package system

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/atlasos/calypso/internal/common/logger"
)

// RRDService handles RRD database operations for network monitoring
type RRDService struct {
	logger        *logger.Logger
	rrdDir        string
	interfaceName string
}

// NewRRDService creates a new RRD service
func NewRRDService(log *logger.Logger, rrdDir string, interfaceName string) *RRDService {
	return &RRDService{
		logger:        log,
		rrdDir:        rrdDir,
		interfaceName: interfaceName,
	}
}

// NetworkStats represents network interface statistics
type NetworkStats struct {
	Interface string    `json:"interface"`
	RxBytes   uint64    `json:"rx_bytes"`
	TxBytes   uint64    `json:"tx_bytes"`
	RxPackets uint64    `json:"rx_packets"`
	TxPackets uint64    `json:"tx_packets"`
	Timestamp time.Time `json:"timestamp"`
}

// GetNetworkStats reads network statistics from /proc/net/dev
func (r *RRDService) GetNetworkStats(ctx context.Context, interfaceName string) (*NetworkStats, error) {
	data, err := os.ReadFile("/proc/net/dev")
	if err != nil {
		return nil, fmt.Errorf("failed to read /proc/net/dev: %w", err)
	}

	lines := strings.Split(string(data), "\n")
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if !strings.HasPrefix(line, interfaceName+":") {
			continue
		}

		// Parse line: interface: rx_bytes rx_packets ... tx_bytes tx_packets ...
		parts := strings.Fields(line)
		if len(parts) < 17 {
			continue
		}

		// Extract statistics
		// Format: interface: rx_bytes rx_packets rx_errs rx_drop ... tx_bytes tx_packets ...
		rxBytes, err := strconv.ParseUint(parts[1], 10, 64)
		if err != nil {
			continue
		}
		rxPackets, err := strconv.ParseUint(parts[2], 10, 64)
		if err != nil {
			continue
		}
		txBytes, err := strconv.ParseUint(parts[9], 10, 64)
		if err != nil {
			continue
		}
		txPackets, err := strconv.ParseUint(parts[10], 10, 64)
		if err != nil {
			continue
		}

		return &NetworkStats{
			Interface: interfaceName,
			RxBytes:   rxBytes,
			TxBytes:   txBytes,
			RxPackets: rxPackets,
			TxPackets: txPackets,
			Timestamp: time.Now(),
		}, nil
	}

	return nil, fmt.Errorf("interface %s not found in /proc/net/dev", interfaceName)
}

// InitializeRRD creates RRD database if it doesn't exist
func (r *RRDService) InitializeRRD(ctx context.Context) error {
	// Ensure RRD directory exists
	if err := os.MkdirAll(r.rrdDir, 0755); err != nil {
		return fmt.Errorf("failed to create RRD directory: %w", err)
	}

	rrdFile := filepath.Join(r.rrdDir, fmt.Sprintf("network-%s.rrd", r.interfaceName))

	// Check if RRD file already exists
	if _, err := os.Stat(rrdFile); err == nil {
		r.logger.Info("RRD file already exists", "file", rrdFile)
		return nil
	}

	// Create RRD database
	// Use COUNTER type to track cumulative bytes, RRD will calculate rate automatically
	// DS:inbound:COUNTER:20:0:U - inbound cumulative bytes, 20s heartbeat
	// DS:outbound:COUNTER:20:0:U - outbound cumulative bytes, 20s heartbeat
	// RRA:AVERAGE:0.5:1:600 - 1 sample per step, 600 steps (100 minutes at 10s interval)
	// RRA:AVERAGE:0.5:6:700 - 6 samples per step, 700 steps (11.6 hours at 1min interval)
	// RRA:AVERAGE:0.5:60:730 - 60 samples per step, 730 steps (5 days at 1hour interval)
	// RRA:MAX:0.5:1:600 - Max values for same intervals
	// RRA:MAX:0.5:6:700
	// RRA:MAX:0.5:60:730
	cmd := exec.CommandContext(ctx, "rrdtool", "create", rrdFile,
		"--step", "10", // 10 second step
		"DS:inbound:COUNTER:20:0:U",  // Inbound cumulative bytes, 20s heartbeat
		"DS:outbound:COUNTER:20:0:U", // Outbound cumulative bytes, 20s heartbeat
		"RRA:AVERAGE:0.5:1:600",      // 10s resolution, 100 minutes
		"RRA:AVERAGE:0.5:6:700",      // 1min resolution, 11.6 hours
		"RRA:AVERAGE:0.5:60:730",     // 1hour resolution, 5 days
		"RRA:MAX:0.5:1:600",          // Max values
		"RRA:MAX:0.5:6:700",
		"RRA:MAX:0.5:60:730",
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to create RRD: %s: %w", string(output), err)
	}

	r.logger.Info("RRD database created", "file", rrdFile)
	return nil
}

// UpdateRRD updates RRD database with new network statistics
func (r *RRDService) UpdateRRD(ctx context.Context, stats *NetworkStats) error {
	rrdFile := filepath.Join(r.rrdDir, fmt.Sprintf("network-%s.rrd", stats.Interface))

	// Update with cumulative byte counts (COUNTER type)
	// RRD will automatically calculate the rate (bytes per second)
	cmd := exec.CommandContext(ctx, "rrdtool", "update", rrdFile,
		fmt.Sprintf("%d:%d:%d", stats.Timestamp.Unix(), stats.RxBytes, stats.TxBytes),
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to update RRD: %s: %w", string(output), err)
	}

	return nil
}

// FetchRRDData fetches data from RRD database for graphing
func (r *RRDService) FetchRRDData(ctx context.Context, startTime time.Time, endTime time.Time, resolution string) ([]NetworkDataPoint, error) {
	rrdFile := filepath.Join(r.rrdDir, fmt.Sprintf("network-%s.rrd", r.interfaceName))

	// Check if RRD file exists
	if _, err := os.Stat(rrdFile); os.IsNotExist(err) {
		return []NetworkDataPoint{}, nil
	}

	// Fetch data using rrdtool fetch
	// Use AVERAGE consolidation with appropriate resolution
	cmd := exec.CommandContext(ctx, "rrdtool", "fetch", rrdFile,
		"AVERAGE",
		"--start", fmt.Sprintf("%d", startTime.Unix()),
		"--end", fmt.Sprintf("%d", endTime.Unix()),
		"--resolution", resolution,
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf("failed to fetch RRD data: %s: %w", string(output), err)
	}

	// Parse rrdtool fetch output
	// Format:
	// inbound outbound
	// 1234567890: 1.2345678901e+06 2.3456789012e+06
	points := []NetworkDataPoint{}
	lines := strings.Split(string(output), "\n")

	// Skip header lines
	dataStart := false
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}

		// Check if this is the data section
		if strings.Contains(line, "inbound") && strings.Contains(line, "outbound") {
			dataStart = true
			continue
		}

		if !dataStart {
			continue
		}

		// Parse data line: timestamp: inbound_value outbound_value
		parts := strings.Fields(line)
		if len(parts) < 3 {
			continue
		}

		// Parse timestamp
		timestampStr := strings.TrimSuffix(parts[0], ":")
		timestamp, err := strconv.ParseInt(timestampStr, 10, 64)
		if err != nil {
			continue
		}

		// Parse inbound (bytes per second from COUNTER, convert to Mbps)
		inboundStr := parts[1]
		inbound, err := strconv.ParseFloat(inboundStr, 64)
		if err != nil || inbound < 0 {
			// Skip NaN or negative values
			continue
		}
		// Convert bytes per second to Mbps (bytes/s * 8 / 1000000)
		inboundMbps := inbound * 8 / 1000000

		// Parse outbound
		outboundStr := parts[2]
		outbound, err := strconv.ParseFloat(outboundStr, 64)
		if err != nil || outbound < 0 {
			// Skip NaN or negative values
			continue
		}
		outboundMbps := outbound * 8 / 1000000

		// Format time as MM:SS
		t := time.Unix(timestamp, 0)
		timeStr := fmt.Sprintf("%02d:%02d", t.Minute(), t.Second())

		points = append(points, NetworkDataPoint{
			Time:     timeStr,
			Inbound:  inboundMbps,
			Outbound: outboundMbps,
		})
	}

	return points, nil
}

// NetworkDataPoint represents a single data point for graphing
type NetworkDataPoint struct {
	Time     string  `json:"time"`
	Inbound  float64 `json:"inbound"`  // Mbps
	Outbound float64 `json:"outbound"` // Mbps
}

// StartCollector starts a background goroutine to periodically collect and update RRD
func (r *RRDService) StartCollector(ctx context.Context, interval time.Duration) error {
	// Initialize RRD if needed
	if err := r.InitializeRRD(ctx); err != nil {
		return fmt.Errorf("failed to initialize RRD: %w", err)
	}

	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()

		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				// Get current stats
				stats, err := r.GetNetworkStats(ctx, r.interfaceName)
				if err != nil {
					r.logger.Warn("Failed to get network stats", "error", err)
					continue
				}

				// Update RRD with cumulative byte counts
				// RRD COUNTER type will automatically calculate rate
				if err := r.UpdateRRD(ctx, stats); err != nil {
					r.logger.Warn("Failed to update RRD", "error", err)
				}
			}
		}
	}()

	return nil
}