package parsers

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

	"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/your-org/mev-bot/pkg/cache"
	mevtypes "github.com/your-org/mev-bot/pkg/types"
)

// Curve StableSwap TokenExchange event signature:
// event TokenExchange(address indexed buyer, int128 sold_id, uint256 tokens_sold, int128 bought_id, uint256 tokens_bought)
var (
	// CurveTokenExchangeSignature is the event signature for Curve TokenExchange events
	CurveTokenExchangeSignature = crypto.Keccak256Hash([]byte("TokenExchange(address,int128,uint256,int128,uint256)"))

	// CurveTokenExchangeUnderlyingSignature is for pools with underlying tokens
	CurveTokenExchangeUnderlyingSignature = crypto.Keccak256Hash([]byte("TokenExchangeUnderlying(address,int128,uint256,int128,uint256)"))
)

// CurveParser implements the Parser interface for Curve StableSwap pools
type CurveParser struct {
	cache  cache.PoolCache
	logger mevtypes.Logger
}

// NewCurveParser creates a new Curve parser
func NewCurveParser(cache cache.PoolCache, logger mevtypes.Logger) *CurveParser {
	return &CurveParser{
		cache:  cache,
		logger: logger,
	}
}

// Protocol returns the protocol type this parser handles
func (p *CurveParser) Protocol() mevtypes.ProtocolType {
	return mevtypes.ProtocolCurve
}

// SupportsLog checks if this parser can handle the given log
func (p *CurveParser) SupportsLog(log types.Log) bool {
	// Check if log has the TokenExchange or TokenExchangeUnderlying event signature
	if len(log.Topics) == 0 {
		return false
	}
	return log.Topics[0] == CurveTokenExchangeSignature ||
		log.Topics[0] == CurveTokenExchangeUnderlyingSignature
}

// ParseLog parses a Curve TokenExchange event from a log
func (p *CurveParser) ParseLog(ctx context.Context, log types.Log, tx *types.Transaction) (*mevtypes.SwapEvent, error) {
	// Verify this is a TokenExchange event
	if !p.SupportsLog(log) {
		return nil, fmt.Errorf("unsupported log")
	}

	// Get pool info from cache to extract token addresses and decimals
	poolInfo, err := p.cache.GetByAddress(ctx, log.Address)
	if err != nil {
		return nil, fmt.Errorf("pool not found in cache: %w", err)
	}

	// Parse event data
	// Data contains: sold_id, tokens_sold, bought_id, tokens_bought (non-indexed)
	// Topics contain: [signature, buyer] (indexed)
	if len(log.Topics) != 2 {
		return nil, fmt.Errorf("invalid number of topics: expected 2, got %d", len(log.Topics))
	}

	// Define ABI for data decoding
	int128Type, err := abi.NewType("int128", "", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create int128 type: %w", err)
	}

	uint256Type, err := abi.NewType("uint256", "", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create uint256 type: %w", err)
	}

	arguments := abi.Arguments{
		{Type: int128Type, Name: "sold_id"},
		{Type: uint256Type, Name: "tokens_sold"},
		{Type: int128Type, Name: "bought_id"},
		{Type: uint256Type, Name: "tokens_bought"},
	}

	// Decode data
	values, err := arguments.Unpack(log.Data)
	if err != nil {
		return nil, fmt.Errorf("failed to decode event data: %w", err)
	}

	if len(values) != 4 {
		return nil, fmt.Errorf("invalid number of values: expected 4, got %d", len(values))
	}

	// Extract buyer from topics
	buyer := common.BytesToAddress(log.Topics[1].Bytes())

	// Extract coin indices and amounts
	soldID := values[0].(*big.Int)
	tokensSold := values[1].(*big.Int)
	boughtID := values[2].(*big.Int)
	tokensBought := values[3].(*big.Int)

	// Convert coin indices to uint
	soldIndex := int(soldID.Int64())
	boughtIndex := int(boughtID.Int64())

	// Determine which token is token0 and token1
	// Curve pools typically have 2-4 coins, we'll handle the common case of 2 coins
	var token0, token1 common.Address
	var token0Decimals, token1Decimals uint8
	var amount0In, amount1In, amount0Out, amount1Out *big.Int

	// Map coin indices to tokens
	// For simplicity, we assume sold_id < bought_id means token0 → token1
	if soldIndex == 0 && boughtIndex == 1 {
		// Selling token0 for token1
		token0 = poolInfo.Token0
		token1 = poolInfo.Token1
		token0Decimals = poolInfo.Token0Decimals
		token1Decimals = poolInfo.Token1Decimals
		amount0In = tokensSold
		amount1In = big.NewInt(0)
		amount0Out = big.NewInt(0)
		amount1Out = tokensBought
	} else if soldIndex == 1 && boughtIndex == 0 {
		// Selling token1 for token0
		token0 = poolInfo.Token0
		token1 = poolInfo.Token1
		token0Decimals = poolInfo.Token0Decimals
		token1Decimals = poolInfo.Token1Decimals
		amount0In = big.NewInt(0)
		amount1In = tokensSold
		amount0Out = tokensBought
		amount1Out = big.NewInt(0)
	} else {
		// For multi-coin pools (3+ coins), we need more complex logic
		// For now, we'll use the pool's token0 and token1 as defaults
		token0 = poolInfo.Token0
		token1 = poolInfo.Token1
		token0Decimals = poolInfo.Token0Decimals
		token1Decimals = poolInfo.Token1Decimals

		// Assume if sold_id is 0, we're selling token0
		if soldIndex == 0 {
			amount0In = tokensSold
			amount1In = big.NewInt(0)
			amount0Out = big.NewInt(0)
			amount1Out = tokensBought
		} else {
			amount0In = big.NewInt(0)
			amount1In = tokensSold
			amount0Out = tokensBought
			amount1Out = big.NewInt(0)
		}
	}

	// Scale amounts to 18 decimals for internal representation
	amount0InScaled := mevtypes.ScaleToDecimals(amount0In, token0Decimals, 18)
	amount1InScaled := mevtypes.ScaleToDecimals(amount1In, token1Decimals, 18)
	amount0OutScaled := mevtypes.ScaleToDecimals(amount0Out, token0Decimals, 18)
	amount1OutScaled := mevtypes.ScaleToDecimals(amount1Out, token1Decimals, 18)

	// Create swap event
	event := &mevtypes.SwapEvent{
		TxHash:         tx.Hash(),
		BlockNumber:    log.BlockNumber,
		LogIndex:       uint(log.Index),
		PoolAddress:    log.Address,
		Protocol:       mevtypes.ProtocolCurve,
		Token0:         token0,
		Token1:         token1,
		Token0Decimals: token0Decimals,
		Token1Decimals: token1Decimals,
		Amount0In:      amount0InScaled,
		Amount1In:      amount1InScaled,
		Amount0Out:     amount0OutScaled,
		Amount1Out:     amount1OutScaled,
		Sender:         buyer,
		Recipient:      buyer, // In Curve, buyer is both sender and recipient
		Fee:            big.NewInt(int64(poolInfo.Fee)), // Curve pools have variable fees
	}

	// Validate the parsed event
	if err := event.Validate(); err != nil {
		return nil, fmt.Errorf("validation failed: %w", err)
	}

	p.logger.Debug("parsed Curve swap event",
		"txHash", event.TxHash.Hex(),
		"pool", event.PoolAddress.Hex(),
		"soldID", soldIndex,
		"boughtID", boughtIndex,
		"tokensSold", tokensSold.String(),
		"tokensBought", tokensBought.String(),
	)

	return event, nil
}

// ParseReceipt parses all Curve TokenExchange events from a transaction receipt
func (p *CurveParser) ParseReceipt(ctx context.Context, receipt *types.Receipt, tx *types.Transaction) ([]*mevtypes.SwapEvent, error) {
	var events []*mevtypes.SwapEvent

	for _, log := range receipt.Logs {
		if p.SupportsLog(*log) {
			event, err := p.ParseLog(ctx, *log, tx)
			if err != nil {
				// Log error but continue processing other logs
				p.logger.Warn("failed to parse log",
					"txHash", tx.Hash().Hex(),
					"logIndex", log.Index,
					"error", err,
				)
				continue
			}
			events = append(events, event)
		}
	}

	return events, nil
}