package proxyd

import (
	"context"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/ethereum/go-ethereum/common/hexutil"

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

const (
	MetricsNamespace = "proxyd"

	RPCRequestSourceHTTP = "http"
	RPCRequestSourceWS   = "ws"

	BackendProxyd = "proxyd"
	SourceClient  = "client"
	SourceBackend = "backend"
	MethodUnknown = "unknown"
)

var PayloadSizeBuckets = []float64{10, 50, 100, 500, 1000, 5000, 10000, 100000, 1000000}
var MillisecondDurationBuckets = []float64{1, 10, 50, 100, 500, 1000, 5000, 10000, 100000}

var (
	rpcRequestsTotal = promauto.NewCounter(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rpc_requests_total",
		Help:      "Count of total client RPC requests.",
	})

	rpcForwardsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rpc_forwards_total",
		Help:      "Count of total RPC requests forwarded to each backend.",
	}, []string{
		"auth",
		"backend_name",
		"method_name",
		"source",
	})

	rpcBackendHTTPResponseCodesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rpc_backend_http_response_codes_total",
		Help:      "Count of total backend responses by HTTP status code.",
	}, []string{
		"auth",
		"backend_name",
		"method_name",
		"status_code",
		"batched",
	})

	rpcErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rpc_errors_total",
		Help:      "Count of total RPC errors.",
	}, []string{
		"auth",
		"backend_name",
		"method_name",
		"error_code",
	})

	rpcSpecialErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rpc_special_errors_total",
		Help:      "Count of total special RPC errors.",
	}, []string{
		"auth",
		"backend_name",
		"method_name",
		"error_type",
	})

	rpcBackendRequestDurationSumm = promauto.NewSummaryVec(prometheus.SummaryOpts{
		Namespace:  MetricsNamespace,
		Name:       "rpc_backend_request_duration_seconds",
		Help:       "Summary of backend response times broken down by backend and method name.",
		Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.95: 0.005, 0.99: 0.001},
	}, []string{
		"backend_name",
		"method_name",
		"batched",
	})

	activeClientWsConnsGauge = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "active_client_ws_conns",
		Help:      "Gauge of active client WS connections.",
	}, []string{
		"auth",
	})

	activeBackendWsConnsGauge = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "active_backend_ws_conns",
		Help:      "Gauge of active backend WS connections.",
	}, []string{
		"backend_name",
	})

	unserviceableRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "unserviceable_requests_total",
		Help:      "Count of total requests that were rejected due to no backends being available.",
	}, []string{
		"auth",
		"request_source",
	})

	httpResponseCodesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "http_response_codes_total",
		Help:      "Count of total HTTP response codes.",
	}, []string{
		"status_code",
	})

	httpRequestDurationSumm = promauto.NewSummary(prometheus.SummaryOpts{
		Namespace:  MetricsNamespace,
		Name:       "http_request_duration_seconds",
		Help:       "Summary of HTTP request durations, in seconds.",
		Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.95: 0.005, 0.99: 0.001},
	})

	wsMessagesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "ws_messages_total",
		Help:      "Count of total websocket messages including protocol control.",
	}, []string{
		"auth",
		"backend_name",
		"source",
	})

	redisErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "redis_errors_total",
		Help:      "Count of total Redis errors.",
	}, []string{
		"source",
	})

	requestPayloadSizesGauge = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Namespace: MetricsNamespace,
		Name:      "request_payload_sizes",
		Help:      "Histogram of client request payload sizes.",
		Buckets:   PayloadSizeBuckets,
	}, []string{
		"auth",
	})

	responsePayloadSizesGauge = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Namespace: MetricsNamespace,
		Name:      "response_payload_sizes",
		Help:      "Histogram of client response payload sizes.",
		Buckets:   PayloadSizeBuckets,
	}, []string{
		"auth",
	})

	cacheHitsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "cache_hits_total",
		Help:      "Number of cache hits.",
	}, []string{
		"method",
	})

	cacheMissesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "cache_misses_total",
		Help:      "Number of cache misses.",
	}, []string{
		"method",
	})

	cacheErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "cache_errors_total",
		Help:      "Number of cache errors.",
	}, []string{
		"method",
	})

	batchRPCShortCircuitsTotal = promauto.NewCounter(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "batch_rpc_short_circuits_total",
		Help:      "Count of total batch RPC short-circuits.",
	})

	rpcSpecialErrors = []string{
		"nonce too low",
		"gas price too high",
		"gas price too low",
		"invalid parameters",
	}

	redisCacheDurationSumm = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Namespace: MetricsNamespace,
		Name:      "redis_cache_duration_milliseconds",
		Help:      "Histogram of Redis command durations, in milliseconds.",
		Buckets:   MillisecondDurationBuckets,
	}, []string{"command"})

	tooManyRequestErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "too_many_request_errors_total",
		Help:      "Count of request timeouts due to too many concurrent RPCs.",
	}, []string{
		"backend_name",
	})

	batchSizeHistogram = promauto.NewHistogram(prometheus.HistogramOpts{
		Namespace: MetricsNamespace,
		Name:      "batch_size_summary",
		Help:      "Summary of batch sizes",
		Buckets: []float64{
			1,
			5,
			10,
			25,
			50,
			100,
		},
	})

	frontendRateLimitTakeErrors = promauto.NewCounter(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "rate_limit_take_errors",
		Help:      "Count of errors taking frontend rate limits",
	})

	consensusLatestBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_latest_block",
		Help:      "Consensus latest block",
	}, []string{
		"backend_group_name",
	})

	consensusSafeBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_safe_block",
		Help:      "Consensus safe block",
	}, []string{
		"backend_group_name",
	})

	consensusFinalizedBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_finalized_block",
		Help:      "Consensus finalized block",
	}, []string{
		"backend_group_name",
	})

	consensusHAError = promauto.NewCounterVec(prometheus.CounterOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_ha_error",
		Help:      "Consensus HA error count",
	}, []string{
		"error",
	})

	consensusHALatestBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_ha_latest_block",
		Help:      "Consensus HA latest block",
	}, []string{
		"backend_group_name",
		"leader",
	})

	consensusHASafeBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_ha_safe_block",
		Help:      "Consensus HA safe block",
	}, []string{
		"backend_group_name",
		"leader",
	})

	consensusHAFinalizedBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_ha_finalized_block",
		Help:      "Consensus HA finalized block",
	}, []string{
		"backend_group_name",
		"leader",
	})

	backendLatestBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_latest_block",
		Help:      "Current latest block observed per backend",
	}, []string{
		"backend_name",
	})

	backendSafeBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_safe_block",
		Help:      "Current safe block observed per backend",
	}, []string{
		"backend_name",
	})

	backendFinalizedBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_finalized_block",
		Help:      "Current finalized block observed per backend",
	}, []string{
		"backend_name",
	})

	backendUnexpectedBlockTagsBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_unexpected_block_tags",
		Help:      "Bool gauge for unexpected block tags",
	}, []string{
		"backend_name",
	})

	consensusGroupCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_count",
		Help:      "Consensus group serving traffic count",
	}, []string{
		"backend_group_name",
	})

	consensusGroupFilteredCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_filtered_count",
		Help:      "Consensus group filtered out from serving traffic count",
	}, []string{
		"backend_group_name",
	})

	consensusGroupTotalCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "group_consensus_total_count",
		Help:      "Total count of candidates to be part of consensus group",
	}, []string{
		"backend_group_name",
	})

	consensusBannedBackends = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "consensus_backend_banned",
		Help:      "Bool gauge for banned backends",
	}, []string{
		"backend_name",
	})

	consensusPeerCountBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "consensus_backend_peer_count",
		Help:      "Peer count",
	}, []string{
		"backend_name",
	})

	consensusInSyncBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "consensus_backend_in_sync",
		Help:      "Bool gauge for backends in sync",
	}, []string{
		"backend_name",
	})

	consensusUpdateDelayBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "consensus_backend_update_delay",
		Help:      "Delay (ms) for backend update",
	}, []string{
		"backend_name",
	})

	avgLatencyBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_avg_latency",
		Help:      "Average latency per backend",
	}, []string{
		"backend_name",
	})

	degradedBackends = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_degraded",
		Help:      "Bool gauge for degraded backends",
	}, []string{
		"backend_name",
	})

	networkErrorRateBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_error_rate",
		Help:      "Request error rate per backend",
	}, []string{
		"backend_name",
	})

	healthyPrimaryCandidates = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "healthy_candidates",
		Help:      "Record the number of healthy primary candidates",
	}, []string{
		"backend_group_name",
	})

	backendGroupFallbackBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Namespace: MetricsNamespace,
		Name:      "backend_group_fallback_backenend",
		Help:      "Bool gauge for if a backend is a fallback for a backend group",
	}, []string{
		"backend_group",
		"backend_name",
		"fallback",
	})
)

func RecordRedisError(source string) {
	redisErrorsTotal.WithLabelValues(source).Inc()
}

func RecordRPCError(ctx context.Context, backendName, method string, err error) {
	rpcErr, ok := err.(*RPCErr)
	var code int
	if ok {
		MaybeRecordSpecialRPCError(ctx, backendName, method, rpcErr)
		code = rpcErr.Code
	} else {
		code = -1
	}

	rpcErrorsTotal.WithLabelValues(GetAuthCtx(ctx), backendName, method, strconv.Itoa(code)).Inc()
}

func RecordWSMessage(ctx context.Context, backendName, source string) {
	wsMessagesTotal.WithLabelValues(GetAuthCtx(ctx), backendName, source).Inc()
}

func RecordUnserviceableRequest(ctx context.Context, source string) {
	unserviceableRequestsTotal.WithLabelValues(GetAuthCtx(ctx), source).Inc()
}

func RecordRPCForward(ctx context.Context, backendName, method, source string) {
	rpcForwardsTotal.WithLabelValues(GetAuthCtx(ctx), backendName, method, source).Inc()
}

func MaybeRecordSpecialRPCError(ctx context.Context, backendName, method string, rpcErr *RPCErr) {
	errMsg := strings.ToLower(rpcErr.Message)
	for _, errStr := range rpcSpecialErrors {
		if strings.Contains(errMsg, errStr) {
			rpcSpecialErrorsTotal.WithLabelValues(GetAuthCtx(ctx), backendName, method, errStr).Inc()
			return
		}
	}
}

func RecordRequestPayloadSize(ctx context.Context, payloadSize int) {
	requestPayloadSizesGauge.WithLabelValues(GetAuthCtx(ctx)).Observe(float64(payloadSize))
}

func RecordResponsePayloadSize(ctx context.Context, payloadSize int) {
	responsePayloadSizesGauge.WithLabelValues(GetAuthCtx(ctx)).Observe(float64(payloadSize))
}

func RecordCacheHit(method string) {
	cacheHitsTotal.WithLabelValues(method).Inc()
}

func RecordCacheMiss(method string) {
	cacheMissesTotal.WithLabelValues(method).Inc()
}

func RecordCacheError(method string) {
	cacheErrorsTotal.WithLabelValues(method).Inc()
}

func RecordBatchSize(size int) {
	batchSizeHistogram.Observe(float64(size))
}

var nonAlphanumericRegex = regexp.MustCompile(`[^a-zA-Z ]+`)

func RecordGroupConsensusError(group *BackendGroup, label string, err error) {
	errClean := nonAlphanumericRegex.ReplaceAllString(err.Error(), "")
	errClean = strings.ReplaceAll(errClean, " ", "_")
	errClean = strings.ReplaceAll(errClean, "__", "_")
	label = fmt.Sprintf("%s.%s", label, errClean)
	consensusHAError.WithLabelValues(label).Inc()
}

func RecordGroupConsensusHALatestBlock(group *BackendGroup, leader string, blockNumber hexutil.Uint64) {
	consensusHALatestBlock.WithLabelValues(group.Name, leader).Set(float64(blockNumber))
}

func RecordGroupConsensusHASafeBlock(group *BackendGroup, leader string, blockNumber hexutil.Uint64) {
	consensusHASafeBlock.WithLabelValues(group.Name, leader).Set(float64(blockNumber))
}

func RecordGroupConsensusHAFinalizedBlock(group *BackendGroup, leader string, blockNumber hexutil.Uint64) {
	consensusHAFinalizedBlock.WithLabelValues(group.Name, leader).Set(float64(blockNumber))
}

func RecordGroupConsensusLatestBlock(group *BackendGroup, blockNumber hexutil.Uint64) {
	consensusLatestBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
}

func RecordGroupConsensusSafeBlock(group *BackendGroup, blockNumber hexutil.Uint64) {
	consensusSafeBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
}

func RecordGroupConsensusFinalizedBlock(group *BackendGroup, blockNumber hexutil.Uint64) {
	consensusFinalizedBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
}

func RecordGroupConsensusCount(group *BackendGroup, count int) {
	consensusGroupCount.WithLabelValues(group.Name).Set(float64(count))
}

func RecordGroupConsensusFilteredCount(group *BackendGroup, count int) {
	consensusGroupFilteredCount.WithLabelValues(group.Name).Set(float64(count))
}

func RecordGroupTotalCount(group *BackendGroup, count int) {
	consensusGroupTotalCount.WithLabelValues(group.Name).Set(float64(count))
}

func RecordBackendLatestBlock(b *Backend, blockNumber hexutil.Uint64) {
	backendLatestBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
}

func RecordBackendSafeBlock(b *Backend, blockNumber hexutil.Uint64) {
	backendSafeBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
}

func RecordBackendFinalizedBlock(b *Backend, blockNumber hexutil.Uint64) {
	backendFinalizedBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
}

func RecordBackendUnexpectedBlockTags(b *Backend, unexpected bool) {
	backendUnexpectedBlockTagsBackend.WithLabelValues(b.Name).Set(boolToFloat64(unexpected))
}

func RecordConsensusBackendBanned(b *Backend, banned bool) {
	consensusBannedBackends.WithLabelValues(b.Name).Set(boolToFloat64(banned))
}

func RecordHealthyCandidates(b *BackendGroup, candidates int) {
	healthyPrimaryCandidates.WithLabelValues(b.Name).Set(float64(candidates))
}

func RecordConsensusBackendPeerCount(b *Backend, peerCount uint64) {
	consensusPeerCountBackend.WithLabelValues(b.Name).Set(float64(peerCount))
}

func RecordConsensusBackendInSync(b *Backend, inSync bool) {
	consensusInSyncBackend.WithLabelValues(b.Name).Set(boolToFloat64(inSync))
}

func RecordConsensusBackendUpdateDelay(b *Backend, lastUpdate time.Time) {
	// avoid recording the delay for the first update
	if lastUpdate.IsZero() {
		return
	}
	delay := time.Since(lastUpdate)
	consensusUpdateDelayBackend.WithLabelValues(b.Name).Set(float64(delay.Milliseconds()))
}

func RecordBackendNetworkLatencyAverageSlidingWindow(b *Backend, avgLatency time.Duration) {
	avgLatencyBackend.WithLabelValues(b.Name).Set(float64(avgLatency.Milliseconds()))
	degradedBackends.WithLabelValues(b.Name).Set(boolToFloat64(b.IsDegraded()))
}

func RecordBackendNetworkErrorRateSlidingWindow(b *Backend, rate float64) {
	networkErrorRateBackend.WithLabelValues(b.Name).Set(rate)
}

func RecordBackendGroupFallbacks(bg *BackendGroup, name string, fallback bool) {
	backendGroupFallbackBackend.WithLabelValues(bg.Name, name, strconv.FormatBool(fallback)).Set(boolToFloat64(fallback))
}

func boolToFloat64(b bool) float64 {
	if b {
		return 1
	}
	return 0
}