0 means no limit.
	LabelNameLengthLimit uint `yaml:"label_name_length_limit,omitempty"`
	// More than this label value length post metric-relabeling will cause the
	// scrape to fail. 0 means no limit.
	LabelValueLengthLimit uint `yaml:"label_value_length_limit,omitempty"`
	// Keep no more than this many dropped targets per job.
	// 0 means no limit.
	KeepDroppedTargets uint `yaml:"keep_dropped_targets,omitempty"`
	// Allow UTF8 Metric and Label Names.
	MetricNameValidationScheme string `yaml:"metric_name_validation_scheme,omitempty"`
}

// ScrapeProtocol represents supported protocol for scraping metrics.
type ScrapeProtocol string

// Validate returns error if given scrape protocol is not supported.
func (s ScrapeProtocol) Validate() error {
	if _, ok := ScrapeProtocolsHeaders[s]; !ok {
		return fmt.Errorf("unknown scrape protocol %v, supported: %v",
			s, func() (ret []string) {
				for k := range ScrapeProtocolsHeaders {
					ret = append(ret, string(k))
				}
				sort.Strings(ret)
				return ret
			}())
	}
	return nil
}

var (
	PrometheusProto      ScrapeProtocol = "PrometheusProto"
	PrometheusText0_0_4  ScrapeProtocol = "PrometheusText0.0.4"
	OpenMetricsText0_0_1 ScrapeProtocol = "OpenMetricsText0.0.1"
	OpenMetricsText1_0_0 ScrapeProtocol = "OpenMetricsText1.0.0"
	UTF8NamesHeader      string         = model.EscapingKey + "=" + model.AllowUTF8

	ScrapeProtocolsHeaders = map[ScrapeProtocol]string{
		PrometheusProto:      "application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited",
		PrometheusText0_0_4:  "text/plain;version=0.0.4",
		OpenMetricsText0_0_1: "application/openmetrics-text;version=0.0.1",
		OpenMetricsText1_0_0: "application/openmetrics-text;version=1.0.0",
	}

	// DefaultScrapeProtocols is the set of scrape protocols that will be proposed
	// to scrape target, ordered by priority.
	DefaultScrapeProtocols = []ScrapeProtocol{
		OpenMetricsText1_0_0,
		OpenMetricsText0_0_1,
		PrometheusText0_0_4,
	}

	// DefaultProtoFirstScrapeProtocols is like DefaultScrapeProtocols, but it
	// favors protobuf Prometheus exposition format.
	// Used by default for certain feature-flags like
	// "native-histograms" and "created-timestamp-zero-ingestion".
	DefaultProtoFirstScrapeProtocols = []ScrapeProtocol{
		PrometheusProto,
		OpenMetricsText1_0_0,
		OpenMetricsText0_0_1,
		PrometheusText0_0_4,
	}
)

// validateAcceptScrapeProtocols return errors if we see problems with accept scrape protocols option.
func validateAcceptScrapeProtocols(sps []ScrapeProtocol) error {
	if len(sps) == 0 {
		return errors.New("scrape_protocols cannot be empty")
	}
	dups := map[string]struct{}{}
	for _, sp := range sps {
		if _, ok := dups[strings.ToLower(string(sp))]; ok {
			return fmt.Errorf("duplicated protocol in scrape_protocols, got %v", sps)
		}
		if err := sp.Validate(); err != nil {
			return fmt.Errorf("scrape_protocols: %w", err)
		}
		dups[strings.ToLower(string(sp))] = struct{}{}
	}
	return nil
}

// SetDirectory joins any relative file paths with dir.
func (c *GlobalConfig) SetDirectory(dir string) {
	c.QueryLogFile = config.JoinDir(dir, c.QueryLogFile)
	c.ScrapeFailureLogFile = config.JoinDir(dir, c.ScrapeFailureLogFile)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *GlobalConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	// Create a clean global config as the previous one was already populated
	// by the default due to the YAML parser behavior for empty blocks.
	gc := &GlobalConfig{}
	type plain GlobalConfig
	if err := unmarshal((*plain)(gc)); err != nil {
		return err
	}

	if err := gc.ExternalLabels.Validate(func(l labels.Label) error {
		if !model.LabelName(l.Name).IsValid() {
			return fmt.Errorf("%q is not a valid label name", l.Name)
		}
		if !model.LabelValue(l.Value).IsValid() {
			return fmt.Errorf("%q is not a valid label value", l.Value)
		}
		return nil
	}); err != nil {
		return err
	}

	// First set the correct scrape interval, then check that the timeout
	// (inferred or explicit) is not greater than that.
	if gc.ScrapeInterval == 0 {
		gc.ScrapeInterval = DefaultGlobalConfig.ScrapeInterval
	}
	if gc.ScrapeTimeout > gc.ScrapeInterval {
		return errors.New("global scrape timeout greater than scrape interval")
	}
	if gc.ScrapeTimeout == 0 {
		if DefaultGlobalConfig.ScrapeTimeout > gc.ScrapeInterval {
			gc.ScrapeTimeout = gc.ScrapeInterval
		} else {
			gc.ScrapeTimeout = DefaultGlobalConfig.ScrapeTimeout
		}
	}
	if gc.EvaluationInterval == 0 {
		gc.EvaluationInterval = DefaultGlobalConfig.EvaluationInterval
	}

	if gc.ScrapeProtocols == nil {
		gc.ScrapeProtocols = DefaultGlobalConfig.ScrapeProtocols
	}
	if err := validateAcceptScrapeProtocols(gc.ScrapeProtocols); err != nil {
		return fmt.Errorf("%w for global config", err)
	}

	*c = *gc
	return nil
}

// isZero returns true iff the global config is the zero value.
func (c *GlobalConfig) isZero() bool {
	return c.ExternalLabels.IsEmpty() &&
		c.ScrapeInterval == 0 &&
		c.ScrapeTimeout == 0 &&
		c.EvaluationInterval == 0 &&
		c.RuleQueryOffset == 0 &&
		c.QueryLogFile == "" &&
		c.ScrapeFailureLogFile == "" &&
		c.ScrapeProtocols == nil
}

// RuntimeConfig configures the values for the process behavior.
type RuntimeConfig struct {
	// The Go garbage collection target percentage.
	GoGC int `yaml:"gogc,omitempty"`
}

// isZero returns true iff the global config is the zero value.
func (c *RuntimeConfig) isZero() bool {
	return c.GoGC == 0
}

type ScrapeConfigs struct {
	ScrapeConfigs []*ScrapeConfig `yaml:"scrape_configs,omitempty"`
}

// ScrapeConfig configures a scraping unit for Prometheus.
type ScrapeConfig struct {
	// The job name to which the job label is set by default.
	JobName string `yaml:"job_name"`
	// Indicator whether the scraped metrics should remain unmodified.
	HonorLabels bool `yaml:"honor_labels,omitempty"`
	// Indicator whether the scraped timestamps should be respected.
	HonorTimestamps bool `yaml:"honor_timestamps"`
	// Indicator whether to track the staleness of the scraped timestamps.
	TrackTimestampsStaleness bool `yaml:"track_timestamps_staleness"`
	// A set of query parameters with which the target is scraped.
	Params url.Values `yaml:"params,omitempty"`
	// How frequently to scrape the targets of this scrape config.
	ScrapeInterval model.Duration `yaml:"scrape_interval,omitempty"`
	// The timeout for scraping targets of this config.
	ScrapeTimeout model.Duration `yaml:"scrape_timeout,omitempty"`
	// The protocols to negotiate during a scrape. It tells clients what
	// protocol are accepted by Prometheus and with what preference (most wanted is first).
	// Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
	// OpenMetricsText1.0.0, PrometheusText0.0.4.
	ScrapeProtocols []ScrapeProtocol `yaml:"scrape_protocols,omitempty"`
	// Whether to scrape a classic histogram that is also exposed as a native histogram.
	ScrapeClassicHistograms bool `yaml:"scrape_classic_histograms,omitempty"`
	// File to which scrape failures are logged.
	ScrapeFailureLogFile string `yaml:"scrape_failure_log_file,omitempty"`
	// The HTTP resource path on which to fetch metrics from targets.
	MetricsPath string `yaml:"metrics_path,omitempty"`
	// The URL scheme with which to fetch metrics from targets.
	Scheme string `yaml:"scheme,omitempty"`
	// Indicator whether to request compressed response from the target.
	EnableCompression bool `yaml:"enable_compression"`
	// An uncompressed response body larger than this many bytes will cause the
	// scrape to fail. 0 means no limit.
	BodySizeLimit units.Base2Bytes `yaml:"body_size_limit,omitempty"`
	// More than this many samples post metric-relabeling will cause the scrape to
	// fail. 0 means no limit.
	SampleLimit uint `yaml:"sample_limit,omitempty"`
	// More than this many targets after the target relabeling will cause the
	// scrapes to fail. 0 means no limit.
	TargetLimit uint `yaml:"target_limit,omitempty"`
	// More than this many labels post metric-relabeling will cause the scrape to
	// fail. 0 means no limit.
	LabelLimit uint `yaml:"label_limit,omitempty"`
	// More than this label name length post metric-relabeling will cause the
	// scrape to fail. 0 means no limit.
	LabelNameLengthLimit uint `yaml:"label_name_length_limit,omitempty"`
	// More than this label value length post metric-relabeling will cause the
	// scrape to fail. 0 means no limit.
	LabelValueLengthLimit uint `yaml:"label_value_length_limit,omitempty"`
	// If there are more than this many buckets in a native histogram,
	// buckets will be merged to stay within the limit.
	NativeHistogramBucketLimit uint `yaml:"native_histogram_bucket_limit,omitempty"`
	// If the growth factor of one bucket to the next is smaller than this,
	// buckets will be merged to increase the factor sufficiently.
	NativeHistogramMinBucketFactor float64 `yaml:"native_histogram_min_bucket_factor,omitempty"`
	// Keep no more than this many dropped targets per job.
	// 0 means no limit.
	KeepDroppedTargets uint `yaml:"keep_dropped_targets,omitempty"`
	// Allow UTF8 Metric and Label Names.
	MetricNameValidationScheme string `yaml:"metric_name_validation_scheme,omitempty"`

	// We cannot do proper Go type embedding below as the parser will then parse
	// values arbitrarily into the overflow maps of further-down types.

	ServiceDiscoveryConfigs discovery.Configs       `yaml:"-"`
	HTTPClientConfig        config.HTTPClientConfig `yaml:",inline"`

	// List of target relabel configurations.
	RelabelConfigs []*relabel.Config `yaml:"relabel_configs,omitempty"`
	// List of metric relabel configurations.
	MetricRelabelConfigs []*relabel.Config `yaml:"metric_relabel_configs,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *ScrapeConfig) SetDirectory(dir string) {
	c.ServiceDiscoveryConfigs.SetDirectory(dir)
	c.HTTPClientConfig.SetDirectory(dir)
	c.ScrapeFailureLogFile = config.JoinDir(dir, c.ScrapeFailureLogFile)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *ScrapeConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultScrapeConfig
	if err := discovery.UnmarshalYAMLWithInlineConfigs(c, unmarshal); err != nil {
		return err
	}
	if len(c.JobName) == 0 {
		return errors.New("job_name is empty")
	}

	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
	// We cannot make it a pointer as the parser panics for inlined pointer structs.
	// Thus we just do its validation here.
	if err := c.HTTPClientConfig.Validate(); err != nil {
		return err
	}

	// Check for users putting URLs in target groups.
	if len(c.RelabelConfigs) == 0 {
		if err := checkStaticTargets(c.ServiceDiscoveryConfigs); err != nil {
			return err
		}
	}

	for _, rlcfg := range c.RelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null target relabeling rule in scrape config")
		}
	}
	for _, rlcfg := range c.MetricRelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null metric relabeling rule in scrape config")
		}
	}

	return nil
}

// Validate validates scrape config, but also fills relevant default values from global config if needed.
func (c *ScrapeConfig) Validate(globalConfig GlobalConfig) error {
	if c == nil {
		return errors.New("empty or null scrape config section")
	}
	// First set the correct scrape interval, then check that the timeout
	// (inferred or explicit) is not greater than that.
	if c.ScrapeInterval == 0 {
		c.ScrapeInterval = globalConfig.ScrapeInterval
	}
	if c.ScrapeTimeout > c.ScrapeInterval {
		return fmt.Errorf("scrape timeout greater than scrape interval for scrape config with job name %q", c.JobName)
	}
	if c.ScrapeTimeout == 0 {
		if globalConfig.ScrapeTimeout > c.ScrapeInterval {
			c.ScrapeTimeout = c.ScrapeInterval
		} else {
			c.ScrapeTimeout = globalConfig.ScrapeTimeout
		}
	}
	if c.BodySizeLimit == 0 {
		c.BodySizeLimit = globalConfig.BodySizeLimit
	}
	if c.SampleLimit == 0 {
		c.SampleLimit = globalConfig.SampleLimit
	}
	if c.TargetLimit == 0 {
		c.TargetLimit = globalConfig.TargetLimit
	}
	if c.LabelLimit == 0 {
		c.LabelLimit = globalConfig.LabelLimit
	}
	if c.LabelNameLengthLimit == 0 {
		c.LabelNameLengthLimit = globalConfig.LabelNameLengthLimit
	}
	if c.LabelValueLengthLimit == 0 {
		c.LabelValueLengthLimit = globalConfig.LabelValueLengthLimit
	}
	if c.KeepDroppedTargets == 0 {
		c.KeepDroppedTargets = globalConfig.KeepDroppedTargets
	}
	if c.ScrapeFailureLogFile == "" {
		c.ScrapeFailureLogFile = globalConfig.ScrapeFailureLogFile
	}

	if c.ScrapeProtocols == nil {
		c.ScrapeProtocols = globalConfig.ScrapeProtocols
	}
	if err := validateAcceptScrapeProtocols(c.ScrapeProtocols); err != nil {
		return fmt.Errorf("%w for scrape config with job name %q", err, c.JobName)
	}

	switch globalConfig.MetricNameValidationScheme {
	case LegacyValidationConfig:
	case "", UTF8ValidationConfig:
		if model.NameValidationScheme != model.UTF8Validation {
			panic("utf8 name validation requested but model.NameValidationScheme is not set to UTF8")
		}
	default:
		return fmt.Errorf("unknown name validation method specified, must be either 'legacy' or 'utf8', got %s", globalConfig.MetricNameValidationScheme)
	}
	if c.MetricNameValidationScheme == "" {
		c.MetricNameValidationScheme = globalConfig.MetricNameValidationScheme
	}

	return nil
}

// MarshalYAML implements the yaml.Marshaler interface.
func (c *ScrapeConfig) MarshalYAML() (interface{}, error) {
	return discovery.MarshalYAMLWithInlineConfigs(c)
}

// StorageConfig configures runtime reloadable configuration options.
type StorageConfig struct {
	TSDBConfig      *TSDBConfig      `yaml:"tsdb,omitempty"`
	ExemplarsConfig *ExemplarsConfig `yaml:"exemplars,omitempty"`
}

// TSDBConfig configures runtime reloadable configuration options.
type TSDBConfig struct {
	// OutOfOrderTimeWindow sets how long back in time an out-of-order sample can be inserted
	// into the TSDB. This flag is typically set while unmarshaling the configuration file and translating
	// OutOfOrderTimeWindowFlag's duration. The unit of this flag is expected to be the same as any
	// other timestamp in the TSDB.
	OutOfOrderTimeWindow int64

	// OutOfOrderTimeWindowFlag holds the parsed duration from the config file.
	// During unmarshall, this is converted into milliseconds and stored in OutOfOrderTimeWindow.
	// This should not be used directly and must be converted into OutOfOrderTimeWindow.
	OutOfOrderTimeWindowFlag model.Duration `yaml:"out_of_order_time_window,omitempty"`
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (t *TSDBConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*t = TSDBConfig{}
	type plain TSDBConfig
	if err := unmarshal((*plain)(t)); err != nil {
		return err
	}

	t.OutOfOrderTimeWindow = time.Duration(t.OutOfOrderTimeWindowFlag).Milliseconds()

	return nil
}

type TracingClientType string

const (
	TracingClientHTTP TracingClientType = "http"
	TracingClientGRPC TracingClientType = "grpc"

	GzipCompression = "gzip"
)

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (t *TracingClientType) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*t = TracingClientType("")
	type plain TracingClientType
	if err := unmarshal((*plain)(t)); err != nil {
		return err
	}

	if *t != TracingClientHTTP && *t != TracingClientGRPC {
		return fmt.Errorf("expected tracing client type to be to be %s or %s, but got %s",
			TracingClientHTTP, TracingClientGRPC, *t,
		)
	}

	return nil
}

// TracingConfig configures the tracing options.
type TracingConfig struct {
	ClientType       TracingClientType `yaml:"client_type,omitempty"`
	Endpoint         string            `yaml:"endpoint,omitempty"`
	SamplingFraction float64           `yaml:"sampling_fraction,omitempty"`
	Insecure         bool              `yaml:"insecure,omitempty"`
	TLSConfig        config.TLSConfig  `yaml:"tls_config,omitempty"`
	Headers          map[string]string `yaml:"headers,omitempty"`
	Compression      string            `yaml:"compression,omitempty"`
	Timeout          model.Duration    `yaml:"timeout,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (t *TracingConfig) SetDirectory(dir string) {
	t.TLSConfig.SetDirectory(dir)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (t *TracingConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*t = TracingConfig{
		ClientType: TracingClientGRPC,
	}
	type plain TracingConfig
	if err := unmarshal((*plain)(t)); err != nil {
		return err
	}

	if err := validateHeadersForTracing(t.Headers); err != nil {
		return err
	}

	if t.Endpoint == "" {
		return errors.New("tracing endpoint must be set")
	}

	if t.Compression != "" && t.Compression != GzipCompression {
		return fmt.Errorf("invalid compression type %s provided, valid options: %s",
			t.Compression, GzipCompression)
	}

	return nil
}

// ExemplarsConfig configures runtime reloadable configuration options.
type ExemplarsConfig struct {
	// MaxExemplars sets the size, in # of exemplars stored, of the single circular buffer used to store exemplars in memory.
	// Use a value of 0 or less than 0 to disable the storage without having to restart Prometheus.
	MaxExemplars int64 `yaml:"max_exemplars,omitempty"`
}

// AlertingConfig configures alerting and alertmanager related configs.
type AlertingConfig struct {
	AlertRelabelConfigs []*relabel.Config   `yaml:"alert_relabel_configs,omitempty"`
	AlertmanagerConfigs AlertmanagerConfigs `yaml:"alertmanagers,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *AlertingConfig) SetDirectory(dir string) {
	for _, c := range c.AlertmanagerConfigs {
		c.SetDirectory(dir)
	}
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *AlertingConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	// Create a clean global config as the previous one was already populated
	// by the default due to the YAML parser behavior for empty blocks.
	*c = AlertingConfig{}
	type plain AlertingConfig
	if err := unmarshal((*plain)(c)); err != nil {
		return err
	}

	for _, rlcfg := range c.AlertRelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null alert relabeling rule")
		}
	}
	return nil
}

// AlertmanagerConfigs is a slice of *AlertmanagerConfig.
type AlertmanagerConfigs []*AlertmanagerConfig

// ToMap converts a slice of *AlertmanagerConfig to a map.
func (a AlertmanagerConfigs) ToMap() map[string]*AlertmanagerConfig {
	ret := make(map[string]*AlertmanagerConfig)
	for i := range a {
		ret[fmt.Sprintf("config-%d", i)] = a[i]
	}
	return ret
}

// AlertmanagerAPIVersion represents a version of the
// github.com/prometheus/alertmanager/api, e.g. 'v1' or 'v2'.
type AlertmanagerAPIVersion string

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (v *AlertmanagerAPIVersion) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*v = AlertmanagerAPIVersion("")
	type plain AlertmanagerAPIVersion
	if err := unmarshal((*plain)(v)); err != nil {
		return err
	}

	for _, supportedVersion := range SupportedAlertmanagerAPIVersions {
		if *v == supportedVersion {
			return nil
		}
	}

	return fmt.Errorf("expected Alertmanager api version to be one of %v but got %v", SupportedAlertmanagerAPIVersions, *v)
}

const (
	// AlertmanagerAPIVersionV1 represents
	// github.com/prometheus/alertmanager/api/v1.
	AlertmanagerAPIVersionV1 AlertmanagerAPIVersion = "v1"
	// AlertmanagerAPIVersionV2 represents
	// github.com/prometheus/alertmanager/api/v2.
	AlertmanagerAPIVersionV2 AlertmanagerAPIVersion = "v2"
)

var SupportedAlertmanagerAPIVersions = []AlertmanagerAPIVersion{
	AlertmanagerAPIVersionV1, AlertmanagerAPIVersionV2,
}

// AlertmanagerConfig configures how Alertmanagers can be discovered and communicated with.
type AlertmanagerConfig struct {
	// We cannot do proper Go type embedding below as the parser will then parse
	// values arbitrarily into the overflow maps of further-down types.

	ServiceDiscoveryConfigs discovery.Configs       `yaml:"-"`
	HTTPClientConfig        config.HTTPClientConfig `yaml:",inline"`
	SigV4Config             *sigv4.SigV4Config      `yaml:"sigv4,omitempty"`

	// The URL scheme to use when talking to Alertmanagers.
	Scheme string `yaml:"scheme,omitempty"`
	// Path prefix to add in front of the push endpoint path.
	PathPrefix string `yaml:"path_prefix,omitempty"`
	// The timeout used when sending alerts.
	Timeout model.Duration `yaml:"timeout,omitempty"`

	// The api version of Alertmanager.
	APIVersion AlertmanagerAPIVersion `yaml:"api_version"`

	// List of Alertmanager relabel configurations.
	RelabelConfigs []*relabel.Config `yaml:"relabel_configs,omitempty"`
	// Relabel alerts before sending to the specific alertmanager.
	AlertRelabelConfigs []*relabel.Config `yaml:"alert_relabel_configs,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *AlertmanagerConfig) SetDirectory(dir string) {
	c.ServiceDiscoveryConfigs.SetDirectory(dir)
	c.HTTPClientConfig.SetDirectory(dir)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *AlertmanagerConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultAlertmanagerConfig
	if err := discovery.UnmarshalYAMLWithInlineConfigs(c, unmarshal); err != nil {
		return err
	}

	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
	// We cannot make it a pointer as the parser panics for inlined pointer structs.
	// Thus we just do its validation here.
	if err := c.HTTPClientConfig.Validate(); err != nil {
		return err
	}

	httpClientConfigAuthEnabled := c.HTTPClientConfig.BasicAuth != nil ||
		c.HTTPClientConfig.Authorization != nil || c.HTTPClientConfig.OAuth2 != nil

	if httpClientConfigAuthEnabled && c.SigV4Config != nil {
		return fmt.Errorf("at most one of basic_auth, authorization, oauth2, & sigv4 must be configured")
	}

	// Check for users putting URLs in target groups.
	if len(c.RelabelConfigs) == 0 {
		if err := checkStaticTargets(c.ServiceDiscoveryConfigs); err != nil {
			return err
		}
	}

	for _, rlcfg := range c.RelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null Alertmanager target relabeling rule")
		}
	}

	for _, rlcfg := range c.AlertRelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null Alertmanager alert relabeling rule")
		}
	}

	return nil
}

// MarshalYAML implements the yaml.Marshaler interface.
func (c *AlertmanagerConfig) MarshalYAML() (interface{}, error) {
	return discovery.MarshalYAMLWithInlineConfigs(c)
}

func checkStaticTargets(configs discovery.Configs) error {
	for _, cfg := range configs {
		sc, ok := cfg.(discovery.StaticConfig)
		if !ok {
			continue
		}
		for _, tg := range sc {
			for _, t := range tg.Targets {
				if err := CheckTargetAddress(t[model.AddressLabel]); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

// CheckTargetAddress checks if target address is valid.
func CheckTargetAddress(address model.LabelValue) error {
	// For now check for a URL, we may want to expand this later.
	if strings.Contains(string(address), "/") {
		return fmt.Errorf("%q is not a valid hostname", address)
	}
	return nil
}

// RemoteWriteProtoMsg represents the known protobuf message for the remote write
// 1.0 and 2.0 specs.
type RemoteWriteProtoMsg string

// Validate returns error if the given reference for the protobuf message is not supported.
func (s RemoteWriteProtoMsg) Validate() error {
	switch s {
	case RemoteWriteProtoMsgV1, RemoteWriteProtoMsgV2:
		return nil
	default:
		return fmt.Errorf("unknown remote write protobuf message %v, supported: %v", s, RemoteWriteProtoMsgs{RemoteWriteProtoMsgV1, RemoteWriteProtoMsgV2}.String())
	}
}

type RemoteWriteProtoMsgs []RemoteWriteProtoMsg

func (m RemoteWriteProtoMsgs) Strings() []string {
	ret := make([]string, 0, len(m))
	for _, typ := range m {
		ret = append(ret, string(typ))
	}
	return ret
}

func (m RemoteWriteProtoMsgs) String() string {
	return strings.Join(m.Strings(), ", ")
}

var (
	// RemoteWriteProtoMsgV1 represents the `prometheus.WriteRequest` protobuf
	// message introduced in the https://prometheus.io/docs/specs/remote_write_spec/,
	// which will eventually be deprecated.
	//
	// NOTE: This string is used for both HTTP header values and config value, so don't change
	// this reference.
	RemoteWriteProtoMsgV1 RemoteWriteProtoMsg = "prometheus.WriteRequest"
	// RemoteWriteProtoMsgV2 represents the `io.prometheus.write.v2.Request` protobuf
	// message introduced in https://prometheus.io/docs/specs/remote_write_spec_2_0/
	//
	// NOTE: This string is used for both HTTP header values and config value, so don't change
	// this reference.
	RemoteWriteProtoMsgV2 RemoteWriteProtoMsg = "io.prometheus.write.v2.Request"
)

// RemoteWriteConfig is the configuration for writing to remote storage.
type RemoteWriteConfig struct {
	URL                  *config.URL       `yaml:"url"`
	RemoteTimeout        model.Duration    `yaml:"remote_timeout,omitempty"`
	Headers              map[string]string `yaml:"headers,omitempty"`
	WriteRelabelConfigs  []*relabel.Config `yaml:"write_relabel_configs,omitempty"`
	Name                 string            `yaml:"name,omitempty"`
	SendExemplars        bool              `yaml:"send_exemplars,omitempty"`
	SendNativeHistograms bool              `yaml:"send_native_histograms,omitempty"`
	// ProtobufMessage specifies the protobuf message to use against the remote
	// receiver as specified in https://prometheus.io/docs/specs/remote_write_spec_2_0/
	ProtobufMessage RemoteWriteProtoMsg `yaml:"protobuf_message,omitempty"`

	// We cannot do proper Go type embedding below as the parser will then parse
	// values arbitrarily into the overflow maps of further-down types.
	HTTPClientConfig config.HTTPClientConfig `yaml:",inline"`
	QueueConfig      QueueConfig             `yaml:"queue_config,omitempty"`
	MetadataConfig   MetadataConfig          `yaml:"metadata_config,omitempty"`
	SigV4Config      *sigv4.SigV4Config      `yaml:"sigv4,omitempty"`
	AzureADConfig    *azuread.AzureADConfig  `yaml:"azuread,omitempty"`
	GoogleIAMConfig  *googleiam.Config       `yaml:"google_iam,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *RemoteWriteConfig) SetDirectory(dir string) {
	c.HTTPClientConfig.SetDirectory(dir)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *RemoteWriteConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultRemoteWriteConfig
	type plain RemoteWriteConfig
	if err := unmarshal((*plain)(c)); err != nil {
		return err
	}
	if c.URL == nil {
		return errors.New("url for remote_write is empty")
	}
	for _, rlcfg := range c.WriteRelabelConfigs {
		if rlcfg == nil {
			return errors.New("empty or null relabeling rule in remote write config")
		}
	}
	if err := validateHeaders(c.Headers); err != nil {
		return err
	}

	if err := c.ProtobufMessage.Validate(); err != nil {
		return fmt.Errorf("invalid protobuf_message value: %w", err)
	}

	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
	// We cannot make it a pointer as the parser panics for inlined pointer structs.
	// Thus we just do its validation here.
	if err := c.HTTPClientConfig.Validate(); err != nil {
		return err
	}

	return validateAuthConfigs(c)
}

// validateAuthConfigs validates that at most one of basic_auth, authorization, oauth2, sigv4, azuread or google_iam must be configured.
func validateAuthConfigs(c *RemoteWriteConfig) error {
	var authConfigured []string
	if c.HTTPClientConfig.BasicAuth != nil {
		authConfigured = append(authConfigured, "basic_auth")
	}
	if c.HTTPClientConfig.Authorization != nil {
		authConfigured = append(authConfigured, "authorization")
	}
	if c.HTTPClientConfig.OAuth2 != nil {
		authConfigured = append(authConfigured, "oauth2")
	}
	if c.SigV4Config != nil {
		authConfigured = append(authConfigured, "sigv4")
	}
	if c.AzureADConfig != nil {
		authConfigured = append(authConfigured, "azuread")
	}
	if c.GoogleIAMConfig != nil {
		authConfigured = append(authConfigured, "google_iam")
	}
	if len(authConfigured) > 1 {
		return fmt.Errorf("at most one of basic_auth, authorization, oauth2, sigv4, azuread or google_iam must be configured. Currently configured: %v", authConfigured)
	}
	return nil
}

func validateHeadersForTracing(headers map[string]string) error {
	for header := range headers {
		if strings.ToLower(header) == "authorization" {
			return errors.New("custom authorization header configuration is not yet supported")
		}
		if _, ok := reservedHeaders[strings.ToLower(header)]; ok {
			return fmt.Errorf("%s is a reserved header. It must not be changed", header)
		}
	}
	return nil
}

func validateHeaders(headers map[string]string) error {
	for header := range headers {
		if strings.ToLower(header) == "authorization" {
			return errors.New("authorization header must be changed via the basic_auth, authorization, oauth2, sigv4, azuread or google_iam parameter")
		}
		if _, ok := reservedHeaders[strings.ToLower(header)]; ok {
			return fmt.Errorf("%s is a reserved header. It must not be changed", header)
		}
	}
	return nil
}

// QueueConfig is the configuration for the queue used to write to remote
// storage.
type QueueConfig struct {
	// Number of samples to buffer per shard before we block. Defaults to
	// MaxSamplesPerSend.
	Capacity int `yaml:"capacity,omitempty"`

	// Max number of shards, i.e. amount of concurrency.
	MaxShards int `yaml:"max_shards,omitempty"`

	// Min number of shards, i.e. amount of concurrency.
	MinShards int `yaml:"min_shards,omitempty"`

	// Maximum number of samples per send.
	MaxSamplesPerSend int `yaml:"max_samples_per_send,omitempty"`

	// Maximum time sample will wait in buffer.
	BatchSendDeadline model.Duration `yaml:"batch_send_deadline,omitempty"`

	// On recoverable errors, backoff exponentially.
	MinBackoff       model.Duration `yaml:"min_backoff,omitempty"`
	MaxBackoff       model.Duration `yaml:"max_backoff,omitempty"`
	RetryOnRateLimit bool           `yaml:"retry_on_http_429,omitempty"`

	// Samples older than the limit will be dropped.
	SampleAgeLimit model.Duration `yaml:"sample_age_limit,omitempty"`
}

// MetadataConfig is the configuration for sending metadata to remote
// storage.
type MetadataConfig struct {
	// Send controls whether we send metric metadata to remote storage.
	Send bool `yaml:"send"`
	// SendInterval controls how frequently we send metric metadata.
	SendInterval model.Duration `yaml:"send_interval"`
	// Maximum number of samples per send.
	MaxSamplesPerSend int `yaml:"max_samples_per_send,omitempty"`
}

const (
	// DefaultChunkedReadLimit is the default value for the maximum size of the protobuf frame client allows.
	// 50MB is the default. This is equivalent to ~100k full XOR chunks and average labelset.
	DefaultChunkedReadLimit = 5e+7
)

// RemoteReadConfig is the configuration for reading from remote storage.
type RemoteReadConfig struct {
	URL              *config.URL       `yaml:"url"`
	RemoteTimeout    model.Duration    `yaml:"remote_timeout,omitempty"`
	ChunkedReadLimit uint64            `yaml:"chunked_read_limit,omitempty"`
	Headers          map[string]string `yaml:"headers,omitempty"`
	ReadRecent       bool              `yaml:"read_recent,omitempty"`
	Name             string            `yaml:"name,omitempty"`

	// We cannot do proper Go type embedding below as the parser will then parse
	// values arbitrarily into the overflow maps of further-down types.
	HTTPClientConfig config.HTTPClientConfig `yaml:",inline"`

	// RequiredMatchers is an optional list of equality matchers which have to
	// be present in a selector to query the remote read endpoint.
	RequiredMatchers model.LabelSet `yaml:"required_matchers,omitempty"`

	// Whether to use the external labels as selectors for the remote read endpoint.
	FilterExternalLabels bool `yaml:"filter_external_labels,omitempty"`
}

// SetDirectory joins any relative file paths with dir.
func (c *RemoteReadConfig) SetDirectory(dir string) {
	c.HTTPClientConfig.SetDirectory(dir)
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *RemoteReadConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultRemoteReadConfig
	type plain RemoteReadConfig
	if err := unmarshal((*plain)(c)); err != nil {
		return err
	}
	if c.URL == nil {
		return errors.New("url for remote_read is empty")
	}
	if err := validateHeaders(c.Headers); err != nil {
		return err
	}
	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
	// We cannot make it a pointer as the parser panics for inlined pointer structs.
	// Thus we just do its validation here.
	return c.HTTPClientConfig.Validate()
}

func filePath(filename string) string {
	absPath, err := filepath.Abs(filename)
	if err != nil {
		return filename
	}
	return absPath
}

func fileErr(filename string, err error) error {
	return fmt.Errorf("%q: %w", filePath(filename), err)
}

func getGoGCEnv() int {
	goGCEnv := os.Getenv("GOGC")
	// If the GOGC env var is set, use the same logic as upstream Go.
	if goGCEnv != "" {
		// Special case for GOGC=off.
		if strings.ToLower(goGCEnv) == "off" {
			return -1
		}
		i, err := strconv.Atoi(goGCEnv)
		if err == nil {
			return i
		}
	}
	return DefaultRuntimeConfig.GoGC
}

// OTLPConfig is the configuration for writing to the OTLP endpoint.
type OTLPConfig struct {
	PromoteResourceAttributes []string `yaml:"promote_resource_attributes,omitempty"`
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (c *OTLPConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultOTLPConfig
	type plain OTLPConfig
	if err := unmarshal((*plain)(c)); err != nil {
		return err
	}

	seen := map[string]struct{}{}
	var err error
	for i, attr := range c.PromoteResourceAttributes {
		attr = strings.TrimSpace(attr)
		if attr == "" {
			err = errors.Join(err, fmt.Errorf("empty promoted OTel resource attribute"))
			continue
		}
		if _, exists := seen[attr]; exists {
			err = errors.Join(err, fmt.Errorf("duplicated promoted OTel resource attribute %q", attr))
			continue
		}

		seen[attr] = struct{}{}
		c.PromoteResourceAttributes[i] = attr
	}
	return err
}