package arbitrum

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"math/big"
	"time"

	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/fraktal/mev-beta/internal/logger"
)

// L2MessageParser parses Arbitrum L2 messages and transactions
type L2MessageParser struct {
	logger             *logger.Logger
	uniswapV2RouterABI abi.ABI
	uniswapV3RouterABI abi.ABI

	// Known DEX contract addresses on Arbitrum
	knownRouters map[common.Address]string
	knownPools   map[common.Address]string
}

// NewL2MessageParser creates a new L2 message parser
func NewL2MessageParser(logger *logger.Logger) *L2MessageParser {
	parser := &L2MessageParser{
		logger:       logger,
		knownRouters: make(map[common.Address]string),
		knownPools:   make(map[common.Address]string),
	}

	// Initialize known Arbitrum DEX addresses
	parser.initializeKnownAddresses()

	// Load ABIs for parsing
	parser.loadABIs()

	return parser
}

// initializeKnownAddresses sets up known DEX addresses on Arbitrum
func (p *L2MessageParser) initializeKnownAddresses() {
	// Uniswap V3 on Arbitrum
	p.knownRouters[common.HexToAddress("0xE592427A0AEce92De3Edee1F18E0157C05861564")] = "UniswapV3"
	p.knownRouters[common.HexToAddress("0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45")] = "UniswapV3Router2"

	// Uniswap V2 on Arbitrum
	p.knownRouters[common.HexToAddress("0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D")] = "UniswapV2"

	// SushiSwap on Arbitrum
	p.knownRouters[common.HexToAddress("0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506")] = "SushiSwap"

	// Camelot DEX (Arbitrum native)
	p.knownRouters[common.HexToAddress("0xc873fEcbd354f5A56E00E710B90EF4201db2448d")] = "Camelot"

	// GMX
	p.knownRouters[common.HexToAddress("0x327df1e6de05895d2ab08513aadd9317845f20d9")] = "GMX"

	// Balancer V2
	p.knownRouters[common.HexToAddress("0xBA12222222228d8Ba445958a75a0704d566BF2C8")] = "BalancerV2"

	// Curve
	p.knownRouters[common.HexToAddress("0x98EE8517825C0bd778a57471a27555614F97F48D")] = "Curve"

	// Popular pools on Arbitrum
	p.knownPools[common.HexToAddress("0xC31E54c7a869B9FcBEcc14363CF510d1c41fa443")] = "ETH/USDC-0.05%"
	p.knownPools[common.HexToAddress("0x17c14D2c404D167802b16C450d3c99F88F2c4F4d")] = "ETH/USDC-0.3%"
	p.knownPools[common.HexToAddress("0x88e6A0c2dDD26FEEb64F039a2c41296FcB3f5640")] = "ETH/USDC-0.05%"
	p.knownPools[common.HexToAddress("0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc")] = "ETH/USDC-0.3%"
}

// loadABIs loads the required ABI definitions
func (p *L2MessageParser) loadABIs() {
	// Simplified ABI loading - in production, load from files
	uniswapV2RouterABI := `[
		{
			"inputs": [
				{"internalType": "uint256", "name": "amountIn", "type": "uint256"},
				{"internalType": "uint256", "name": "amountOutMin", "type": "uint256"},
				{"internalType": "address[]", "name": "path", "type": "address[]"},
				{"internalType": "address", "name": "to", "type": "address"},
				{"internalType": "uint256", "name": "deadline", "type": "uint256"}
			],
			"name": "swapExactTokensForTokens",
			"outputs": [{"internalType": "uint256[]", "name": "amounts", "type": "uint256[]"}],
			"stateMutability": "nonpayable",
			"type": "function"
		}
	]`

	var err error
	p.uniswapV2RouterABI, err = abi.JSON(bytes.NewReader([]byte(uniswapV2RouterABI)))
	if err != nil {
		p.logger.Error(fmt.Sprintf("Failed to load Uniswap V2 Router ABI: %v", err))
	}
}

// ParseL2Message parses an L2 message and extracts relevant information
func (p *L2MessageParser) ParseL2Message(messageData []byte, messageNumber *big.Int, timestamp uint64) (*L2Message, error) {
	// Validate inputs
	if messageData == nil {
		return nil, fmt.Errorf("message data is nil")
	}

	if len(messageData) < 4 {
		return nil, fmt.Errorf("message data too short: %d bytes", len(messageData))
	}

	// Validate message number
	if messageNumber == nil {
		return nil, fmt.Errorf("message number is nil")
	}

	// Validate timestamp (should be a reasonable Unix timestamp)
	if timestamp > uint64(time.Now().Unix()+86400) || timestamp < 1609459200 { // 1609459200 = 2021-01-01
		p.logger.Warn(fmt.Sprintf("Suspicious timestamp: %d", timestamp))
		// We'll still process it but log the warning
	}

	l2Message := &L2Message{
		MessageNumber: messageNumber,
		Data:          messageData,
		Timestamp:     timestamp,
		Type:          L2Unknown,
	}

	// Parse message type from first bytes
	msgType := binary.BigEndian.Uint32(messageData[:4])

	// Validate message type
	if msgType != 3 && msgType != 7 {
		p.logger.Debug(fmt.Sprintf("Unknown L2 message type: %d", msgType))
		// We'll still return the message but mark it as unknown
		return l2Message, nil
	}

	switch msgType {
	case 3: // L2 Transaction
		return p.parseL2Transaction(l2Message, messageData[4:])
	case 7: // Batch submission
		return p.parseL2Batch(l2Message, messageData[4:])
	default:
		p.logger.Debug(fmt.Sprintf("Unknown L2 message type: %d", msgType))
		return l2Message, nil
	}
}

// parseL2Transaction parses an L2 transaction message
func (p *L2MessageParser) parseL2Transaction(l2Message *L2Message, data []byte) (*L2Message, error) {
	// Validate inputs
	if l2Message == nil {
		return nil, fmt.Errorf("l2Message is nil")
	}

	if data == nil {
		return nil, fmt.Errorf("transaction data is nil")
	}

	// Validate data length
	if len(data) == 0 {
		return nil, fmt.Errorf("transaction data is empty")
	}

	l2Message.Type = L2Transaction

	// Parse RLP-encoded transaction
	tx := &types.Transaction{}
	if err := tx.UnmarshalBinary(data); err != nil {
		return nil, fmt.Errorf("failed to unmarshal transaction: %v", err)
	}

	// Validate the parsed transaction
	if tx == nil {
		return nil, fmt.Errorf("parsed transaction is nil")
	}

	// Additional validation for transaction fields
	if tx.Gas() == 0 && len(tx.Data()) == 0 {
		p.logger.Warn("Transaction has zero gas and no data")
	}

	l2Message.ParsedTx = tx

	// Extract sender (this might require signature recovery)
	if tx.To() != nil {
		// For now, we'll extract what we can without signature recovery
		l2Message.Sender = common.HexToAddress("0x0") // Placeholder
	}

	return l2Message, nil
}

// parseL2Batch parses a batch submission message
func (p *L2MessageParser) parseL2Batch(l2Message *L2Message, data []byte) (*L2Message, error) {
	// Validate inputs
	if l2Message == nil {
		return nil, fmt.Errorf("l2Message is nil")
	}

	if data == nil {
		return nil, fmt.Errorf("batch data is nil")
	}

	l2Message.Type = L2BatchSubmission

	// Parse batch data structure
	if len(data) < 32 {
		return nil, fmt.Errorf("batch data too short: %d bytes", len(data))
	}

	// Extract batch index
	batchIndex := new(big.Int).SetBytes(data[:32])

	// Validate batch index
	if batchIndex == nil || batchIndex.Sign() < 0 {
		return nil, fmt.Errorf("invalid batch index")
	}

	l2Message.BatchIndex = batchIndex

	// Parse individual transactions in the batch
	remainingData := data[32:]

	// Validate remaining data
	if remainingData == nil {
		// No transactions in the batch, which is valid
		l2Message.InnerTxs = []*types.Transaction{}
		return l2Message, nil
	}

	var innerTxs []*types.Transaction

	for len(remainingData) > 0 {
		// Each transaction is prefixed with its length
		if len(remainingData) < 4 {
			// Incomplete data, log warning but continue with what we have
			p.logger.Warn("Incomplete transaction length prefix in batch")
			break
		}

		txLength := binary.BigEndian.Uint32(remainingData[:4])

		// Validate transaction length
		if txLength == 0 {
			p.logger.Warn("Zero-length transaction in batch")
			remainingData = remainingData[4:]
			continue
		}

		if uint32(len(remainingData)) < 4+txLength {
			// Incomplete transaction data, log warning but continue with what we have
			p.logger.Warn(fmt.Sprintf("Incomplete transaction data in batch: expected %d bytes, got %d", txLength, len(remainingData)-4))
			break
		}

		txData := remainingData[4 : 4+txLength]
		tx := &types.Transaction{}

		if err := tx.UnmarshalBinary(txData); err == nil {
			// Validate the parsed transaction
			if tx != nil {
				innerTxs = append(innerTxs, tx)
			} else {
				p.logger.Warn("Parsed nil transaction in batch")
			}
		} else {
			// Log the error but continue processing other transactions
			p.logger.Warn(fmt.Sprintf("Failed to unmarshal transaction in batch: %v", err))
		}

		remainingData = remainingData[4+txLength:]
	}

	l2Message.InnerTxs = innerTxs
	return l2Message, nil
}

// ParseDEXInteraction extracts DEX interaction details from a transaction
func (p *L2MessageParser) ParseDEXInteraction(tx *types.Transaction) (*DEXInteraction, error) {
	// Validate inputs
	if tx == nil {
		return nil, fmt.Errorf("transaction is nil")
	}

	if tx.To() == nil {
		return nil, fmt.Errorf("contract creation transaction")
	}

	to := *tx.To()

	// Validate address
	if to == (common.Address{}) {
		return nil, fmt.Errorf("invalid contract address")
	}

	protocol, isDEX := p.knownRouters[to]
	if !isDEX {
		// Also check if this might be a direct pool interaction
		if poolName, isPool := p.knownPools[to]; isPool {
			protocol = poolName
		} else {
			return nil, fmt.Errorf("not a known DEX router or pool")
		}
	}

	data := tx.Data()

	// Validate transaction data
	if data == nil {
		return nil, fmt.Errorf("transaction data is nil")
	}

	if len(data) < 4 {
		return nil, fmt.Errorf("transaction data too short: %d bytes", len(data))
	}

	// Validate function selector (first 4 bytes)
	selector := data[:4]
	if len(selector) != 4 {
		return nil, fmt.Errorf("invalid function selector length: %d", len(selector))
	}

	interaction := &DEXInteraction{
		Protocol:      protocol,
		Router:        to,
		Timestamp:     uint64(time.Now().Unix()), // Use current time as default
		MessageNumber: big.NewInt(0),             // Will be set by caller
	}

	// Parse based on function selector
	switch common.Bytes2Hex(selector) {
	case "38ed1739": // swapExactTokensForTokens (Uniswap V2)
		return p.parseSwapExactTokensForTokens(interaction, data[4:])
	case "8803dbee": // swapTokensForExactTokens (Uniswap V2)
		return p.parseSwapTokensForExactTokens(interaction, data[4:])
	case "18cbafe5": // swapExactTokensForTokensSupportingFeeOnTransferTokens (Uniswap V2)
		return p.parseSwapExactTokensForTokens(interaction, data[4:])
	case "414bf389": // exactInputSingle (Uniswap V3)
		return p.parseExactInputSingle(interaction, data[4:])
	case "db3e2198": // exactInput (Uniswap V3)
		return p.parseExactInput(interaction, data[4:])
	case "f305d719": // exactOutputSingle (Uniswap V3)
		return p.parseExactOutputSingle(interaction, data[4:])
	case "04e45aaf": // exactOutput (Uniswap V3)
		return p.parseExactOutput(interaction, data[4:])
	case "7ff36ab5": // swapExactETHForTokens (Uniswap V2)
		return p.parseSwapExactETHForTokens(interaction, data[4:])
	case "18cffa1c": // swapExactETHForTokensSupportingFeeOnTransferTokens (Uniswap V2)
		return p.parseSwapExactETHForTokens(interaction, data[4:])
	case "b6f9de95": // swapExactTokensForETH (Uniswap V2)
		return p.parseSwapExactTokensForETH(interaction, data[4:])
	case "791ac947": // swapExactTokensForETHSupportingFeeOnTransferTokens (Uniswap V2)
		return p.parseSwapExactTokensForETH(interaction, data[4:])
	case "5ae401dc": // multicall (Uniswap V3)
		return p.parseMulticall(interaction, data[4:])
	default:
		return nil, fmt.Errorf("unknown DEX function selector: %s", common.Bytes2Hex(selector))
	}
}

// parseSwapExactTokensForTokens parses Uniswap V2 style swap
func (p *L2MessageParser) parseSwapExactTokensForTokens(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Validate inputs
	if interaction == nil {
		return nil, fmt.Errorf("interaction is nil")
	}

	if data == nil {
		return nil, fmt.Errorf("data is nil")
	}

	// Decode ABI data
	method, err := p.uniswapV2RouterABI.MethodById(crypto.Keccak256([]byte("swapExactTokensForTokens(uint256,uint256,address[],address,uint256)"))[:4])
	if err != nil {
		return nil, fmt.Errorf("failed to get ABI method: %v", err)
	}

	// Validate data length before unpacking
	if len(data) == 0 {
		return nil, fmt.Errorf("data is empty")
	}

	inputs, err := method.Inputs.Unpack(data)
	if err != nil {
		return nil, fmt.Errorf("failed to unpack ABI data: %v", err)
	}

	if len(inputs) < 5 {
		return nil, fmt.Errorf("insufficient swap parameters: got %d, expected 5", len(inputs))
	}

	// Extract parameters with validation
	amountIn, ok := inputs[0].(*big.Int)
	if !ok {
		return nil, fmt.Errorf("amountIn is not a *big.Int")
	}

	// Validate amountIn is not negative
	if amountIn.Sign() < 0 {
		return nil, fmt.Errorf("negative amountIn")
	}

	interaction.AmountIn = amountIn

	// amountOutMin := inputs[1].(*big.Int)
	path, ok := inputs[2].([]common.Address)
	if !ok {
		return nil, fmt.Errorf("path is not []common.Address")
	}

	// Validate path
	if len(path) < 2 {
		return nil, fmt.Errorf("path must contain at least 2 tokens, got %d", len(path))
	}

	// Validate addresses in path are not zero
	for i, addr := range path {
		if addr == (common.Address{}) {
			return nil, fmt.Errorf("zero address in path at index %d", i)
		}
	}

	recipient, ok := inputs[3].(common.Address)
	if !ok {
		return nil, fmt.Errorf("recipient is not common.Address")
	}

	// Validate recipient is not zero
	if recipient == (common.Address{}) {
		return nil, fmt.Errorf("recipient address is zero")
	}

	interaction.Recipient = recipient
	interaction.Deadline = inputs[4].(*big.Int).Uint64()

	interaction.TokenIn = path[0]
	interaction.TokenOut = path[len(path)-1]

	return interaction, nil
}

// parseSwapTokensForExactTokens parses exact output swaps
func (p *L2MessageParser) parseSwapTokensForExactTokens(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Similar to above but for exact output
	// Implementation would be similar to parseSwapExactTokensForTokens
	// but with different parameter ordering
	return interaction, fmt.Errorf("not implemented yet")
}

// parseSwapExactETHForTokens parses ETH to token swaps
func (p *L2MessageParser) parseSwapExactETHForTokens(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Implementation for ETH to token swaps
	return interaction, fmt.Errorf("not implemented yet")
}

// parseSwapExactTokensForETH parses token to ETH swaps
func (p *L2MessageParser) parseSwapExactTokensForETH(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Implementation for token to ETH swaps
	return interaction, fmt.Errorf("not implemented yet")
}

// parseExactOutputSingle parses Uniswap V3 exact output single pool swap
func (p *L2MessageParser) parseExactOutputSingle(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Implementation for exact output swaps
	return interaction, fmt.Errorf("not implemented yet")
}

// parseExactOutput parses Uniswap V3 exact output multi-hop swap
func (p *L2MessageParser) parseExactOutput(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Implementation for exact output multi-hop swaps
	return interaction, fmt.Errorf("not implemented yet")
}

// parseMulticall parses Uniswap V3 multicall transactions
func (p *L2MessageParser) parseMulticall(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Implementation for multicall transactions
	return interaction, fmt.Errorf("not implemented yet")
}

// parseExactInputSingle parses Uniswap V3 single pool swap
func (p *L2MessageParser) parseExactInputSingle(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// Validate inputs
	if interaction == nil {
		return nil, fmt.Errorf("interaction is nil")
	}

	if data == nil {
		return nil, fmt.Errorf("data is nil")
	}

	// Uniswap V3 exactInputSingle structure:
	// struct ExactInputSingleParams {
	//     address tokenIn;
	//     address tokenOut;
	//     uint24 fee;
	//     address recipient;
	//     uint256 deadline;
	//     uint256 amountIn;
	//     uint256 amountOutMinimum;
	//     uint160 sqrtPriceLimitX96;
	// }

	// Validate minimum data length (at least 8 parameters * 32 bytes each)
	if len(data) < 256 {
		return nil, fmt.Errorf("insufficient data for exactInputSingle: %d bytes", len(data))
	}

	// Parse parameters with bounds checking
	// tokenIn (first parameter) - bytes 0-31, address is in last 20 bytes (12-31)
	if len(data) >= 32 {
		interaction.TokenIn = common.BytesToAddress(data[12:32])
	}

	// tokenOut (second parameter) - bytes 32-63, address is in last 20 bytes (44-63)
	if len(data) >= 64 {
		interaction.TokenOut = common.BytesToAddress(data[44:64])
	}

	// recipient (fourth parameter) - bytes 96-127, address is in last 20 bytes (108-127)
	if len(data) >= 128 {
		interaction.Recipient = common.BytesToAddress(data[108:128])
	}

	// deadline (fifth parameter) - bytes 128-159, uint64 is in last 8 bytes (152-159)
	if len(data) >= 160 {
		interaction.Deadline = binary.BigEndian.Uint64(data[152:160])
	}

	// amountIn (sixth parameter) - bytes 160-191
	if len(data) >= 192 {
		amountIn := new(big.Int).SetBytes(data[160:192])
		// Validate amount is reasonable (not negative)
		if amountIn.Sign() < 0 {
			return nil, fmt.Errorf("negative amountIn")
		}
		interaction.AmountIn = amountIn
	}

	// Set default values for fields that might not be parsed
	if interaction.AmountOut == nil {
		interaction.AmountOut = big.NewInt(0)
	}

	// Validate that we have required fields
	if interaction.TokenIn == (common.Address{}) && interaction.TokenOut == (common.Address{}) {
		// If both are zero, we likely don't have valid data
		return nil, fmt.Errorf("unable to parse token addresses from data")
	}

	// Note: We're not strictly validating that addresses are non-zero since some
	// transactions might legitimately use zero addresses in certain contexts
	// The calling code should validate addresses as appropriate for their use case

	return interaction, nil
}

// parseExactInput parses Uniswap V3 multi-hop swap
func (p *L2MessageParser) parseExactInput(interaction *DEXInteraction, data []byte) (*DEXInteraction, error) {
	// This would parse the more complex multi-hop swap structure
	return interaction, fmt.Errorf("not implemented yet")
}

// IsSignificantSwap determines if a DEX interaction is significant enough to monitor
func (p *L2MessageParser) IsSignificantSwap(interaction *DEXInteraction, minAmountUSD float64) bool {
	// Validate inputs
	if interaction == nil {
		p.logger.Warn("IsSignificantSwap called with nil interaction")
		return false
	}

	// Validate minAmountUSD
	if minAmountUSD < 0 {
		p.logger.Warn(fmt.Sprintf("Negative minAmountUSD: %f", minAmountUSD))
		return false
	}

	// This would implement logic to determine if the swap is large enough
	// to be worth monitoring for arbitrage opportunities

	// For now, check if amount is above a threshold
	if interaction.AmountIn == nil {
		return false
	}

	// Validate AmountIn is not negative
	if interaction.AmountIn.Sign() < 0 {
		p.logger.Warn("Negative AmountIn in DEX interaction")
		return false
	}

	// Simplified check - in practice, you'd convert to USD value
	threshold := new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil) // 1 ETH worth

	// Validate threshold
	if threshold == nil || threshold.Sign() <= 0 {
		p.logger.Error("Invalid threshold calculation")
		return false
	}

	return interaction.AmountIn.Cmp(threshold) >= 0
}