// Copyright 2025, IPng Networks GmbH, Pim van Pelt <pim@ipng.ch>

package vppstats

import (
	"flag"
	"time"

	"go.fd.io/govpp/adapter/socketclient"
	"go.fd.io/govpp/adapter/statsclient"
	"go.fd.io/govpp/api"
	"go.fd.io/govpp/binapi/vpe"
	"go.fd.io/govpp/core"

	"govpp-snmp-agentx/logger"
)

type StatsCallback func(*api.InterfaceStats)

var (
	// Flags for VPP stats configuration
	ApiAddr       = flag.String("vppstats.api.addr", "/var/run/vpp/api.sock", "VPP API socket path")
	StatsAddr     = flag.String("vppstats.stats.addr", "/var/run/vpp/stats.sock", "VPP stats socket path")
	IfIndexOffset = flag.Int("vppstats.ifindex-offset", 1000, "Offset to add to VPP interface indices for SNMP")
	Period        = flag.Int("vppstats.period", 10, "Interval in seconds for querying VPP interface stats")
)

// StartStatsRoutine starts a goroutine that queries VPP interface stats at the configured interval
func StartStatsRoutine(callback StatsCallback) {
	period := time.Duration(*Period) * time.Second
	go statsRoutine(period, callback)
}

func statsRoutine(period time.Duration, callback StatsCallback) {
	logger.Debugf("Starting VPP stats routine with API: %s, Stats: %s, period: %v", *ApiAddr, *StatsAddr, period)

	var conn *core.Connection
	var statsConn *core.StatsConnection
	var connected = false
	var wasConnected = false

	ticker := time.NewTicker(period)
	defer ticker.Stop()

	defer func() {
		// Safely disconnect connections with panic recovery
		if conn != nil {
			func() {
				defer func() {
					if r := recover(); r != nil {
						logger.Debugf("Recovered from conn.Disconnect panic: %v", r)
					}
				}()
				conn.Disconnect()
			}()
		}
		if statsConn != nil {
			func() {
				defer func() {
					if r := recover(); r != nil {
						logger.Debugf("Recovered from statsConn.Disconnect panic: %v", r)
					}
				}()
				statsConn.Disconnect()
			}()
		}
	}()

	for {
		// Check if we need to connect/reconnect
		if !connected {
			// Clean up existing connections
			if conn != nil {
				func() {
					defer func() {
						if r := recover(); r != nil {
							logger.Debugf("Recovered from conn.Disconnect during reconnect: %v", r)
						}
					}()
					conn.Disconnect()
				}()
				conn = nil
			}
			if statsConn != nil {
				func() {
					defer func() {
						if r := recover(); r != nil {
							logger.Debugf("Recovered from statsConn.Disconnect during reconnect: %v", r)
						}
					}()
					statsConn.Disconnect()
				}()
				statsConn = nil
			}

			// Create API connection first - only proceed if this succeeds
			var err error
			conn, err = core.Connect(socketclient.NewVppClient(*ApiAddr))
			if err != nil {
				if wasConnected {
					logger.Printf("VPP API connection lost: %v", err)
					wasConnected = false
				} else {
					logger.Debugf("Failed to connect to VPP API: %v", err)
				}
				connected = false
				time.Sleep(time.Second)
				continue
			}

			// Only try stats connection if API connection succeeded
			statsClient := statsclient.NewStatsClient(*StatsAddr)
			statsConn, err = core.ConnectStats(statsClient)
			if err != nil {
				logger.Printf("VPP stats connection failed: %v", err)
				// Close the API connection since we can't get stats
				func() {
					defer func() {
						if r := recover(); r != nil {
							logger.Debugf("Recovered from conn.Disconnect during stats error: %v", r)
						}
					}()
					conn.Disconnect()
				}()
				conn = nil
				connected = false
				time.Sleep(time.Second)
				continue
			}

			logger.Printf("Connected to VPP (API: %s, Stats: %s)", *ApiAddr, *StatsAddr)
			connected = true
			wasConnected = true
		}

		// Query stats if connected
		if connected {
			if !queryInterfaceStats(conn, statsConn, callback) {
				connected = false
				continue
			}
		}

		// Wait for next tick
		select {
		case <-ticker.C:
			continue
		}
	}
}

func queryInterfaceStats(conn *core.Connection, statsConn *core.StatsConnection, callback StatsCallback) bool {
	// Check VPP liveness using API call
	if !checkVPPLiveness(conn) {
		logger.Printf("VPP liveness check failed")
		return false
	}

	// Create the proper struct for interface stats
	stats := new(api.InterfaceStats)

	// Use the GetInterfaceStats method - this is the correct approach
	if err := statsConn.GetInterfaceStats(stats); err != nil {
		logger.Printf("Failed to get interface stats: %v", err)
		return false
	}

	// Always log basic info
	logger.Printf("Retrieved stats for %d interfaces", len(stats.Interfaces))

	// Debug logging for individual interfaces
	for _, iface := range stats.Interfaces {
		logger.Debugf("Interface %d (%s): RX %d pkts/%d bytes, TX %d pkts/%d bytes",
			iface.InterfaceIndex, iface.InterfaceName,
			iface.Rx.Packets, iface.Rx.Bytes,
			iface.Tx.Packets, iface.Tx.Bytes)
	}

	// Call the callback to update the MIB
	if callback != nil {
		callback(stats)
	}

	return true
}

func checkVPPLiveness(conn *core.Connection) bool {
	// Create a channel for the API call
	ch, err := conn.NewAPIChannel()
	if err != nil {
		logger.Debugf("Failed to create API channel: %v", err)
		return false
	}

	// Use a flag to track if channel was closed successfully
	var channelClosed bool
	defer func() {
		if !channelClosed {
			// Recover from potential panic when closing already closed channel
			defer func() {
				if r := recover(); r != nil {
					logger.Debugf("Recovered from channel close panic: %v", r)
				}
			}()
			ch.Close()
		}
	}()

	// Create ShowVersion request
	req := &vpe.ShowVersion{}
	reply := &vpe.ShowVersionReply{}

	// Send the request with timeout
	if err := ch.SendRequest(req).ReceiveReply(reply); err != nil {
		logger.Debugf("VPP ShowVersion failed: %v", err)
		// Try to close the channel properly on error
		func() {
			defer func() {
				if r := recover(); r != nil {
					logger.Debugf("Channel already closed during error handling")
				}
			}()
			ch.Close()
			channelClosed = true
		}()
		return false
	}

	// Close channel successfully
	ch.Close()
	channelClosed = true

	// If we got here, VPP is responsive
	logger.Debugf("VPP liveness check passed (version: %s)", string(reply.Version))
	return true
}