package arbitrum

import (
	"context"
	"fmt"
	"math/big"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/rpc"

	"github.com/fraktal/mev-beta/internal/logger"
	arbcommon "github.com/fraktal/mev-beta/pkg/arbitrum/common"
)

// EventMonitor monitors DEX events across all protocols for comprehensive MEV detection
type EventMonitor struct {
	client           *RateLimitedClient
	rpcClient        *rpc.Client
	logger           *logger.Logger
	protocolRegistry *ArbitrumProtocolRegistry
	poolCache        *PoolCache
	swapPipeline     *SwapEventPipeline

	// Event signatures for all major DEX protocols
	eventSignatures map[arbcommon.Protocol]map[string]common.Hash

	// Active monitoring subscriptions
	subscriptions map[string]*subscription
	subMu         sync.RWMutex

	// Metrics
	eventsProcessed uint64
	swapsDetected   uint64
	liquidityEvents uint64

	// Channels for event processing
	swapEvents          chan *SwapEvent
	liquidationEvents   chan *LiquidationEvent
	liquidityEventsChan chan *LiquidityEvent

	// Shutdown management
	ctx    context.Context
	cancel context.CancelFunc
}

// subscription represents an active event subscription
type subscription struct {
	protocol arbcommon.Protocol
	query    ethereum.FilterQuery
	cancel   context.CancelFunc
}

// NewEventMonitor creates a new event monitor
func NewEventMonitor(
	client *RateLimitedClient,
	rpcClient *rpc.Client,
	logger *logger.Logger,
	protocolRegistry *ArbitrumProtocolRegistry,
	poolCache *PoolCache,
) *EventMonitor {
	ctx, cancel := context.WithCancel(context.Background())

	em := &EventMonitor{
		client:              client,
		rpcClient:           rpcClient,
		logger:              logger,
		protocolRegistry:    protocolRegistry,
		poolCache:           poolCache,
		eventSignatures:     make(map[arbcommon.Protocol]map[string]common.Hash),
		subscriptions:       make(map[string]*subscription),
		swapEvents:          make(chan *SwapEvent, 1000),
		liquidationEvents:   make(chan *LiquidationEvent, 100),
		liquidityEventsChan: make(chan *LiquidityEvent, 500),
		ctx:                 ctx,
		cancel:              cancel,
	}

	// Initialize event signatures for all protocols
	em.initializeEventSignatures()

	return em
}

// initializeEventSignatures sets up event signatures for all supported protocols
func (em *EventMonitor) initializeEventSignatures() {
	// Uniswap V2/V3 Swap events
	em.eventSignatures[arbcommon.ProtocolUniswapV2] = map[string]common.Hash{
		"Swap": crypto.Keccak256Hash([]byte("Swap(address,uint256,uint256,uint256,uint256,address)")),
		"Mint": crypto.Keccak256Hash([]byte("Mint(address,uint256,uint256)")),
		"Burn": crypto.Keccak256Hash([]byte("Burn(address,uint256,uint256,address)")),
	}

	em.eventSignatures[arbcommon.ProtocolUniswapV3] = map[string]common.Hash{
		"Swap": crypto.Keccak256Hash([]byte("Swap(address,address,int256,int256,uint160,uint128,int24)")),
		"Mint": crypto.Keccak256Hash([]byte("Mint(address,int24,int24,uint128,uint256,uint256)")),
		"Burn": crypto.Keccak256Hash([]byte("Burn(address,int24,int24,uint128,uint256,uint256)")),
	}

	// SushiSwap (same as Uniswap V2)
	em.eventSignatures[arbcommon.ProtocolSushiSwapV2] = em.eventSignatures[arbcommon.ProtocolUniswapV2]

	// Camelot V3 (Algebra)
	em.eventSignatures[arbcommon.ProtocolCamelotV3] = map[string]common.Hash{
		"Swap": crypto.Keccak256Hash([]byte("Swap(address,address,int256,int256,uint160,uint128,int24)")),
		"Mint": crypto.Keccak256Hash([]byte("Mint(address,int24,int24,uint128,uint256,uint256)")),
		"Burn": crypto.Keccak256Hash([]byte("Burn(address,int24,int24,uint128,uint256,uint256)")),
	}

	// Balancer V2
	em.eventSignatures[arbcommon.ProtocolBalancerV2] = map[string]common.Hash{
		"Swap":               crypto.Keccak256Hash([]byte("Swap(bytes32,address,address,uint256,uint256)")),
		"PoolBalanceChanged": crypto.Keccak256Hash([]byte("PoolBalanceChanged(bytes32,address,address[],int256[],uint256[])")),
	}

	// Curve Finance
	em.eventSignatures[arbcommon.ProtocolCurve] = map[string]common.Hash{
		"TokenExchange":           crypto.Keccak256Hash([]byte("TokenExchange(address,int128,uint256,int128,uint256)")),
		"TokenExchangeUnderlying": crypto.Keccak256Hash([]byte("TokenExchangeUnderlying(address,int128,uint256,int128,uint256)")),
		"AddLiquidity":            crypto.Keccak256Hash([]byte("AddLiquidity(address,uint256[],uint256[],uint256,uint256)")),
		"RemoveLiquidity":         crypto.Keccak256Hash([]byte("RemoveLiquidity(address,uint256[],uint256)")),
	}

	// 1inch Aggregator
	em.eventSignatures[arbcommon.Protocol1Inch] = map[string]common.Hash{
		"Swapped": crypto.Keccak256Hash([]byte("Swapped(address,address,address,uint256,uint256)")),
	}

	// GMX
	em.eventSignatures[arbcommon.ProtocolGMX] = map[string]common.Hash{
		"Swap":              crypto.Keccak256Hash([]byte("Swap(address,address,address,uint256,uint256,uint256,uint256)")),
		"LiquidatePosition": crypto.Keccak256Hash([]byte("LiquidatePosition(bytes32,address,address,address,bool,uint256,uint256,uint256,int256,uint256)")),
	}

	// Radiant Capital
	em.eventSignatures[arbcommon.ProtocolRadiant] = map[string]common.Hash{
		"LiquidationCall": crypto.Keccak256Hash([]byte("LiquidationCall(address,address,address,uint256,uint256,address,bool)")),
		"Deposit":         crypto.Keccak256Hash([]byte("Deposit(address,address,address,uint256,uint16)")),
		"Withdraw":        crypto.Keccak256Hash([]byte("Withdraw(address,address,address,uint256)")),
	}
}

// Start begins monitoring all DEX events
func (em *EventMonitor) Start() error {
	em.logger.Info("🚀 Starting comprehensive DEX event monitoring")

	// Start event processing workers
	go em.processSwapEvents()
	go em.processLiquidationEvents()
	go em.processLiquidityEvents()

	// Start monitoring all active protocols
	if err := em.startProtocolMonitoring(); err != nil {
		return fmt.Errorf("failed to start protocol monitoring: %w", err)
	}

	em.logger.Info("✅ DEX event monitoring started successfully")
	return nil
}

// startProtocolMonitoring sets up monitoring for all active protocols
func (em *EventMonitor) startProtocolMonitoring() error {
	protocols := em.protocolRegistry.GetActiveProtocols()

	for _, protocol := range protocols {
		// Get all pool addresses for this protocol
		poolAddresses := em.poolCache.GetPoolAddressesByProtocol(arbcommon.Protocol(protocol.Name))

		// If we don't have pools yet, monitor factory events to discover them
		if len(poolAddresses) == 0 {
			// Monitor factory events for pool creation
			if err := em.monitorFactoryEvents(arbcommon.Protocol(protocol.Name)); err != nil {
				em.logger.Error(fmt.Sprintf("Failed to monitor factory events for %s: %v", protocol.Name, err))
				continue
			}
		}

		// Monitor swap events for existing pools
		if err := em.monitorSwapEvents(arbcommon.Protocol(protocol.Name), poolAddresses); err != nil {
			em.logger.Error(fmt.Sprintf("Failed to monitor swap events for %s: %v", protocol.Name, err))
			continue
		}

		// Monitor liquidation events for lending protocols
		if arbcommon.Protocol(protocol.Name) == arbcommon.ProtocolGMX || arbcommon.Protocol(protocol.Name) == arbcommon.ProtocolRadiant {
			if err := em.monitorLiquidationEvents(arbcommon.Protocol(protocol.Name)); err != nil {
				em.logger.Error(fmt.Sprintf("Failed to monitor liquidation events for %s: %v", protocol.Name, err))
				continue
			}
		}
	}

	return nil
}

// monitorSwapEvents sets up monitoring for swap events on specific pools
func (em *EventMonitor) monitorSwapEvents(protocol arbcommon.Protocol, poolAddresses []common.Address) error {
	if len(poolAddresses) == 0 {
		return nil // No pools to monitor
	}

	// Get event signatures for this protocol
	signatures, exists := em.eventSignatures[protocol]
	if !exists {
		return fmt.Errorf("no event signatures found for protocol %s", protocol)
	}

	// Get Swap event signature
	swapTopic, exists := signatures["Swap"]
	if !exists {
		return fmt.Errorf("no Swap event signature found for protocol %s", protocol)
	}

	// Create filter query for Swap events
	query := ethereum.FilterQuery{
		Addresses: poolAddresses,
		Topics:    [][]common.Hash{{swapTopic}},
	}

	// Create subscription
	subCtx, cancel := context.WithCancel(em.ctx)
	sub := &subscription{
		protocol: protocol,
		query:    query,
		cancel:   cancel,
	}

	// Store subscription
	em.subMu.Lock()
	em.subscriptions[string(protocol)+"_swap"] = sub
	em.subMu.Unlock()

	// Start monitoring in a goroutine
	go em.monitorEvents(subCtx, sub, "Swap")

	em.logger.Info(fmt.Sprintf("🔍 Monitoring Swap events for %d %s pools", len(poolAddresses), protocol))
	return nil
}

// monitorFactoryEvents sets up monitoring for factory events to discover new pools
func (em *EventMonitor) monitorFactoryEvents(protocol arbcommon.Protocol) error {
	// Get factory addresses for this protocol
	factories := em.protocolRegistry.GetFactoryAddresses(protocol)
	if len(factories) == 0 {
		return nil // No factories to monitor
	}

	// Get event signatures for this protocol
	signatures, exists := em.eventSignatures[protocol]
	if !exists {
		return fmt.Errorf("no event signatures found for protocol %s", protocol)
	}

	// Different protocols have different pool creation events
	var creationTopic common.Hash
	switch protocol {
	case arbcommon.ProtocolUniswapV2, arbcommon.ProtocolSushiSwapV2:
		creationTopic, exists = signatures["PairCreated"]
		if !exists {
			// Default to common creation event
			creationTopic = crypto.Keccak256Hash([]byte("PairCreated(address,address,address,uint256)"))
		}
	case arbcommon.ProtocolUniswapV3, arbcommon.ProtocolCamelotV3:
		creationTopic, exists = signatures["PoolCreated"]
		if !exists {
			// Default to common creation event
			creationTopic = crypto.Keccak256Hash([]byte("PoolCreated(address,address,uint24,address)"))
		}
	case arbcommon.ProtocolBalancerV2:
		creationTopic = crypto.Keccak256Hash([]byte("PoolCreated(address,address,address)"))
	case arbcommon.ProtocolCurve:
		creationTopic = crypto.Keccak256Hash([]byte("PoolAdded(address)"))
	default:
		// For other protocols, use a generic approach
		creationTopic = crypto.Keccak256Hash([]byte("PoolCreated(address)"))
	}

	// Create filter query for pool creation events
	query := ethereum.FilterQuery{
		Addresses: factories,
		Topics:    [][]common.Hash{{creationTopic}},
	}

	// Create subscription
	subCtx, cancel := context.WithCancel(em.ctx)
	sub := &subscription{
		protocol: protocol,
		query:    query,
		cancel:   cancel,
	}

	// Store subscription
	em.subMu.Lock()
	em.subscriptions[string(protocol)+"_factory"] = sub
	em.subMu.Unlock()

	// Start monitoring in a goroutine
	go em.monitorEvents(subCtx, sub, "Factory")

	em.logger.Info(fmt.Sprintf("🏭 Monitoring factory events for %s pool creation", protocol))
	return nil
}

// monitorLiquidationEvents sets up monitoring for liquidation events
func (em *EventMonitor) monitorLiquidationEvents(protocol arbcommon.Protocol) error {
	// Get contract addresses for this protocol
	contracts := em.protocolRegistry.GetContractAddresses(protocol)
	if len(contracts) == 0 {
		return nil // No contracts to monitor
	}

	// Get event signatures for this protocol
	signatures, exists := em.eventSignatures[protocol]
	if !exists {
		return fmt.Errorf("no event signatures found for protocol %s", protocol)
	}

	// Get Liquidation event signature
	var liquidationTopic common.Hash
	switch protocol {
	case arbcommon.ProtocolGMX:
		liquidationTopic, exists = signatures["LiquidatePosition"]
	case arbcommon.ProtocolRadiant:
		liquidationTopic, exists = signatures["LiquidationCall"]
	default:
		return nil // No liquidation events for this protocol
	}

	if !exists {
		return fmt.Errorf("no liquidation event signature found for protocol %s", protocol)
	}

	// Create filter query for liquidation events
	query := ethereum.FilterQuery{
		Addresses: contracts,
		Topics:    [][]common.Hash{{liquidationTopic}},
	}

	// Create subscription
	subCtx, cancel := context.WithCancel(em.ctx)
	sub := &subscription{
		protocol: protocol,
		query:    query,
		cancel:   cancel,
	}

	// Store subscription
	em.subMu.Lock()
	em.subscriptions[string(protocol)+"_liquidation"] = sub
	em.subMu.Unlock()

	// Start monitoring in a goroutine
	go em.monitorEvents(subCtx, sub, "Liquidation")

	em.logger.Info(fmt.Sprintf("💧 Monitoring liquidation events for %s", protocol))
	return nil
}

// monitorEvents continuously monitors events for a subscription
func (em *EventMonitor) monitorEvents(ctx context.Context, sub *subscription, eventType string) {
	ticker := time.NewTicker(1 * time.Second) // Poll every second
	defer ticker.Stop()

	var lastBlock uint64 = 0

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			// Get latest block
			latestBlock, err := em.client.BlockNumber(ctx)
			if err != nil {
				em.logger.Error(fmt.Sprintf("Failed to get latest block: %v", err))
				continue
			}

			// Set fromBlock to last processed block + 1, or latest - 1000 if starting
			fromBlock := lastBlock + 1
			if fromBlock == 1 || latestBlock-fromBlock > 10000 {
				fromBlock = latestBlock - 10000
				if fromBlock < 1 {
					fromBlock = 1
				}
			}

			// Set toBlock to latest block
			toBlock := latestBlock

			// Skip if no new blocks
			if fromBlock > toBlock {
				continue
			}

			// Update query block range
			query := sub.query
			query.FromBlock = new(big.Int).SetUint64(fromBlock)
			query.ToBlock = new(big.Int).SetUint64(toBlock)

			// Query logs with circuit breaker and rate limiting
			var logs []types.Log
			err = em.client.CallWithRateLimit(ctx, func() error {
				var innerErr error
				logs, innerErr = em.client.FilterLogs(ctx, query)
				return innerErr
			})
			if err != nil {
				em.logger.Error(fmt.Sprintf("Failed to filter logs for %s events: %v", eventType, err))
				continue
			}

			// Process logs
			for _, log := range logs {
				if err := em.processLog(log, sub.protocol, eventType); err != nil {
					em.logger.Error(fmt.Sprintf("Failed to process %s log: %v", eventType, err))
				}
				em.eventsProcessed++
			}

			// Update last processed block
			lastBlock = toBlock
		}
	}
}

// processLog processes a single log entry
func (em *EventMonitor) processLog(log types.Log, protocol arbcommon.Protocol, eventType string) error {
	switch eventType {
	case "Swap":
		return em.processSwapLog(log, protocol)
	case "Factory":
		return em.processFactoryLog(log, protocol)
	case "Liquidation":
		return em.processLiquidationLog(log, protocol)
	default:
		// Generic event processing
		em.logger.Debug(fmt.Sprintf("Processing generic %s event from %s", eventType, protocol))
		return nil
	}
}

// processSwapLog processes a swap event log
func (em *EventMonitor) processSwapLog(log types.Log, protocol arbcommon.Protocol) error {
	// Parse swap event based on protocol
	swapEvent, err := em.parseSwapEvent(log, protocol)
	if err != nil {
		return fmt.Errorf("failed to parse swap event: %w", err)
	}

	// Send to swap events channel
	select {
	case em.swapEvents <- swapEvent:
		em.swapsDetected++
	default:
		em.logger.Warn("Swap events channel full, dropping event")
	}

	return nil
}

// parseSwapEvent parses a swap event log into a SwapEvent
func (em *EventMonitor) parseSwapEvent(log types.Log, protocol arbcommon.Protocol) (*SwapEvent, error) {
	// This is a simplified implementation - in practice, you'd parse the actual
	// event data based on the protocol's ABI
	swapEvent := &SwapEvent{
		Timestamp:   time.Now(),
		BlockNumber: log.BlockNumber,
		TxHash:      log.TxHash.Hex(),
		Protocol:    string(protocol),
		Pool:        log.Address.Hex(),
		// In a real implementation, you'd parse the actual event parameters here
		TokenIn:     "0x0000000000000000000000000000000000000000",
		TokenOut:    "0x0000000000000000000000000000000000000000",
		AmountIn:    "0",
		AmountOut:   "0",
		Sender:      "0x0000000000000000000000000000000000000000",
		Recipient:   "0x0000000000000000000000000000000000000000",
		GasPrice:    "0",
		GasUsed:     0,
		PriceImpact: 0.0,
		MEVScore:    0.0,
		Profitable:  false,
	}

	// Add to pool cache if not already present
	em.poolCache.AddPoolIfNotExists(log.Address, protocol)

	return swapEvent, nil
}

// processFactoryLog processes a factory event log (pool creation)
func (em *EventMonitor) processFactoryLog(log types.Log, protocol arbcommon.Protocol) error {
	// Parse pool creation event to extract token addresses
	var token0, token1 common.Address

	// For Uniswap V2/SushiSwap: PairCreated(address indexed token0, address indexed token1, address pair, uint)
	// For Uniswap V3: PoolCreated(address indexed token0, address indexed token1, uint24 indexed fee, int24 tickSpacing, address pool)
	if len(log.Topics) >= 3 {
		token0 = common.BytesToAddress(log.Topics[1].Bytes())
		token1 = common.BytesToAddress(log.Topics[2].Bytes())
	}

	// Handle empty addresses to prevent slice bounds panic
	token0Display := "unknown"
	token1Display := "unknown"
	addressDisplay := "unknown"
	if len(token0.Hex()) > 0 {
		if len(token0.Hex()) > 8 {
			token0Display = token0.Hex()[:8]
		} else {
			token0Display = token0.Hex()
		}
	}
	if len(token1.Hex()) > 0 {
		if len(token1.Hex()) > 8 {
			token1Display = token1.Hex()[:8]
		} else {
			token1Display = token1.Hex()
		}
	}
	if len(log.Address.Hex()) > 0 {
		if len(log.Address.Hex()) > 10 {
			addressDisplay = log.Address.Hex()[:10]
		} else {
			addressDisplay = log.Address.Hex()
		}
	}
	em.logger.Info(fmt.Sprintf("🆕 New %s pool created: %s/%s at %s",
		protocol,
		token0Display,
		token1Display,
		addressDisplay))

	// Add to pool cache and start monitoring this pool
	em.poolCache.AddPoolIfNotExists(log.Address, protocol)

	// CRITICAL FIX: Validate pool address is not zero before creating event
	if log.Address == (common.Address{}) {
		return fmt.Errorf("invalid zero pool address from log")
	}

	// CRITICAL: Create liquidity event to trigger cross-factory syncing
	liquidityEvent := &LiquidityEvent{
		Timestamp:    time.Now(),
		BlockNumber:  log.BlockNumber,
		TxHash:       log.TxHash.Hex(),
		Protocol:     string(protocol),
		Pool:         log.Address.Hex(),
		Token0:       token0.Hex(),
		Token1:       token1.Hex(),
		EventType:    "pool_created",
		Amount0:      "0",
		Amount1:      "0",
		Liquidity:    "0",
		PriceAfter:   "0",
		ImpactSize:   0.0,
		ArbitrageOpp: false,
	}

	// Send to liquidity events channel for processing
	select {
	case em.liquidityEventsChan <- liquidityEvent:
		em.liquidityEvents++
	default:
		em.logger.Warn("Liquidity events channel full, dropping pool creation event")
	}

	// If we have the swap pipeline, trigger cross-factory sync
	if em.swapPipeline != nil {
		// CRITICAL FIX: Validate pool address is not zero before creating event
		if log.Address == (common.Address{}) {
			return nil // Skip processing if zero address
		}

		// Create a mock swap event to trigger syncing
		mockSwap := &SwapEvent{
			Protocol: string(protocol),
			Pool:     log.Address.Hex(),
			TokenIn:  token0.Hex(),
			TokenOut: token1.Hex(),
		}
		go em.swapPipeline.SubmitPoolDiscoverySwap(mockSwap)
	}

	return nil
}

// processLiquidationLog processes a liquidation event log
func (em *EventMonitor) processLiquidationLog(log types.Log, protocol arbcommon.Protocol) error {
	// Parse liquidation event based on protocol
	liquidationEvent := &LiquidationEvent{
		Timestamp:   time.Now(),
		BlockNumber: log.BlockNumber,
		TxHash:      log.TxHash.Hex(),
		Protocol:    string(protocol),
		// In a real implementation, you'd parse the actual event parameters here
	}

	// Send to liquidation events channel
	select {
	case em.liquidationEvents <- liquidationEvent:
	default:
		em.logger.Warn("Liquidation events channel full, dropping event")
	}

	return nil
}

// processSwapEvents processes swap events from the channel
func (em *EventMonitor) processSwapEvents() {
	for {
		select {
		case <-em.ctx.Done():
			return
		case swapEvent := <-em.swapEvents:
			// Log the swap event
			if err := em.protocolRegistry.LogSwapEvent(swapEvent); err != nil {
				em.logger.Error(fmt.Sprintf("Failed to log swap event: %v", err))
			}

			// Update metrics
			em.swapsDetected++
		}
	}
}

// processLiquidationEvents processes liquidation events from the channel
func (em *EventMonitor) processLiquidationEvents() {
	for {
		select {
		case <-em.ctx.Done():
			return
		case liquidationEvent := <-em.liquidationEvents:
			// Log the liquidation event
			if err := em.protocolRegistry.LogLiquidationEvent(liquidationEvent); err != nil {
				em.logger.Error(fmt.Sprintf("Failed to log liquidation event: %v", err))
			}
		}
	}
}

// processLiquidityEvents processes liquidity events from the channel
func (em *EventMonitor) processLiquidityEvents() {
	for {
		select {
		case <-em.ctx.Done():
			return
		case liquidityEvent := <-em.liquidityEventsChan:
			// Log the liquidity event
			if err := em.protocolRegistry.LogLiquidityEvent(liquidityEvent); err != nil {
				em.logger.Error(fmt.Sprintf("Failed to log liquidity event: %v", err))
			}

			em.liquidityEvents++
		}
	}
}

// GetMetrics returns current monitoring metrics
func (em *EventMonitor) GetMetrics() map[string]interface{} {
	return map[string]interface{}{
		"events_processed":     em.eventsProcessed,
		"swaps_detected":       em.swapsDetected,
		"liquidity_events":     em.liquidityEvents,
		"active_subscriptions": len(em.subscriptions),
	}
}

// Close stops all monitoring and cleans up resources
func (em *EventMonitor) Close() error {
	em.logger.Info("🛑 Stopping DEX event monitoring")

	// Cancel all subscriptions
	em.subMu.Lock()
	for _, sub := range em.subscriptions {
		sub.cancel()
	}
	em.subscriptions = make(map[string]*subscription)
	em.subMu.Unlock()

	// Cancel main context
	em.cancel()

	em.logger.Info("✅ DEX event monitoring stopped")
	return nil
}