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"
)

// BalancerPoolDetector implements PoolDetector for Balancer
type BalancerPoolDetector struct {
	client *ethclient.Client
	logger *logger.Logger
	config *ExchangeConfig
}

// NewBalancerPoolDetector creates a new Balancer pool detector
func NewBalancerPoolDetector(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig) *BalancerPoolDetector {
	return &BalancerPoolDetector{
		client: client,
		logger: logger,
		config: config,
	}
}

// GetAllPools returns all pools containing the specified tokens
func (d *BalancerPoolDetector) GetAllPools(token0, token1 common.Address) ([]common.Address, error) {
	// In a real implementation, this would query the Vault or pool registry 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 *BalancerPoolDetector) GetPoolForPair(token0, token1 common.Address) (common.Address, error) {
	// In a real implementation, this would query the registry for pools
	// containing both tokens
	poolAddress := common.HexToAddress("0x0") // Placeholder

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

// GetSupportedFeeTiers returns supported fee tiers for Balancer (varies by pool)
func (d *BalancerPoolDetector) GetSupportedFeeTiers() []int64 {
	// Balancer pools can have different fee tiers
	return []int64{100, 500, 1000, 5000} // 0.01%, 0.5%, 1%, 5% in basis points
}

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

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

// NewBalancerLiquidityFetcher creates a new Balancer liquidity fetcher
func NewBalancerLiquidityFetcher(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig, engine *math.ExchangePricingEngine) *BalancerLiquidityFetcher {
	return &BalancerLiquidityFetcher{
		client: client,
		logger: logger,
		config: config,
		engine: engine,
	}
}

// GetPoolData fetches pool information for Balancer
func (f *BalancerLiquidityFetcher) GetPoolData(poolAddress common.Address) (*math.PoolData, error) {
	// In a real implementation, this would call the pool contract to get reserves and weights
	// For now, return a placeholder pool data with Balancer-specific fields

	fee, err := math.NewUniversalDecimal(big.NewInt(250), 4, "FEE")
	if err != nil {
		return nil, fmt.Errorf("error creating fee decimal: %w", err)
	}

	reserve0Value := new(big.Int)
	reserve0Value.SetString("1000000000000000000000", 10) // WETH - 1000 ETH in wei
	reserve0, err := math.NewUniversalDecimal(reserve0Value, 18, "RESERVE0")
	if err != nil {
		return nil, fmt.Errorf("error creating reserve0 decimal: %w", err)
	}

	reserve1Value := new(big.Int)
	reserve1Value.SetString("1000000000000", 10) // USDC - 1000000 USDC in smallest units
	reserve1, err := math.NewUniversalDecimal(reserve1Value, 6, "RESERVE1")
	if err != nil {
		return nil, fmt.Errorf("error creating reserve1 decimal: %w", err)
	}

	weightsValue0 := new(big.Int)
	weightsValue0.SetString("5000", 10) // 50% weight
	weightsValue1 := new(big.Int)
	weightsValue1.SetString("5000", 10) // 50% weight

	weight0, err := math.NewUniversalDecimal(weightsValue0, 4, "WEIGHT0")
	if err != nil {
		return nil, fmt.Errorf("error creating weight0 decimal: %w", err)
	}

	weight1, err := math.NewUniversalDecimal(weightsValue1, 4, "WEIGHT1")
	if err != nil {
		return nil, fmt.Errorf("error creating weight1 decimal: %w", err)
	}

	swapFeeRateValue := new(big.Int)
	swapFeeRateValue.SetString("250", 10) // 0.25%
	swapFeeRate, err := math.NewUniversalDecimal(swapFeeRateValue, 4, "SWAP_FEE_RATE")
	if err != nil {
		return nil, fmt.Errorf("error creating swap fee rate decimal: %w", err)
	}

	return &math.PoolData{
		Address:      poolAddress.Hex(),
		ExchangeType: math.ExchangeBalancer,
		Fee:          fee,
		Token0:       math.TokenInfo{Address: "0x0", Symbol: "WETH", Decimals: 18},
		Token1:       math.TokenInfo{Address: "0x1", Symbol: "USDC", Decimals: 6},
		Reserve0:     reserve0,
		Reserve1:     reserve1,
		Weights: []*math.UniversalDecimal{
			weight0, // 50% weight
			weight1, // 50% weight
		},
		SwapFeeRate: swapFeeRate,
	}, nil
}

// GetTokenReserves fetches reserves for a specific token pair in a pool
func (f *BalancerLiquidityFetcher) 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
	reserve0 := new(big.Int)
	reserve0.SetString("1000000000000000000000", 10) // WETH - 1000 ETH in wei
	reserve1 := new(big.Int)
	reserve1.SetString("1000000000000", 10) // USDC - 1000000 USDC in smallest units
	return reserve0, reserve1, nil
}

// GetPoolPrice calculates the price of token1 in terms of token0 using Balancer's weighted formula
func (f *BalancerLiquidityFetcher) 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 using Balancer's weighted formula
func (f *BalancerLiquidityFetcher) GetLiquidityDepth(poolAddress, tokenIn common.Address, amount *big.Int) (*big.Int, error) {
	// In a real implementation, this would calculate liquidity with Balancer's weighted formula
	return amount, nil
}

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

// NewBalancerSwapRouter creates a new Balancer swap router
func NewBalancerSwapRouter(client *ethclient.Client, logger *logger.Logger, config *ExchangeConfig, engine *math.ExchangePricingEngine) *BalancerSwapRouter {
	return &BalancerSwapRouter{
		client: client,
		logger: logger,
		config: config,
		engine: engine,
	}
}

// CalculateSwap calculates the expected output amount for a swap using Balancer's weighted formula
func (r *BalancerSwapRouter) 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 using Balancer's weighted formula
	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 *BalancerSwapRouter) findPoolForPair(token0, token1 common.Address) (common.Address, error) {
	// In a real implementation, this would query the Balancer Vault or registry 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 *BalancerSwapRouter) GetPoolData(poolAddress common.Address) (*math.PoolData, error) {
	fetcher := NewBalancerLiquidityFetcher(r.client, r.logger, r.config, r.engine)
	return fetcher.GetPoolData(poolAddress)
}

// GenerateSwapData generates the calldata for a swap transaction using Balancer's batchSwap
func (r *BalancerSwapRouter) 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 Balancer, this would typically be batchSwap or singleSwap
	return []byte{}, nil
}

// GetSwapRoute returns the route for a swap (for Balancer, this can involve multiple tokens in a pool)
func (r *BalancerSwapRouter) GetSwapRoute(tokenIn, tokenOut common.Address) ([]common.Address, error) {
	// For Balancer, the route could be within a multi-token pool
	// For now, return the token pair as a direct route in the pool
	return []common.Address{tokenIn, tokenOut}, nil
}

// ValidateSwap validates a Balancer swap before execution
func (r *BalancerSwapRouter) 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
}

// RegisterBalancerWithRegistry registers Balancer implementation with the exchange registry
func RegisterBalancerWithRegistry(registry *ExchangeRegistry) error {
	config := &ExchangeConfig{
		Type:                   math.ExchangeBalancer,
		Name:                   "Balancer",
		FactoryAddress:         common.HexToAddress("0x47b489bf5836f83abd8a1514a8b289b4f5a8a189"), // Balancer V2 Weighted Pool Factory placeholder
		RouterAddress:          common.HexToAddress("0xba12222222228d8ba445958a75a0704d566bf2c8"), // Balancer Vault
		PoolInitCodeHash:       "",
		SwapSelector:           []byte{0x3e, 0x2, 0x76, 0x5e}, // swap function
		StableSwapSelector:     []byte{},
		ChainID:                1, // Ethereum mainnet
		SupportsFlashSwaps:     true,
		RequiresApproval:       true,
		MaxHops:                3,
		DefaultSlippagePercent: 0.3,
		Url:                    "https://balancer.fi",
		ApiUrl:                 "https://api.balancer.fi",
	}

	registry.exchanges[math.ExchangeBalancer] = config

	// Register the implementations as well
	return nil
}