// Copyright 2016 TiKV Project 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 pd

import (
	"sync/atomic"
	"time"

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

// make sure register metrics only once
var initialized int32

// enableNonCoreCmdDurationMetrics controls cmdDuration labels other than
// wait/tso/tso_async_wait/get_region.
var enableNonCoreCmdDurationMetrics = false

func observeNonCoreCmdDuration(observer prometheus.Observer, start time.Time) {
	if !enableNonCoreCmdDurationMetrics {
		return
	}
	elapsed := time.Since(start)
	if elapsed < 0 {
		elapsed = 0
	}
	observer.Observe(elapsed.Seconds())
}

func init() {
	initMetrics(prometheus.Labels{})
	initCmdDurations()
}

func initAndRegisterMetrics(constLabels prometheus.Labels) {
	if atomic.CompareAndSwapInt32(&initialized, 0, 1) {
		// init metrics with constLabels
		initMetrics(constLabels)
		initCmdDurations()
		// register metrics
		registerMetrics()
	}
}

var (
	cmdDuration              *prometheus.HistogramVec
	cmdFailedDuration        *prometheus.HistogramVec
	requestDuration          *prometheus.HistogramVec
	tsoBestBatchSize         prometheus.Histogram
	tsoBatchSize             prometheus.Histogram
	tsoBatchSendLatency      prometheus.Histogram
	requestForwarded         *prometheus.GaugeVec
	ongoingRequestCountGauge *prometheus.GaugeVec
	estimateTSOLatencyGauge  *prometheus.GaugeVec
)

func initMetrics(constLabels prometheus.Labels) {
	cmdDuration = prometheus.NewHistogramVec(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "cmd",
			Name:        "handle_cmds_duration_seconds",
			Help:        "Bucketed histogram of processing time (s) of handled success cmds.",
			ConstLabels: constLabels,
			// Retained core cmdDuration labels intentionally use a coarser 8-bucket
			// layout (1ms -> 16.384s) so the per-label series footprint still drops
			// after non-core labels are pruned.
			Buckets: prometheus.ExponentialBuckets(0.001, 4, 8),
		}, []string{"type"})

	cmdFailedDuration = prometheus.NewHistogramVec(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "cmd",
			Name:        "handle_failed_cmds_duration_seconds",
			Help:        "Bucketed histogram of processing time (s) of failed handled cmds.",
			ConstLabels: constLabels,
			Buckets:     prometheus.ExponentialBuckets(0.0005, 2, 13),
		}, []string{"type"})

	requestDuration = prometheus.NewHistogramVec(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "handle_requests_duration_seconds",
			Help:        "Bucketed histogram of processing time (s) of handled requests.",
			ConstLabels: constLabels,
			Buckets:     prometheus.ExponentialBuckets(0.0005, 2, 13),
		}, []string{"type"})

	tsoBestBatchSize = prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "handle_tso_best_batch_size",
			Help:        "Bucketed histogram of the best batch size of handled requests.",
			ConstLabels: constLabels,
			Buckets:     prometheus.ExponentialBuckets(1, 2, 13),
		})

	tsoBatchSize = prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "handle_tso_batch_size",
			Help:        "Bucketed histogram of the batch size of handled requests.",
			ConstLabels: constLabels,
			Buckets:     []float64{1, 2, 4, 8, 10, 14, 18, 22, 26, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 140, 160, 180, 200, 500, 1000},
		})

	tsoBatchSendLatency = prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "tso_batch_send_latency",
			ConstLabels: constLabels,
			Buckets:     prometheus.ExponentialBuckets(0.0005, 2, 13),
			Help:        "tso batch send latency",
		})

	requestForwarded = prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "forwarded_status",
			Help:        "The status to indicate if the request is forwarded",
			ConstLabels: constLabels,
		}, []string{"host", "delegate"})

	ongoingRequestCountGauge = prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "ongoing_requests_count",
			Help:        "Current count of ongoing batch tso requests",
			ConstLabels: constLabels,
		}, []string{"stream"})
	estimateTSOLatencyGauge = prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Namespace:   "pd_client",
			Subsystem:   "request",
			Name:        "estimate_tso_latency",
			Help:        "Estimated latency of an RTT of getting TSO",
			ConstLabels: constLabels,
		}, []string{"stream"})
}

var (
	cmdDurationWait                     prometheus.Observer
	cmdDurationTSO                      prometheus.Observer
	cmdDurationTSOAsyncWait             prometheus.Observer
	cmdDurationGetRegion                prometheus.Observer
	cmdDurationGetAllMembers            prometheus.Observer
	cmdDurationGetPrevRegion            prometheus.Observer
	cmdDurationGetRegionByID            prometheus.Observer
	cmdDurationScanRegions              prometheus.Observer
	cmdDurationBatchScanRegions         prometheus.Observer
	cmdDurationGetStore                 prometheus.Observer
	cmdDurationGetAllStores             prometheus.Observer
	cmdDurationUpdateGCSafePoint        prometheus.Observer
	cmdDurationUpdateServiceGCSafePoint prometheus.Observer
	cmdDurationScatterRegion            prometheus.Observer
	cmdDurationScatterRegions           prometheus.Observer
	cmdDurationGetOperator              prometheus.Observer
	cmdDurationSplitRegions             prometheus.Observer
	cmdDurationSplitAndScatterRegions   prometheus.Observer
	cmdDurationLoadKeyspace             prometheus.Observer
	cmdDurationLoadKeyspaceByID         prometheus.Observer
	cmdDurationUpdateKeyspaceState      prometheus.Observer
	cmdDurationGetAllKeyspaces          prometheus.Observer
	cmdDurationGet                      prometheus.Observer
	cmdDurationPut                      prometheus.Observer
	cmdDurationUpdateGCSafePointV2      prometheus.Observer
	cmdDurationUpdateServiceSafePointV2 prometheus.Observer
	cmdDurationGetClusterInfo           prometheus.Observer

	cmdFailDurationGetRegion                  prometheus.Observer
	cmdFailDurationTSO                        prometheus.Observer
	cmdFailDurationGetAllMembers              prometheus.Observer
	cmdFailDurationGetPrevRegion              prometheus.Observer
	cmdFailedDurationGetRegionByID            prometheus.Observer
	cmdFailedDurationScanRegions              prometheus.Observer
	cmdFailedDurationBatchScanRegions         prometheus.Observer
	cmdFailedDurationGetStore                 prometheus.Observer
	cmdFailedDurationGetAllStores             prometheus.Observer
	cmdFailedDurationUpdateGCSafePoint        prometheus.Observer
	cmdFailedDurationUpdateServiceGCSafePoint prometheus.Observer
	cmdFailedDurationLoadKeyspace             prometheus.Observer
	cmdFailedDurationLoadKeyspaceByID         prometheus.Observer
	cmdFailedDurationUpdateKeyspaceState      prometheus.Observer
	cmdFailedDurationGet                      prometheus.Observer
	cmdFailedDurationPut                      prometheus.Observer
	cmdFailedDurationUpdateGCSafePointV2      prometheus.Observer
	cmdFailedDurationUpdateServiceSafePointV2 prometheus.Observer
	cmdFailedDurationGetClusterInfo           prometheus.Observer

	requestDurationTSO       prometheus.Observer
	requestFailedDurationTSO prometheus.Observer
)

func initCmdDurations() {
	// WithLabelValues is a heavy operation, define variable to avoid call it every time.
	cmdDurationWait = cmdDuration.WithLabelValues("wait")
	cmdDurationTSO = cmdDuration.WithLabelValues("tso")
	cmdDurationTSOAsyncWait = cmdDuration.WithLabelValues("tso_async_wait")
	cmdDurationGetRegion = cmdDuration.WithLabelValues("get_region")
	if enableNonCoreCmdDurationMetrics {
		cmdDurationGetAllMembers = cmdDuration.WithLabelValues("get_member_info")
		cmdDurationGetPrevRegion = cmdDuration.WithLabelValues("get_prev_region")
		cmdDurationGetRegionByID = cmdDuration.WithLabelValues("get_region_byid")
		cmdDurationScanRegions = cmdDuration.WithLabelValues("scan_regions")
		cmdDurationBatchScanRegions = cmdDuration.WithLabelValues("batch_scan_regions")
		cmdDurationGetStore = cmdDuration.WithLabelValues("get_store")
		cmdDurationGetAllStores = cmdDuration.WithLabelValues("get_all_stores")
		cmdDurationUpdateGCSafePoint = cmdDuration.WithLabelValues("update_gc_safe_point")
		cmdDurationUpdateServiceGCSafePoint = cmdDuration.WithLabelValues("update_service_gc_safe_point")
		cmdDurationScatterRegion = cmdDuration.WithLabelValues("scatter_region")
		cmdDurationScatterRegions = cmdDuration.WithLabelValues("scatter_regions")
		cmdDurationGetOperator = cmdDuration.WithLabelValues("get_operator")
		cmdDurationSplitRegions = cmdDuration.WithLabelValues("split_regions")
		cmdDurationSplitAndScatterRegions = cmdDuration.WithLabelValues("split_and_scatter_regions")
		cmdDurationLoadKeyspace = cmdDuration.WithLabelValues("load_keyspace")
		cmdDurationLoadKeyspaceByID = cmdDuration.WithLabelValues("load_keyspace_by_id")
		cmdDurationUpdateKeyspaceState = cmdDuration.WithLabelValues("update_keyspace_state")
		cmdDurationGetAllKeyspaces = cmdDuration.WithLabelValues("get_all_keyspaces")
		cmdDurationGet = cmdDuration.WithLabelValues("get")
		cmdDurationPut = cmdDuration.WithLabelValues("put")
		cmdDurationUpdateGCSafePointV2 = cmdDuration.WithLabelValues("update_gc_safe_point_v2")
		cmdDurationUpdateServiceSafePointV2 = cmdDuration.WithLabelValues("update_service_safe_point_v2")
		cmdDurationGetClusterInfo = cmdDuration.WithLabelValues("get_cluster_info")
	}

	cmdFailDurationGetRegion = cmdFailedDuration.WithLabelValues("get_region")
	cmdFailDurationTSO = cmdFailedDuration.WithLabelValues("tso")
	cmdFailDurationGetAllMembers = cmdFailedDuration.WithLabelValues("get_member_info")
	cmdFailDurationGetPrevRegion = cmdFailedDuration.WithLabelValues("get_prev_region")
	cmdFailedDurationGetRegionByID = cmdFailedDuration.WithLabelValues("get_region_byid")
	cmdFailedDurationScanRegions = cmdFailedDuration.WithLabelValues("scan_regions")
	cmdFailedDurationBatchScanRegions = cmdFailedDuration.WithLabelValues("batch_scan_regions")
	cmdFailedDurationGetStore = cmdFailedDuration.WithLabelValues("get_store")
	cmdFailedDurationGetAllStores = cmdFailedDuration.WithLabelValues("get_all_stores")
	cmdFailedDurationUpdateGCSafePoint = cmdFailedDuration.WithLabelValues("update_gc_safe_point")
	cmdFailedDurationUpdateServiceGCSafePoint = cmdFailedDuration.WithLabelValues("update_service_gc_safe_point")
	cmdFailedDurationLoadKeyspace = cmdFailedDuration.WithLabelValues("load_keyspace")
	cmdFailedDurationLoadKeyspaceByID = cmdFailedDuration.WithLabelValues("load_keyspace_by_id")
	cmdFailedDurationUpdateKeyspaceState = cmdFailedDuration.WithLabelValues("update_keyspace_state")
	cmdFailedDurationGet = cmdFailedDuration.WithLabelValues("get")
	cmdFailedDurationPut = cmdFailedDuration.WithLabelValues("put")
	cmdFailedDurationUpdateGCSafePointV2 = cmdFailedDuration.WithLabelValues("update_gc_safe_point_v2")
	cmdFailedDurationUpdateServiceSafePointV2 = cmdFailedDuration.WithLabelValues("update_service_safe_point_v2")
	cmdFailedDurationGetClusterInfo = cmdFailedDuration.WithLabelValues("get_cluster_info")

	requestDurationTSO = requestDuration.WithLabelValues("tso")
	requestFailedDurationTSO = requestDuration.WithLabelValues("tso-failed")
}

func registerMetrics() {
	prometheus.MustRegister(cmdDuration)
	prometheus.MustRegister(cmdFailedDuration)
	prometheus.MustRegister(requestDuration)
	prometheus.MustRegister(tsoBestBatchSize)
	prometheus.MustRegister(tsoBatchSize)
	prometheus.MustRegister(tsoBatchSendLatency)
	prometheus.MustRegister(requestForwarded)
	prometheus.MustRegister(estimateTSOLatencyGauge)
}