metrics

type Counter interface {
	Metric

	// Inc increments the counter by 1.
	Inc()

	// Add adds the given value to the counter.
	Add(value float64)

	// Value returns the current value of the counter.
	Value() float64
}

type CounterBuilder interface {
	// Name sets the counter name.
	Name(name string) CounterBuilder

	// Description sets the counter description.
	Description(desc string) CounterBuilder

	// Tag adds a tag to the counter.
	Tag(key, value string) CounterBuilder

	// Build creates the counter.
	Build() Counter
}

type Gauge interface {
	Metric

	// Set sets the gauge to the given value.
	Set(value float64)

	// Inc increments the gauge by 1.
	Inc()

	// Dec decrements the gauge by 1.
	Dec()

	// Add adds the given value to the gauge.
	Add(value float64)

	// Sub subtracts the given value from the gauge.
	Sub(value float64)

	// Value returns the current value of the gauge.
	Value() float64
}

type GaugeBuilder interface {
	// Name sets the gauge name.
	Name(name string) GaugeBuilder

	// Description sets the gauge description.
	Description(desc string) GaugeBuilder

	// Tag adds a tag to the gauge.
	Tag(key, value string) GaugeBuilder

	// Build creates the gauge.
	Build() Gauge
}

type Histogram interface {
	Metric

	// Observe adds a single observation to the histogram.
	Observe(value float64)

	// Buckets returns the bucket boundaries.
	Buckets() []float64
}

type HistogramBuilder interface {
	// Name sets the histogram name.
	Name(name string) HistogramBuilder

	// Description sets the histogram description.
	Description(desc string) HistogramBuilder

	// Tag adds a tag to the histogram.
	Tag(key, value string) HistogramBuilder

	// Buckets sets the bucket boundaries.
	Buckets(buckets []float64) HistogramBuilder

	// Build creates the histogram.
	Build() Histogram
}

type Metric interface {
	// Name returns the metric name.
	Name() string

	// Description returns the metric description.
	Description() string

	// Type returns the metric type.
	Type() MetricType

	// Tags returns the metric tags.
	Tags() Tags

	// WithTags returns a new metric with the given tags.
	WithTags(tags Tags) Metric
}

type MetricType string

type MetricsExporter interface {
	// Export metrics to the backend.
	Export(snapshot MetricsSnapshot) error

	// Start the exporter.
	Start() error

	// Stop the exporter.
	Stop() error

	// Return an HTTP handler for exposing metrics.
	Handler() http.Handler
}

type MetricsFilter interface {
	// Filter returns true if metrics should be collected for the request.
	Filter(r *http.Request) bool
}

type MetricsMiddleware interface {
	// Wrap an HTTP handler with metrics collection.
	Handler(name string, handler http.Handler) http.Handler

	// Configure the middleware.
	Configure(config MetricsMiddlewareConfig) MetricsMiddleware

	// Add a filter to the middleware.
	WithFilter(filter MetricsFilter) MetricsMiddleware

	// Add a sampler to the middleware.
	WithSampler(sampler MetricsSampler) MetricsMiddleware
}

type MetricsMiddlewareConfig struct {
	// EnableLatency enables latency metrics.
	EnableLatency bool

	// EnableThroughput enables throughput metrics.
	EnableThroughput bool

	// EnableQPS enables queries per second metrics.
	EnableQPS bool

	// EnableErrors enables error metrics.
	EnableErrors bool

	// SamplingRate is the rate at which to sample requests.
	SamplingRate float64

	// DefaultTags are tags to add to all metrics.
	DefaultTags Tags
}

type MetricsMiddlewareImpl struct {
	// contains filtered or unexported fields
}

type MetricsRegistry interface {
	// Register a metric with the registry.
	Register(metric Metric) error

	// Get a metric by name.
	Get(name string) (Metric, bool)

	// Unregister a metric from the registry.
	Unregister(name string) bool

	// Clear all metrics from the registry.
	Clear()

	// Get a snapshot of all metrics.
	Snapshot() MetricsSnapshot

	// Create a new registry with the given tags.
	WithTags(tags Tags) MetricsRegistry

	// Create a new counter builder.
	NewCounter() CounterBuilder

	// Create a new gauge builder.
	NewGauge() GaugeBuilder

	// Create a new histogram builder.
	NewHistogram() HistogramBuilder

	// Create a new summary builder.
	NewSummary() SummaryBuilder
}

type MetricsSampler interface {
	// Sample returns true if the request should be sampled.
	Sample() bool
}

type MetricsSnapshot interface {
	// Counters returns all counters in the snapshot.
	Counters() []Counter

	// Gauges returns all gauges in the snapshot.
	Gauges() []Gauge

	// Histograms returns all histograms in the snapshot.
	Histograms() []Histogram

	// Summaries returns all summaries in the snapshot.
	Summaries() []Summary
}

type RandomSampler struct {
	// contains filtered or unexported fields
}

type Summary interface {
	Metric

	// Observe adds a single observation to the summary.
	Observe(value float64)

	// Objectives returns the quantile objectives.
	Objectives() map[float64]float64
}

type SummaryBuilder interface {
	// Name sets the summary name.
	Name(name string) SummaryBuilder

	// Description sets the summary description.
	Description(desc string) SummaryBuilder

	// Tag adds a tag to the summary.
	Tag(key, value string) SummaryBuilder

	// Objectives sets the quantile objectives.
	Objectives(objectives map[float64]float64) SummaryBuilder

	// MaxAge sets the maximum age of observations.
	MaxAge(maxAge time.Duration) SummaryBuilder

	// AgeBuckets sets the number of age buckets.
	AgeBuckets(ageBuckets int) SummaryBuilder

	// Build creates the summary.
	Build() Summary
}

type Tags map[string]string