package storage

import (
	"context"
	"encoding/json"
	"fmt"
	"sort"
	"sync"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

// MonitoringSystem provides comprehensive monitoring for the storage system
type MonitoringSystem struct {
	mu                sync.RWMutex
	nodeID            string
	metrics           *StorageMetrics
	alerts            *AlertManager
	healthChecker     *HealthChecker
	performanceProfiler *PerformanceProfiler
	logger            *StructuredLogger
	notifications     chan *MonitoringEvent
	stopCh            chan struct{}
}

// StorageMetrics contains all Prometheus metrics for storage operations
type StorageMetrics struct {
	// Operation counters
	StoreOperations     prometheus.Counter
	RetrieveOperations  prometheus.Counter
	DeleteOperations    prometheus.Counter
	UpdateOperations    prometheus.Counter
	SearchOperations    prometheus.Counter
	BatchOperations     prometheus.Counter

	// Error counters
	StoreErrors         prometheus.Counter
	RetrieveErrors      prometheus.Counter
	EncryptionErrors    prometheus.Counter
	DecryptionErrors    prometheus.Counter
	ReplicationErrors   prometheus.Counter
	CacheErrors         prometheus.Counter
	IndexErrors         prometheus.Counter

	// Latency histograms
	StoreLatency        prometheus.Histogram
	RetrieveLatency     prometheus.Histogram
	EncryptionLatency   prometheus.Histogram
	DecryptionLatency   prometheus.Histogram
	ReplicationLatency  prometheus.Histogram
	SearchLatency       prometheus.Histogram

	// Cache metrics
	CacheHits           prometheus.Counter
	CacheMisses         prometheus.Counter
	CacheEvictions      prometheus.Counter
	CacheSize           prometheus.Gauge

	// Storage size metrics
	LocalStorageSize    prometheus.Gauge
	DistributedStorageSize prometheus.Gauge
	CompressedStorageSize  prometheus.Gauge
	IndexStorageSize       prometheus.Gauge

	// Replication metrics
	ReplicationFactor   prometheus.Gauge
	HealthyReplicas     prometheus.Gauge
	UnderReplicated     prometheus.Gauge
	ReplicationLag      prometheus.Histogram

	// Encryption metrics
	EncryptedContexts   prometheus.Gauge
	KeyRotations        prometheus.Counter
	AccessDenials       prometheus.Counter
	ActiveKeys          prometheus.Gauge

	// Performance metrics
	Throughput          prometheus.Gauge
	ConcurrentOperations prometheus.Gauge
	QueueDepth          prometheus.Gauge

	// Health metrics
	StorageHealth       prometheus.Gauge
	NodeConnectivity    prometheus.Gauge
	SyncLatency         prometheus.Histogram
}

// AlertManager handles storage-related alerts and notifications
type AlertManager struct {
	mu           sync.RWMutex
	rules        []*AlertRule
	activealerts map[string]*Alert
	notifiers    []AlertNotifier
	history      []*Alert
	maxHistory   int
}

// AlertRule defines conditions for triggering alerts
type AlertRule struct {
	ID          string             `json:"id"`
	Name        string             `json:"name"`
	Description string             `json:"description"`
	Metric      string             `json:"metric"`
	Condition   string             `json:"condition"` // >, <, ==, !=, etc.
	Threshold   float64            `json:"threshold"`
	Duration    time.Duration      `json:"duration"`
	Severity    AlertSeverity      `json:"severity"`
	Labels      map[string]string  `json:"labels"`
	Enabled     bool               `json:"enabled"`
}

// Alert represents an active or resolved alert
type Alert struct {
	ID          string            `json:"id"`
	RuleID      string            `json:"rule_id"`
	Name        string            `json:"name"`
	Description string            `json:"description"`
	Severity    AlertSeverity     `json:"severity"`
	Status      AlertStatus       `json:"status"`
	Value       float64           `json:"value"`
	Threshold   float64           `json:"threshold"`
	Labels      map[string]string `json:"labels"`
	StartTime   time.Time         `json:"start_time"`
	EndTime     *time.Time        `json:"end_time,omitempty"`
	LastUpdate  time.Time         `json:"last_update"`
}

// AlertSeverity defines alert severity levels
type AlertSeverity string

const (
	SeverityInfo     AlertSeverity = "info"
	SeverityWarning  AlertSeverity = "warning"
	SeverityError    AlertSeverity = "error"
	SeverityCritical AlertSeverity = "critical"
)

// AlertStatus defines alert status
type AlertStatus string

const (
	StatusPending  AlertStatus = "pending"
	StatusFiring   AlertStatus = "firing"
	StatusResolved AlertStatus = "resolved"
)

// AlertNotifier interface for sending alert notifications
type AlertNotifier interface {
	Notify(alert *Alert) error
	GetType() string
}

// HealthChecker monitors the overall health of the storage system
type HealthChecker struct {
	mu            sync.RWMutex
	checks        map[string]HealthCheck
	status        *SystemHealth
	checkInterval time.Duration
	timeout       time.Duration
}

// HealthCheck defines a single health check
type HealthCheck struct {
	Name        string                                `json:"name"`
	Description string                                `json:"description"`
	Checker     func(ctx context.Context) HealthResult `json:"-"`
	Interval    time.Duration                        `json:"interval"`
	Timeout     time.Duration                        `json:"timeout"`
	Enabled     bool                                 `json:"enabled"`
}

// HealthResult represents the result of a health check
type HealthResult struct {
	Healthy   bool              `json:"healthy"`
	Message   string            `json:"message"`
	Latency   time.Duration     `json:"latency"`
	Metadata  map[string]interface{} `json:"metadata"`
	Timestamp time.Time         `json:"timestamp"`
}

// SystemHealth represents the overall health of the storage system
type SystemHealth struct {
	OverallStatus  HealthStatus           `json:"overall_status"`
	Components     map[string]HealthResult `json:"components"`
	LastUpdate     time.Time              `json:"last_update"`
	Uptime         time.Duration          `json:"uptime"`
	StartTime      time.Time              `json:"start_time"`
}

// HealthStatus represents system health status
type HealthStatus string

const (
	HealthHealthy   HealthStatus = "healthy"
	HealthDegraded  HealthStatus = "degraded"
	HealthUnhealthy HealthStatus = "unhealthy"
)

// PerformanceProfiler analyzes storage performance patterns
type PerformanceProfiler struct {
	mu               sync.RWMutex
	operationProfiles map[string]*OperationProfile
	resourceUsage    *ResourceUsage
	bottlenecks      []*Bottleneck
	recommendations  []*PerformanceRecommendation
}

// OperationProfile contains performance analysis for a specific operation type
type OperationProfile struct {
	Operation       string            `json:"operation"`
	TotalOperations int64             `json:"total_operations"`
	AverageLatency  time.Duration     `json:"average_latency"`
	P50Latency      time.Duration     `json:"p50_latency"`
	P95Latency      time.Duration     `json:"p95_latency"`
	P99Latency      time.Duration     `json:"p99_latency"`
	Throughput      float64           `json:"throughput"`
	ErrorRate       float64           `json:"error_rate"`
	LatencyHistory  []time.Duration   `json:"-"`
	LastUpdated     time.Time         `json:"last_updated"`
}

// ResourceUsage tracks resource consumption
type ResourceUsage struct {
	CPUUsage       float64   `json:"cpu_usage"`
	MemoryUsage    int64     `json:"memory_usage"`
	DiskUsage      int64     `json:"disk_usage"`
	NetworkIn      int64     `json:"network_in"`
	NetworkOut     int64     `json:"network_out"`
	OpenFiles      int       `json:"open_files"`
	Goroutines     int       `json:"goroutines"`
	LastUpdated    time.Time `json:"last_updated"`
}

// Bottleneck represents a performance bottleneck
type Bottleneck struct {
	ID          string            `json:"id"`
	Type        string            `json:"type"` // cpu, memory, disk, network, etc.
	Component   string            `json:"component"`
	Description string            `json:"description"`
	Severity    AlertSeverity     `json:"severity"`
	Impact      float64           `json:"impact"`
	DetectedAt  time.Time         `json:"detected_at"`
	Metadata    map[string]interface{} `json:"metadata"`
}

// PerformanceRecommendation suggests optimizations
type PerformanceRecommendation struct {
	ID          string            `json:"id"`
	Type        string            `json:"type"`
	Title       string            `json:"title"`
	Description string            `json:"description"`
	Priority    int               `json:"priority"`
	Impact      string            `json:"impact"`
	Effort      string            `json:"effort"`
	GeneratedAt time.Time         `json:"generated_at"`
	Metadata    map[string]interface{} `json:"metadata"`
}

// MonitoringEvent represents a monitoring system event
type MonitoringEvent struct {
	Type        string            `json:"type"`
	Level       string            `json:"level"`
	Message     string            `json:"message"`
	Component   string            `json:"component"`
	NodeID      string            `json:"node_id"`
	Timestamp   time.Time         `json:"timestamp"`
	Metadata    map[string]interface{} `json:"metadata"`
}

// StructuredLogger provides structured logging for storage operations
type StructuredLogger struct {
	mu       sync.RWMutex
	level    LogLevel
	output   LogOutput
	formatter LogFormatter
	buffer   []*LogEntry
	maxBuffer int
}

// LogLevel defines logging levels
type LogLevel int

const (
	LogDebug LogLevel = iota
	LogInfo
	LogWarning
	LogError
	LogCritical
)

// LogOutput interface for different output destinations
type LogOutput interface {
	Write(entry *LogEntry) error
	Flush() error
}

// LogFormatter interface for different log formats
type LogFormatter interface {
	Format(entry *LogEntry) ([]byte, error)
}

// LogEntry represents a single log entry
type LogEntry struct {
	Level     LogLevel          `json:"level"`
	Message   string            `json:"message"`
	Component string            `json:"component"`
	Operation string            `json:"operation"`
	NodeID    string            `json:"node_id"`
	Timestamp time.Time         `json:"timestamp"`
	Fields    map[string]interface{} `json:"fields"`
	Error     error             `json:"error,omitempty"`
}

// NewMonitoringSystem creates a new monitoring system
func NewMonitoringSystem(nodeID string) *MonitoringSystem {
	ms := &MonitoringSystem{
		nodeID:        nodeID,
		metrics:       initializeMetrics(nodeID),
		alerts:        newAlertManager(),
		healthChecker: newHealthChecker(),
		performanceProfiler: newPerformanceProfiler(),
		logger:        newStructuredLogger(),
		notifications: make(chan *MonitoringEvent, 1000),
		stopCh:        make(chan struct{}),
	}

	// Start monitoring goroutines
	go ms.monitoringLoop()
	go ms.healthCheckLoop()
	go ms.alertEvaluationLoop()
	go ms.performanceAnalysisLoop()

	return ms
}

// initializeMetrics creates and registers all Prometheus metrics
func initializeMetrics(nodeID string) *StorageMetrics {
	labels := prometheus.Labels{"node_id": nodeID}

	return &StorageMetrics{
		// Operation counters
		StoreOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_store_operations_total",
			Help:        "Total number of store operations",
			ConstLabels: labels,
		}),
		RetrieveOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_retrieve_operations_total",
			Help:        "Total number of retrieve operations",
			ConstLabels: labels,
		}),
		DeleteOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_delete_operations_total",
			Help:        "Total number of delete operations",
			ConstLabels: labels,
		}),
		UpdateOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_update_operations_total",
			Help:        "Total number of update operations",
			ConstLabels: labels,
		}),
		SearchOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_search_operations_total",
			Help:        "Total number of search operations",
			ConstLabels: labels,
		}),
		BatchOperations: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_batch_operations_total",
			Help:        "Total number of batch operations",
			ConstLabels: labels,
		}),

		// Error counters
		StoreErrors: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_store_errors_total",
			Help:        "Total number of store errors",
			ConstLabels: labels,
		}),
		RetrieveErrors: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_retrieve_errors_total",
			Help:        "Total number of retrieve errors",
			ConstLabels: labels,
		}),
		EncryptionErrors: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_encryption_errors_total",
			Help:        "Total number of encryption errors",
			ConstLabels: labels,
		}),

		// Latency histograms
		StoreLatency: promauto.NewHistogram(prometheus.HistogramOpts{
			Name:        "slurp_storage_store_latency_seconds",
			Help:        "Store operation latency in seconds",
			ConstLabels: labels,
			Buckets:     prometheus.DefBuckets,
		}),
		RetrieveLatency: promauto.NewHistogram(prometheus.HistogramOpts{
			Name:        "slurp_storage_retrieve_latency_seconds",
			Help:        "Retrieve operation latency in seconds",
			ConstLabels: labels,
			Buckets:     prometheus.DefBuckets,
		}),

		// Cache metrics
		CacheHits: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_cache_hits_total",
			Help:        "Total number of cache hits",
			ConstLabels: labels,
		}),
		CacheMisses: promauto.NewCounter(prometheus.CounterOpts{
			Name:        "slurp_storage_cache_misses_total",
			Help:        "Total number of cache misses",
			ConstLabels: labels,
		}),

		// Storage size gauges
		LocalStorageSize: promauto.NewGauge(prometheus.GaugeOpts{
			Name:        "slurp_storage_local_size_bytes",
			Help:        "Local storage size in bytes",
			ConstLabels: labels,
		}),
		DistributedStorageSize: promauto.NewGauge(prometheus.GaugeOpts{
			Name:        "slurp_storage_distributed_size_bytes",
			Help:        "Distributed storage size in bytes",
			ConstLabels: labels,
		}),

		// Health metrics
		StorageHealth: promauto.NewGauge(prometheus.GaugeOpts{
			Name:        "slurp_storage_health_status",
			Help:        "Storage health status (1=healthy, 0=unhealthy)",
			ConstLabels: labels,
		}),
	}
}

// Recording methods for metrics

func (ms *MonitoringSystem) RecordStoreOperation(duration time.Duration, success bool) {
	ms.metrics.StoreOperations.Inc()
	ms.metrics.StoreLatency.Observe(duration.Seconds())
	if !success {
		ms.metrics.StoreErrors.Inc()
	}
}

func (ms *MonitoringSystem) RecordRetrieveOperation(duration time.Duration, success bool, cacheHit bool) {
	ms.metrics.RetrieveOperations.Inc()
	ms.metrics.RetrieveLatency.Observe(duration.Seconds())
	if !success {
		ms.metrics.RetrieveErrors.Inc()
	}
	if cacheHit {
		ms.metrics.CacheHits.Inc()
	} else {
		ms.metrics.CacheMisses.Inc()
	}
}

func (ms *MonitoringSystem) RecordEncryptionOperation(duration time.Duration, success bool) {
	ms.metrics.EncryptionLatency.Observe(duration.Seconds())
	if !success {
		ms.metrics.EncryptionErrors.Inc()
	}
}

func (ms *MonitoringSystem) UpdateStorageSize(local, distributed, compressed, index int64) {
	ms.metrics.LocalStorageSize.Set(float64(local))
	ms.metrics.DistributedStorageSize.Set(float64(distributed))
	ms.metrics.CompressedStorageSize.Set(float64(compressed))
	ms.metrics.IndexStorageSize.Set(float64(index))
}

func (ms *MonitoringSystem) UpdateHealthStatus(healthy bool) {
	if healthy {
		ms.metrics.StorageHealth.Set(1)
	} else {
		ms.metrics.StorageHealth.Set(0)
	}
}

// Main monitoring loops

func (ms *MonitoringSystem) monitoringLoop() {
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			ms.collectSystemMetrics()
		case event := <-ms.notifications:
			ms.processMonitoringEvent(event)
		case <-ms.stopCh:
			return
		}
	}
}

func (ms *MonitoringSystem) healthCheckLoop() {
	ticker := time.NewTicker(1 * time.Minute)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			ms.performHealthChecks()
		case <-ms.stopCh:
			return
		}
	}
}

func (ms *MonitoringSystem) alertEvaluationLoop() {
	ticker := time.NewTicker(15 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			ms.evaluateAlertRules()
		case <-ms.stopCh:
			return
		}
	}
}

func (ms *MonitoringSystem) performanceAnalysisLoop() {
	ticker := time.NewTicker(5 * time.Minute)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			ms.analyzePerformance()
		case <-ms.stopCh:
			return
		}
	}
}

// Implementation of monitoring functions (simplified)

func (ms *MonitoringSystem) collectSystemMetrics() {
	// Collect system-level metrics
	// This would integrate with system monitoring tools
}

func (ms *MonitoringSystem) processMonitoringEvent(event *MonitoringEvent) {
	// Process monitoring events
	ms.logger.LogEvent(event)
}

func (ms *MonitoringSystem) performHealthChecks() {
	// Execute all registered health checks
	ms.healthChecker.mu.RLock()
	checks := ms.healthChecker.checks
	ms.healthChecker.mu.RUnlock()

	for _, check := range checks {
		if check.Enabled {
			go ms.executeHealthCheck(check)
		}
	}
}

func (ms *MonitoringSystem) executeHealthCheck(check HealthCheck) {
	ctx, cancel := context.WithTimeout(context.Background(), check.Timeout)
	defer cancel()

	result := check.Checker(ctx)
	
	ms.healthChecker.mu.Lock()
	ms.healthChecker.status.Components[check.Name] = result
	ms.healthChecker.mu.Unlock()
}

func (ms *MonitoringSystem) evaluateAlertRules() {
	// Evaluate alert rules against current metrics
	// This would query Prometheus metrics and trigger alerts
}

func (ms *MonitoringSystem) analyzePerformance() {
	// Analyze performance patterns and generate recommendations
	ms.performanceProfiler.analyzeBottlenecks()
	ms.performanceProfiler.generateRecommendations()
}

// Helper functions and implementations

func newAlertManager() *AlertManager {
	return &AlertManager{
		rules:       make([]*AlertRule, 0),
		activealerts: make(map[string]*Alert),
		notifiers:    make([]AlertNotifier, 0),
		history:     make([]*Alert, 0),
		maxHistory:  1000,
	}
}

func newHealthChecker() *HealthChecker {
	return &HealthChecker{
		checks:        make(map[string]HealthCheck),
		status:        &SystemHealth{
			OverallStatus: HealthHealthy,
			Components:   make(map[string]HealthResult),
			StartTime:    time.Now(),
		},
		checkInterval: 1 * time.Minute,
		timeout:       30 * time.Second,
	}
}

func newPerformanceProfiler() *PerformanceProfiler {
	return &PerformanceProfiler{
		operationProfiles: make(map[string]*OperationProfile),
		resourceUsage:     &ResourceUsage{},
		bottlenecks:       make([]*Bottleneck, 0),
		recommendations:   make([]*PerformanceRecommendation, 0),
	}
}

func newStructuredLogger() *StructuredLogger {
	return &StructuredLogger{
		level:     LogInfo,
		buffer:    make([]*LogEntry, 0),
		maxBuffer: 10000,
	}
}

func (sl *StructuredLogger) LogEvent(event *MonitoringEvent) {
	entry := &LogEntry{
		Level:     LogInfo,
		Message:   event.Message,
		Component: event.Component,
		NodeID:    event.NodeID,
		Timestamp: event.Timestamp,
		Fields:    event.Metadata,
	}

	sl.mu.Lock()
	sl.buffer = append(sl.buffer, entry)
	if len(sl.buffer) > sl.maxBuffer {
		sl.buffer = sl.buffer[1:] // Remove oldest entry
	}
	sl.mu.Unlock()
}

func (pp *PerformanceProfiler) analyzeBottlenecks() {
	// Analyze performance data to identify bottlenecks
	// This would examine latency patterns, error rates, etc.
}

func (pp *PerformanceProfiler) generateRecommendations() {
	// Generate performance improvement recommendations
	// This would analyze patterns and suggest optimizations
}

// GetMonitoringStats returns comprehensive monitoring statistics
func (ms *MonitoringSystem) GetMonitoringStats() (*MonitoringStats, error) {
	ms.mu.RLock()
	defer ms.mu.RUnlock()

	stats := &MonitoringStats{
		NodeID:      ms.nodeID,
		Timestamp:   time.Now(),
		HealthStatus: ms.healthChecker.status.OverallStatus,
		ActiveAlerts: len(ms.alerts.activealerts),
		Bottlenecks:  len(ms.performanceProfiler.bottlenecks),
	}

	return stats, nil
}

// MonitoringStats contains monitoring system statistics
type MonitoringStats struct {
	NodeID       string       `json:"node_id"`
	Timestamp    time.Time    `json:"timestamp"`
	HealthStatus HealthStatus `json:"health_status"`
	ActiveAlerts int          `json:"active_alerts"`
	Bottlenecks  int          `json:"bottlenecks"`
}

// Close shuts down the monitoring system
func (ms *MonitoringSystem) Close() error {
	close(ms.stopCh)
	return nil
}
