package consensus

import (
	"strings"
	"time"

	"github.com/go-kit/kit/metrics"
	"github.com/go-kit/kit/metrics/discard"

	cstypes "github.com/tendermint/tendermint/internal/consensus/types"
	"github.com/tendermint/tendermint/types"

	prometheus "github.com/go-kit/kit/metrics/prometheus"
	stdprometheus "github.com/prometheus/client_golang/prometheus"
)

const (
	// MetricsSubsystem is a subsystem shared by all metrics exposed by this
	// package.
	MetricsSubsystem = "consensus"
)

// Metrics contains metrics exposed by this package.
type Metrics struct {
	// Height of the chain.
	Height metrics.Gauge

	// ValidatorLastSignedHeight of a validator.
	ValidatorLastSignedHeight metrics.Gauge

	// Number of rounds.
	Rounds metrics.Gauge

	// Histogram of round duration.
	RoundDuration metrics.Histogram

	// Number of validators.
	Validators metrics.Gauge
	// Total power of all validators.
	ValidatorsPower metrics.Gauge
	// Power of a validator.
	ValidatorPower metrics.Gauge
	// Amount of blocks missed by a validator.
	ValidatorMissedBlocks metrics.Gauge
	// Number of validators who did not sign.
	MissingValidators metrics.Gauge
	// Total power of the missing validators.
	MissingValidatorsPower metrics.Gauge
	// Number of validators who tried to double sign.
	ByzantineValidators metrics.Gauge
	// Total power of the byzantine validators.
	ByzantineValidatorsPower metrics.Gauge

	// Time between this and the last block.
	BlockIntervalSeconds metrics.Histogram

	// Number of transactions.
	NumTxs metrics.Gauge
	// Size of the block.
	BlockSizeBytes metrics.Histogram
	// Total number of transactions.
	TotalTxs metrics.Gauge
	// The latest block height.
	CommittedHeight metrics.Gauge
	// Whether or not a node is block syncing. 1 if yes, 0 if no.
	BlockSyncing metrics.Gauge
	// Whether or not a node is state syncing. 1 if yes, 0 if no.
	StateSyncing metrics.Gauge

	// Number of blockparts transmitted by peer.
	BlockParts metrics.Counter

	// Histogram of step duration.
	StepDuration metrics.Histogram
	stepStart    time.Time

	// Histogram of time taken to receive a block in seconds, measured between when a new block is first
	// discovered to when the block is completed.
	BlockGossipReceiveLatency metrics.Histogram
	blockGossipStart          time.Time

	// Number of block parts received by the node, separated by whether the part
	// was relevant to the block the node is trying to gather or not.
	BlockGossipPartsReceived metrics.Counter

	// QuroumPrevoteMessageDelay is the interval in seconds between the proposal
	// timestamp and the timestamp of the earliest prevote that achieved a quorum
	// during the prevote step.
	//
	// To compute it, sum the voting power over each prevote received, in increasing
	// order of timestamp. The timestamp of the first prevote to increase the sum to
	// be above 2/3 of the total voting power of the network defines the endpoint
	// the endpoint of the interval. Subtract the proposal timestamp from this endpoint
	// to obtain the quorum delay.
	QuorumPrevoteMessageDelay metrics.Gauge

	// FullPrevoteMessageDelay is the interval in seconds between the proposal
	// timestamp and the timestamp of the latest prevote in a round where 100%
	// of the voting power on the network issued prevotes.
	FullPrevoteMessageDelay metrics.Gauge

	// ProposalTimestampDifference is the difference between the timestamp in
	// the proposal message and the local time of the validator at the time
	// that the validator received the message.
	ProposalTimestampDifference metrics.Histogram
}

// PrometheusMetrics returns Metrics build using Prometheus client library.
// Optionally, labels can be provided along with their values ("foo",
// "fooValue").
func PrometheusMetrics(namespace string, labelsAndValues ...string) *Metrics {
	labels := []string{}
	for i := 0; i < len(labelsAndValues); i += 2 {
		labels = append(labels, labelsAndValues[i])
	}
	return &Metrics{
		Height: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "height",
			Help:      "Height of the chain.",
		}, labels).With(labelsAndValues...),
		Rounds: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "rounds",
			Help:      "Number of rounds.",
		}, labels).With(labelsAndValues...),
		RoundDuration: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "round_duration",
			Help:      "Time spent in a round.",
			Buckets:   stdprometheus.ExponentialBucketsRange(0.1, 100, 8),
		}, labels).With(labelsAndValues...),
		Validators: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "validators",
			Help:      "Number of validators.",
		}, labels).With(labelsAndValues...),
		ValidatorLastSignedHeight: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "validator_last_signed_height",
			Help:      "Last signed height for a validator",
		}, append(labels, "validator_address")).With(labelsAndValues...),
		ValidatorMissedBlocks: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "validator_missed_blocks",
			Help:      "Total missed blocks for a validator",
		}, append(labels, "validator_address")).With(labelsAndValues...),
		ValidatorsPower: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "validators_power",
			Help:      "Total power of all validators.",
		}, labels).With(labelsAndValues...),
		ValidatorPower: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "validator_power",
			Help:      "Power of a validator",
		}, append(labels, "validator_address")).With(labelsAndValues...),
		MissingValidators: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "missing_validators",
			Help:      "Number of validators who did not sign.",
		}, labels).With(labelsAndValues...),
		MissingValidatorsPower: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "missing_validators_power",
			Help:      "Total power of the missing validators.",
		}, labels).With(labelsAndValues...),
		ByzantineValidators: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "byzantine_validators",
			Help:      "Number of validators who tried to double sign.",
		}, labels).With(labelsAndValues...),
		ByzantineValidatorsPower: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "byzantine_validators_power",
			Help:      "Total power of the byzantine validators.",
		}, labels).With(labelsAndValues...),
		BlockIntervalSeconds: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_interval_seconds",
			Help:      "Time between this and the last block.",
		}, labels).With(labelsAndValues...),
		NumTxs: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "num_txs",
			Help:      "Number of transactions.",
		}, labels).With(labelsAndValues...),
		BlockSizeBytes: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_size_bytes",
			Help:      "Size of the block.",
		}, labels).With(labelsAndValues...),
		TotalTxs: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "total_txs",
			Help:      "Total number of transactions.",
		}, labels).With(labelsAndValues...),
		CommittedHeight: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "latest_block_height",
			Help:      "The latest block height.",
		}, labels).With(labelsAndValues...),
		BlockSyncing: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_syncing",
			Help:      "Whether or not a node is block syncing. 1 if yes, 0 if no.",
		}, labels).With(labelsAndValues...),
		StateSyncing: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "state_syncing",
			Help:      "Whether or not a node is state syncing. 1 if yes, 0 if no.",
		}, labels).With(labelsAndValues...),
		BlockParts: prometheus.NewCounterFrom(stdprometheus.CounterOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_parts",
			Help:      "Number of blockparts transmitted by peer.",
		}, append(labels, "peer_id")).With(labelsAndValues...),
		BlockGossipReceiveLatency: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_gossip_receive_latency",
			Help: "Difference in seconds between when the validator learns of a new block" +
				"and when the validator receives the last piece of the block.",
			Buckets: stdprometheus.ExponentialBucketsRange(0.1, 100, 8),
		}, labels).With(labelsAndValues...),
		BlockGossipPartsReceived: prometheus.NewCounterFrom(stdprometheus.CounterOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "block_gossip_parts_received",
			Help: "Number of block parts received by the node, labeled by whether the " +
				"part was relevant to the block the node was currently gathering or not.",
		}, append(labels, "matches_current")).With(labelsAndValues...),
		StepDuration: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "step_duration",
			Help:      "Time spent per step.",
			Buckets:   stdprometheus.ExponentialBucketsRange(0.1, 100, 8),
		}, append(labels, "step")).With(labelsAndValues...),
		QuorumPrevoteMessageDelay: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "quorum_prevote_message_delay",
			Help: "Difference in seconds between the proposal timestamp and the timestamp " +
				"of the latest prevote that achieved a quorum in the prevote step.",
		}, append(labels, "proposer_address")).With(labelsAndValues...),
		FullPrevoteMessageDelay: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "full_prevote_message_delay",
			Help: "Difference in seconds between the proposal timestamp and the timestamp " +
				"of the latest prevote that achieved 100% of the voting power in the prevote step.",
		}, append(labels, "proposer_address")).With(labelsAndValues...),
		ProposalTimestampDifference: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
			Namespace: namespace,
			Subsystem: MetricsSubsystem,
			Name:      "proposal_timestamp_difference",
			Help: "Difference in seconds between the timestamp in the proposal " +
				"message and the local time when the message was received. " +
				"Only calculated when a new block is proposed.",
			Buckets: []float64{-10, -.5, -.025, 0, .1, .5, 1, 1.5, 2, 10},
		}, append(labels, "is_timely")).With(labelsAndValues...),
	}
}

// NopMetrics returns no-op Metrics.
func NopMetrics() *Metrics {
	return &Metrics{
		Height: discard.NewGauge(),

		ValidatorLastSignedHeight: discard.NewGauge(),

		Rounds:        discard.NewGauge(),
		RoundDuration: discard.NewHistogram(),
		StepDuration:  discard.NewHistogram(),

		Validators:               discard.NewGauge(),
		ValidatorsPower:          discard.NewGauge(),
		ValidatorPower:           discard.NewGauge(),
		ValidatorMissedBlocks:    discard.NewGauge(),
		MissingValidators:        discard.NewGauge(),
		MissingValidatorsPower:   discard.NewGauge(),
		ByzantineValidators:      discard.NewGauge(),
		ByzantineValidatorsPower: discard.NewGauge(),

		BlockIntervalSeconds: discard.NewHistogram(),

		NumTxs:                      discard.NewGauge(),
		BlockSizeBytes:              discard.NewHistogram(),
		TotalTxs:                    discard.NewGauge(),
		CommittedHeight:             discard.NewGauge(),
		BlockSyncing:                discard.NewGauge(),
		StateSyncing:                discard.NewGauge(),
		BlockParts:                  discard.NewCounter(),
		BlockGossipReceiveLatency:   discard.NewHistogram(),
		BlockGossipPartsReceived:    discard.NewCounter(),
		QuorumPrevoteMessageDelay:   discard.NewGauge(),
		FullPrevoteMessageDelay:     discard.NewGauge(),
		ProposalTimestampDifference: discard.NewHistogram(),
	}
}

// RecordConsMetrics uses for recording the block related metrics during fast-sync.
func (m *Metrics) RecordConsMetrics(block *types.Block) {
	m.NumTxs.Set(float64(len(block.Data.Txs)))
	m.TotalTxs.Add(float64(len(block.Data.Txs)))
	m.BlockSizeBytes.Observe(float64(block.Size()))
	m.CommittedHeight.Set(float64(block.Height))
}

func (m *Metrics) MarkBlockGossipStarted() {
	m.blockGossipStart = time.Now()
}

func (m *Metrics) MarkBlockGossipComplete() {
	m.BlockGossipReceiveLatency.Observe(time.Since(m.blockGossipStart).Seconds())
}

func (m *Metrics) MarkRound(r int32, st time.Time) {
	m.Rounds.Set(float64(r))
	roundTime := time.Since(st).Seconds()
	m.RoundDuration.Observe(roundTime)
}

func (m *Metrics) MarkStep(s cstypes.RoundStepType) {
	if !m.stepStart.IsZero() {
		stepTime := time.Since(m.stepStart).Seconds()
		stepName := strings.TrimPrefix(s.String(), "RoundStep")
		m.StepDuration.With("step", stepName).Observe(stepTime)
	}
	m.stepStart = time.Now()
}