package monitor

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

	"github.com/fraktal/mev-beta/internal/config"
	"github.com/fraktal/mev-beta/internal/logger"
	"github.com/fraktal/mev-beta/internal/ratelimit"
	"github.com/fraktal/mev-beta/pkg/arbitrum"
	"github.com/fraktal/mev-beta/pkg/market"
	"github.com/fraktal/mev-beta/pkg/scanner"
	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethclient"
	"golang.org/x/time/rate"
)

// ArbitrumMonitor monitors the Arbitrum sequencer for transactions with concurrency support
type ArbitrumMonitor struct {
	config       *config.ArbitrumConfig
	botConfig    *config.BotConfig
	client       *ethclient.Client
	l2Parser     *arbitrum.ArbitrumL2Parser
	logger       *logger.Logger
	rateLimiter  *ratelimit.LimiterManager
	marketMgr    *market.MarketManager
	scanner      *scanner.MarketScanner
	pipeline     *market.Pipeline
	fanManager   *market.FanManager
	limiter      *rate.Limiter
	pollInterval time.Duration
	running      bool
	mu           sync.RWMutex
}

// NewArbitrumMonitor creates a new Arbitrum monitor with rate limiting
func NewArbitrumMonitor(
	arbCfg *config.ArbitrumConfig,
	botCfg *config.BotConfig,
	logger *logger.Logger,
	rateLimiter *ratelimit.LimiterManager,
	marketMgr *market.MarketManager,
	scanner *scanner.MarketScanner,
) (*ArbitrumMonitor, error) {
	// Create Ethereum client
	client, err := ethclient.Dial(arbCfg.RPCEndpoint)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to Arbitrum node: %v", err)
	}

	// Create L2 parser for Arbitrum transaction parsing
	l2Parser, err := arbitrum.NewArbitrumL2Parser(arbCfg.RPCEndpoint, logger)
	if err != nil {
		return nil, fmt.Errorf("failed to create L2 parser: %v", err)
	}

	// Create rate limiter based on config
	limiter := rate.NewLimiter(
		rate.Limit(arbCfg.RateLimit.RequestsPerSecond),
		arbCfg.RateLimit.Burst,
	)

	// Create pipeline
	pipeline := market.NewPipeline(botCfg, logger, marketMgr, scanner, client)
	
	// Add default stages
	pipeline.AddDefaultStages()

	// Create fan manager
	fanManager := market.NewFanManager(
		&config.Config{
			Arbitrum: *arbCfg,
			Bot:      *botCfg,
		},
		logger,
		rateLimiter,
	)

	return &ArbitrumMonitor{
		config:       arbCfg,
		botConfig:    botCfg,
		client:       client,
		l2Parser:     l2Parser,
		logger:       logger,
		rateLimiter:  rateLimiter,
		marketMgr:    marketMgr,
		scanner:      scanner,
		pipeline:     pipeline,
		fanManager:   fanManager,
		limiter:      limiter,
		pollInterval: time.Duration(botCfg.PollingInterval) * time.Second,
		running:      false,
	}, nil
}

// Start begins monitoring the Arbitrum sequencer
func (m *ArbitrumMonitor) Start(ctx context.Context) error {
	m.mu.Lock()
	m.running = true
	m.mu.Unlock()

	m.logger.Info("Starting Arbitrum sequencer monitoring...")

	// Get the latest block to start from
	if err := m.rateLimiter.WaitForLimit(ctx, m.config.RPCEndpoint); err != nil {
		return fmt.Errorf("rate limit error: %v", err)
	}

	header, err := m.client.HeaderByNumber(ctx, nil)
	if err != nil {
		return fmt.Errorf("failed to get latest block header: %v", err)
	}

	lastBlock := header.Number.Uint64()
	m.logger.Info(fmt.Sprintf("Starting from block: %d", lastBlock))

	// Subscribe to DEX events for real-time monitoring
	if err := m.subscribeToDEXEvents(ctx); err != nil {
		m.logger.Warn(fmt.Sprintf("Failed to subscribe to DEX events: %v", err))
	} else {
		m.logger.Info("Subscribed to DEX events")
	}

	for {
		m.mu.RLock()
		running := m.running
		m.mu.RUnlock()

		if !running {
			break
		}

		select {
		case <-ctx.Done():
			m.Stop()
			return nil
		case <-time.After(m.pollInterval):
			// Get the latest block
			if err := m.rateLimiter.WaitForLimit(ctx, m.config.RPCEndpoint); err != nil {
				m.logger.Error(fmt.Sprintf("Rate limit error: %v", err))
				continue
			}

			header, err := m.client.HeaderByNumber(ctx, nil)
			if err != nil {
				m.logger.Error(fmt.Sprintf("Failed to get latest block header: %v", err))
				continue
			}

			currentBlock := header.Number.Uint64()

			// Process blocks from lastBlock+1 to currentBlock
			for blockNum := lastBlock + 1; blockNum <= currentBlock; blockNum++ {
				if err := m.processBlock(ctx, blockNum); err != nil {
					m.logger.Error(fmt.Sprintf("Failed to process block %d: %v", blockNum, err))
				}
			}

			lastBlock = currentBlock
		}
	}

	return nil
}

// Stop stops the monitor
func (m *ArbitrumMonitor) Stop() {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.running = false
	m.logger.Info("Stopping Arbitrum monitor...")
}

// processBlock processes a single block for potential swap transactions with enhanced L2 parsing
func (m *ArbitrumMonitor) processBlock(ctx context.Context, blockNumber uint64) error {
	m.logger.Debug(fmt.Sprintf("Processing block %d", blockNumber))

	// Wait for rate limiter
	if err := m.rateLimiter.WaitForLimit(ctx, m.config.RPCEndpoint); err != nil {
		return fmt.Errorf("rate limit error: %v", err)
	}

	// Get block using L2 parser to bypass transaction type issues
	l2Block, err := m.l2Parser.GetBlockByNumber(ctx, blockNumber)
	if err != nil {
		m.logger.Error(fmt.Sprintf("Failed to get L2 block %d: %v", blockNumber, err))
		return fmt.Errorf("failed to get L2 block %d: %v", blockNumber, err)
	}

	// Parse DEX transactions from the block
	dexTransactions := m.l2Parser.ParseDEXTransactions(ctx, l2Block)
	
	m.logger.Info(fmt.Sprintf("Block %d: Processing %d transactions, found %d DEX transactions", 
		blockNumber, len(l2Block.Transactions), len(dexTransactions)))

	// Process DEX transactions
	if len(dexTransactions) > 0 {
		m.logger.Info(fmt.Sprintf("Block %d contains %d DEX transactions:", blockNumber, len(dexTransactions)))
		for i, dexTx := range dexTransactions {
			m.logger.Info(fmt.Sprintf("  [%d] %s: %s -> %s (%s) calling %s (%s)", 
				i+1, dexTx.Hash, dexTx.From, dexTx.To, dexTx.ContractName, 
				dexTx.FunctionName, dexTx.Protocol))
		}

		// TODO: Convert DEX transactions to standard format and process through pipeline
		// For now, we're successfully detecting and logging DEX transactions
	}

	// If no DEX transactions found, report empty block
	if len(dexTransactions) == 0 {
		if len(l2Block.Transactions) == 0 {
			m.logger.Info(fmt.Sprintf("Block %d: Empty block", blockNumber))
		} else {
			m.logger.Info(fmt.Sprintf("Block %d: No DEX transactions found in %d total transactions", 
				blockNumber, len(l2Block.Transactions)))
		}
	}

	return nil
}

// subscribeToDEXEvents subscribes to DEX contract events for real-time monitoring
func (m *ArbitrumMonitor) subscribeToDEXEvents(ctx context.Context) error {
	// Define official DEX contract addresses for Arbitrum mainnet
	dexContracts := []struct {
		Address common.Address
		Name    string
	}{
		// Official Arbitrum DEX Factories
		{common.HexToAddress("0xf1D7CC64Fb4452F05c498126312eBE29f30Fbcf9"), "UniswapV2Factory"}, // Official Uniswap V2 Factory
		{common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984"), "UniswapV3Factory"}, // Official Uniswap V3 Factory  
		{common.HexToAddress("0xc35DADB65012eC5796536bD9864eD8773aBc74C4"), "SushiSwapFactory"}, // Official SushiSwap V2 Factory
		
		// Official Arbitrum DEX Routers  
		{common.HexToAddress("0x4752ba5dbc23f44d87826276bf6fd6b1c372ad24"), "UniswapV2Router02"}, // Official Uniswap V2 Router02
		{common.HexToAddress("0xE592427A0AEce92De3Edee1F18E0157C05861564"), "UniswapV3Router"}, // Official Uniswap V3 SwapRouter
		{common.HexToAddress("0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45"), "UniswapV3Router02"}, // Official Uniswap V3 SwapRouter02
		{common.HexToAddress("0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506"), "SushiSwapRouter"}, // Official SushiSwap Router
		{common.HexToAddress("0xC36442b4a4522E871399CD717aBDD847Ab11FE88"), "UniswapV3PositionManager"}, // Official Position Manager
		
		// Additional official routers
		{common.HexToAddress("0xa51afafe0263b40edaef0df8781ea9aa03e381a3"), "UniversalRouter"}, // Universal Router
		{common.HexToAddress("0x4C60051384bd2d3C01bfc845Cf5F4b44bcbE9de5"), "GMX Router"}, // GMX DEX Router
		
		// Popular Arbitrum pools (verified high volume pools)
		{common.HexToAddress("0xC6962004f452bE9203591991D15f6b388e09E8D0"), "USDC/WETH UniswapV3 0.05%"}, // High volume pool
		{common.HexToAddress("0x17c14D2c404D167802b16C450d3c99F88F2c4F4d"), "USDC/WETH UniswapV3 0.3%"},  // High volume pool
		{common.HexToAddress("0x2f5e87C9312fa29aed5c179E456625D79015299c"), "WBTC/WETH UniswapV3 0.05%"}, // High volume pool
		{common.HexToAddress("0x149e36E72726e0BceA5c59d40df2c43F60f5A22D"), "WBTC/WETH UniswapV3 0.3%"},  // High volume pool 
		{common.HexToAddress("0x641C00A822e8b671738d32a431a4Fb6074E5c79d"), "USDT/WETH UniswapV3 0.05%"}, // High volume pool
		{common.HexToAddress("0xFe7D6a84287235C7b4b57C4fEb9a44d4C6Ed3BB8"), "ARB/WETH UniswapV3 0.05%"},  // ARB native token pool
	}

	// Define common DEX event signatures
	eventSignatures := []common.Hash{
		common.HexToHash("0xd78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822"), // Swap (Uniswap V2)
		common.HexToHash("0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67"), // Swap (Uniswap V3)
		common.HexToHash("0x4c209b5fc8ad50758f13e2e1088ba56a560dff690a1c6fef26394f4c03821c4f"), // Mint (Uniswap V2)
		common.HexToHash("0x7a53080ba414158be7ec69b987b5fb7d07dee101fe85488f0853ae16239d0bde"), // Burn (Uniswap V2)
		common.HexToHash("0x783cca1c0412dd0d695e784568c96da2e9c22ff989357a2e8b1d9b2b4e6b7118"), // Mint (Uniswap V3)
		common.HexToHash("0x0c396cd989a39f49a56c8a608a0409f2075c6b60e9c44533b5cf87abdbe393f1"), // Burn (Uniswap V3)
	}

	// Create filter query for DEX events
	addresses := make([]common.Address, len(dexContracts))
	for i, dex := range dexContracts {
		addresses[i] = dex.Address
	}

	topics := [][]common.Hash{{}}
	topics[0] = eventSignatures

	query := ethereum.FilterQuery{
		Addresses: addresses,
		Topics:    topics,
	}

	// Subscribe to logs
	logs := make(chan types.Log)
	sub, err := m.client.SubscribeFilterLogs(context.Background(), query, logs)
	if err != nil {
		return fmt.Errorf("failed to subscribe to DEX events: %v", err)
	}
	
	m.logger.Info("Subscribed to DEX events")

	// Process logs in a goroutine
	go func() {
		defer func() {
			if r := recover(); r != nil {
				m.logger.Error(fmt.Sprintf("Panic in DEX event processor: %v", r))
			}
		}()
		
		defer sub.Unsubscribe()

		for {
			select {
			case log := <-logs:
				m.processDEXEvent(ctx, log)
			case err := <-sub.Err():
				if err != nil {
					m.logger.Error(fmt.Sprintf("DEX event subscription error: %v", err))
				}
				return
			case <-ctx.Done():
				return
			}
		}
	}()

	return nil
}

// processDEXEvent processes a DEX event log
func (m *ArbitrumMonitor) processDEXEvent(ctx context.Context, log types.Log) {
	m.logger.Debug(fmt.Sprintf("Processing DEX event from contract %s, topic count: %d", log.Address.Hex(), len(log.Topics)))

	// Check if this is a swap event
	if len(log.Topics) > 0 {
		eventSig := log.Topics[0]

		// Check for common swap event signatures
		switch eventSig.Hex() {
		case "0xd78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822": // Uniswap V2 Swap
			m.logger.Info(fmt.Sprintf("Uniswap V2 Swap event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		case "0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67": // Uniswap V3 Swap
			m.logger.Info(fmt.Sprintf("Uniswap V3 Swap event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		case "0x4c209b5fc8ad50758f13e2e1088ba56a560dff690a1c6fef26394f4c03821c4f": // Uniswap V2 Mint
			m.logger.Info(fmt.Sprintf("Uniswap V2 Mint event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		case "0x7a53080ba414158be7ec69b987b5fb7d07dee101fe85488f0853ae16239d0bde": // Uniswap V2 Burn
			m.logger.Info(fmt.Sprintf("Uniswap V2 Burn event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		case "0x783cca1c0412dd0d695e784568c96da2e9c22ff989357a2e8b1d9b2b4e6b7118": // Uniswap V3 Mint
			m.logger.Info(fmt.Sprintf("Uniswap V3 Mint event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		case "0x0c396cd989a39f49a56c8a608a0409f2075c6b60e9c44533b5cf87abdbe393f1": // Uniswap V3 Burn
			m.logger.Info(fmt.Sprintf("Uniswap V3 Burn event detected: Contract=%s, TxHash=%s", 
				log.Address.Hex(), log.TxHash.Hex()))
		default:
			m.logger.Debug(fmt.Sprintf("Other DEX event detected: Contract=%s, EventSig=%s, TxHash=%s", 
				log.Address.Hex(), eventSig.Hex(), log.TxHash.Hex()))
		}

		// Fetch transaction receipt for detailed analysis
		receipt, err := m.client.TransactionReceipt(ctx, log.TxHash)
		if err != nil {
			m.logger.Error(fmt.Sprintf("Failed to fetch receipt for transaction %s: %v", log.TxHash.Hex(), err))
			return
		}

		// Process the transaction through the pipeline
		// This will parse the DEX events and look for arbitrage opportunities
		m.processTransactionReceipt(ctx, receipt, log.BlockNumber, log.BlockHash)
	}
}

// processTransactionReceipt processes a transaction receipt for DEX events
func (m *ArbitrumMonitor) processTransactionReceipt(ctx context.Context, receipt *types.Receipt, blockNumber uint64, blockHash common.Hash) {
	if receipt == nil {
		return
	}

	m.logger.Debug(fmt.Sprintf("Processing transaction receipt %s from block %d", 
		receipt.TxHash.Hex(), blockNumber))

	// Process transaction logs for DEX events
	dexEvents := 0
	for _, log := range receipt.Logs {
		if len(log.Topics) > 0 {
			eventSig := log.Topics[0]
			
			// Check for common DEX event signatures
			switch eventSig.Hex() {
			case "0xd78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822": // Uniswap V2 Swap
				m.logger.Info(fmt.Sprintf("DEX Swap event detected in transaction %s: Uniswap V2", receipt.TxHash.Hex()))
				dexEvents++
			case "0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67": // Uniswap V3 Swap
				m.logger.Info(fmt.Sprintf("DEX Swap event detected in transaction %s: Uniswap V3", receipt.TxHash.Hex()))
				dexEvents++
			case "0x4c209b5fc8ad50758f13e2e1088ba56a560dff690a1c6fef26394f4c03821c4f": // Uniswap V2 Mint
				m.logger.Info(fmt.Sprintf("DEX Mint event detected in transaction %s: Uniswap V2", receipt.TxHash.Hex()))
				dexEvents++
			case "0x7a53080ba414158be7ec69b987b5fb7d07dee101fe85488f0853ae16239d0bde": // Uniswap V2 Burn
				m.logger.Info(fmt.Sprintf("DEX Burn event detected in transaction %s: Uniswap V2", receipt.TxHash.Hex()))
				dexEvents++
			case "0x783cca1c0412dd0d695e784568c96da2e9c22ff989357a2e8b1d9b2b4e6b7118": // Uniswap V3 Mint
				m.logger.Info(fmt.Sprintf("DEX Mint event detected in transaction %s: Uniswap V3", receipt.TxHash.Hex()))
				dexEvents++
			case "0x0c396cd989a39f49a56c8a608a0409f2075c6b60e9c44533b5cf87abdbe393f1": // Uniswap V3 Burn
				m.logger.Info(fmt.Sprintf("DEX Burn event detected in transaction %s: Uniswap V3", receipt.TxHash.Hex()))
				dexEvents++
			}
		}
	}
	
	if dexEvents > 0 {
		m.logger.Info(fmt.Sprintf("Transaction %s contains %d DEX events", receipt.TxHash.Hex(), dexEvents))
	}
	
	// Create a minimal transaction for the pipeline
	// This is just a stub since we don't have the full transaction data
	tx := types.NewTransaction(0, common.Address{}, big.NewInt(0), 0, big.NewInt(0), nil)

	// Create a slice with just this transaction
	transactions := []*types.Transaction{tx}

	// Process through the pipeline
	if err := m.pipeline.ProcessTransactions(ctx, transactions, blockNumber, uint64(time.Now().Unix())); err != nil {
		m.logger.Error(fmt.Sprintf("Pipeline processing error for receipt %s: %v", receipt.TxHash.Hex(), err))
	}
}

// processTransaction analyzes a transaction for potential swap opportunities
func (m *ArbitrumMonitor) processTransaction(ctx context.Context, tx *types.Transaction) error {
	// Check if this is a potential swap transaction
	// This is a simplified check - in practice, you would check for
	// specific function signatures of Uniswap-like contracts

	// For now, we'll just log all transactions
	from, err := m.client.TransactionSender(ctx, tx, common.Hash{}, 0)
	if err != nil {
		// This can happen for pending transactions
		from = common.HexToAddress("0x0")
	}

	m.logger.Debug(fmt.Sprintf("Transaction: %s, From: %s, To: %s, Value: %s ETH",
		tx.Hash().Hex(),
		from.Hex(),
		func() string {
			if tx.To() != nil {
				return tx.To().Hex()
			}
			return "contract creation"
		}(),
		new(big.Float).Quo(new(big.Float).SetInt(tx.Value()), big.NewFloat(1e18)).String(),
	))

	// TODO: Add logic to detect swap transactions and analyze them
	// This would involve:
	// 1. Checking if the transaction is calling a Uniswap-like contract
	// 2. Decoding the swap function call
	// 3. Extracting the token addresses and amounts
	// 4. Calculating potential price impact

	return nil
}

// GetPendingTransactions retrieves pending transactions from the mempool
func (m *ArbitrumMonitor) GetPendingTransactions(ctx context.Context) ([]*types.Transaction, error) {
	// This is a simplified implementation
	// In practice, you might need to use a different approach to access pending transactions

	// Query for pending transactions
	txs := make([]*types.Transaction, 0)

	return txs, nil
}

// getTransactionReceiptWithRetry attempts to get a transaction receipt with exponential backoff retry
func (m *ArbitrumMonitor) getTransactionReceiptWithRetry(ctx context.Context, txHash common.Hash, maxRetries int) (*types.Receipt, error) {
	for attempt := 0; attempt < maxRetries; attempt++ {
		m.logger.Debug(fmt.Sprintf("Attempting to fetch receipt for transaction %s (attempt %d/%d)", txHash.Hex(), attempt+1, maxRetries))
		
		// Try to fetch the transaction receipt
		receipt, err := m.client.TransactionReceipt(ctx, txHash)
		if err == nil {
			m.logger.Debug(fmt.Sprintf("Successfully fetched receipt for transaction %s on attempt %d", txHash.Hex(), attempt+1))
			return receipt, nil
		}
		
		// Check for specific error types that shouldn't be retried
		if ctx.Err() != nil {
			return nil, ctx.Err()
		}
		
		// Log retry attempt for other errors
		if attempt < maxRetries-1 {
			backoffDuration := time.Duration(1<<uint(attempt)) * time.Second
			m.logger.Warn(fmt.Sprintf("Receipt fetch for transaction %s attempt %d failed: %v, retrying in %v", 
				txHash.Hex(), attempt+1, err, backoffDuration))
			
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-time.After(backoffDuration):
				// Continue to next attempt
			}
		} else {
			m.logger.Error(fmt.Sprintf("Receipt fetch for transaction %s failed after %d attempts: %v", txHash.Hex(), maxRetries, err))
		}
	}
	
	return nil, fmt.Errorf("failed to fetch receipt for transaction %s after %d attempts", txHash.Hex(), maxRetries)
}