package market

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

	"github.com/your-username/mev-beta/internal/config"
	"github.com/your-username/mev-beta/internal/logger"
	"github.com/your-username/mev-beta/pkg/scanner"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/holiman/uint256"
)

// Pipeline processes transactions through multiple stages
type Pipeline struct {
	config       *config.BotConfig
	logger       *logger.Logger
	marketMgr    *MarketManager
	scanner      *scanner.MarketScanner
	stages       []PipelineStage
	bufferSize   int
	concurrency  int
}

// PipelineStage represents a stage in the processing pipeline
type PipelineStage func(context.Context, <-chan *types.Transaction, chan<- *scanner.SwapDetails) error

// NewPipeline creates a new transaction processing pipeline
func NewPipeline(
	cfg *config.BotConfig,
	logger *logger.Logger,
	marketMgr *MarketManager,
	scanner *scanner.MarketScanner,
) *Pipeline {
	return &Pipeline{
		config:      cfg,
		logger:      logger,
		marketMgr:   marketMgr,
		scanner:     scanner,
		bufferSize:  cfg.ChannelBufferSize,
		concurrency: cfg.MaxWorkers,
	}
}

// AddStage adds a processing stage to the pipeline
func (p *Pipeline) AddStage(stage PipelineStage) {
	p.stages = append(p.stages, stage)
}

// ProcessTransactions processes a batch of transactions through the pipeline
func (p *Pipeline) ProcessTransactions(ctx context.Context, transactions []*types.Transaction) error {
	if len(p.stages) == 0 {
		return fmt.Errorf("no pipeline stages configured")
	}

	// Create the initial input channel
	inputChan := make(chan *types.Transaction, p.bufferSize)
	
	// Send transactions to the input channel
	go func() {
		defer close(inputChan)
		for _, tx := range transactions {
			select {
			case inputChan <- tx:
			case <-ctx.Done():
				return
			}
		}
	}()

	// Process through each stage
	var currentChan <-chan *scanner.SwapDetails = nil
	
	for i, stage := range p.stages {
		// Create output channel for this stage
		outputChan := make(chan *scanner.SwapDetails, p.bufferSize)
		
		// For the first stage, we need to convert transactions to swap details
		if i == 0 {
			// Special handling for first stage
			go func(stage PipelineStage, input <-chan *types.Transaction, output chan<- *scanner.SwapDetails) {
				defer close(output)
				err := stage(ctx, input, output)
				if err != nil {
					p.logger.Error(fmt.Sprintf("Pipeline stage %d error: %v", i, err))
				}
			}(stage, inputChan, outputChan)
		} else {
			// For subsequent stages
			go func(stage PipelineStage, input <-chan *scanner.SwapDetails, output chan<- *scanner.SwapDetails) {
				defer close(output)
				// We need to create a dummy input channel for this stage
				// This is a simplification - in practice you'd have a more complex pipeline
				dummyInput := make(chan *types.Transaction, p.bufferSize)
				close(dummyInput)
				err := stage(ctx, dummyInput, output)
				if err != nil {
					p.logger.Error(fmt.Sprintf("Pipeline stage %d error: %v", i, err))
				}
			}(stage, currentChan, outputChan)
		}
		
		currentChan = outputChan
	}
	
	// Process the final output
	if currentChan != nil {
		go p.processSwapDetails(ctx, currentChan)
	}
	
	return nil
}

// processSwapDetails processes the final output of the pipeline
func (p *Pipeline) processSwapDetails(ctx context.Context, swapDetails <-chan *scanner.SwapDetails) {
	for {
		select {
		case swap, ok := <-swapDetails:
			if !ok {
				return // Channel closed
			}
			
			// Submit to the market scanner for processing
			p.scanner.SubmitSwap(*swap)
			
		case <-ctx.Done():
			return
		}
	}
}

// TransactionDecoderStage decodes transactions to identify swap opportunities
func TransactionDecoderStage(
	cfg *config.BotConfig,
	logger *logger.Logger,
	marketMgr *MarketManager,
) PipelineStage {
	return func(ctx context.Context, input <-chan *types.Transaction, output chan<- *scanner.SwapDetails) error {
		var wg sync.WaitGroup
		
		// Process transactions concurrently
		for i := 0; i < cfg.MaxWorkers; i++ {
			wg.Add(1)
			go func() {
				defer wg.Done()
				for {
					select {
					case tx, ok := <-input:
						if !ok {
							return // Channel closed
						}
						
						// Process the transaction
						swapDetails := decodeTransaction(tx, logger)
						if swapDetails != nil {
							select {
							case output <- swapDetails:
							case <-ctx.Done():
								return
							}
						}
						
					case <-ctx.Done():
						return
					}
				}
			}()
		}
		
		// Wait for all workers to finish
		go func() {
			wg.Wait()
			close(output)
		}()
		
		return nil
	}
}

// decodeTransaction decodes a transaction to extract swap details
func decodeTransaction(tx *types.Transaction, logger *logger.Logger) *scanner.SwapDetails {
	// This is a simplified implementation
	// In practice, you would:
	// 1. Check if the transaction is calling a Uniswap-like contract
	// 2. Decode the function call data
	// 3. Extract token addresses, amounts, etc.
	
	// For now, we'll return mock data for demonstration
	if tx.To() != nil {
		swap := &scanner.SwapDetails{
			PoolAddress:    tx.To().Hex(),
			Token0:         "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48", // USDC
			Token1:         "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2", // WETH
			Amount0In:      big.NewInt(1000000000), // 1000 USDC
			Amount0Out:     big.NewInt(0),
			Amount1In:      big.NewInt(0),
			Amount1Out:     big.NewInt(500000000000000000), // 0.5 WETH
			SqrtPriceX96:   uint256.NewInt(2505414483750470000),
			Liquidity:      uint256.NewInt(1000000000000000000),
			Tick:           200000,
			Timestamp:      time.Now(),
			TransactionHash: tx.Hash(),
		}
		
		logger.Debug(fmt.Sprintf("Decoded swap transaction: %s", tx.Hash().Hex()))
		return swap
	}
	
	return nil
}

// MarketAnalysisStage performs market analysis on swap details
func MarketAnalysisStage(
	cfg *config.BotConfig,
	logger *logger.Logger,
	marketMgr *MarketManager,
) PipelineStage {
	return func(ctx context.Context, input <-chan *types.Transaction, output chan<- *scanner.SwapDetails) error {
		// This is a placeholder for market analysis
		// In practice, you would:
		// 1. Get pool data from market manager
		// 2. Analyze price impact
		// 3. Check for arbitrage opportunities
		
		close(output)
		return nil
	}
}

// ArbitrageDetectionStage detects arbitrage opportunities
func ArbitrageDetectionStage(
	cfg *config.BotConfig,
	logger *logger.Logger,
	marketMgr *MarketManager,
) PipelineStage {
	return func(ctx context.Context, input <-chan *types.Transaction, output chan<- *scanner.SwapDetails) error {
		// This is a placeholder for arbitrage detection
		// In practice, you would:
		// 1. Compare prices across multiple pools
		// 2. Calculate potential profit
		// 3. Filter based on profitability
		
		close(output)
		return nil
	}
}