package discovery

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

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

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

// ArbitrageCalculator handles arbitrage opportunity calculations
type ArbitrageCalculator struct {
	logger   *logger.Logger
	config   *ArbitrageConfig
	mathCalc *exchangeMath.MathCalculator
}

// NewArbitrageCalculator creates a new arbitrage calculator
func NewArbitrageCalculator(logger *logger.Logger, config *ArbitrageConfig, mathCalc *exchangeMath.MathCalculator) *ArbitrageCalculator {
	return &ArbitrageCalculator{
		logger:   logger,
		config:   config,
		mathCalc: mathCalc,
	}
}

// findArbitrageOpportunities finds arbitrage opportunities across all pools
func (ac *ArbitrageCalculator) findArbitrageOpportunities(ctx context.Context, gasPrice *big.Int, pools map[common.Address]*PoolInfoDetailed, logger *logger.Logger, config *ArbitrageConfig, mathCalc *exchangeMath.MathCalculator) []*ArbitrageOpportunityDetailed {
	opportunities := make([]*ArbitrageOpportunityDetailed, 0)

	// Group pools by token pairs
	tokenPairPools := ac.groupPoolsByTokenPairs(pools)

	// Check each token pair for arbitrage
	for tokenPair, pools := range tokenPairPools {
		if len(pools) < 2 {
			continue // Need at least 2 pools for arbitrage
		}

		// Check all pool combinations
		for i := 0; i < len(pools); i++ {
			for j := i + 1; j < len(pools); j++ {
				poolA := pools[i]
				poolB := pools[j]

				// Skip if same factory type (no arbitrage opportunity)
				if poolA.FactoryType == poolB.FactoryType {
					continue
				}

				// Calculate arbitrage
				arb := ac.calculateArbitrage(poolA, poolB, gasPrice, tokenPair, mathCalc)
				if arb != nil && arb.NetProfit.Sign() > 0 {
					opportunities = append(opportunities, arb)
				}
			}
		}
	}

	// Sort by net profit (highest first)
	for i := 0; i < len(opportunities)-1; i++ {
		for j := i + 1; j < len(opportunities); j++ {
			if opportunities[i].NetProfit.Cmp(opportunities[j].NetProfit) < 0 {
				opportunities[i], opportunities[j] = opportunities[j], opportunities[i]
			}
		}
	}

	return opportunities
}

// calculateArbitrage calculates arbitrage between two pools
func (ac *ArbitrageCalculator) calculateArbitrage(poolA, poolB *PoolInfoDetailed, gasPrice *big.Int, tokenPair string, mathCalc *exchangeMath.MathCalculator) *ArbitrageOpportunityDetailed {
	// Skip pools with zero or nil reserves (uninitialized pools)
	if poolA.Reserve0 == nil || poolA.Reserve1 == nil || poolB.Reserve0 == nil || poolB.Reserve1 == nil ||
		poolA.Reserve0.Sign() <= 0 || poolA.Reserve1.Sign() <= 0 || poolB.Reserve0.Sign() <= 0 || poolB.Reserve1.Sign() <= 0 {
		return nil
	}

	// Get math calculators for each pool type
	mathA := mathCalc.GetMathForExchange(poolA.FactoryType)
	mathB := mathCalc.GetMathForExchange(poolB.FactoryType)

	// Get spot prices
	priceA, err := mathA.GetSpotPrice(poolA.Reserve0, poolA.Reserve1)
	if err != nil {
		return nil
	}

	// Check if priceA is valid (not zero, infinity, or NaN)
	priceAFloat, _ := priceA.Float64()
	if priceA.Cmp(big.NewFloat(0)) == 0 || math.IsInf(priceAFloat, 0) || math.IsNaN(priceAFloat) {
		return nil // Invalid priceA value
	}

	priceB, err := mathB.GetSpotPrice(poolB.Reserve0, poolB.Reserve1)
	if err != nil {
		return nil
	}

	// Check if priceB is valid (not zero, infinity, or NaN)
	priceBFloat, _ := priceB.Float64()
	if priceB.Cmp(big.NewFloat(0)) == 0 || math.IsInf(priceBFloat, 0) || math.IsNaN(priceBFloat) {
		return nil // Invalid priceB value
	}

	// Calculate price difference
	priceDiff := new(big.Float).Sub(priceA, priceB)

	// Additional check if priceA is infinity, NaN, or zero before division
	priceAFloatCheck, _ := priceA.Float64()
	priceBFloatCheck, _ := priceB.Float64()

	if math.IsNaN(priceAFloatCheck) || math.IsNaN(priceBFloatCheck) ||
		math.IsInf(priceAFloatCheck, 0) || math.IsInf(priceBFloatCheck, 0) ||
		priceA.Cmp(big.NewFloat(0)) == 0 {
		return nil // Invalid price values
	}

	// Perform the division
	priceDiff.Quo(priceDiff, priceA)

	// Check if the result of the division is valid (not NaN or Infinity)
	priceDiffFloat, accuracy := priceDiff.Float64()
	if math.IsNaN(priceDiffFloat) || math.IsInf(priceDiffFloat, 0) || accuracy != big.Exact {
		return nil // Invalid price difference value
	}

	// Check if price difference exceeds minimum threshold
	minThreshold, exists := ac.config.ProfitMargins["arbitrage"]
	if !exists {
		minThreshold = 0.001 // Default to 0.1% if not specified
	}
	if abs(priceDiffFloat) < minThreshold {
		return nil
	}

	// Calculate optimal arbitrage amount (simplified)
	amountIn := big.NewInt(100000000000000000) // 0.1 ETH test amount

	// Calculate amounts
	amountOutA, _ := mathA.CalculateAmountOut(amountIn, poolA.Reserve0, poolA.Reserve1, poolA.Fee)
	if amountOutA == nil {
		return nil
	}

	amountOutB, _ := mathB.CalculateAmountIn(amountOutA, poolB.Reserve1, poolB.Reserve0, poolB.Fee)
	if amountOutB == nil {
		return nil
	}

	// Calculate profit
	profit := new(big.Int).Sub(amountOutB, amountIn)
	if profit.Sign() <= 0 {
		return nil
	}

	// Calculate gas cost
	gasCost := new(big.Int).Mul(gasPrice, big.NewInt(300000)) // ~300k gas

	// Net profit
	netProfit := new(big.Int).Sub(profit, gasCost)
	if netProfit.Sign() <= 0 {
		return nil
	}

	// Convert to USD (simplified - assume ETH price)
	profitUSD := float64(netProfit.Uint64()) / 1e18 * 2000 // Assume $2000 ETH

	if profitUSD < ac.config.MinProfitUSD {
		return nil
	}

	// Calculate price impacts with validation
	priceImpactA, errA := mathA.CalculatePriceImpact(amountIn, poolA.Reserve0, poolA.Reserve1)
	priceImpactB, errB := mathB.CalculatePriceImpact(amountOutA, poolB.Reserve1, poolB.Reserve0)

	// Validate price impacts to prevent NaN or Infinity
	if errA != nil || errB != nil {
		return nil
	}

	// Check if price impacts are valid numbers
	if math.IsNaN(priceImpactA) || math.IsInf(priceImpactA, 0) ||
		math.IsNaN(priceImpactB) || math.IsInf(priceImpactB, 0) {
		return nil
	}

	return &ArbitrageOpportunityDetailed{
		ID:                fmt.Sprintf("arb_%d_%s", time.Now().Unix(), tokenPair),
		Type:              "arbitrage",
		TokenIn:           poolA.Token0,
		TokenOut:          poolA.Token1,
		AmountIn:          amountIn,
		ExpectedAmountOut: amountOutA,
		ActualAmountOut:   amountOutB,
		Profit:            profit,
		ProfitUSD:         profitUSD,
		ProfitMargin:      priceDiffFloat,
		GasCost:           gasCost,
		NetProfit:         netProfit,
		ExchangeA:         poolA.FactoryType,
		ExchangeB:         poolB.FactoryType,
		PoolA:             poolA.Address,
		PoolB:             poolB.Address,
		PriceImpactA:      priceImpactA,
		PriceImpactB:      priceImpactB,
		Confidence:        0.8,
		RiskScore:         0.3,
		ExecutionTime:     time.Duration(15) * time.Second,
		Timestamp:         time.Now(),
	}
}

// Helper methods
func abs(x float64) float64 {
	if x < 0 {
		return -x
	}
	return x
}

// groupPoolsByTokenPairs groups pools by token pairs
func (ac *ArbitrageCalculator) groupPoolsByTokenPairs(pools map[common.Address]*PoolInfoDetailed) map[string][]*PoolInfoDetailed {
	groups := make(map[string][]*PoolInfoDetailed)

	for _, pool := range pools {
		if !pool.Active {
			continue
		}

		// Create token pair key (sorted)
		var pairKey string
		if pool.Token0.Big().Cmp(pool.Token1.Big()) < 0 {
			pairKey = fmt.Sprintf("%s-%s", pool.Token0.Hex(), pool.Token1.Hex())
		} else {
			pairKey = fmt.Sprintf("%s-%s", pool.Token1.Hex(), pool.Token0.Hex())
		}

		groups[pairKey] = append(groups[pairKey], pool)
	}

	return groups
}