package security

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"errors"
	"fmt"
	"math/rand"
	"net/http"
	"os"
	"reflect"
	"sync"
	"time"

	"golang.org/x/time/rate"

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

// SecurityManager provides centralized security management for the MEV bot
type SecurityManager struct {
	keyManager     *KeyManager
	inputValidator *InputValidator
	rateLimiter    *RateLimiter
	monitor        *SecurityMonitor
	config         *SecurityConfig
	logger         *logger.Logger

	// Circuit breakers for different components
	rpcCircuitBreaker       *CircuitBreaker
	arbitrageCircuitBreaker *CircuitBreaker

	// TLS configuration
	tlsConfig *tls.Config

	// Rate limiters for different operations
	transactionLimiter *rate.Limiter
	rpcLimiter         *rate.Limiter

	// Security state
	emergencyMode  bool
	securityAlerts []SecurityAlert
	alertsMutex    sync.RWMutex

	// Metrics
	managerMetrics *ManagerMetrics

	rpcHTTPClient *http.Client
}

// SecurityConfig contains all security-related configuration
type SecurityConfig struct {
	// Key management
	KeyStoreDir       string `yaml:"keystore_dir"`
	EncryptionEnabled bool   `yaml:"encryption_enabled"`

	// Rate limiting
	TransactionRPS int `yaml:"transaction_rps"`
	RPCRPS         int `yaml:"rpc_rps"`
	MaxBurstSize   int `yaml:"max_burst_size"`

	// Circuit breaker settings
	FailureThreshold int           `yaml:"failure_threshold"`
	RecoveryTimeout  time.Duration `yaml:"recovery_timeout"`

	// TLS settings
	TLSMinVersion   uint16   `yaml:"tls_min_version"`
	TLSCipherSuites []uint16 `yaml:"tls_cipher_suites"`

	// Emergency settings
	EmergencyStopFile string `yaml:"emergency_stop_file"`
	MaxGasPrice       string `yaml:"max_gas_price"`

	// Monitoring
	AlertWebhookURL string `yaml:"alert_webhook_url"`
	LogLevel        string `yaml:"log_level"`

	// RPC endpoint used by secure RPC call delegation
	RPCURL string `yaml:"rpc_url"`
}

// Additional security metrics for SecurityManager
type ManagerMetrics struct {
	AuthenticationAttempts int64 `json:"authentication_attempts"`
	FailedAuthentications  int64 `json:"failed_authentications"`
	CircuitBreakerTrips    int64 `json:"circuit_breaker_trips"`
	EmergencyStops         int64 `json:"emergency_stops"`
	TLSHandshakeFailures   int64 `json:"tls_handshake_failures"`
}

// CircuitBreaker implements the circuit breaker pattern for fault tolerance
type CircuitBreaker struct {
	name            string
	failureCount    int
	lastFailureTime time.Time
	state           CircuitBreakerState
	config          CircuitBreakerConfig
	mutex           sync.RWMutex
}

type CircuitBreakerState int

const (
	CircuitBreakerClosed CircuitBreakerState = iota
	CircuitBreakerOpen
	CircuitBreakerHalfOpen
)

type CircuitBreakerConfig struct {
	FailureThreshold int
	RecoveryTimeout  time.Duration
	MaxRetries       int
}

// NewSecurityManager creates a new security manager with comprehensive protection
func NewSecurityManager(config *SecurityConfig) (*SecurityManager, error) {
	if config == nil {
		return nil, fmt.Errorf("security config cannot be nil")
	}

	// Initialize key manager - get encryption key from environment or fail
	encryptionKey := os.Getenv("MEV_BOT_ENCRYPTION_KEY")
	if encryptionKey == "" {
		return nil, fmt.Errorf("MEV_BOT_ENCRYPTION_KEY environment variable is required")
	}

	keyManagerConfig := &KeyManagerConfig{
		KeyDir:            config.KeyStoreDir,
		KeystorePath:      config.KeyStoreDir,
		EncryptionKey:     encryptionKey,
		BackupEnabled:     true,
		MaxFailedAttempts: 3,
		LockoutDuration:   5 * time.Minute,
	}
	keyManager, err := NewKeyManager(keyManagerConfig, logger.New("info", "json", "logs/keymanager.log"))
	if err != nil {
		return nil, fmt.Errorf("failed to initialize key manager: %w", err)
	}

	// Initialize input validator
	inputValidator := NewInputValidator(1) // Default chain ID

	// Initialize rate limiter
	rateLimiterConfig := &RateLimiterConfig{
		IPRequestsPerSecond:   100,
		IPBurstSize:           config.MaxBurstSize,
		IPBlockDuration:       5 * time.Minute,
		UserRequestsPerSecond: config.TransactionRPS,
		UserBurstSize:         config.MaxBurstSize,
		UserBlockDuration:     5 * time.Minute,
		CleanupInterval:       5 * time.Minute,
	}
	rateLimiter := NewRateLimiter(rateLimiterConfig)

	// Initialize security monitor
	monitorConfig := &MonitorConfig{
		EnableAlerts:    true,
		AlertBuffer:     1000,
		AlertRetention:  24 * time.Hour,
		MaxEvents:       10000,
		EventRetention:  7 * 24 * time.Hour,
		MetricsInterval: time.Minute,
		CleanupInterval: time.Hour,
	}
	monitor := NewSecurityMonitor(monitorConfig)

	// Create TLS configuration with security best practices
	tlsConfig := &tls.Config{
		MinVersion:               tls.VersionTLS12, // Enforce TLS 1.2 minimum
		CipherSuites:             config.TLSCipherSuites,
		InsecureSkipVerify:       false,
		PreferServerCipherSuites: true,
	}

	// Initialize circuit breakers
	rpcCircuitBreaker := &CircuitBreaker{
		name: "rpc",
		config: CircuitBreakerConfig{
			FailureThreshold: config.FailureThreshold,
			RecoveryTimeout:  config.RecoveryTimeout,
			MaxRetries:       3,
		},
		state: CircuitBreakerClosed,
	}

	arbitrageCircuitBreaker := &CircuitBreaker{
		name: "arbitrage",
		config: CircuitBreakerConfig{
			FailureThreshold: config.FailureThreshold,
			RecoveryTimeout:  config.RecoveryTimeout,
			MaxRetries:       3,
		},
		state: CircuitBreakerClosed,
	}

	// Initialize rate limiters
	transactionLimiter := rate.NewLimiter(rate.Limit(config.TransactionRPS), config.MaxBurstSize)
	rpcLimiter := rate.NewLimiter(rate.Limit(config.RPCRPS), config.MaxBurstSize)

	// Create logger instance
	securityLogger := logger.New("info", "json", "logs/security.log")

	httpTransport := &http.Transport{
		TLSClientConfig: tlsConfig,
	}

	sm := &SecurityManager{
		keyManager:              keyManager,
		inputValidator:          inputValidator,
		rateLimiter:             rateLimiter,
		monitor:                 monitor,
		config:                  config,
		logger:                  securityLogger,
		rpcCircuitBreaker:       rpcCircuitBreaker,
		arbitrageCircuitBreaker: arbitrageCircuitBreaker,
		tlsConfig:               tlsConfig,
		transactionLimiter:      transactionLimiter,
		rpcLimiter:              rpcLimiter,
		emergencyMode:           false,
		securityAlerts:          make([]SecurityAlert, 0),
		managerMetrics:          &ManagerMetrics{},
		rpcHTTPClient: &http.Client{
			Timeout:   30 * time.Second,
			Transport: httpTransport,
		},
	}

	// Start security monitoring
	go sm.startSecurityMonitoring()

	sm.logger.Info("Security manager initialized successfully")
	return sm, nil
}

// ValidateTransaction performs comprehensive transaction validation
func (sm *SecurityManager) ValidateTransaction(ctx context.Context, txParams *TransactionParams) error {
	// Check rate limiting
	if !sm.transactionLimiter.Allow() {
		if sm.monitor != nil {
			sm.monitor.RecordEvent(EventTypeError, "security_manager", "Transaction rate limit exceeded", SeverityMedium, map[string]interface{}{
				"limit_type": "transaction",
			})
		}
		return fmt.Errorf("transaction rate limit exceeded")
	}

	// Check emergency mode
	if sm.emergencyMode {
		return fmt.Errorf("system in emergency mode - transactions disabled")
	}

	// Validate input parameters (simplified validation)
	if txParams.To == nil {
		return fmt.Errorf("transaction validation failed: missing recipient")
	}
	if txParams.Value == nil {
		return fmt.Errorf("transaction validation failed: missing value")
	}

	// Check circuit breaker state
	if sm.arbitrageCircuitBreaker.state == CircuitBreakerOpen {
		return fmt.Errorf("arbitrage circuit breaker is open")
	}

	return nil
}

// SecureRPCCall performs RPC calls with security controls
func (sm *SecurityManager) SecureRPCCall(ctx context.Context, method string, params interface{}) (interface{}, error) {
	// Check rate limiting
	if !sm.rpcLimiter.Allow() {
		if sm.monitor != nil {
			sm.monitor.RecordEvent(EventTypeError, "security_manager", "RPC rate limit exceeded", SeverityMedium, map[string]interface{}{
				"limit_type": "rpc",
				"method":     method,
			})
		}
		return nil, fmt.Errorf("RPC rate limit exceeded")
	}

	// Check circuit breaker
	if sm.rpcCircuitBreaker.state == CircuitBreakerOpen {
		return nil, fmt.Errorf("RPC circuit breaker is open")
	}

	if sm.config.RPCURL == "" {
		err := errors.New("RPC endpoint not configured in security manager")
		sm.RecordFailure("rpc", err)
		return nil, err
	}

	paramList, err := normalizeRPCParams(params)
	if err != nil {
		sm.RecordFailure("rpc", err)
		return nil, err
	}

	requestPayload := jsonRPCRequest{
		JSONRPC: "2.0",
		Method:  method,
		Params:  paramList,
		ID:      fmt.Sprintf("sm-%d", rand.Int63()),
	}

	body, err := json.Marshal(requestPayload)
	if err != nil {
		sm.RecordFailure("rpc", err)
		return nil, fmt.Errorf("failed to marshal RPC request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, sm.config.RPCURL, bytes.NewReader(body))
	if err != nil {
		sm.RecordFailure("rpc", err)
		return nil, fmt.Errorf("failed to create RPC request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := sm.rpcHTTPClient.Do(req)
	if err != nil {
		sm.RecordFailure("rpc", err)
		return nil, fmt.Errorf("RPC call failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		sm.RecordFailure("rpc", fmt.Errorf("rpc endpoint returned status %d", resp.StatusCode))
		return nil, fmt.Errorf("rpc endpoint returned status %d", resp.StatusCode)
	}

	var rpcResp jsonRPCResponse
	if err := json.NewDecoder(resp.Body).Decode(&rpcResp); err != nil {
		sm.RecordFailure("rpc", err)
		return nil, fmt.Errorf("failed to decode RPC response: %w", err)
	}

	if rpcResp.Error != nil {
		err := fmt.Errorf("rpc error %d: %s", rpcResp.Error.Code, rpcResp.Error.Message)
		sm.RecordFailure("rpc", err)
		return nil, err
	}

	var result interface{}
	if len(rpcResp.Result) > 0 {
		if err := json.Unmarshal(rpcResp.Result, &result); err != nil {
			// If we cannot unmarshal into interface{}, return raw JSON
			result = string(rpcResp.Result)
		}
	}

	sm.RecordSuccess("rpc")
	return result, nil
}

// TriggerEmergencyStop activates emergency mode
func (sm *SecurityManager) TriggerEmergencyStop(reason string) error {
	sm.emergencyMode = true
	sm.managerMetrics.EmergencyStops++

	alert := SecurityAlert{
		ID:          fmt.Sprintf("emergency-%d", time.Now().Unix()),
		Timestamp:   time.Now(),
		Level:       AlertLevelCritical,
		Type:        AlertTypeConfiguration,
		Title:       "Emergency Stop Activated",
		Description: fmt.Sprintf("Emergency stop triggered: %s", reason),
		Source:      "security_manager",
		Data: map[string]interface{}{
			"reason": reason,
		},
		Actions: []string{"investigate_cause", "review_logs", "manual_restart_required"},
	}

	sm.addSecurityAlert(alert)
	sm.logger.Error("Emergency stop triggered: " + reason)

	return nil
}

// RecordFailure records a failure for circuit breaker logic
func (sm *SecurityManager) RecordFailure(component string, err error) {
	var cb *CircuitBreaker

	switch component {
	case "rpc":
		cb = sm.rpcCircuitBreaker
	case "arbitrage":
		cb = sm.arbitrageCircuitBreaker
	default:
		return
	}

	cb.mutex.Lock()
	defer cb.mutex.Unlock()

	cb.failureCount++
	cb.lastFailureTime = time.Now()

	if cb.failureCount >= cb.config.FailureThreshold && cb.state == CircuitBreakerClosed {
		cb.state = CircuitBreakerOpen
		sm.managerMetrics.CircuitBreakerTrips++

		alert := SecurityAlert{
			ID:          fmt.Sprintf("circuit-breaker-%s-%d", component, time.Now().Unix()),
			Timestamp:   time.Now(),
			Level:       AlertLevelError,
			Type:        AlertTypePerformance,
			Title:       "Circuit Breaker Opened",
			Description: fmt.Sprintf("Circuit breaker opened for component: %s", component),
			Source:      "security_manager",
			Data: map[string]interface{}{
				"component":     component,
				"failure_count": cb.failureCount,
				"error":         err.Error(),
			},
			Actions: []string{"investigate_failures", "check_component_health", "manual_intervention_required"},
		}

		sm.addSecurityAlert(alert)
		sm.logger.Warn(fmt.Sprintf("Circuit breaker opened for component: %s, failure count: %d", component, cb.failureCount))
	}
}

// RecordSuccess records a success for circuit breaker logic
func (sm *SecurityManager) RecordSuccess(component string) {
	var cb *CircuitBreaker

	switch component {
	case "rpc":
		cb = sm.rpcCircuitBreaker
	case "arbitrage":
		cb = sm.arbitrageCircuitBreaker
	default:
		return
	}

	cb.mutex.Lock()
	defer cb.mutex.Unlock()

	if cb.state == CircuitBreakerHalfOpen {
		cb.state = CircuitBreakerClosed
		cb.failureCount = 0
		sm.logger.Info(fmt.Sprintf("Circuit breaker closed for component: %s", component))
	}
}

// addSecurityAlert adds a security alert to the system
func (sm *SecurityManager) addSecurityAlert(alert SecurityAlert) {
	sm.alertsMutex.Lock()
	defer sm.alertsMutex.Unlock()

	sm.securityAlerts = append(sm.securityAlerts, alert)
	// Send alert to monitor if available
	if sm.monitor != nil {
		sm.monitor.TriggerAlert(alert.Level, alert.Type, alert.Title, alert.Description, alert.Source, alert.Data, alert.Actions)
	}

	// Keep only last 1000 alerts
	if len(sm.securityAlerts) > 1000 {
		sm.securityAlerts = sm.securityAlerts[len(sm.securityAlerts)-1000:]
	}
}

// startSecurityMonitoring starts background security monitoring
func (sm *SecurityManager) startSecurityMonitoring() {
	ticker := time.NewTicker(1 * time.Minute)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			sm.performSecurityChecks()
		}
	}
}

// performSecurityChecks performs periodic security checks
func (sm *SecurityManager) performSecurityChecks() {
	// Check circuit breakers for recovery
	sm.checkCircuitBreakerRecovery(sm.rpcCircuitBreaker)
	sm.checkCircuitBreakerRecovery(sm.arbitrageCircuitBreaker)

	// Check for emergency stop file
	if sm.config.EmergencyStopFile != "" {
		if _, err := os.Stat(sm.config.EmergencyStopFile); err == nil {
			sm.TriggerEmergencyStop("emergency stop file detected")
		}
	}
}

// checkCircuitBreakerRecovery checks if circuit breakers can transition to half-open
func (sm *SecurityManager) checkCircuitBreakerRecovery(cb *CircuitBreaker) {
	cb.mutex.Lock()
	defer cb.mutex.Unlock()

	if cb.state == CircuitBreakerOpen &&
		time.Since(cb.lastFailureTime) > cb.config.RecoveryTimeout {
		cb.state = CircuitBreakerHalfOpen
		sm.logger.Info(fmt.Sprintf("Circuit breaker transitioned to half-open for component: %s", cb.name))
	}
}

// GetManagerMetrics returns current manager metrics
func (sm *SecurityManager) GetManagerMetrics() *ManagerMetrics {
	return sm.managerMetrics
}

// GetSecurityMetrics returns current security metrics from monitor
func (sm *SecurityManager) GetSecurityMetrics() *SecurityMetrics {
	if sm.monitor != nil {
		return sm.monitor.GetMetrics()
	}
	return &SecurityMetrics{}
}

// GetSecurityAlerts returns recent security alerts
func (sm *SecurityManager) GetSecurityAlerts(limit int) []SecurityAlert {
	sm.alertsMutex.RLock()
	defer sm.alertsMutex.RUnlock()

	if limit <= 0 || limit > len(sm.securityAlerts) {
		limit = len(sm.securityAlerts)
	}

	start := len(sm.securityAlerts) - limit
	if start < 0 {
		start = 0
	}

	alerts := make([]SecurityAlert, limit)
	copy(alerts, sm.securityAlerts[start:])

	return alerts
}

// Shutdown gracefully shuts down the security manager
func (sm *SecurityManager) Shutdown(ctx context.Context) error {
	sm.logger.Info("Shutting down security manager")

	// Shutdown components
	if sm.keyManager != nil {
		// Key manager shutdown - simplified (no shutdown method needed)
		sm.logger.Info("Key manager stopped")
	}

	if sm.rateLimiter != nil {
		// Rate limiter shutdown - simplified
		sm.logger.Info("Rate limiter stopped")
	}

	if sm.monitor != nil {
		// Monitor shutdown - simplified
		sm.logger.Info("Security monitor stopped")
	}

	if sm.rpcHTTPClient != nil {
		sm.rpcHTTPClient.CloseIdleConnections()
	}

	return nil
}

type jsonRPCRequest struct {
	JSONRPC string        `json:"jsonrpc"`
	Method  string        `json:"method"`
	Params  []interface{} `json:"params"`
	ID      string        `json:"id"`
}

type jsonRPCError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

type jsonRPCResponse struct {
	JSONRPC string          `json:"jsonrpc"`
	Result  json.RawMessage `json:"result"`
	Error   *jsonRPCError   `json:"error,omitempty"`
	ID      string          `json:"id"`
}

func normalizeRPCParams(params interface{}) ([]interface{}, error) {
	if params == nil {
		return []interface{}{}, nil
	}

	switch v := params.(type) {
	case []interface{}:
		return v, nil
	case []string:
		result := make([]interface{}, len(v))
		for i := range v {
			result[i] = v[i]
		}
		return result, nil
	case []int:
		result := make([]interface{}, len(v))
		for i := range v {
			result[i] = v[i]
		}
		return result, nil
	}

	val := reflect.ValueOf(params)
	if val.Kind() == reflect.Slice || val.Kind() == reflect.Array {
		length := val.Len()
		result := make([]interface{}, length)
		for i := 0; i < length; i++ {
			result[i] = val.Index(i).Interface()
		}
		return result, nil
	}

	return []interface{}{params}, nil
}