package exchanges

import (
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"

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

// UniswapV2PoolDetector implements PoolDetector for Uniswap V2
type UniswapV2PoolDetector struct {
	client *ethclient.Client
	logger *logger.Logger
	config *ExchangeConfig
}

// NewUniswapV2PoolDetector creates a new Uniswap V2 pool detector
func NewUniswapV2PoolDetector(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig) *UniswapV2PoolDetector {
	return &UniswapV2PoolDetector{
		client: client,
		logger: logger,
		config: config,
	}
}

// GetAllPools returns all pools containing the specified tokens
func (d *UniswapV2PoolDetector) GetAllPools(token0, token1 common.Address) ([]common.Address, error) {
	// In a real implementation, this would query the factory contract
	// For now, we'll return an empty slice
	return []common.Address{}, nil
}

// GetPoolForPair returns the pool address for a specific token pair
func (d *UniswapV2PoolDetector) GetPoolForPair(token0, token1 common.Address) (common.Address, error) {
	// Calculate pool address using Uniswap V2 factory formula
	// In a real implementation, this would call the factory's getPair function
	poolAddress := common.HexToAddress("0x0") // Placeholder

	// For now, return empty address to indicate pool not found
	return poolAddress, nil
}

// GetSupportedFeeTiers returns supported fee tiers for Uniswap V2 (standard 0.3%)
func (d *UniswapV2PoolDetector) GetSupportedFeeTiers() []int64 {
	return []int64{3000} // 0.3% in basis points
}

// GetPoolType returns the pool type
func (d *UniswapV2PoolDetector) GetPoolType() string {
	return "uniswap_v2_constant_product"
}

// UniswapV2LiquidityFetcher implements LiquidityFetcher for Uniswap V2
type UniswapV2LiquidityFetcher struct {
	client *ethclient.Client
	logger *logger.Logger
	config *ExchangeConfig
	engine *math.ExchangePricingEngine
}

// NewUniswapV2LiquidityFetcher creates a new Uniswap V2 liquidity fetcher
func NewUniswapV2LiquidityFetcher(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig, engine *math.ExchangePricingEngine) *UniswapV2LiquidityFetcher {
	return &UniswapV2LiquidityFetcher{
		client: client,
		logger: logger,
		config: config,
		engine: engine,
	}
}

// GetPoolData fetches pool information for Uniswap V2
func (f *UniswapV2LiquidityFetcher) GetPoolData(poolAddress common.Address) (*math.PoolData, error) {
	// In a real implementation, this would call the pool contract to get reserves
	// For now, return a placeholder pool data

	fee, err := math.NewUniversalDecimal(big.NewInt(300), 4, "FEE") // 0.3%
	if err != nil {
		return nil, fmt.Errorf("error creating fee decimal: %w", err)
	}

	reserve0, err := math.NewUniversalDecimal(big.NewInt(1000000), 18, "RESERVE0")
	if err != nil {
		return nil, fmt.Errorf("error creating reserve0 decimal: %w", err)
	}

	reserve1, err := math.NewUniversalDecimal(big.NewInt(1000000), 18, "RESERVE1")
	if err != nil {
		return nil, fmt.Errorf("error creating reserve1 decimal: %w", err)
	}

	return &math.PoolData{
		Address:      poolAddress.Hex(),
		ExchangeType: math.ExchangeUniswapV2,
		Fee:          fee,
		Token0:       math.TokenInfo{Address: "0x0", Symbol: "TOKEN0", Decimals: 18},
		Token1:       math.TokenInfo{Address: "0x1", Symbol: "TOKEN1", Decimals: 18},
		Reserve0:     reserve0,
		Reserve1:     reserve1,
	}, nil
}

// GetTokenReserves fetches reserves for a specific token pair in a pool
func (f *UniswapV2LiquidityFetcher) GetTokenReserves(poolAddress, token0, token1 common.Address) (*big.Int, *big.Int, error) {
	// In a real implementation, this would query the pool contract
	// For now, return placeholder values
	return big.NewInt(1000000), big.NewInt(1000000), nil
}

// GetPoolPrice calculates the price of token1 in terms of token0
func (f *UniswapV2LiquidityFetcher) GetPoolPrice(poolAddress common.Address) (*big.Float, error) {
	poolData, err := f.GetPoolData(poolAddress)
	if err != nil {
		return nil, err
	}

	pricer, err := f.engine.GetExchangePricer(poolData.ExchangeType)
	if err != nil {
		return nil, err
	}

	spotPrice, err := pricer.GetSpotPrice(poolData)
	if err != nil {
		return nil, err
	}

	// Convert the UniversalDecimal Value to a *big.Float
	result := new(big.Float).SetInt(spotPrice.Value)
	return result, nil
}

// GetLiquidityDepth calculates the liquidity depth for an amount
func (f *UniswapV2LiquidityFetcher) GetLiquidityDepth(poolAddress, tokenIn common.Address, amount *big.Int) (*big.Int, error) {
	// In a real implementation, this would calculate how much of the token
	// can be swapped before the price impact becomes too large
	return amount, nil
}

// UniswapV2SwapRouter implements SwapRouter for Uniswap V2
type UniswapV2SwapRouter struct {
	client *ethclient.Client
	logger *logger.Logger
	config *ExchangeConfig
	engine *math.ExchangePricingEngine
}

// NewUniswapV2SwapRouter creates a new Uniswap V2 swap router
func NewUniswapV2SwapRouter(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig, engine *math.ExchangePricingEngine) *UniswapV2SwapRouter {
	return &UniswapV2SwapRouter{
		client: client,
		logger: logger,
		config: config,
		engine: engine,
	}
}

// CalculateSwap calculates the expected output amount for a swap
func (r *UniswapV2SwapRouter) CalculateSwap(tokenIn, tokenOut common.Address, amountIn *big.Int) (*big.Int, error) {
	// Find pool for the token pair
	poolAddress, err := r.findPoolForPair(tokenIn, tokenOut)
	if err != nil {
		return nil, fmt.Errorf("failed to find pool for pair: %w", err)
	}

	// Get pool data
	poolData, err := r.GetPoolData(poolAddress)
	if err != nil {
		return nil, fmt.Errorf("failed to get pool data: %w", err)
	}

	// Create a UniversalDecimal from the amountIn
	decimalAmountIn, err := math.NewUniversalDecimal(amountIn, 18, "AMOUNT_IN")
	if err != nil {
		return nil, fmt.Errorf("error creating amount in decimal: %w", err)
	}

	// Get the pricer
	pricer, err := r.engine.GetExchangePricer(poolData.ExchangeType)
	if err != nil {
		return nil, err
	}

	// Calculate amount out
	amountOut, err := pricer.CalculateAmountOut(decimalAmountIn, poolData)
	if err != nil {
		return nil, err
	}

	return amountOut.Value, nil
}

// findPoolForPair finds the pool address for a given token pair
func (r *UniswapV2SwapRouter) findPoolForPair(token0, token1 common.Address) (common.Address, error) {
	// In a real implementation, this would query the factory contract
	// For now, return a placeholder address
	return common.HexToAddress("0x0"), nil
}

// GetPoolData is a helper to fetch pool data (for internal use)
func (r *UniswapV2SwapRouter) GetPoolData(poolAddress common.Address) (*math.PoolData, error) {
	fetcher := NewUniswapV2LiquidityFetcher(r.client, r.logger, r.config, r.engine)
	return fetcher.GetPoolData(poolAddress)
}

// GenerateSwapData generates the calldata for a swap transaction
func (r *UniswapV2SwapRouter) GenerateSwapData(tokenIn, tokenOut common.Address, amountIn, minAmountOut *big.Int, deadline *big.Int) ([]byte, error) {
	// In a real implementation, this would generate the encoded function call
	// For Uniswap V2, this would typically be swapExactTokensForTokens
	return []byte{}, nil
}

// GetSwapRoute returns the route for a swap (for Uniswap V2, this is typically direct)
func (r *UniswapV2SwapRouter) GetSwapRoute(tokenIn, tokenOut common.Address) ([]common.Address, error) {
	// Uniswap V2 typically requires a direct swap
	return []common.Address{tokenIn, tokenOut}, nil
}

// ValidateSwap validates a swap before execution
func (r *UniswapV2SwapRouter) ValidateSwap(tokenIn, tokenOut common.Address, amountIn *big.Int) error {
	if amountIn.Sign() <= 0 {
		return fmt.Errorf("amountIn must be positive")
	}

	if tokenIn == tokenOut {
		return fmt.Errorf("tokenIn and tokenOut cannot be the same")
	}

	if tokenIn == common.HexToAddress("0x0") || tokenOut == common.HexToAddress("0x0") {
		return fmt.Errorf("invalid token addresses")
	}

	return nil
}

// RegisterUniswapV2WithRegistry registers Uniswap V2 implementation with the exchange registry
func RegisterUniswapV2WithRegistry(registry *ExchangeRegistry) error {
	config := &ExchangeConfig{
		Type:                   math.ExchangeUniswapV2,
		Name:                   "Uniswap V2",
		FactoryAddress:         common.HexToAddress("0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f"), // Uniswap V2 Factory on mainnet
		RouterAddress:          common.HexToAddress("0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D"), // Uniswap V2 Router on mainnet
		PoolInitCodeHash:       "0x96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f",
		SwapSelector:           []byte{0x18, 0x2d, 0x2e, 0xdb}, // swapExactTokensForTokens
		StableSwapSelector:     []byte{},
		ChainID:                1, // Ethereum mainnet
		SupportsFlashSwaps:     true,
		RequiresApproval:       true,
		MaxHops:                3,
		DefaultSlippagePercent: 0.5,
		Url:                    "https://uniswap.org",
		ApiUrl:                 "https://api.uniswap.org",
	}

	registry.exchanges[math.ExchangeUniswapV2] = config

	// Register the implementations as well
	return nil
}