package agent

import (
	"fmt"
	"log/slog"
	"path"
	"strings"
	"time"

	"github.com/henrygd/beszel/agent/deltatracker"
	"github.com/henrygd/beszel/internal/entities/system"
	psutilNet "github.com/shirou/gopsutil/v4/net"
)

var netInterfaceDeltaTracker = deltatracker.NewDeltaTracker[string, uint64]()

// NicConfig controls inclusion/exclusion of network interfaces via the NICS env var
//
// Behavior mirrors SensorConfig's matching logic:
// - Leading '-' means blacklist mode; otherwise whitelist mode
// - Supports '*' wildcards using path.Match
// - In whitelist mode with an empty list, no NICs are selected
// - In blacklist mode with an empty list, all NICs are selected
type NicConfig struct {
	nics         map[string]struct{}
	isBlacklist  bool
	hasWildcards bool
}

func newNicConfig(nicsEnvVal string) *NicConfig {
	cfg := &NicConfig{
		nics: make(map[string]struct{}),
	}
	if strings.HasPrefix(nicsEnvVal, "-") {
		cfg.isBlacklist = true
		nicsEnvVal = nicsEnvVal[1:]
	}
	for nic := range strings.SplitSeq(nicsEnvVal, ",") {
		nic = strings.TrimSpace(nic)
		if nic != "" {
			cfg.nics[nic] = struct{}{}
			if strings.Contains(nic, "*") {
				cfg.hasWildcards = true
			}
		}
	}
	return cfg
}

// isValidNic determines if a NIC should be included based on NicConfig rules
func isValidNic(nicName string, cfg *NicConfig) bool {
	// Empty list behavior differs by mode: blacklist: allow all; whitelist: allow none
	if len(cfg.nics) == 0 {
		return cfg.isBlacklist
	}

	// Exact match: return true if whitelist, false if blacklist
	if _, exactMatch := cfg.nics[nicName]; exactMatch {
		return !cfg.isBlacklist
	}

	// If no wildcards, return true if blacklist, false if whitelist
	if !cfg.hasWildcards {
		return cfg.isBlacklist
	}

	// Check for wildcard patterns
	for pattern := range cfg.nics {
		if !strings.Contains(pattern, "*") {
			continue
		}
		if match, _ := path.Match(pattern, nicName); match {
			return !cfg.isBlacklist
		}
	}

	return cfg.isBlacklist
}

func (a *Agent) updateNetworkStats(systemStats *system.Stats) {
	// network stats
	if len(a.netInterfaces) == 0 {
		// if no network interfaces, initialize again
		// this is a fix if agent started before network is online (#466)
		// maybe refactor this in the future to not cache interface names at all so we
		// don't miss an interface that's been added after agent started in any circumstance
		a.initializeNetIoStats()
	}

	if systemStats.NetworkInterfaces == nil {
		systemStats.NetworkInterfaces = make(map[string][4]uint64, 0)
	}

	if netIO, err := psutilNet.IOCounters(true); err == nil {
		msElapsed := uint64(time.Since(a.netIoStats.Time).Milliseconds())
		a.netIoStats.Time = time.Now()
		totalBytesSent := uint64(0)
		totalBytesRecv := uint64(0)
		netInterfaceDeltaTracker.Cycle()
		// sum all bytes sent and received
		for _, v := range netIO {
			// skip if not in valid network interfaces list
			if _, exists := a.netInterfaces[v.Name]; !exists {
				continue
			}
			totalBytesSent += v.BytesSent
			totalBytesRecv += v.BytesRecv

			// track deltas for each network interface
			var upDelta, downDelta uint64
			upKey, downKey := fmt.Sprintf("%sup", v.Name), fmt.Sprintf("%sdown", v.Name)
			netInterfaceDeltaTracker.Set(upKey, v.BytesSent)
			netInterfaceDeltaTracker.Set(downKey, v.BytesRecv)
			if msElapsed > 0 {
				upDelta = netInterfaceDeltaTracker.Delta(upKey) * 1000 / msElapsed
				downDelta = netInterfaceDeltaTracker.Delta(downKey) * 1000 / msElapsed
			}
			// add interface to systemStats
			systemStats.NetworkInterfaces[v.Name] = [4]uint64{upDelta, downDelta, v.BytesSent, v.BytesRecv}
		}

		// add to systemStats
		var bytesSentPerSecond, bytesRecvPerSecond uint64
		if msElapsed > 0 {
			bytesSentPerSecond = (totalBytesSent - a.netIoStats.BytesSent) * 1000 / msElapsed
			bytesRecvPerSecond = (totalBytesRecv - a.netIoStats.BytesRecv) * 1000 / msElapsed
		}
		networkSentPs := bytesToMegabytes(float64(bytesSentPerSecond))
		networkRecvPs := bytesToMegabytes(float64(bytesRecvPerSecond))
		// add check for issue (#150) where sent is a massive number
		if networkSentPs > 10_000 || networkRecvPs > 10_000 {
			slog.Warn("Invalid net stats. Resetting.", "sent", networkSentPs, "recv", networkRecvPs)
			for _, v := range netIO {
				if _, exists := a.netInterfaces[v.Name]; !exists {
					continue
				}
				slog.Info(v.Name, "recv", v.BytesRecv, "sent", v.BytesSent)
			}
			// reset network I/O stats
			a.initializeNetIoStats()
		} else {
			systemStats.NetworkSent = networkSentPs
			systemStats.NetworkRecv = networkRecvPs
			systemStats.Bandwidth[0], systemStats.Bandwidth[1] = bytesSentPerSecond, bytesRecvPerSecond
			// update netIoStats
			a.netIoStats.BytesSent = totalBytesSent
			a.netIoStats.BytesRecv = totalBytesRecv
		}
	}
}

func (a *Agent) initializeNetIoStats() {
	// reset valid network interfaces
	a.netInterfaces = make(map[string]struct{}, 0)

	// parse NICS env var for whitelist / blacklist
	nicsEnvVal, nicsEnvExists := GetEnv("NICS")
	var nicCfg *NicConfig
	if nicsEnvExists {
		nicCfg = newNicConfig(nicsEnvVal)
	}

	// reset network I/O stats
	a.netIoStats.BytesSent = 0
	a.netIoStats.BytesRecv = 0

	// get intial network I/O stats
	if netIO, err := psutilNet.IOCounters(true); err == nil {
		a.netIoStats.Time = time.Now()
		for _, v := range netIO {
			if nicsEnvExists && !isValidNic(v.Name, nicCfg) {
				continue
			}
			if a.skipNetworkInterface(v) {
				continue
			}
			slog.Info("Detected network interface", "name", v.Name, "sent", v.BytesSent, "recv", v.BytesRecv)
			a.netIoStats.BytesSent += v.BytesSent
			a.netIoStats.BytesRecv += v.BytesRecv
			// store as a valid network interface
			a.netInterfaces[v.Name] = struct{}{}
		}
	}
}

func (a *Agent) skipNetworkInterface(v psutilNet.IOCountersStat) bool {
	switch {
	case strings.HasPrefix(v.Name, "lo"),
		strings.HasPrefix(v.Name, "docker"),
		strings.HasPrefix(v.Name, "br-"),
		strings.HasPrefix(v.Name, "veth"),
		strings.HasPrefix(v.Name, "bond"),
		v.BytesRecv == 0,
		v.BytesSent == 0:
		return true
	default:
		return false
	}
}