package execution

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

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

	"github.com/your-org/mev-bot/pkg/arbitrage"
)

// ExecutorConfig contains configuration for the executor
type ExecutorConfig struct {
	// Wallet
	PrivateKey    []byte
	WalletAddress common.Address

	// RPC configuration
	RPCEndpoint        string
	PrivateRPCEndpoint string // Optional private RPC (e.g., Flashbots)
	UsePrivateRPC      bool

	// Transaction settings
	ConfirmationBlocks uint64
	TimeoutPerTx       time.Duration
	MaxRetries         int
	RetryDelay         time.Duration

	// Nonce management
	NonceMargin uint64 // Number of nonces to keep ahead

	// Gas price strategy
	GasPriceStrategy     string  // "fast", "market", "aggressive"
	GasPriceMultiplier   float64 // Multiplier for gas price
	MaxGasPriceIncrement float64 // Max increase for replacement txs

	// Monitoring
	MonitorInterval time.Duration
	CleanupInterval time.Duration
}

// DefaultExecutorConfig returns default executor configuration
func DefaultExecutorConfig() *ExecutorConfig {
	return &ExecutorConfig{
		ConfirmationBlocks:   1,
		TimeoutPerTx:         5 * time.Minute,
		MaxRetries:           3,
		RetryDelay:           5 * time.Second,
		NonceMargin:          2,
		GasPriceStrategy:     "fast",
		GasPriceMultiplier:   1.1, // 10% above market
		MaxGasPriceIncrement: 1.5, // 50% max increase
		MonitorInterval:      1 * time.Second,
		CleanupInterval:      1 * time.Minute,
	}
}

// Executor executes arbitrage transactions
type Executor struct {
	config *ExecutorConfig
	logger *slog.Logger

	// Clients
	client        *ethclient.Client
	privateClient *ethclient.Client // Optional

	// Components
	builder      *TransactionBuilder
	riskManager  *RiskManager
	flashloanMgr *FlashloanManager

	// Nonce management
	mu           sync.Mutex
	currentNonce uint64
	nonceCache   map[uint64]*PendingTransaction

	// Monitoring
	stopCh  chan struct{}
	stopped bool
}

// PendingTransaction tracks a pending transaction
type PendingTransaction struct {
	Hash        common.Hash
	Nonce       uint64
	Opportunity *arbitrage.Opportunity
	SubmittedAt time.Time
	LastChecked time.Time
	Confirmed   bool
	Failed      bool
	FailReason  string
	Receipt     *types.Receipt
	Retries     int
}

// NewExecutor creates a new executor
func NewExecutor(
	config *ExecutorConfig,
	builder *TransactionBuilder,
	riskManager *RiskManager,
	flashloanMgr *FlashloanManager,
	logger *slog.Logger,
) (*Executor, error) {
	if config == nil {
		config = DefaultExecutorConfig()
	}

	// Connect to RPC
	client, err := ethclient.Dial(config.RPCEndpoint)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to RPC: %w", err)
	}

	var privateClient *ethclient.Client
	if config.UsePrivateRPC && config.PrivateRPCEndpoint != "" {
		privateClient, err = ethclient.Dial(config.PrivateRPCEndpoint)
		if err != nil {
			logger.Warn("failed to connect to private RPC", "error", err)
		}
	}

	executor := &Executor{
		config:        config,
		logger:        logger.With("component", "executor"),
		client:        client,
		privateClient: privateClient,
		builder:       builder,
		riskManager:   riskManager,
		flashloanMgr:  flashloanMgr,
		nonceCache:    make(map[uint64]*PendingTransaction),
		stopCh:        make(chan struct{}),
	}

	// Initialize nonce
	err = executor.initializeNonce(context.Background())
	if err != nil {
		return nil, fmt.Errorf("failed to initialize nonce: %w", err)
	}

	// Start monitoring
	go executor.monitorTransactions()
	go executor.cleanupOldTransactions()

	return executor, nil
}

// ExecutionResult contains the result of an execution
type ExecutionResult struct {
	Success      bool
	TxHash       common.Hash
	Receipt      *types.Receipt
	ActualProfit *big.Int
	GasCost      *big.Int
	Error        error
	Duration     time.Duration
}

// Execute executes an arbitrage opportunity
func (e *Executor) Execute(ctx context.Context, opp *arbitrage.Opportunity) (*ExecutionResult, error) {
	startTime := time.Now()

	e.logger.Info("executing opportunity",
		"opportunityID", opp.ID,
		"type", opp.Type,
		"expectedProfit", opp.NetProfit.String(),
	)

	// Build transaction
	tx, err := e.builder.BuildTransaction(ctx, opp, e.config.WalletAddress)
	if err != nil {
		return &ExecutionResult{
			Success:  false,
			Error:    fmt.Errorf("failed to build transaction: %w", err),
			Duration: time.Since(startTime),
		}, nil
	}

	// Risk assessment
	assessment, err := e.riskManager.AssessRisk(ctx, opp, tx)
	if err != nil {
		return &ExecutionResult{
			Success:  false,
			Error:    fmt.Errorf("failed to assess risk: %w", err),
			Duration: time.Since(startTime),
		}, nil
	}

	if !assessment.Approved {
		return &ExecutionResult{
			Success:  false,
			Error:    fmt.Errorf("risk assessment failed: %s", assessment.Reason),
			Duration: time.Since(startTime),
		}, nil
	}

	// Log warnings if any
	for _, warning := range assessment.Warnings {
		e.logger.Warn("risk warning", "warning", warning)
	}

	// Submit transaction
	hash, err := e.submitTransaction(ctx, tx, opp)
	if err != nil {
		return &ExecutionResult{
			Success:  false,
			Error:    fmt.Errorf("failed to submit transaction: %w", err),
			Duration: time.Since(startTime),
		}, nil
	}

	e.logger.Info("transaction submitted",
		"hash", hash.Hex(),
		"opportunityID", opp.ID,
	)

	// Wait for confirmation
	receipt, err := e.waitForConfirmation(ctx, hash)
	if err != nil {
		return &ExecutionResult{
			Success:  false,
			TxHash:   hash,
			Error:    fmt.Errorf("transaction failed: %w", err),
			Duration: time.Since(startTime),
		}, nil
	}

	// Calculate actual profit
	actualProfit := e.calculateActualProfit(receipt, opp)
	gasCost := new(big.Int).Mul(receipt.GasUsed, receipt.EffectiveGasPrice)

	result := &ExecutionResult{
		Success:      receipt.Status == types.ReceiptStatusSuccessful,
		TxHash:       hash,
		Receipt:      receipt,
		ActualProfit: actualProfit,
		GasCost:      gasCost,
		Duration:     time.Since(startTime),
	}

	if result.Success {
		e.logger.Info("execution succeeded",
			"hash", hash.Hex(),
			"actualProfit", actualProfit.String(),
			"gasCost", gasCost.String(),
			"duration", result.Duration,
		)
		e.riskManager.RecordSuccess(hash, actualProfit)
	} else {
		e.logger.Error("execution failed",
			"hash", hash.Hex(),
			"status", receipt.Status,
		)
		e.riskManager.RecordFailure(hash, "transaction reverted")
	}

	return result, nil
}

// submitTransaction submits a transaction to the network
func (e *Executor) submitTransaction(ctx context.Context, tx *SwapTransaction, opp *arbitrage.Opportunity) (common.Hash, error) {
	// Get nonce
	nonce := e.getNextNonce()

	// Sign transaction
	signedTx, err := e.builder.SignTransaction(tx, nonce, e.config.PrivateKey)
	if err != nil {
		e.releaseNonce(nonce)
		return common.Hash{}, fmt.Errorf("failed to sign transaction: %w", err)
	}

	// Choose client (private or public)
	client := e.client
	if e.config.UsePrivateRPC && e.privateClient != nil {
		client = e.privateClient
		e.logger.Debug("using private RPC")
	}

	// Send transaction
	err = client.SendTransaction(ctx, signedTx)
	if err != nil {
		e.releaseNonce(nonce)
		return common.Hash{}, fmt.Errorf("failed to send transaction: %w", err)
	}

	hash := signedTx.Hash()

	// Track transaction
	e.trackPendingTransaction(nonce, hash, opp)
	e.riskManager.TrackTransaction(hash, opp, tx.MaxFeePerGas)

	return hash, nil
}

// waitForConfirmation waits for transaction confirmation
func (e *Executor) waitForConfirmation(ctx context.Context, hash common.Hash) (*types.Receipt, error) {
	timeoutCtx, cancel := context.WithTimeout(ctx, e.config.TimeoutPerTx)
	defer cancel()

	ticker := time.NewTicker(e.config.MonitorInterval)
	defer ticker.Stop()

	for {
		select {
		case <-timeoutCtx.Done():
			return nil, fmt.Errorf("transaction timeout")

		case <-ticker.C:
			receipt, err := e.client.TransactionReceipt(ctx, hash)
			if err != nil {
				// Transaction not yet mined
				continue
			}

			// Check confirmations
			currentBlock, err := e.client.BlockNumber(ctx)
			if err != nil {
				continue
			}

			confirmations := currentBlock - receipt.BlockNumber.Uint64()
			if confirmations >= e.config.ConfirmationBlocks {
				return receipt, nil
			}
		}
	}
}

// monitorTransactions monitors pending transactions
func (e *Executor) monitorTransactions() {
	ticker := time.NewTicker(e.config.MonitorInterval)
	defer ticker.Stop()

	for {
		select {
		case <-e.stopCh:
			return

		case <-ticker.C:
			e.checkPendingTransactions()
		}
	}
}

// checkPendingTransactions checks status of pending transactions
func (e *Executor) checkPendingTransactions() {
	e.mu.Lock()
	defer e.mu.Unlock()

	ctx := context.Background()

	for nonce, pending := range e.nonceCache {
		if pending.Confirmed || pending.Failed {
			continue
		}

		// Check transaction status
		receipt, err := e.client.TransactionReceipt(ctx, pending.Hash)
		if err != nil {
			// Still pending
			pending.LastChecked = time.Now()

			// Check for timeout
			if time.Since(pending.SubmittedAt) > e.config.TimeoutPerTx {
				e.logger.Warn("transaction timeout",
					"hash", pending.Hash.Hex(),
					"nonce", nonce,
				)

				// Attempt replacement
				if pending.Retries < e.config.MaxRetries {
					e.logger.Info("attempting transaction replacement",
						"hash", pending.Hash.Hex(),
						"retry", pending.Retries+1,
					)
					// In production, implement transaction replacement logic
					pending.Retries++
				} else {
					pending.Failed = true
					pending.FailReason = "timeout after retries"
					e.riskManager.RecordFailure(pending.Hash, "timeout")
					e.riskManager.UntrackTransaction(pending.Hash)
				}
			}
			continue
		}

		// Transaction mined
		pending.Receipt = receipt
		pending.Confirmed = true
		pending.LastChecked = time.Now()

		if receipt.Status == types.ReceiptStatusFailed {
			pending.Failed = true
			pending.FailReason = "transaction reverted"
			e.riskManager.RecordFailure(pending.Hash, "reverted")
		}

		e.riskManager.UntrackTransaction(pending.Hash)

		e.logger.Debug("transaction confirmed",
			"hash", pending.Hash.Hex(),
			"nonce", nonce,
			"status", receipt.Status,
		)
	}
}

// cleanupOldTransactions removes old completed transactions
func (e *Executor) cleanupOldTransactions() {
	ticker := time.NewTicker(e.config.CleanupInterval)
	defer ticker.Stop()

	for {
		select {
		case <-e.stopCh:
			return

		case <-ticker.C:
			e.mu.Lock()

			cutoff := time.Now().Add(-1 * time.Hour)
			for nonce, pending := range e.nonceCache {
				if (pending.Confirmed || pending.Failed) && pending.LastChecked.Before(cutoff) {
					delete(e.nonceCache, nonce)
				}
			}

			e.mu.Unlock()
		}
	}
}

// initializeNonce initializes the nonce from the network
func (e *Executor) initializeNonce(ctx context.Context) error {
	nonce, err := e.client.PendingNonceAt(ctx, e.config.WalletAddress)
	if err != nil {
		return fmt.Errorf("failed to get pending nonce: %w", err)
	}

	e.currentNonce = nonce
	e.logger.Info("initialized nonce", "nonce", nonce)

	return nil
}

// getNextNonce gets the next available nonce
func (e *Executor) getNextNonce() uint64 {
	e.mu.Lock()
	defer e.mu.Unlock()

	nonce := e.currentNonce
	e.currentNonce++

	return nonce
}

// releaseNonce releases a nonce back to the pool
func (e *Executor) releaseNonce(nonce uint64) {
	e.mu.Lock()
	defer e.mu.Unlock()

	// Only release if it's the current nonce - 1
	if nonce == e.currentNonce-1 {
		e.currentNonce = nonce
	}
}

// trackPendingTransaction tracks a pending transaction
func (e *Executor) trackPendingTransaction(nonce uint64, hash common.Hash, opp *arbitrage.Opportunity) {
	e.mu.Lock()
	defer e.mu.Unlock()

	e.nonceCache[nonce] = &PendingTransaction{
		Hash:        hash,
		Nonce:       nonce,
		Opportunity: opp,
		SubmittedAt: time.Now(),
		LastChecked: time.Now(),
		Confirmed:   false,
		Failed:      false,
	}
}

// calculateActualProfit calculates the actual profit from a receipt
func (e *Executor) calculateActualProfit(receipt *types.Receipt, opp *arbitrage.Opportunity) *big.Int {
	// In production, parse logs to get actual output amounts
	// For now, estimate based on expected profit and gas cost

	gasCost := new(big.Int).Mul(new(big.Int).SetUint64(receipt.GasUsed), receipt.EffectiveGasPrice)
	estimatedProfit := new(big.Int).Sub(opp.GrossProfit, gasCost)

	return estimatedProfit
}

// GetPendingTransactions returns all pending transactions
func (e *Executor) GetPendingTransactions() []*PendingTransaction {
	e.mu.Lock()
	defer e.mu.Unlock()

	txs := make([]*PendingTransaction, 0, len(e.nonceCache))
	for _, tx := range e.nonceCache {
		if !tx.Confirmed && !tx.Failed {
			txs = append(txs, tx)
		}
	}

	return txs
}

// Stop stops the executor
func (e *Executor) Stop() {
	if !e.stopped {
		close(e.stopCh)
		e.stopped = true
		e.logger.Info("executor stopped")
	}
}