package main

import (
	"context"
	"log"
	"math"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/nutcas3/telecom-platform/apps/api-server/internal/config"
	"github.com/nutcas3/telecom-platform/apps/api-server/internal/database"
	"github.com/nutcas3/telecom-platform/apps/api-server/internal/graphql"
	"github.com/nutcas3/telecom-platform/apps/api-server/internal/metrics"
	"github.com/nutcas3/telecom-platform/apps/api-server/internal/models"
)

func main() {
	// Load configuration
	cfg := config.LoadConfig()

	// Initialize database
	db, err := database.NewDatabase(&cfg.Database)
	if err != nil {
		log.Fatalf("Failed to initialize database: %v", err)
	}
	defer db.Close()

	// Initialize metrics collector
	prometheusCollector := metrics.NewMetricsCollector()
	prometheusCollector.Register()

	// Initialize time-series storage (optional)
	var timeSeriesStorage *metrics.TimeSeriesStorage
	if cfg.InfluxDB.URL != "" {
		timeSeriesStorage, err = metrics.NewTimeSeriesStorage(
			cfg.InfluxDB.URL,
			cfg.InfluxDB.Token,
			cfg.InfluxDB.Org,
			cfg.InfluxDB.Bucket,
		)
		if err != nil {
			log.Printf("Failed to initialize time-series storage: %v", err)
		}
		defer func() {
			if timeSeriesStorage != nil {
				timeSeriesStorage.Close()
			}
		}()
	}

	// Create metrics collector with time-series
	var metricsCollector *metrics.MetricsCollectorWithTimeSeries
	if timeSeriesStorage != nil {
		metricsCollector = metrics.NewMetricsCollectorWithTimeSeries(prometheusCollector, timeSeriesStorage)
	} else {
		metricsCollector = &metrics.MetricsCollectorWithTimeSeries{
			MetricsCollector: prometheusCollector,
		}
	}

	// Initialize GraphQL resolver
	resolver := graphql.NewResolver(db, cfg)

	// Setup HTTP server with GraphQL handler
	router := gin.Default()
	graphql.SetupGraphQLHandler(router, resolver)

	// Add metrics middleware
	router.Use(func(c *gin.Context) {
		// Create a wrapper handler that calls the next handler
		next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			c.Next()
		})

		// Apply prometheus middleware
		middlewareHandler := prometheusCollector.HTTPMiddleware(next)
		middlewareHandler.ServeHTTP(c.Writer, c.Request)
	})

	// Add metrics endpoint
	router.GET("/metrics", gin.WrapH(prometheusCollector.Handler()))

	// Add health check endpoint
	router.GET("/health", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{
			"status":  "healthy",
			"service": "api-server",
		})
	})

	// Create server
	server := &http.Server{
		Addr:         ":" + cfg.Server.Port,
		Handler:      router,
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 30 * time.Second,
	}

	// Start metrics server in background
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	go func() {
		metricsAddr := cfg.Server.MetricsPort
		if metricsAddr == "" {
			metricsAddr = "9090"
		}
		log.Printf("Starting metrics server on port %s", metricsAddr)
		if err := prometheusCollector.StartMetricsServer(ctx, ":"+metricsAddr); err != nil {
			log.Printf("Metrics server error: %v", err)
		}
	}()

	// Start periodic metrics collection
	go startMetricsCollection(ctx, metricsCollector, db)

	// Start server in a goroutine
	go func() {
		log.Printf("Starting API server on port %s", cfg.Server.Port)
		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("Server failed to start: %v", err)
		}
	}()

	// Wait for interrupt signal to gracefully shutdown the server
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	<-quit

	log.Println("Shutting down server...")

	// Shutdown server with timeout
	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer shutdownCancel()

	if err := server.Shutdown(shutdownCtx); err != nil {
		log.Printf("Server forced to shutdown: %v", err)
	}

	log.Println("Server exited")
}

// startMetricsCollection periodically collects and stores metrics
func startMetricsCollection(ctx context.Context, mc *metrics.MetricsCollectorWithTimeSeries, db *database.Database) {
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			collectMetrics(ctx, mc, db)
		}
	}
}

// collectMetrics gathers metrics from various sources
func collectMetrics(ctx context.Context, mc *metrics.MetricsCollectorWithTimeSeries, db *database.Database) {
	// Collect subscriber metrics
	totalSubs, activeSubs, suspendedSubs := getSubscriberStats(db)
	mc.UpdateSubscriberMetrics(totalSubs, activeSubs, suspendedSubs)

	// Collect system metrics
	systemMetrics := metrics.SystemMetrics{
		ActiveSessions: getActiveSessionsCount(db),
		CPUUsage:       getCPUUsage(),
		MemoryUsage:    getMemoryUsage(),
		NetworkRX:      getNetworkRX(),
		NetworkTX:      getNetworkTX(),
		Timestamp:      time.Now(),
	}

	// Store in time-series if available
	if ts := mc.GetTimeSeriesStorage(); ts != nil {
		if err := ts.StoreSystemMetrics(ctx, systemMetrics); err != nil {
			log.Printf("Failed to store system metrics: %v", err)
		}
	}
}

// Helper functions for metrics collection (actual implementations)
func getSubscriberStats(db *database.Database) (total, active, suspended int) {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	// Count total subscribers using GORM
	var totalCount int64
	if err := db.DB.WithContext(ctx).Model(&models.Subscriber{}).Count(&totalCount).Error; err != nil {
		log.Printf("Error counting total subscribers: %v", err)
		return 0, 0, 0
	}

	// Count active subscribers
	var activeCount int64
	if err := db.DB.WithContext(ctx).Model(&models.Subscriber{}).Where("status = ?", "active").Count(&activeCount).Error; err != nil {
		log.Printf("Error counting active subscribers: %v", err)
		return int(totalCount), 0, 0
	}

	// Count suspended subscribers
	var suspendedCount int64
	if err := db.DB.WithContext(ctx).Model(&models.Subscriber{}).Where("status IN ?", []string{"suspended", "deactivated", "blocked"}).Count(&suspendedCount).Error; err != nil {
		log.Printf("Error counting suspended subscribers: %v", err)
		return int(totalCount), int(activeCount), 0
	}

	return int(totalCount), int(activeCount), int(suspendedCount)
}

func getActiveSessionsCount(db *database.Database) int {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	// Count active charging sessions using GORM
	var count int64
	if err := db.DB.WithContext(ctx).Model(&models.Session{}).Where(
		"status IN ? AND end_time IS NULL",
		[]string{"active", "connected", "established"},
	).Count(&count).Error; err != nil {
		log.Printf("Error counting active sessions: %v", err)
		return 0
	}

	return int(count)
}

func getCPUUsage() float64 {
	// Read CPU usage from /proc/stat on Linux systems
	data, err := os.ReadFile("/proc/stat")
	if err != nil {
		log.Printf("Error reading /proc/stat: %v", err)
		return 0
	}

	lines := strings.Split(string(data), "\n")
	if len(lines) == 0 {
		return 0
	}

	// Parse the first line (total CPU usage)
	fields := strings.Fields(lines[0])
	if len(fields) < 8 || fields[0] != "cpu" {
		return 0
	}

	// Parse CPU time values (user, nice, system, idle, iowait, irq, softirq, steal)
	var totalCPU, idleCPU float64
	for i, field := range fields[1:8] {
		val, err := strconv.ParseFloat(field, 64)
		if err != nil {
			continue
		}
		totalCPU += val
		if i == 3 { // idle time
			idleCPU = val
		}
	}

	if totalCPU == 0 {
		return 0
	}

	// Calculate CPU usage percentage (non-idle time)
	cpuUsage := ((totalCPU - idleCPU) / totalCPU) * 100
	return math.Min(cpuUsage, 100.0) // Cap at 100%
}

func getMemoryUsage() float64 {
	// Read memory usage from /proc/meminfo on Linux systems
	data, err := os.ReadFile("/proc/meminfo")
	if err != nil {
		log.Printf("Error reading /proc/meminfo: %v", err)
		return 0
	}

	lines := strings.Split(string(data), "\n")
	var totalMem, availableMem float64

	// Parse memory information
	for _, line := range lines {
		fields := strings.Fields(line)
		if len(fields) < 2 {
			continue
		}

		switch fields[0] {
		case "MemTotal:":
			if val, err := strconv.ParseFloat(fields[1], 64); err == nil {
				totalMem = val * 1024 // Convert KB to bytes
			}
		case "MemAvailable:":
			if val, err := strconv.ParseFloat(fields[1], 64); err == nil {
				availableMem = val * 1024 // Convert KB to bytes
			}
		}
	}

	if totalMem == 0 {
		return 0
	}

	// Calculate memory usage percentage
	usedMem := totalMem - availableMem
	memoryUsage := (usedMem / totalMem) * 100
	return math.Min(memoryUsage, 100.0) // Cap at 100%
}

func getNetworkRX() int64 {
	// Read network statistics from /proc/net/dev on Linux systems
	data, err := os.ReadFile("/proc/net/dev")
	if err != nil {
		log.Printf("Error reading /proc/net/dev: %v", err)
		return 0
	}

	lines := strings.Split(string(data), "\n")
	var totalRX int64

	// Skip header lines (first two lines)
	for i, line := range lines {
		if i < 2 {
			continue
		}

		fields := strings.Fields(line)
		if len(fields) < 10 {
			continue
		}

		// Skip loopback interface
		if strings.HasPrefix(fields[0], "lo:") {
			continue
		}

		// RX bytes are in field 1 (after interface name)
		if rxBytes, err := strconv.ParseInt(fields[1], 10, 64); err == nil {
			totalRX += rxBytes
		}
	}

	return totalRX
}

func getNetworkTX() int64 {
	// Read network statistics from /proc/net/dev on Linux systems
	data, err := os.ReadFile("/proc/net/dev")
	if err != nil {
		log.Printf("Error reading /proc/net/dev: %v", err)
		return 0
	}

	lines := strings.Split(string(data), "\n")
	var totalTX int64

	// Skip header lines (first two lines)
	for i, line := range lines {
		if i < 2 {
			continue
		}

		fields := strings.Fields(line)
		if len(fields) < 10 {
			continue
		}

		// Skip loopback interface
		if strings.HasPrefix(fields[0], "lo:") {
			continue
		}

		// TX bytes are in field 9 (after interface name and RX stats)
		if txBytes, err := strconv.ParseInt(fields[9], 10, 64); err == nil {
			totalTX += txBytes
		}
	}

	return totalTX
}