package ha

import (
	"context"
	"fmt"
	"log"
	"sync"
	"time"

	"containr/internal/deployment"
	"containr/internal/metrics"
)

// HighAvailabilityManager manages high availability features
type HighAvailabilityManager struct {
	scheduler         *deployment.Scheduler
	metricsCollector  *metrics.MetricsCollector
	failoverManager   *FailoverManager
	healthChecker     *HealthChecker
	alertManager      *AlertManager
	mu                sync.RWMutex
	enabled           bool
	checkInterval     time.Duration
	failoverThreshold int
}

// FailoverManager handles service failover operations
type FailoverManager struct {
	scheduler        *deployment.Scheduler
	failoverPolicies map[string]*FailoverPolicy
	mu               sync.RWMutex
}

// FailoverPolicy defines failover behavior for a service
type FailoverPolicy struct {
	ServiceID         string             `json:"service_id"`
	Enabled           bool               `json:"enabled"`
	MinHealthyNodes   int                `json:"min_healthy_nodes"`
	MaxFailures       int                `json:"max_failures"`
	FailoverTimeout   time.Duration      `json:"failover_timeout"`
	RecoveryTimeout   time.Duration      `json:"recovery_timeout"`
	FailoverStrategy  FailoverStrategy   `json:"failover_strategy"`
	BackupNodes       []string           `json:"backup_nodes"`
	HealthCheckConfig *HealthCheckConfig `json:"health_check_config"`
}

// FailoverStrategy defines how failover is performed
type FailoverStrategy string

const (
	FailoverStrategyActivePassive FailoverStrategy = "active_passive"
	FailoverStrategyActiveActive  FailoverStrategy = "active_active"
	FailoverStrategyGraceful      FailoverStrategy = "graceful"
)

// HealthCheckConfig defines health check parameters
type HealthCheckConfig struct {
	Interval           time.Duration `json:"interval"`
	Timeout            time.Duration `json:"timeout"`
	UnhealthyThreshold int           `json:"unhealthy_threshold"`
	HealthyThreshold   int           `json:"healthy_threshold"`
	Path               string        `json:"path"`
	Port               int           `json:"port"`
	Protocol           string        `json:"protocol"`
}

// HealthChecker performs health checks on services and nodes
type HealthChecker struct {
	scheduler     *deployment.Scheduler
	checks        map[string]*HealthCheck
	results       map[string]*HealthCheckResult
	mu            sync.RWMutex
	checkInterval time.Duration
}

// HealthCheck represents a health check configuration
type HealthCheck struct {
	ID        string            `json:"id"`
	ServiceID string            `json:"service_id"`
	NodeID    string            `json:"node_id"`
	Type      HealthCheckType   `json:"type"`
	Config    HealthCheckConfig `json:"config"`
	LastCheck time.Time         `json:"last_check"`
	Status    HealthStatus      `json:"status"`
}

// HealthCheckType represents the type of health check
type HealthCheckType string

const (
	HealthCheckTypeHTTP    HealthCheckType = "http"
	HealthCheckTypeTCP     HealthCheckType = "tcp"
	HealthCheckTypeCommand HealthCheckType = "command"
)

// HealthStatus represents the health status
type HealthStatus string

const (
	HealthStatusHealthy   HealthStatus = "healthy"
	HealthStatusUnhealthy HealthStatus = "unhealthy"
	HealthStatusUnknown   HealthStatus = "unknown"
)

// HealthCheckResult represents the result of a health check
type HealthCheckResult struct {
	CheckID   string        `json:"check_id"`
	Status    HealthStatus  `json:"status"`
	Message   string        `json:"message"`
	Latency   time.Duration `json:"latency"`
	Timestamp time.Time     `json:"timestamp"`
	ErrorCode string        `json:"error_code,omitempty"`
}

// AlertManager handles alerting and notifications
type AlertManager struct {
	rules        map[string]*AlertRule
	activeAlerts map[string]*Alert
	notifiers    map[string]Notifier
	mu           sync.RWMutex
}

// AlertRule defines when alerts should be triggered
type AlertRule struct {
	ID          string            `json:"id"`
	Name        string            `json:"name"`
	Description string            `json:"description"`
	Enabled     bool              `json:"enabled"`
	Condition   AlertCondition    `json:"condition"`
	Severity    AlertSeverity     `json:"severity"`
	Labels      map[string]string `json:"labels"`
	Annotations map[string]string `json:"annotations"`
	Notifiers   []string          `json:"notifiers"`
	Cooldown    time.Duration     `json:"cooldown"`
}

// AlertCondition defines the condition for triggering an alert
type AlertCondition struct {
	Metric    string        `json:"metric"`
	Operator  string        `json:"operator"` // >, <, >=, <=, ==, !=
	Threshold float64       `json:"threshold"`
	Duration  time.Duration `json:"duration"`
}

// AlertSeverity represents the severity level of an alert
type AlertSeverity string

const (
	AlertSeverityCritical AlertSeverity = "critical"
	AlertSeverityWarning  AlertSeverity = "warning"
	AlertSeverityInfo     AlertSeverity = "info"
)

// Alert represents an active alert
type Alert struct {
	ID          string            `json:"id"`
	RuleID      string            `json:"rule_id"`
	Status      AlertStatus       `json:"status"`
	Severity    AlertSeverity     `json:"severity"`
	Message     string            `json:"message"`
	Labels      map[string]string `json:"labels"`
	Annotations map[string]string `json:"annotations"`
	StartsAt    time.Time         `json:"starts_at"`
	EndsAt      *time.Time        `json:"ends_at,omitempty"`
	UpdatedAt   time.Time         `json:"updated_at"`
}

// AlertStatus represents the status of an alert
type AlertStatus string

const (
	AlertStatusFiring   AlertStatus = "firing"
	AlertStatusResolved AlertStatus = "resolved"
)

// Notifier sends alert notifications
type Notifier interface {
	Send(ctx context.Context, alert *Alert) error
	Type() string
}

// NewHighAvailabilityManager creates a new HA manager
func NewHighAvailabilityManager(scheduler *deployment.Scheduler, metricsCollector *metrics.MetricsCollector) *HighAvailabilityManager {
	failoverManager := &FailoverManager{
		scheduler:        scheduler,
		failoverPolicies: make(map[string]*FailoverPolicy),
	}

	healthChecker := &HealthChecker{
		scheduler:     scheduler,
		checks:        make(map[string]*HealthCheck),
		results:       make(map[string]*HealthCheckResult),
		checkInterval: 30 * time.Second,
	}

	alertManager := &AlertManager{
		rules:        make(map[string]*AlertRule),
		activeAlerts: make(map[string]*Alert),
		notifiers:    make(map[string]Notifier),
	}

	return &HighAvailabilityManager{
		scheduler:         scheduler,
		metricsCollector:  metricsCollector,
		failoverManager:   failoverManager,
		healthChecker:     healthChecker,
		alertManager:      alertManager,
		enabled:           true,
		checkInterval:     30 * time.Second,
		failoverThreshold: 3,
	}
}

// Start starts the HA management process
func (ha *HighAvailabilityManager) Start(ctx context.Context) error {
	ticker := time.NewTicker(ha.checkInterval)
	defer ticker.Stop()

	log.Printf("HighAvailabilityManager started with check interval: %v", ha.checkInterval)

	// Start health checker
	go ha.healthChecker.Start(ctx)

	// Start alert manager
	go ha.alertManager.Start(ctx)

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
			if ha.enabled {
				if err := ha.checkHighAvailability(ctx); err != nil {
					log.Printf("Error during HA check: %v", err)
				}
			}
		}
	}
}

// checkHighAvailability performs HA checks and takes action if needed
func (ha *HighAvailabilityManager) checkHighAvailability(ctx context.Context) error {
	// Check node health
	nodes := ha.scheduler.GetNodes()
	unhealthyNodes := 0

	for _, node := range nodes {
		if !ha.isNodeHealthy(node) {
			unhealthyNodes++
			log.Printf("Node %s is unhealthy", node.ID)
		}
	}

	// Trigger failover if too many nodes are unhealthy
	if unhealthyNodes >= ha.failoverThreshold {
		log.Printf("Failover threshold reached: %d unhealthy nodes", unhealthyNodes)
		if err := ha.failoverManager.TriggerFailover(ctx, "node_failure"); err != nil {
			return fmt.Errorf("failed to trigger failover: %w", err)
		}
	}

	return nil
}

// isNodeHealthy checks if a node is healthy
func (ha *HighAvailabilityManager) isNodeHealthy(node *deployment.Node) bool {
	// Check if node is ready
	if node.Status != "ready" {
		return false
	}

	// Check heartbeat
	if time.Since(node.LastHeartbeat) > 2*time.Minute {
		return false
	}

	// Check resource usage
	if node.Usage.CPU > 95 || node.Usage.Memory > int64(float64(node.Capacity.Memory)*0.95) {
		return false
	}

	return true
}

// SetFailoverPolicy sets or updates a failover policy
func (ha *HighAvailabilityManager) SetFailoverPolicy(policy *FailoverPolicy) error {
	ha.mu.Lock()
	defer ha.mu.Unlock()

	ha.failoverManager.SetFailoverPolicy(policy)
	return nil
}

// GetFailoverPolicy returns a failover policy
func (ha *HighAvailabilityManager) GetFailoverPolicy(serviceID string) (*FailoverPolicy, error) {
	ha.mu.RLock()
	defer ha.mu.RUnlock()

	return ha.failoverManager.GetFailoverPolicy(serviceID)
}

// TriggerFailover manually triggers a failover
func (ha *HighAvailabilityManager) TriggerFailover(ctx context.Context, reason string) error {
	return ha.failoverManager.TriggerFailover(ctx, reason)
}

// GetHealthStatus returns the health status of all services and nodes
func (ha *HighAvailabilityManager) GetHealthStatus() map[string]interface{} {
	ha.mu.RLock()
	defer ha.mu.RUnlock()

	nodes := ha.scheduler.GetNodes()
	healthyNodes := 0
	unhealthyNodes := 0

	for _, node := range nodes {
		if ha.isNodeHealthy(node) {
			healthyNodes++
		} else {
			unhealthyNodes++
		}
	}

	healthChecks := ha.healthChecker.GetAllHealthChecks()
	healthyChecks := 0
	unhealthyChecks := 0

	for _, result := range ha.healthChecker.GetAllResults() {
		if result.Status == HealthStatusHealthy {
			healthyChecks++
		} else {
			unhealthyChecks++
		}
	}

	activeAlerts := ha.alertManager.GetActiveAlerts()

	return map[string]interface{}{
		"nodes": map[string]interface{}{
			"total":     len(nodes),
			"healthy":   healthyNodes,
			"unhealthy": unhealthyNodes,
		},
		"health_checks": map[string]interface{}{
			"total":     len(healthChecks),
			"healthy":   healthyChecks,
			"unhealthy": unhealthyChecks,
		},
		"alerts": map[string]interface{}{
			"active": len(activeAlerts),
		},
		"enabled": ha.enabled,
	}
}

// Enable enables the HA manager
func (ha *HighAvailabilityManager) Enable() {
	ha.mu.Lock()
	defer ha.mu.Unlock()
	ha.enabled = true
}

// Disable disables the HA manager
func (ha *HighAvailabilityManager) Disable() {
	ha.mu.Lock()
	defer ha.mu.Unlock()
	ha.enabled = false
}

// IsEnabled returns whether the HA manager is enabled
func (ha *HighAvailabilityManager) IsEnabled() bool {
	ha.mu.RLock()
	defer ha.mu.RUnlock()
	return ha.enabled
}

// FailoverManager methods

// SetFailoverPolicy sets a failover policy
func (fm *FailoverManager) SetFailoverPolicy(policy *FailoverPolicy) {
	fm.mu.Lock()
	defer fm.mu.Unlock()
	fm.failoverPolicies[policy.ServiceID] = policy
}

// GetFailoverPolicy returns a failover policy
func (fm *FailoverManager) GetFailoverPolicy(serviceID string) (*FailoverPolicy, error) {
	fm.mu.RLock()
	defer fm.mu.RUnlock()

	policy, exists := fm.failoverPolicies[serviceID]
	if !exists {
		return nil, fmt.Errorf("no failover policy found for service: %s", serviceID)
	}

	return policy, nil
}

// TriggerFailover triggers a failover for affected services
func (fm *FailoverManager) TriggerFailover(ctx context.Context, reason string) error {
	fm.mu.RLock()
	policies := make([]*FailoverPolicy, 0, len(fm.failoverPolicies))
	for _, policy := range fm.failoverPolicies {
		if policy.Enabled {
			policies = append(policies, policy)
		}
	}
	fm.mu.RUnlock()

	for _, policy := range policies {
		if err := fm.performFailover(ctx, policy, reason); err != nil {
			log.Printf("Failed to perform failover for service %s: %v", policy.ServiceID, err)
		}
	}

	return nil
}

// performFailover performs failover for a specific service
func (fm *FailoverManager) performFailover(ctx context.Context, policy *FailoverPolicy, reason string) error {
	log.Printf("Performing failover for service %s: %s", policy.ServiceID, reason)

	// In a real implementation, this would:
	// 1. Identify healthy backup nodes
	// 2. Start new instances on backup nodes
	// 3. Update DNS/load balancer to point to new instances
	// 4. Wait for health checks to pass
	// 5. Shut down unhealthy instances

	// For now, we'll just log the action
	log.Printf("Failover completed for service %s", policy.ServiceID)

	return nil
}

// HealthChecker methods

// Start starts the health checker
func (hc *HealthChecker) Start(ctx context.Context) error {
	ticker := time.NewTicker(hc.checkInterval)
	defer ticker.Stop()

	log.Printf("HealthChecker started with check interval: %v", hc.checkInterval)

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
			if err := hc.performHealthChecks(ctx); err != nil {
				log.Printf("Error during health checks: %v", err)
			}
		}
	}
}

// performHealthChecks performs all configured health checks
func (hc *HealthChecker) performHealthChecks(ctx context.Context) error {
	hc.mu.RLock()
	checks := make([]*HealthCheck, 0, len(hc.checks))
	for _, check := range hc.checks {
		checks = append(checks, check)
	}
	hc.mu.RUnlock()

	for _, check := range checks {
		result := hc.performHealthCheck(ctx, check)
		hc.mu.Lock()
		hc.results[check.ID] = result
		hc.mu.Unlock()
	}

	return nil
}

// performHealthCheck performs a single health check
func (hc *HealthChecker) performHealthCheck(ctx context.Context, check *HealthCheck) *HealthCheckResult {
	start := time.Now()
	result := &HealthCheckResult{
		CheckID:   check.ID,
		Timestamp: start,
		Status:    HealthStatusUnknown,
	}

	// In a real implementation, this would perform actual health checks
	// For now, we'll simulate the check
	time.Sleep(10 * time.Millisecond) // Simulate network latency

	// Simulate healthy/unhealthy based on some logic
	if time.Now().Unix()%10 == 0 { // 10% chance of being unhealthy
		result.Status = HealthStatusUnhealthy
		result.Message = "Service not responding"
		result.ErrorCode = "TIMEOUT"
	} else {
		result.Status = HealthStatusHealthy
		result.Message = "Service is healthy"
	}

	result.Latency = time.Since(start)
	return result
}

// AddHealthCheck adds a new health check
func (hc *HealthChecker) AddHealthCheck(check *HealthCheck) {
	hc.mu.Lock()
	defer hc.mu.Unlock()
	hc.checks[check.ID] = check
}

// RemoveHealthCheck removes a health check
func (hc *HealthChecker) RemoveHealthCheck(checkID string) {
	hc.mu.Lock()
	defer hc.mu.Unlock()
	delete(hc.checks, checkID)
	delete(hc.results, checkID)
}

// GetAllHealthChecks returns all health checks
func (hc *HealthChecker) GetAllHealthChecks() map[string]*HealthCheck {
	hc.mu.RLock()
	defer hc.mu.RUnlock()

	result := make(map[string]*HealthCheck)
	for id, check := range hc.checks {
		result[id] = check
	}

	return result
}

// GetAllResults returns all health check results
func (hc *HealthChecker) GetAllResults() map[string]*HealthCheckResult {
	hc.mu.RLock()
	defer hc.mu.RUnlock()

	result := make(map[string]*HealthCheckResult)
	for id, checkResult := range hc.results {
		result[id] = checkResult
	}

	return result
}

// AlertManager methods

// Start starts the alert manager
func (am *AlertManager) Start(ctx context.Context) error {
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	log.Printf("AlertManager started")

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
			if err := am.evaluateAlertRules(ctx); err != nil {
				log.Printf("Error evaluating alert rules: %v", err)
			}
		}
	}
}

// evaluateAlertRules evaluates all alert rules and triggers alerts if needed
func (am *AlertManager) evaluateAlertRules(ctx context.Context) error {
	am.mu.RLock()
	rules := make([]*AlertRule, 0, len(am.rules))
	for _, rule := range am.rules {
		if rule.Enabled {
			rules = append(rules, rule)
		}
	}
	am.mu.RUnlock()

	for _, rule := range rules {
		if am.shouldTriggerAlert(rule) {
			alert := am.createAlert(rule)
			if err := am.triggerAlert(ctx, alert); err != nil {
				log.Printf("Failed to trigger alert: %v", err)
			}
		}
	}

	return nil
}

// shouldTriggerAlert checks if an alert should be triggered
func (am *AlertManager) shouldTriggerAlert(rule *AlertRule) bool {
	// In a real implementation, this would query metrics and evaluate the condition
	// For now, we'll simulate based on time
	return time.Now().Unix()%20 == 0 // 5% chance of triggering
}

// createAlert creates an alert from a rule
func (am *AlertManager) createAlert(rule *AlertRule) *Alert {
	return &Alert{
		ID:          fmt.Sprintf("alert_%s_%d", rule.ID, time.Now().Unix()),
		RuleID:      rule.ID,
		Status:      AlertStatusFiring,
		Severity:    rule.Severity,
		Message:     fmt.Sprintf("Alert triggered: %s", rule.Name),
		Labels:      rule.Labels,
		Annotations: rule.Annotations,
		StartsAt:    time.Now(),
		UpdatedAt:   time.Now(),
	}
}

// triggerAlert triggers an alert
func (am *AlertManager) triggerAlert(ctx context.Context, alert *Alert) error {
	am.mu.Lock()
	am.activeAlerts[alert.ID] = alert
	am.mu.Unlock()

	// Send notifications
	for _, notifierID := range am.getAlertRule(alert.RuleID).Notifiers {
		if notifier, exists := am.notifiers[notifierID]; exists {
			if err := notifier.Send(ctx, alert); err != nil {
				log.Printf("Failed to send notification via %s: %v", notifierID, err)
			}
		}
	}

	log.Printf("Alert triggered: %s", alert.ID)
	return nil
}

// getAlertRule returns the rule for an alert
func (am *AlertManager) getAlertRule(ruleID string) *AlertRule {
	am.mu.RLock()
	defer am.mu.RUnlock()
	return am.rules[ruleID]
}

// AddAlertRule adds a new alert rule
func (am *AlertManager) AddAlertRule(rule *AlertRule) {
	am.mu.Lock()
	defer am.mu.Unlock()
	am.rules[rule.ID] = rule
}

// RemoveAlertRule removes an alert rule
func (am *AlertManager) RemoveAlertRule(ruleID string) {
	am.mu.Lock()
	defer am.mu.Unlock()
	delete(am.rules, ruleID)
}

// AddNotifier adds a new notifier
func (am *AlertManager) AddNotifier(id string, notifier Notifier) {
	am.mu.Lock()
	defer am.mu.Unlock()
	am.notifiers[id] = notifier
}

// GetActiveAlerts returns all active alerts
func (am *AlertManager) GetActiveAlerts() map[string]*Alert {
	am.mu.RLock()
	defer am.mu.RUnlock()

	result := make(map[string]*Alert)
	for id, alert := range am.activeAlerts {
		result[id] = alert
	}

	return result
}

// ResolveAlert resolves an alert
func (am *AlertManager) ResolveAlert(alertID string) {
	am.mu.Lock()
	defer am.mu.Unlock()

	if alert, exists := am.activeAlerts[alertID]; exists {
		now := time.Now()
		alert.Status = AlertStatusResolved
		alert.EndsAt = &now
		alert.UpdatedAt = now
	}

	delete(am.activeAlerts, alertID)
}

// Mock Notifier implementations

// EmailNotifier sends alerts via email
type EmailNotifier struct {
	SMTPHost string
	SMTPPort int
	Username string
	Password string
	From     string
	To       []string
}

func (n *EmailNotifier) Send(ctx context.Context, alert *Alert) error {
	log.Printf("Sending email alert: %s", alert.Message)
	// In a real implementation, this would send an actual email
	return nil
}

func (n *EmailNotifier) Type() string {
	return "email"
}

// SlackNotifier sends alerts to Slack
type SlackNotifier struct {
	WebhookURL string
	Channel    string
}

func (n *SlackNotifier) Send(ctx context.Context, alert *Alert) error {
	log.Printf("Sending Slack alert: %s", alert.Message)
	// In a real implementation, this would send to Slack webhook
	return nil
}

func (n *SlackNotifier) Type() string {
	return "slack"
}

// WebhookNotifier sends alerts via webhook
type WebhookNotifier struct {
	URL string
}

func (n *WebhookNotifier) Send(ctx context.Context, alert *Alert) error {
	log.Printf("Sending webhook alert: %s", alert.Message)
	// In a real implementation, this would send HTTP request
	return nil
}

func (n *WebhookNotifier) Type() string {
	return "webhook"
}
