// Package metrics defines the Prometheus metrics served on the admin port.
package metrics

import (
	"github.com/prometheus/client_golang/prometheus"
)

// Metrics holds every collector; fields are exported for tests.
type Metrics struct {
	Requests      *prometheus.CounterVec   // route, status
	Duration      *prometheus.HistogramVec // route
	Increments    *prometheus.CounterVec   // level, flow
	LimitReached  *prometheus.CounterVec   // level, flow
	Notifications *prometheus.CounterVec   // level, result (sent|failed|disabled)
	RedisErrors   *prometheus.CounterVec   // op
	CDBDomains    prometheus.Gauge
	CDBReloads    *prometheus.CounterVec // result (success|failure)
	Dropped       *prometheus.CounterVec // route: requests refused because the counting queue was full
	QueueDepth    prometheus.Gauge
	QueueWait     prometheus.Histogram
}

// New creates the collectors and registers them with reg.
func New(reg prometheus.Registerer) *Metrics {
	m := &Metrics{
		Requests: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_requests_total",
			Help: "HTTP requests by route and status code.",
		}, []string{"route", "status"}),
		Duration: prometheus.NewHistogramVec(prometheus.HistogramOpts{
			Name:    "migadu_counters_request_duration_seconds",
			Help:    "Request latency by route.",
			Buckets: []float64{.0005, .001, .0025, .005, .01, .025, .05, .1, .25, .5, 1, 2.5},
		}, []string{"route"}),
		Increments: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_increments_total",
			Help: "Counter increments by level (A, D, O) and flow (i, o).",
		}, []string{"level", "flow"}),
		LimitReached: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_limit_reached_total",
			Help: "Increments that crossed a configured limit, by level and flow.",
		}, []string{"level", "flow"}),
		Notifications: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_notifications_total",
			Help: "Web app notifications by level and result (sent, failed, disabled).",
		}, []string{"level", "result"}),
		RedisErrors: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_redis_errors_total",
			Help: "Failed Redis operations by op (incr, mget, ping).",
		}, []string{"op"}),
		CDBDomains: prometheus.NewGauge(prometheus.GaugeOpts{
			Name: "migadu_counters_cdb_domains",
			Help: "Domains in the currently loaded domains CDB.",
		}),
		CDBReloads: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_cdb_reloads_total",
			Help: "Domains CDB reload attempts by result (success, failure).",
		}, []string{"result"}),
		Dropped: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "migadu_counters_dropped_total",
			Help: "Validated requests refused with 503 because the counting queue was full, by route.",
		}, []string{"route"}),
		QueueDepth: prometheus.NewGauge(prometheus.GaugeOpts{
			Name: "migadu_counters_queue_depth",
			Help: "Jobs waiting in the counting queue.",
		}),
		QueueWait: prometheus.NewHistogram(prometheus.HistogramOpts{
			Name:    "migadu_counters_queue_wait_seconds",
			Help:    "Time a job waited in the counting queue before a worker took it.",
			Buckets: []float64{.0001, .0005, .001, .0025, .005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5},
		}),
	}
	reg.MustRegister(m.Requests, m.Duration, m.Increments, m.LimitReached, m.Notifications, m.RedisErrors, m.CDBDomains, m.CDBReloads,
		m.Dropped, m.QueueDepth, m.QueueWait)
	return m
}

// RecordDropped counts a request refused because the queue was full.
func (m *Metrics) RecordDropped(route string) { m.Dropped.WithLabelValues(route).Inc() }

// SetQueueDepth publishes the current queue depth.
func (m *Metrics) SetQueueDepth(n int) { m.QueueDepth.Set(float64(n)) }

// ObserveQueueWait records how long a job waited for a worker.
func (m *Metrics) ObserveQueueWait(seconds float64) { m.QueueWait.Observe(seconds) }

// RecordRequest counts one HTTP request and observes its latency.
func (m *Metrics) RecordRequest(route, status string, seconds float64) {
	m.Requests.WithLabelValues(route, status).Inc()
	m.Duration.WithLabelValues(route).Observe(seconds)
}

// RecordIncrement counts one counter increment.
func (m *Metrics) RecordIncrement(level, flow string) {
	m.Increments.WithLabelValues(level, flow).Inc()
}

// RecordLimitReached counts one limit crossing.
func (m *Metrics) RecordLimitReached(level, flow string) {
	m.LimitReached.WithLabelValues(level, flow).Inc()
}

// RecordNotification counts one notification outcome.
func (m *Metrics) RecordNotification(level, result string) {
	m.Notifications.WithLabelValues(level, result).Inc()
}

// RecordRedisError counts one failed Redis operation.
func (m *Metrics) RecordRedisError(op string) { m.RedisErrors.WithLabelValues(op).Inc() }

// SetCDBDomains publishes the record count of the loaded CDB.
func (m *Metrics) SetCDBDomains(n int) { m.CDBDomains.Set(float64(n)) }

// RecordReload counts one CDB reload attempt.
func (m *Metrics) RecordReload(ok bool) {
	result := "failure"
	if ok {
		result = "success"
	}
	m.CDBReloads.WithLabelValues(result).Inc()
}