package validation

import (
	"flag"
	"time"

	"github.com/grafana/loki/pkg/util/flagext"
)

const (
	// Local ingestion rate strategy
	LocalIngestionRateStrategy = "local"

	// Global ingestion rate strategy
	GlobalIngestionRateStrategy = "global"

	bytesInMB = 1048576
)

// Limits describe all the limits for users; can be used to describe global default
// limits via flags, or per-user limits via yaml config.
type Limits struct {
	// Distributor enforced limits.
	IngestionRateStrategy  string           `yaml:"ingestion_rate_strategy"`
	IngestionRateMB        float64          `yaml:"ingestion_rate_mb"`
	IngestionBurstSizeMB   float64          `yaml:"ingestion_burst_size_mb"`
	MaxLabelNameLength     int              `yaml:"max_label_name_length"`
	MaxLabelValueLength    int              `yaml:"max_label_value_length"`
	MaxLabelNamesPerSeries int              `yaml:"max_label_names_per_series"`
	RejectOldSamples       bool             `yaml:"reject_old_samples"`
	RejectOldSamplesMaxAge time.Duration    `yaml:"reject_old_samples_max_age"`
	CreationGracePeriod    time.Duration    `yaml:"creation_grace_period"`
	EnforceMetricName      bool             `yaml:"enforce_metric_name"`
	MaxLineSize            flagext.ByteSize `yaml:"max_line_size"`

	// Ingester enforced limits.
	MaxLocalStreamsPerUser  int `yaml:"max_streams_per_user"`
	MaxGlobalStreamsPerUser int `yaml:"max_global_streams_per_user"`

	// Querier enforced limits.
	MaxChunksPerQuery          int           `yaml:"max_chunks_per_query"`
	MaxQuerySeries             int           `yaml:"max_query_series"`
	MaxQueryLength             time.Duration `yaml:"max_query_length"`
	MaxQueryParallelism        int           `yaml:"max_query_parallelism"`
	CardinalityLimit           int           `yaml:"cardinality_limit"`
	MaxStreamsMatchersPerQuery int           `yaml:"max_streams_matchers_per_query"`
	MaxConcurrentTailRequests  int           `yaml:"max_concurrent_tail_requests"`
	MaxEntriesLimitPerQuery    int           `yaml:"max_entries_limit_per_query"`
	MaxCacheFreshness          time.Duration `yaml:"max_cache_freshness_per_query"`

	// Query frontend enforced limits. The default is actually parameterized by the queryrange config.
	QuerySplitDuration time.Duration `yaml:"split_queries_by_interval"`

	// Config for overrides, convenient if it goes here.
	PerTenantOverrideConfig string        `yaml:"per_tenant_override_config"`
	PerTenantOverridePeriod time.Duration `yaml:"per_tenant_override_period"`
}

// RegisterFlags adds the flags required to config this to the given FlagSet
func (l *Limits) RegisterFlags(f *flag.FlagSet) {
	f.StringVar(&l.IngestionRateStrategy, "distributor.ingestion-rate-limit-strategy", "local", "Whether the ingestion rate limit should be applied individually to each distributor instance (local), or evenly shared across the cluster (global).")
	f.Float64Var(&l.IngestionRateMB, "distributor.ingestion-rate-limit-mb", 4, "Per-user ingestion rate limit in sample size per second. Units in MB.")
	f.Float64Var(&l.IngestionBurstSizeMB, "distributor.ingestion-burst-size-mb", 6, "Per-user allowed ingestion burst size (in sample size). Units in MB.")
	f.Var(&l.MaxLineSize, "distributor.max-line-size", "maximum line length allowed, i.e. 100mb. Default (0) means unlimited.")
	f.IntVar(&l.MaxLabelNameLength, "validation.max-length-label-name", 1024, "Maximum length accepted for label names")
	f.IntVar(&l.MaxLabelValueLength, "validation.max-length-label-value", 2048, "Maximum length accepted for label value. This setting also applies to the metric name")
	f.IntVar(&l.MaxLabelNamesPerSeries, "validation.max-label-names-per-series", 30, "Maximum number of label names per series.")
	f.BoolVar(&l.RejectOldSamples, "validation.reject-old-samples", false, "Reject old samples.")
	f.DurationVar(&l.RejectOldSamplesMaxAge, "validation.reject-old-samples.max-age", 14*24*time.Hour, "Maximum accepted sample age before rejecting.")
	f.DurationVar(&l.CreationGracePeriod, "validation.create-grace-period", 10*time.Minute, "Duration which table will be created/deleted before/after it's needed; we won't accept sample from before this time.")
	f.BoolVar(&l.EnforceMetricName, "validation.enforce-metric-name", true, "Enforce every sample has a metric name.")
	f.IntVar(&l.MaxEntriesLimitPerQuery, "validation.max-entries-limit", 5000, "Per-user entries limit per query")

	f.IntVar(&l.MaxLocalStreamsPerUser, "ingester.max-streams-per-user", 10e3, "Maximum number of active streams per user, per ingester. 0 to disable.")
	f.IntVar(&l.MaxGlobalStreamsPerUser, "ingester.max-global-streams-per-user", 0, "Maximum number of active streams per user, across the cluster. 0 to disable.")

	f.IntVar(&l.MaxChunksPerQuery, "store.query-chunk-limit", 2e6, "Maximum number of chunks that can be fetched in a single query.")
	f.DurationVar(&l.MaxQueryLength, "store.max-query-length", 0, "Limit to length of chunk store queries, 0 to disable.")
	f.IntVar(&l.MaxQuerySeries, "querier.max-query-series", 500, "Limit the maximum of unique series returned by a metric query. When the limit is reached an error is returned.")
	f.IntVar(&l.MaxQueryParallelism, "querier.max-query-parallelism", 14, "Maximum number of queries will be scheduled in parallel by the frontend.")
	f.IntVar(&l.CardinalityLimit, "store.cardinality-limit", 1e5, "Cardinality limit for index queries.")
	f.IntVar(&l.MaxStreamsMatchersPerQuery, "querier.max-streams-matcher-per-query", 1000, "Limit the number of streams matchers per query")
	f.IntVar(&l.MaxConcurrentTailRequests, "querier.max-concurrent-tail-requests", 10, "Limit the number of concurrent tail requests")
	f.DurationVar(&l.MaxCacheFreshness, "frontend.max-cache-freshness", 1*time.Minute, "Most recent allowed cacheable result per-tenant, to prevent caching very recent results that might still be in flux.")

	f.StringVar(&l.PerTenantOverrideConfig, "limits.per-user-override-config", "", "File name of per-user overrides.")
	f.DurationVar(&l.PerTenantOverridePeriod, "limits.per-user-override-period", 10*time.Second, "Period with this to reload the overrides.")
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (l *Limits) UnmarshalYAML(unmarshal func(interface{}) error) error {
	// 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.  See prometheus/config.

	// During startup we wont have a default value so we don't want to overwrite them
	if defaultLimits != nil {
		*l = *defaultLimits
	}
	type plain Limits
	return unmarshal((*plain)(l))
}

// When we load YAML from disk, we want the various per-customer limits
// to default to any values specified on the command line, not default
// command line values.  This global contains those values.  I (Tom) cannot
// find a nicer way I'm afraid.
var defaultLimits *Limits

// SetDefaultLimitsForYAMLUnmarshalling sets global default limits, used when loading
// Limits from YAML files. This is used to ensure per-tenant limits are defaulted to
// those values.
func SetDefaultLimitsForYAMLUnmarshalling(defaults Limits) {
	defaultLimits = &defaults
}

// TenantLimits is a function that returns limits for given tenant, or
// nil, if there are no tenant-specific limits.
type TenantLimits func(userID string) *Limits

// Overrides periodically fetch a set of per-user overrides, and provides convenience
// functions for fetching the correct value.
type Overrides struct {
	defaultLimits *Limits
	tenantLimits  TenantLimits
}

// NewOverrides makes a new Overrides.
func NewOverrides(defaults Limits, tenantLimits TenantLimits) (*Overrides, error) {
	return &Overrides{
		tenantLimits:  tenantLimits,
		defaultLimits: &defaults,
	}, nil
}

// IngestionRateStrategy returns whether the ingestion rate limit should be individually applied
// to each distributor instance (local) or evenly shared across the cluster (global).
func (o *Overrides) IngestionRateStrategy() string {
	// The ingestion rate strategy can't be overridden on a per-tenant basis,
	// so here we just pick the value for a not-existing user ID (empty string).
	return o.getOverridesForUser("").IngestionRateStrategy
}

// IngestionRateBytes returns the limit on ingester rate (MBs per second).
func (o *Overrides) IngestionRateBytes(userID string) float64 {
	return o.getOverridesForUser(userID).IngestionRateMB * bytesInMB
}

// IngestionBurstSizeBytes returns the burst size for ingestion rate.
func (o *Overrides) IngestionBurstSizeBytes(userID string) int {
	return int(o.getOverridesForUser(userID).IngestionBurstSizeMB * bytesInMB)
}

// MaxLabelNameLength returns maximum length a label name can be.
func (o *Overrides) MaxLabelNameLength(userID string) int {
	return o.getOverridesForUser(userID).MaxLabelNameLength
}

// MaxLabelValueLength returns maximum length a label value can be. This also is
// the maximum length of a metric name.
func (o *Overrides) MaxLabelValueLength(userID string) int {
	return o.getOverridesForUser(userID).MaxLabelValueLength
}

// MaxLabelNamesPerSeries returns maximum number of label/value pairs timeseries.
func (o *Overrides) MaxLabelNamesPerSeries(userID string) int {
	return o.getOverridesForUser(userID).MaxLabelNamesPerSeries
}

// RejectOldSamples returns true when we should reject samples older than certain
// age.
func (o *Overrides) RejectOldSamples(userID string) bool {
	return o.getOverridesForUser(userID).RejectOldSamples
}

// RejectOldSamplesMaxAge returns the age at which samples should be rejected.
func (o *Overrides) RejectOldSamplesMaxAge(userID string) time.Duration {
	return o.getOverridesForUser(userID).RejectOldSamplesMaxAge
}

// CreationGracePeriod is misnamed, and actually returns how far into the future
// we should accept samples.
func (o *Overrides) CreationGracePeriod(userID string) time.Duration {
	return o.getOverridesForUser(userID).CreationGracePeriod
}

// MaxLocalStreamsPerUser returns the maximum number of streams a user is allowed to store
// in a single ingester.
func (o *Overrides) MaxLocalStreamsPerUser(userID string) int {
	return o.getOverridesForUser(userID).MaxLocalStreamsPerUser
}

// MaxGlobalStreamsPerUser returns the maximum number of streams a user is allowed to store
// across the cluster.
func (o *Overrides) MaxGlobalStreamsPerUser(userID string) int {
	return o.getOverridesForUser(userID).MaxGlobalStreamsPerUser
}

// MaxChunksPerQuery returns the maximum number of chunks allowed per query.
func (o *Overrides) MaxChunksPerQuery(userID string) int {
	return o.getOverridesForUser(userID).MaxChunksPerQuery
}

// MaxQueryLength returns the limit of the length (in time) of a query.
func (o *Overrides) MaxQueryLength(userID string) time.Duration {
	return o.getOverridesForUser(userID).MaxQueryLength
}

// MaxQueryLength returns the limit of the series of metric queries.
func (o *Overrides) MaxQuerySeries(userID string) int {
	return o.getOverridesForUser(userID).MaxQuerySeries
}

// MaxQueryParallelism returns the limit to the number of sub-queries the
// frontend will process in parallel.
func (o *Overrides) MaxQueryParallelism(userID string) int {
	return o.getOverridesForUser(userID).MaxQueryParallelism
}

// EnforceMetricName whether to enforce the presence of a metric name.
func (o *Overrides) EnforceMetricName(userID string) bool {
	return o.getOverridesForUser(userID).EnforceMetricName
}

// CardinalityLimit whether to enforce the presence of a metric name.
func (o *Overrides) CardinalityLimit(userID string) int {
	return o.getOverridesForUser(userID).CardinalityLimit
}

// MaxStreamsMatchersPerQuery returns the limit to number of streams matchers per query.
func (o *Overrides) MaxStreamsMatchersPerQuery(userID string) int {
	return o.getOverridesForUser(userID).MaxStreamsMatchersPerQuery
}

// QuerySplitDuration returns the tenant specific splitby interval applied in the query frontend.
func (o *Overrides) QuerySplitDuration(userID string) time.Duration {
	return o.getOverridesForUser(userID).QuerySplitDuration
}

// MaxConcurrentTailRequests returns the limit to number of concurrent tail requests.
func (o *Overrides) MaxConcurrentTailRequests(userID string) int {
	return o.getOverridesForUser(userID).MaxConcurrentTailRequests
}

// MaxLineSize returns the maximum size in bytes the distributor should allow.
func (o *Overrides) MaxLineSize(userID string) int {
	return o.getOverridesForUser(userID).MaxLineSize.Val()
}

// MaxEntriesLimitPerQuery returns the limit to number of entries the querier should return per query.
func (o *Overrides) MaxEntriesLimitPerQuery(userID string) int {
	return o.getOverridesForUser(userID).MaxEntriesLimitPerQuery
}

func (o *Overrides) MaxCacheFreshness(userID string) time.Duration {
	return o.getOverridesForUser(userID).MaxCacheFreshness
}

func (o *Overrides) getOverridesForUser(userID string) *Limits {
	if o.tenantLimits != nil {
		l := o.tenantLimits(userID)
		if l != nil {
			return l
		}
	}
	return o.defaultLimits
}