package metrics

import (
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/fraktal/mev-beta/internal/auth"
	"github.com/fraktal/mev-beta/internal/logger"
)

// MetricsCollector collects and exposes MEV bot metrics
type MetricsCollector struct {
	logger *logger.Logger
	mu     sync.RWMutex

	// L2 Message Metrics
	L2MessagesProcessed uint64
	L2MessagesPerSecond float64
	L2MessageLag        time.Duration
	BatchesProcessed    uint64

	// DEX Interaction Metrics
	DEXInteractionsFound   uint64
	SwapOpportunities      uint64
	ArbitrageOpportunities uint64
	OpportunitiesDropped   uint64
	OpportunityQueueLength uint64

	// Performance Metrics
	ProcessingLatency time.Duration
	ErrorRate         float64
	SuccessfulTrades  uint64
	FailedTrades      uint64

	// Financial Metrics
	TotalProfit   float64
	TotalLoss     float64
	GasCostsSpent float64
	NetProfit     float64

	// Gas Metrics
	AverageGasPrice    uint64
	L1DataFeesSpent    float64
	L2ComputeFeesSpent float64
	ProfitFactor       float64
	UptimeSeries       []float64

	// Health Metrics
	UptimeSeconds   uint64
	LastHealthCheck time.Time

	// Start time for calculations
	startTime time.Time
}

// NewMetricsCollector creates a new metrics collector
func NewMetricsCollector(logger *logger.Logger) *MetricsCollector {
	return &MetricsCollector{
		logger:          logger,
		startTime:       time.Now(),
		LastHealthCheck: time.Now(),
		UptimeSeries:    make([]float64, 0, 1024),
	}
}

// RecordL2Message records processing of an L2 message
func (m *MetricsCollector) RecordL2Message(processingTime time.Duration) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.L2MessagesProcessed++
	m.ProcessingLatency = processingTime

	// Calculate messages per second
	elapsed := time.Since(m.startTime).Seconds()
	if elapsed > 0 {
		m.L2MessagesPerSecond = float64(m.L2MessagesProcessed) / elapsed
	}
}

// RecordL2MessageLag records lag in L2 message processing
func (m *MetricsCollector) RecordL2MessageLag(lag time.Duration) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.L2MessageLag = lag
}

// RecordBatchProcessed records processing of a batch
func (m *MetricsCollector) RecordBatchProcessed() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.BatchesProcessed++
}

// RecordDEXInteraction records finding a DEX interaction
func (m *MetricsCollector) RecordDEXInteraction() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.DEXInteractionsFound++
}

// RecordSwapOpportunity records finding a swap opportunity
func (m *MetricsCollector) RecordSwapOpportunity() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.SwapOpportunities++
}

// RecordArbitrageOpportunity records finding an arbitrage opportunity
func (m *MetricsCollector) RecordArbitrageOpportunity() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.ArbitrageOpportunities++
}

// RecordDroppedOpportunity increments the dropped opportunity counter.
func (m *MetricsCollector) RecordDroppedOpportunity() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.OpportunitiesDropped++
}

// RecordSuccessfulTrade records a successful trade
func (m *MetricsCollector) RecordSuccessfulTrade(profit float64, gasCost float64) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.SuccessfulTrades++
	m.TotalProfit += profit
	m.GasCostsSpent += gasCost
	m.NetProfit = m.TotalProfit - m.TotalLoss - m.GasCostsSpent
	m.updateProfitFactor()

	// Update error rate
	totalTrades := m.SuccessfulTrades + m.FailedTrades
	if totalTrades > 0 {
		m.ErrorRate = float64(m.FailedTrades) / float64(totalTrades)
	}
}

// RecordFailedTrade records a failed trade
func (m *MetricsCollector) RecordFailedTrade(loss float64, gasCost float64) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.FailedTrades++
	m.TotalLoss += loss
	m.GasCostsSpent += gasCost
	m.NetProfit = m.TotalProfit - m.TotalLoss - m.GasCostsSpent
	m.updateProfitFactor()

	// Update error rate
	totalTrades := m.SuccessfulTrades + m.FailedTrades
	if totalTrades > 0 {
		m.ErrorRate = float64(m.FailedTrades) / float64(totalTrades)
	}
}

func (m *MetricsCollector) updateProfitFactor() {
	if m.GasCostsSpent <= 0 {
		m.ProfitFactor = 0
		return
	}
	m.ProfitFactor = (m.TotalProfit - m.TotalLoss) / m.GasCostsSpent
}

// RecordGasMetrics records gas-related metrics
func (m *MetricsCollector) RecordGasMetrics(gasPrice uint64, l1DataFee, l2ComputeFee float64) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.AverageGasPrice = gasPrice
	m.L1DataFeesSpent += l1DataFee
	m.L2ComputeFeesSpent += l2ComputeFee
}

// UpdateHealthCheck updates the health check timestamp
func (m *MetricsCollector) UpdateHealthCheck() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.LastHealthCheck = time.Now()
	m.UptimeSeconds = uint64(time.Since(m.startTime).Seconds())
	m.UptimeSeries = append(m.UptimeSeries, float64(m.UptimeSeconds))
}

// GetSnapshot returns a snapshot of current metrics
func (m *MetricsCollector) GetSnapshot() MetricsSnapshot {
	m.mu.RLock()
	defer m.mu.RUnlock()

	return MetricsSnapshot{
		L2MessagesProcessed:    m.L2MessagesProcessed,
		L2MessagesPerSecond:    m.L2MessagesPerSecond,
		L2MessageLag:           m.L2MessageLag,
		BatchesProcessed:       m.BatchesProcessed,
		DEXInteractionsFound:   m.DEXInteractionsFound,
		SwapOpportunities:      m.SwapOpportunities,
		ArbitrageOpportunities: m.ArbitrageOpportunities,
		ProcessingLatency:      m.ProcessingLatency,
		ErrorRate:              m.ErrorRate,
		SuccessfulTrades:       m.SuccessfulTrades,
		FailedTrades:           m.FailedTrades,
		TotalProfit:            m.TotalProfit,
		TotalLoss:              m.TotalLoss,
		GasCostsSpent:          m.GasCostsSpent,
		NetProfit:              m.NetProfit,
		ProfitFactor:           m.ProfitFactor,
		AverageGasPrice:        m.AverageGasPrice,
		L1DataFeesSpent:        m.L1DataFeesSpent,
		L2ComputeFeesSpent:     m.L2ComputeFeesSpent,
		UptimeSeconds:          m.UptimeSeconds,
		LastHealthCheck:        m.LastHealthCheck,
	}
}

// MetricsSnapshot represents a point-in-time view of metrics
type MetricsSnapshot struct {
	L2MessagesProcessed    uint64        `json:"l2_messages_processed"`
	L2MessagesPerSecond    float64       `json:"l2_messages_per_second"`
	L2MessageLag           time.Duration `json:"l2_message_lag_ms"`
	BatchesProcessed       uint64        `json:"batches_processed"`
	DEXInteractionsFound   uint64        `json:"dex_interactions_found"`
	SwapOpportunities      uint64        `json:"swap_opportunities"`
	ArbitrageOpportunities uint64        `json:"arbitrage_opportunities"`
	OpportunitiesDropped   uint64        `json:"opportunities_dropped"`
	OpportunityQueueLength uint64        `json:"opportunity_queue_length"`
	ProcessingLatency      time.Duration `json:"processing_latency_ms"`
	ErrorRate              float64       `json:"error_rate"`
	SuccessfulTrades       uint64        `json:"successful_trades"`
	FailedTrades           uint64        `json:"failed_trades"`
	TotalProfit            float64       `json:"total_profit_eth"`
	TotalLoss              float64       `json:"total_loss_eth"`
	GasCostsSpent          float64       `json:"gas_costs_spent_eth"`
	NetProfit              float64       `json:"net_profit_eth"`
	AverageGasPrice        uint64        `json:"average_gas_price_gwei"`
	L1DataFeesSpent        float64       `json:"l1_data_fees_spent_eth"`
	L2ComputeFeesSpent     float64       `json:"l2_compute_fees_spent_eth"`
	ProfitFactor           float64       `json:"profit_factor"`
	UptimeSeconds          uint64        `json:"uptime_seconds"`
	LastHealthCheck        time.Time     `json:"last_health_check"`
}

// MetricsServer serves metrics over HTTP
type MetricsServer struct {
	collector  *MetricsCollector
	logger     *logger.Logger
	server     *http.Server
	middleware *auth.Middleware
}

// NewMetricsServer creates a new metrics server
func NewMetricsServer(collector *MetricsCollector, logger *logger.Logger, port string) *MetricsServer {
	mux := http.NewServeMux()

	// Create authentication configuration
	authConfig := &auth.AuthConfig{
		Logger:       logger,
		RequireHTTPS: false,                        // Set to true in production
		AllowedIPs:   []string{"127.0.0.1", "::1"}, // Localhost only by default
	}

	// Create authentication middleware
	middleware := auth.NewMiddleware(authConfig)

	server := &MetricsServer{
		collector: collector,
		logger:    logger,
		server: &http.Server{
			Addr:              ":" + port,
			Handler:           mux,
			ReadHeaderTimeout: 5 * time.Second, // Prevent Slowloris attacks
		},
		middleware: middleware,
	}

	// Register endpoints with authentication
	mux.HandleFunc("/metrics", middleware.RequireAuthentication(server.handleMetrics))
	mux.HandleFunc("/health", middleware.RequireAuthentication(server.handleHealth))
	mux.HandleFunc("/metrics/prometheus", middleware.RequireAuthentication(server.handlePrometheus))

	return server
}

// Start starts the metrics server
func (s *MetricsServer) Start() error {
	s.logger.Info("Starting metrics server on " + s.server.Addr)
	return s.server.ListenAndServe()
}

// Stop stops the metrics server
func (s *MetricsServer) Stop() error {
	s.logger.Info("Stopping metrics server")
	return s.server.Close()
}

// handleMetrics serves metrics in JSON format
func (s *MetricsServer) handleMetrics(w http.ResponseWriter, r *http.Request) {
	snapshot := s.collector.GetSnapshot()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)

	// Simple JSON serialization
	response := `{
  "l2_messages_processed": ` + uintToString(snapshot.L2MessagesProcessed) + `,
  "l2_messages_per_second": ` + floatToString(snapshot.L2MessagesPerSecond) + `,
  "l2_message_lag_ms": ` + durationToString(snapshot.L2MessageLag) + `,
  "batches_processed": ` + uintToString(snapshot.BatchesProcessed) + `,
  "dex_interactions_found": ` + uintToString(snapshot.DEXInteractionsFound) + `,
  "swap_opportunities": ` + uintToString(snapshot.SwapOpportunities) + `,
  "arbitrage_opportunities": ` + uintToString(snapshot.ArbitrageOpportunities) + `,
  "processing_latency_ms": ` + durationToString(snapshot.ProcessingLatency) + `,
  "error_rate": ` + floatToString(snapshot.ErrorRate) + `,
  "successful_trades": ` + uintToString(snapshot.SuccessfulTrades) + `,
  "failed_trades": ` + uintToString(snapshot.FailedTrades) + `,
  "total_profit_eth": ` + floatToString(snapshot.TotalProfit) + `,
  "total_loss_eth": ` + floatToString(snapshot.TotalLoss) + `,
  "gas_costs_spent_eth": ` + floatToString(snapshot.GasCostsSpent) + `,
  "net_profit_eth": ` + floatToString(snapshot.NetProfit) + `,
  "profit_factor": ` + floatToString(snapshot.ProfitFactor) + `,
  "average_gas_price_gwei": ` + uintToString(snapshot.AverageGasPrice) + `,
  "l1_data_fees_spent_eth": ` + floatToString(snapshot.L1DataFeesSpent) + `,
  "l2_compute_fees_spent_eth": ` + floatToString(snapshot.L2ComputeFeesSpent) + `,
  "uptime_seconds": ` + uintToString(snapshot.UptimeSeconds) + `
}`

	w.Write([]byte(response))
}

// handleHealth serves health check
func (s *MetricsServer) handleHealth(w http.ResponseWriter, r *http.Request) {
	s.collector.UpdateHealthCheck()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(`{"status": "healthy", "timestamp": "` + time.Now().Format(time.RFC3339) + `"}`))
}

// handlePrometheus serves metrics in Prometheus format
func (s *MetricsServer) handlePrometheus(w http.ResponseWriter, r *http.Request) {
	snapshot := s.collector.GetSnapshot()

	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)

	prometheus := `# HELP mev_bot_l2_messages_processed Total L2 messages processed
# TYPE mev_bot_l2_messages_processed counter
mev_bot_l2_messages_processed ` + uintToString(snapshot.L2MessagesProcessed) + `

# HELP mev_bot_l2_messages_per_second L2 messages processed per second
# TYPE mev_bot_l2_messages_per_second gauge
mev_bot_l2_messages_per_second ` + floatToString(snapshot.L2MessagesPerSecond) + `

# HELP mev_bot_processing_latency_ms Latest pipeline processing latency in milliseconds
# TYPE mev_bot_processing_latency_ms gauge
mev_bot_processing_latency_ms ` + durationToString(snapshot.ProcessingLatency) + `

# HELP mev_bot_successful_trades Total successful trades
# TYPE mev_bot_successful_trades counter
mev_bot_successful_trades ` + uintToString(snapshot.SuccessfulTrades) + `

# HELP mev_bot_failed_trades Total failed trades
# TYPE mev_bot_failed_trades counter
mev_bot_failed_trades ` + uintToString(snapshot.FailedTrades) + `

# HELP mev_bot_trade_error_rate Fraction of failed trades over total attempts
# TYPE mev_bot_trade_error_rate gauge
mev_bot_trade_error_rate ` + floatToString(snapshot.ErrorRate) + `

# HELP mev_bot_net_profit_eth Net profit in ETH
# TYPE mev_bot_net_profit_eth gauge
mev_bot_net_profit_eth ` + floatToString(snapshot.NetProfit) + `

# HELP mev_bot_profit_factor Profit factor (net profit divided by gas costs)
# TYPE mev_bot_profit_factor gauge
mev_bot_profit_factor ` + floatToString(snapshot.ProfitFactor) + `

# HELP mev_bot_total_profit_eth Cumulative gross profit in ETH
# TYPE mev_bot_total_profit_eth counter
mev_bot_total_profit_eth ` + floatToString(snapshot.TotalProfit) + `

# HELP mev_bot_gas_spent_eth Cumulative gas spend in ETH
# TYPE mev_bot_gas_spent_eth counter
mev_bot_gas_spent_eth ` + floatToString(snapshot.GasCostsSpent) + `

# HELP mev_bot_uptime_seconds Bot uptime in seconds
# TYPE mev_bot_uptime_seconds counter
mev_bot_uptime_seconds ` + uintToString(snapshot.UptimeSeconds) + `
`

	w.Write([]byte(prometheus))
}

// Helper functions for string conversion
func uintToString(val uint64) string {
	return fmt.Sprintf("%d", val)
}

func floatToString(val float64) string {
	return fmt.Sprintf("%.6f", val)
}

func durationToString(val time.Duration) string {
	return fmt.Sprintf("%.2f", float64(val.Nanoseconds())/1000000.0)
}