mev-beta/pkg/transport/provider_pools.go

package transport

import (
	"context"
	"fmt"
	"os/exec"
	"strconv"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum/ethclient"
	"github.com/ethereum/go-ethereum/rpc"
)

// ProviderHealthCheckFunc defines the function signature for performing health checks
type ProviderHealthCheckFunc func(ctx context.Context, provider *Provider) error

// performProviderHealthCheckWithMetrics is a shared utility function that performs health checks on providers
// and updates additional metrics for execution pools
func performProviderHealthCheckWithMetrics(provider *Provider, checkFunc ProviderHealthCheckFunc) {
	if !provider.Config.HealthCheck.Enabled {
		return
	}

	ctx, cancel := context.WithTimeout(context.Background(), provider.Config.HealthCheck.Timeout)
	defer cancel()

	start := time.Now()
	var err error

	// Execute the provider-specific health check
	err = checkFunc(ctx, provider)

	provider.mutex.Lock()
	provider.LastHealthCheck = time.Now()
	provider.IsHealthy = (err == nil)
	if err == nil {
		provider.AvgResponseTime = time.Since(start)
	}
	if err != nil {
		provider.ErrorCount++
	}
	provider.RequestCount++
	provider.mutex.Unlock()
}

// performProviderHealthCheck is a shared utility function that performs health checks on providers
func performProviderHealthCheck(provider *Provider, checkFunc ProviderHealthCheckFunc) {
	if !provider.Config.HealthCheck.Enabled {
		return
	}

	ctx, cancel := context.WithTimeout(context.Background(), provider.Config.HealthCheck.Timeout)
	defer cancel()

	start := time.Now()
	var err error

	// Execute the provider-specific health check
	err = checkFunc(ctx, provider)

	provider.mutex.Lock()
	provider.LastHealthCheck = time.Now()
	provider.IsHealthy = (err == nil)
	if err == nil {
		provider.AvgResponseTime = time.Since(start)
	}
	provider.mutex.Unlock()
}

// ProviderPool interface defines common functionality for all provider pools
type ProviderPool interface {
	GetHTTPClient() (*ethclient.Client, error)
	GetWSClient() (*ethclient.Client, error)
	GetRPCClient(preferWS bool) (*rpc.Client, error)
	GetStats() map[string]interface{}
	Close() error
}

// ReadOnlyProviderPool manages providers optimized for data fetching and real-time events
type ReadOnlyProviderPool struct {
	providers       []*Provider
	config          ProviderPoolConfig
	providerConfigs map[string]ProviderConfig
	currentProvider int
	mutex           sync.RWMutex
	healthTicker    *time.Ticker
	stopChan        chan struct{}
}

// NewReadOnlyProviderPool creates a new read-only provider pool
func NewReadOnlyProviderPool(poolConfig ProviderPoolConfig, providerConfigs map[string]ProviderConfig) (*ReadOnlyProviderPool, error) {
	pool := &ReadOnlyProviderPool{
		config:          poolConfig,
		providerConfigs: providerConfigs,
		stopChan:        make(chan struct{}),
	}

	if err := pool.initializeProviders(); err != nil {
		return nil, fmt.Errorf("failed to initialize read-only providers: %w", err)
	}

	pool.startHealthChecks()
	return pool, nil
}

// initializeProviders sets up all configured providers for read-only operations
func (p *ReadOnlyProviderPool) initializeProviders() error {
	p.providers = make([]*Provider, 0, len(p.config.Providers))

	for _, providerName := range p.config.Providers {
		providerConfig, exists := p.providerConfigs[providerName]
		if !exists {
			continue // Skip missing providers
		}

		provider, err := p.createReadOnlyProvider(providerConfig)
		if err != nil {
			// Log error but continue with other providers
			continue
		}
		p.providers = append(p.providers, provider)
	}

	if len(p.providers) == 0 {
		return fmt.Errorf("no read-only providers successfully initialized")
	}

	return nil
}

// createReadOnlyProvider creates a provider optimized for read-only operations
func (p *ReadOnlyProviderPool) createReadOnlyProvider(config ProviderConfig) (*Provider, error) {
	provider, err := createProvider(config)
	if err != nil {
		return nil, err
	}

	// For read-only pool, prefer WebSocket connections when available
	if config.WSEndpoint != "" && provider.WSClient == nil {
		// Try to establish WebSocket connection again with longer timeout
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		wsClient, err := rpc.DialWebsocket(ctx, config.WSEndpoint, "")
		if err == nil {
			provider.WSConn = wsClient
			provider.WSClient = ethclient.NewClient(wsClient)
		}
	}

	return provider, nil
}

// GetHTTPClient returns an HTTP client optimized for read-only operations
func (p *ReadOnlyProviderPool) GetHTTPClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.HTTPClient == nil {
		return nil, fmt.Errorf("provider %s has no HTTP client", provider.Config.Name)
	}

	return provider.HTTPClient, nil
}

// GetWSClient returns a WebSocket client for real-time events
func (p *ReadOnlyProviderPool) GetWSClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	// Prefer providers with WebSocket support based on strategy
	if p.config.Strategy == "websocket_preferred" {
		for _, provider := range p.providers {
			if p.isProviderUsable(provider) && provider.WSClient != nil {
				return provider.WSClient, nil
			}
		}
	}

	// Fallback to any healthy provider with WebSocket
	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.WSClient == nil {
		return nil, fmt.Errorf("provider %s has no WebSocket client", provider.Config.Name)
	}

	return provider.WSClient, nil
}

// GetRPCClient returns a raw RPC client, preferring WebSocket for real-time operations
func (p *ReadOnlyProviderPool) GetRPCClient(preferWS bool) (*rpc.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	// For read-only operations, prefer WebSocket when available
	if (preferWS || p.config.Strategy == "websocket_preferred") && provider.WSConn != nil {
		return provider.WSConn, nil
	}

	if provider.HTTPConn != nil {
		return provider.HTTPConn, nil
	}

	return nil, fmt.Errorf("provider %s has no available RPC client", provider.Config.Name)
}

// getHealthyProvider returns the next healthy provider based on strategy
func (p *ReadOnlyProviderPool) getHealthyProvider() (*Provider, error) {
	if len(p.providers) == 0 {
		return nil, fmt.Errorf("no providers available")
	}

	switch p.config.Strategy {
	case "websocket_preferred":
		return p.getWebSocketPreferredProvider()
	case "round_robin":
		return p.getRoundRobinProvider()
	case "priority_based":
		return p.getPriorityProvider()
	default:
		return p.getWebSocketPreferredProvider()
	}
}

// getWebSocketPreferredProvider returns a provider, preferring those with WebSocket support
func (p *ReadOnlyProviderPool) getWebSocketPreferredProvider() (*Provider, error) {
	// First try to find a healthy provider with WebSocket
	for _, provider := range p.providers {
		if p.isProviderUsable(provider) && provider.WSClient != nil {
			return provider, nil
		}
	}

	// Fallback to any healthy provider
	for _, provider := range p.providers {
		if p.isProviderUsable(provider) {
			return provider, nil
		}
	}

	return nil, fmt.Errorf("no healthy providers available")
}

// getRoundRobinProvider implements round-robin selection for read-only pool
func (p *ReadOnlyProviderPool) getRoundRobinProvider() (*Provider, error) {
	startIndex := p.currentProvider

	for i := 0; i < len(p.providers); i++ {
		index := (startIndex + i) % len(p.providers)
		provider := p.providers[index]

		if p.isProviderUsable(provider) {
			p.currentProvider = (index + 1) % len(p.providers)
			return provider, nil
		}
	}

	return nil, fmt.Errorf("no healthy providers available")
}

// getPriorityProvider returns the highest priority healthy provider
func (p *ReadOnlyProviderPool) getPriorityProvider() (*Provider, error) {
	var bestProvider *Provider
	highestPriority := int(^uint(0) >> 1) // Max int

	for _, provider := range p.providers {
		if p.isProviderUsable(provider) && provider.Config.Priority < highestPriority {
			bestProvider = provider
			highestPriority = provider.Config.Priority
		}
	}

	if bestProvider == nil {
		return nil, fmt.Errorf("no healthy providers available")
	}

	return bestProvider, nil
}

// isProviderUsable checks if a provider is healthy and within rate limits
func (p *ReadOnlyProviderPool) isProviderUsable(provider *Provider) bool {
	provider.mutex.RLock()
	defer provider.mutex.RUnlock()

	// Check health status
	if p.config.FailoverEnabled && !provider.IsHealthy {
		return false
	}

	// Check rate limit
	if !provider.RateLimiter.Allow() {
		return false
	}

	return true
}

// startHealthChecks starts periodic health checking
func (p *ReadOnlyProviderPool) startHealthChecks() {
	interval, err := time.ParseDuration(p.config.HealthCheckInterval)
	if err != nil {
		interval = time.Minute // Default to 1 minute
	}

	p.healthTicker = time.NewTicker(interval)
	go p.healthCheckLoop()
}

// healthCheckLoop periodically checks provider health
func (p *ReadOnlyProviderPool) healthCheckLoop() {
	for {
		select {
		case <-p.healthTicker.C:
			p.performHealthChecks()
		case <-p.stopChan:
			return
		}
	}
}

// performHealthChecks checks all providers' health
func (p *ReadOnlyProviderPool) performHealthChecks() {
	for _, provider := range p.providers {
		go p.checkProviderHealth(provider)
	}
}

// checkProviderHealth performs a health check on a single provider
func (p *ReadOnlyProviderPool) checkProviderHealth(provider *Provider) {
	performProviderHealthCheck(provider, func(ctx context.Context, provider *Provider) error {
		// For read-only pool, test both HTTP and WebSocket if available
		if provider.WSClient != nil {
			_, err := provider.WSClient.BlockNumber(ctx)
			return err
		} else if provider.HTTPClient != nil {
			_, err := provider.HTTPClient.BlockNumber(ctx)
			return err
		}
		return nil
	})
}

// GetStats returns current read-only provider pool statistics
func (p *ReadOnlyProviderPool) GetStats() map[string]interface{} {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	stats := map[string]interface{}{
		"pool_type":       "read_only",
		"strategy":        p.config.Strategy,
		"total_providers": len(p.providers),
		"providers":       make(map[string]interface{}),
	}

	healthyCount := 0
	wsCount := 0

	for _, provider := range p.providers {
		provider.mutex.RLock()
		providerStats := map[string]interface{}{
			"name":              provider.Config.Name,
			"healthy":           provider.IsHealthy,
			"has_websocket":     provider.WSClient != nil,
			"last_health_check": provider.LastHealthCheck,
			"request_count":     provider.RequestCount,
			"error_count":       provider.ErrorCount,
			"avg_response_time": provider.AvgResponseTime,
		}
		provider.mutex.RUnlock()

		stats["providers"].(map[string]interface{})[provider.Config.Name] = providerStats

		if provider.IsHealthy {
			healthyCount++
		}
		if provider.WSClient != nil {
			wsCount++
		}
	}

	stats["healthy_providers"] = healthyCount
	stats["websocket_providers"] = wsCount

	return stats
}

// Close shuts down the read-only provider pool
func (p *ReadOnlyProviderPool) Close() error {
	close(p.stopChan)

	if p.healthTicker != nil {
		p.healthTicker.Stop()
	}

	// Close all connections
	for _, provider := range p.providers {
		if provider.HTTPConn != nil {
			provider.HTTPConn.Close()
		}
		if provider.WSConn != nil {
			provider.WSConn.Close()
		}
	}

	return nil
}

// ExecutionProviderPool manages providers optimized for transaction execution
type ExecutionProviderPool struct {
	providers       []*Provider
	config          ProviderPoolConfig
	providerConfigs map[string]ProviderConfig
	currentProvider int
	mutex           sync.RWMutex
	healthTicker    *time.Ticker
	stopChan        chan struct{}
}

// NewExecutionProviderPool creates a new execution provider pool
func NewExecutionProviderPool(poolConfig ProviderPoolConfig, providerConfigs map[string]ProviderConfig) (*ExecutionProviderPool, error) {
	pool := &ExecutionProviderPool{
		config:          poolConfig,
		providerConfigs: providerConfigs,
		stopChan:        make(chan struct{}),
	}

	if err := pool.initializeProviders(); err != nil {
		return nil, fmt.Errorf("failed to initialize execution providers: %w", err)
	}

	pool.startHealthChecks()
	return pool, nil
}

// initializeProviders sets up all configured providers for execution operations
func (p *ExecutionProviderPool) initializeProviders() error {
	p.providers = make([]*Provider, 0, len(p.config.Providers))

	for _, providerName := range p.config.Providers {
		providerConfig, exists := p.providerConfigs[providerName]
		if !exists {
			continue // Skip missing providers
		}

		provider, err := p.createExecutionProvider(providerConfig)
		if err != nil {
			// Log error but continue with other providers
			continue
		}
		p.providers = append(p.providers, provider)
	}

	if len(p.providers) == 0 {
		return fmt.Errorf("no execution providers successfully initialized")
	}

	return nil
}

// createExecutionProvider creates a provider optimized for transaction execution
func (p *ExecutionProviderPool) createExecutionProvider(config ProviderConfig) (*Provider, error) {
	provider, err := createProvider(config)
	if err != nil {
		return nil, err
	}

	// For execution pool, ensure HTTP connection is stable and secure
	if provider.HTTPClient == nil {
		return nil, fmt.Errorf("execution provider %s must have HTTP client", config.Name)
	}

	return provider, nil
}

// GetHTTPClient returns an HTTP client optimized for transaction execution
func (p *ExecutionProviderPool) GetHTTPClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.HTTPClient == nil {
		return nil, fmt.Errorf("provider %s has no HTTP client", provider.Config.Name)
	}

	return provider.HTTPClient, nil
}

// GetWSClient returns a WebSocket client (execution pool typically uses HTTP)
func (p *ExecutionProviderPool) GetWSClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.WSClient == nil {
		return nil, fmt.Errorf("provider %s has no WebSocket client", provider.Config.Name)
	}

	return provider.WSClient, nil
}

// GetRPCClient returns a raw RPC client, preferring HTTP for execution reliability
func (p *ExecutionProviderPool) GetRPCClient(preferWS bool) (*rpc.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	// For execution pool, prefer HTTP for reliability unless explicitly requesting WebSocket
	if preferWS && provider.WSConn != nil {
		return provider.WSConn, nil
	}

	if provider.HTTPConn != nil {
		return provider.HTTPConn, nil
	}

	return nil, fmt.Errorf("provider %s has no available RPC client", provider.Config.Name)
}

// getHealthyProvider returns the next healthy provider based on reliability strategy
func (p *ExecutionProviderPool) getHealthyProvider() (*Provider, error) {
	if len(p.providers) == 0 {
		return nil, fmt.Errorf("no providers available")
	}

	switch p.config.Strategy {
	case "reliability_first":
		return p.getReliabilityFirstProvider()
	case "priority_based":
		return p.getPriorityProvider()
	case "round_robin":
		return p.getRoundRobinProvider()
	default:
		return p.getReliabilityFirstProvider()
	}
}

// getReliabilityFirstProvider returns the most reliable provider
func (p *ExecutionProviderPool) getReliabilityFirstProvider() (*Provider, error) {
	var bestProvider *Provider
	bestReliability := -1.0

	for _, provider := range p.providers {
		if !p.isProviderUsable(provider) {
			continue
		}

		// Calculate reliability score based on error rate and response time
		reliability := p.calculateReliabilityScore(provider)
		if reliability > bestReliability {
			bestProvider = provider
			bestReliability = reliability
		}
	}

	if bestProvider == nil {
		return nil, fmt.Errorf("no healthy providers available")
	}

	return bestProvider, nil
}

// calculateReliabilityScore calculates a reliability score for a provider
func (p *ExecutionProviderPool) calculateReliabilityScore(provider *Provider) float64 {
	provider.mutex.RLock()
	defer provider.mutex.RUnlock()

	// Base score on health status
	if !provider.IsHealthy {
		return 0.0
	}

	score := 1.0

	// Factor in error rate
	if provider.RequestCount > 0 {
		errorRate := float64(provider.ErrorCount) / float64(provider.RequestCount)
		score *= (1.0 - errorRate)
	}

	// Factor in response time (prefer faster responses)
	if provider.AvgResponseTime > 0 {
		// Normalize response time (consider anything under 1 second as good)
		responseScore := 1.0 - (float64(provider.AvgResponseTime.Milliseconds()) / 1000.0)
		if responseScore < 0 {
			responseScore = 0.1 // Minimum score for slow but working providers
		}
		score *= responseScore
	}

	return score
}

// getRoundRobinProvider implements round-robin selection for execution pool
func (p *ExecutionProviderPool) getRoundRobinProvider() (*Provider, error) {
	startIndex := p.currentProvider

	for i := 0; i < len(p.providers); i++ {
		index := (startIndex + i) % len(p.providers)
		provider := p.providers[index]

		if p.isProviderUsable(provider) {
			p.currentProvider = (index + 1) % len(p.providers)
			return provider, nil
		}
	}

	return nil, fmt.Errorf("no healthy providers available")
}

// getPriorityProvider returns the highest priority healthy provider
func (p *ExecutionProviderPool) getPriorityProvider() (*Provider, error) {
	var bestProvider *Provider
	highestPriority := int(^uint(0) >> 1) // Max int

	for _, provider := range p.providers {
		if p.isProviderUsable(provider) && provider.Config.Priority < highestPriority {
			bestProvider = provider
			highestPriority = provider.Config.Priority
		}
	}

	if bestProvider == nil {
		return nil, fmt.Errorf("no healthy providers available")
	}

	return bestProvider, nil
}

// isProviderUsable checks if a provider is healthy and within rate limits
func (p *ExecutionProviderPool) isProviderUsable(provider *Provider) bool {
	provider.mutex.RLock()
	defer provider.mutex.RUnlock()

	// Check health status (critical for execution)
	if !provider.IsHealthy {
		return false
	}

	// Check rate limit
	if !provider.RateLimiter.Allow() {
		return false
	}

	return true
}

// startHealthChecks starts periodic health checking for execution pool
func (p *ExecutionProviderPool) startHealthChecks() {
	interval, err := time.ParseDuration(p.config.HealthCheckInterval)
	if err != nil {
		interval = 30 * time.Second // Default to 30 seconds for execution pool
	}

	p.healthTicker = time.NewTicker(interval)
	go p.healthCheckLoop()
}

// healthCheckLoop periodically checks provider health
func (p *ExecutionProviderPool) healthCheckLoop() {
	for {
		select {
		case <-p.healthTicker.C:
			p.performHealthChecks()
		case <-p.stopChan:
			return
		}
	}
}

// performHealthChecks checks all providers' health
func (p *ExecutionProviderPool) performHealthChecks() {
	for _, provider := range p.providers {
		go p.checkProviderHealth(provider)
	}
}

// checkProviderHealth performs a health check on a single provider
func (p *ExecutionProviderPool) checkProviderHealth(provider *Provider) {
	performProviderHealthCheckWithMetrics(provider, func(ctx context.Context, provider *Provider) error {
		// For execution pool, test HTTP client reliability
		if provider.HTTPClient != nil {
			_, err := provider.HTTPClient.BlockNumber(ctx)
			return err
		}
		return nil
	})
}

// GetStats returns current execution provider pool statistics
func (p *ExecutionProviderPool) GetStats() map[string]interface{} {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	stats := map[string]interface{}{
		"pool_type":       "execution",
		"strategy":        p.config.Strategy,
		"total_providers": len(p.providers),
		"providers":       make(map[string]interface{}),
	}

	healthyCount := 0
	totalRequests := int64(0)
	totalErrors := int64(0)

	for _, provider := range p.providers {
		provider.mutex.RLock()
		reliability := p.calculateReliabilityScore(provider)
		providerStats := map[string]interface{}{
			"name":              provider.Config.Name,
			"healthy":           provider.IsHealthy,
			"reliability_score": reliability,
			"last_health_check": provider.LastHealthCheck,
			"request_count":     provider.RequestCount,
			"error_count":       provider.ErrorCount,
			"avg_response_time": provider.AvgResponseTime,
		}
		provider.mutex.RUnlock()

		stats["providers"].(map[string]interface{})[provider.Config.Name] = providerStats

		if provider.IsHealthy {
			healthyCount++
		}
		totalRequests += provider.RequestCount
		totalErrors += provider.ErrorCount
	}

	stats["healthy_providers"] = healthyCount
	stats["total_requests"] = totalRequests
	stats["total_errors"] = totalErrors
	if totalRequests > 0 {
		stats["error_rate"] = float64(totalErrors) / float64(totalRequests)
	}

	return stats
}

// Close shuts down the execution provider pool
func (p *ExecutionProviderPool) Close() error {
	close(p.stopChan)

	if p.healthTicker != nil {
		p.healthTicker.Stop()
	}

	// Close all connections
	for _, provider := range p.providers {
		if provider.HTTPConn != nil {
			provider.HTTPConn.Close()
		}
		if provider.WSConn != nil {
			provider.WSConn.Close()
		}
	}

	return nil
}

// TestingProviderPool manages Anvil forked instances for testing
type TestingProviderPool struct {
	providers       []*Provider
	config          ProviderPoolConfig
	providerConfigs map[string]ProviderConfig
	currentProvider int
	mutex           sync.RWMutex
	healthTicker    *time.Ticker
	stopChan        chan struct{}

	// Anvil-specific management
	anvilProcesses map[string]*exec.Cmd
	processMutex   sync.RWMutex
}

// NewTestingProviderPool creates a new testing provider pool with Anvil support
func NewTestingProviderPool(poolConfig ProviderPoolConfig, providerConfigs map[string]ProviderConfig) (*TestingProviderPool, error) {
	pool := &TestingProviderPool{
		config:          poolConfig,
		providerConfigs: providerConfigs,
		stopChan:        make(chan struct{}),
		anvilProcesses:  make(map[string]*exec.Cmd),
	}

	if err := pool.initializeProviders(); err != nil {
		return nil, fmt.Errorf("failed to initialize testing providers: %w", err)
	}

	pool.startHealthChecks()
	return pool, nil
}

// initializeProviders sets up all configured providers including Anvil instances
func (p *TestingProviderPool) initializeProviders() error {
	p.providers = make([]*Provider, 0, len(p.config.Providers))

	for _, providerName := range p.config.Providers {
		providerConfig, exists := p.providerConfigs[providerName]
		if !exists {
			continue // Skip missing providers
		}

		provider, err := p.createTestingProvider(providerConfig)
		if err != nil {
			// Log error but continue with other providers
			continue
		}
		p.providers = append(p.providers, provider)
	}

	if len(p.providers) == 0 {
		return fmt.Errorf("no testing providers successfully initialized")
	}

	return nil
}

// createTestingProvider creates a provider, starting Anvil if needed
func (p *TestingProviderPool) createTestingProvider(config ProviderConfig) (*Provider, error) {
	// Start Anvil instance if this is an anvil_fork type
	if config.Type == "anvil_fork" {
		if err := p.startAnvilInstance(config); err != nil {
			return nil, fmt.Errorf("failed to start Anvil instance: %w", err)
		}

		// Wait for Anvil to start up
		time.Sleep(2 * time.Second)
	}

	provider, err := createProvider(config)
	if err != nil {
		// If we started an Anvil instance, clean it up
		if config.Type == "anvil_fork" {
			p.stopAnvilInstance(config.Name)
		}
		return nil, err
	}

	return provider, nil
}

// startAnvilInstance starts an Anvil forked instance
func (p *TestingProviderPool) startAnvilInstance(config ProviderConfig) error {
	if config.AnvilConfig == nil {
		return fmt.Errorf("anvil config is required for anvil_fork provider")
	}

	p.processMutex.Lock()
	defer p.processMutex.Unlock()

	// Check if already running
	if _, exists := p.anvilProcesses[config.Name]; exists {
		return nil // Already running
	}

	// Build Anvil command
	args := []string{
		"--fork-url", config.AnvilConfig.ForkURL,
		"--port", strconv.Itoa(config.AnvilConfig.Port),
		"--chain-id", strconv.Itoa(config.AnvilConfig.ChainID),
		"--block-time", strconv.Itoa(config.AnvilConfig.BlockTime),
		"--accounts", "10", // Create 10 test accounts
		"--balance", "10000", // Each account gets 10,000 ETH
	}

	if config.AnvilConfig.AutoImpersonate {
		args = append(args, "--auto-impersonate")
	}

	// Add state interval if specified
	if config.AnvilConfig.StateInterval > 0 {
		args = append(args, "--state-interval", strconv.Itoa(config.AnvilConfig.StateInterval))
	}

	// Start the Anvil process
	cmd := exec.Command("anvil", args...)
	cmd.Stdout = nil // Could pipe to logger if needed
	cmd.Stderr = nil

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("failed to start anvil process: %w", err)
	}

	p.anvilProcesses[config.Name] = cmd

	// Start a goroutine to monitor the process
	go p.monitorAnvilProcess(config.Name, cmd)

	return nil
}

// stopAnvilInstance stops an Anvil instance
func (p *TestingProviderPool) stopAnvilInstance(name string) error {
	p.processMutex.Lock()
	defer p.processMutex.Unlock()

	cmd, exists := p.anvilProcesses[name]
	if !exists {
		return nil // Not running
	}

	// Kill the process
	if err := cmd.Process.Kill(); err != nil {
		return fmt.Errorf("failed to kill anvil process: %w", err)
	}

	// Wait for it to exit
	cmd.Wait()

	// Remove from map
	delete(p.anvilProcesses, name)

	return nil
}

// monitorAnvilProcess monitors an Anvil process and restarts if needed
func (p *TestingProviderPool) monitorAnvilProcess(name string, cmd *exec.Cmd) {
	err := cmd.Wait()

	p.processMutex.Lock()
	defer p.processMutex.Unlock()

	// Remove from map
	delete(p.anvilProcesses, name)

	// If the process exited unexpectedly, we could restart it here
	// For now, just log the exit
	if err != nil {
		// Process exited with error - could implement restart logic
	}
}

// GetHTTPClient returns an HTTP client for testing operations
func (p *TestingProviderPool) GetHTTPClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.HTTPClient == nil {
		return nil, fmt.Errorf("provider %s has no HTTP client", provider.Config.Name)
	}

	return provider.HTTPClient, nil
}

// GetWSClient returns a WebSocket client for testing
func (p *TestingProviderPool) GetWSClient() (*ethclient.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	if provider.WSClient == nil {
		return nil, fmt.Errorf("provider %s has no WebSocket client", provider.Config.Name)
	}

	return provider.WSClient, nil
}

// GetRPCClient returns a raw RPC client for advanced testing operations
func (p *TestingProviderPool) GetRPCClient(preferWS bool) (*rpc.Client, error) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	provider, err := p.getHealthyProvider()
	if err != nil {
		return nil, err
	}

	// For testing pool, prefer local connections
	if preferWS && provider.WSConn != nil {
		return provider.WSConn, nil
	}

	if provider.HTTPConn != nil {
		return provider.HTTPConn, nil
	}

	return nil, fmt.Errorf("provider %s has no available RPC client", provider.Config.Name)
}

// getHealthyProvider returns the next healthy provider based on anvil strategy
func (p *TestingProviderPool) getHealthyProvider() (*Provider, error) {
	if len(p.providers) == 0 {
		return nil, fmt.Errorf("no providers available")
	}

	switch p.config.Strategy {
	case "anvil_preferred":
		return p.getAnvilPreferredProvider()
	case "priority_based":
		return p.getPriorityProvider()
	case "round_robin":
		return p.getRoundRobinProvider()
	default:
		return p.getAnvilPreferredProvider()
	}
}

// getAnvilPreferredProvider returns an Anvil provider if available, otherwise any healthy provider
func (p *TestingProviderPool) getAnvilPreferredProvider() (*Provider, error) {
	// First try to find a healthy Anvil provider
	for _, provider := range p.providers {
		if p.isProviderUsable(provider) && provider.Config.Type == "anvil_fork" {
			return provider, nil
		}
	}

	// Fallback to any healthy provider
	for _, provider := range p.providers {
		if p.isProviderUsable(provider) {
			return provider, nil
		}
	}

	return nil, fmt.Errorf("no healthy providers available")
}

// getRoundRobinProvider implements round-robin selection for testing pool
func (p *TestingProviderPool) getRoundRobinProvider() (*Provider, error) {
	startIndex := p.currentProvider

	for i := 0; i < len(p.providers); i++ {
		index := (startIndex + i) % len(p.providers)
		provider := p.providers[index]

		if p.isProviderUsable(provider) {
			p.currentProvider = (index + 1) % len(p.providers)
			return provider, nil
		}
	}

	return nil, fmt.Errorf("no healthy providers available")
}

// getPriorityProvider returns the highest priority healthy provider
func (p *TestingProviderPool) getPriorityProvider() (*Provider, error) {
	var bestProvider *Provider
	highestPriority := int(^uint(0) >> 1) // Max int

	for _, provider := range p.providers {
		if p.isProviderUsable(provider) && provider.Config.Priority < highestPriority {
			bestProvider = provider
			highestPriority = provider.Config.Priority
		}
	}

	if bestProvider == nil {
		return nil, fmt.Errorf("no healthy providers available")
	}

	return bestProvider, nil
}

// isProviderUsable checks if a provider is healthy and within rate limits
func (p *TestingProviderPool) isProviderUsable(provider *Provider) bool {
	provider.mutex.RLock()
	defer provider.mutex.RUnlock()

	// For testing providers, be more lenient with health checks
	if p.config.FailoverEnabled && !provider.IsHealthy {
		// For Anvil instances, check if the process is still running
		if provider.Config.Type == "anvil_fork" {
			p.processMutex.RLock()
			_, isRunning := p.anvilProcesses[provider.Config.Name]
			p.processMutex.RUnlock()
			return isRunning
		}
		return false
	}

	// Check rate limit (testing usually has very high limits)
	if !provider.RateLimiter.Allow() {
		return false
	}

	return true
}

// startHealthChecks starts periodic health checking for testing pool
func (p *TestingProviderPool) startHealthChecks() {
	interval, err := time.ParseDuration(p.config.HealthCheckInterval)
	if err != nil {
		interval = time.Minute // Default to 1 minute for testing pool
	}

	p.healthTicker = time.NewTicker(interval)
	go p.healthCheckLoop()
}

// healthCheckLoop periodically checks provider health
func (p *TestingProviderPool) healthCheckLoop() {
	for {
		select {
		case <-p.healthTicker.C:
			p.performHealthChecks()
		case <-p.stopChan:
			return
		}
	}
}

// performHealthChecks checks all providers' health
func (p *TestingProviderPool) performHealthChecks() {
	for _, provider := range p.providers {
		go p.checkProviderHealth(provider)
	}
}

// checkProviderHealth performs a health check on a single provider
func (p *TestingProviderPool) checkProviderHealth(provider *Provider) {
	performProviderHealthCheck(provider, func(ctx context.Context, provider *Provider) error {
		// For testing pool, test the most appropriate client
		if provider.HTTPClient != nil {
			_, err := provider.HTTPClient.BlockNumber(ctx)
			return err
		} else if provider.WSClient != nil {
			_, err := provider.WSClient.BlockNumber(ctx)
			return err
		}
		return nil
	})
}

// GetStats returns current testing provider pool statistics
func (p *TestingProviderPool) GetStats() map[string]interface{} {
	p.mutex.RLock()
	defer p.mutex.RUnlock()

	stats := map[string]interface{}{
		"pool_type":       "testing",
		"strategy":        p.config.Strategy,
		"total_providers": len(p.providers),
		"providers":       make(map[string]interface{}),
	}

	healthyCount := 0
	anvilCount := 0
	runningAnvilCount := 0

	p.processMutex.RLock()
	defer p.processMutex.RUnlock()

	for _, provider := range p.providers {
		provider.mutex.RLock()
		isAnvil := provider.Config.Type == "anvil_fork"
		_, anvilRunning := p.anvilProcesses[provider.Config.Name]

		providerStats := map[string]interface{}{
			"name":              provider.Config.Name,
			"type":              provider.Config.Type,
			"healthy":           provider.IsHealthy,
			"is_anvil":          isAnvil,
			"anvil_running":     anvilRunning,
			"last_health_check": provider.LastHealthCheck,
			"request_count":     provider.RequestCount,
			"error_count":       provider.ErrorCount,
			"avg_response_time": provider.AvgResponseTime,
		}

		if isAnvil && provider.Config.AnvilConfig != nil {
			providerStats["anvil_port"] = provider.Config.AnvilConfig.Port
			providerStats["anvil_chain_id"] = provider.Config.AnvilConfig.ChainID
			providerStats["fork_url"] = provider.Config.AnvilConfig.ForkURL
		}

		provider.mutex.RUnlock()

		stats["providers"].(map[string]interface{})[provider.Config.Name] = providerStats

		if provider.IsHealthy {
			healthyCount++
		}
		if isAnvil {
			anvilCount++
			if anvilRunning {
				runningAnvilCount++
			}
		}
	}

	stats["healthy_providers"] = healthyCount
	stats["anvil_providers"] = anvilCount
	stats["running_anvil_instances"] = runningAnvilCount

	return stats
}

// CreateSnapshot creates a state snapshot for testing (if supported)
func (p *TestingProviderPool) CreateSnapshot() (string, error) {
	rpcClient, err := p.GetRPCClient(false)
	if err != nil {
		return "", err
	}

	var snapshotID string
	err = rpcClient.Call(&snapshotID, "evm_snapshot")
	if err != nil {
		return "", fmt.Errorf("failed to create snapshot: %w", err)
	}

	return snapshotID, nil
}

// RevertToSnapshot reverts to a previously created snapshot
func (p *TestingProviderPool) RevertToSnapshot(snapshotID string) error {
	rpcClient, err := p.GetRPCClient(false)
	if err != nil {
		return err
	}

	var success bool
	err = rpcClient.Call(&success, "evm_revert", snapshotID)
	if err != nil {
		return fmt.Errorf("failed to revert to snapshot: %w", err)
	}

	if !success {
		return fmt.Errorf("snapshot revert was not successful")
	}

	return nil
}

// Close shuts down the testing provider pool and all Anvil instances
func (p *TestingProviderPool) Close() error {
	close(p.stopChan)

	if p.healthTicker != nil {
		p.healthTicker.Stop()
	}

	// Stop all Anvil instances
	p.processMutex.Lock()
	for name := range p.anvilProcesses {
		p.stopAnvilInstance(name)
	}
	p.processMutex.Unlock()

	// Close all connections
	for _, provider := range p.providers {
		if provider.HTTPConn != nil {
			provider.HTTPConn.Close()
		}
		if provider.WSConn != nil {
			provider.WSConn.Close()
		}
	}

	return nil
}