// Package cli wires command-line flags to the network monitor and runs it.
package cli

import (
	"context"
	"os"
	"os/signal"
	"runtime"
	"syscall"

	"github.com/spf13/cobra"
	"github.com/spf13/viper"

	"git.eeqj.de/sneak/rtnetmon/internal/monitor"
	"git.eeqj.de/sneak/rtnetmon/internal/netdetect"
)

// config holds the application configuration.
type config struct {
	IfaceA  string
	LabelA  string
	IfaceB  string
	LabelB  string
	Hosts   []string
	LogFile string
}

// defaultReachabilityHosts is the default reachability host list.
func defaultReachabilityHosts() []string {
	return []string{
		"8.8.8.8", "8.8.4.4", "google.com", "github.com",
		"console.aws.amazon.com", "console.cloud.google.com",
		"fast.com", "datavi.be", "captive.apple.com",
	}
}

// defaultPacketLossHosts is the default packet-loss host list.
func defaultPacketLossHosts() []string {
	return []string{
		"github.com", "google.com", "8.8.8.8",
		"captive.apple.com", "62.115.190.68",
	}
}

// defaultTCPHosts is the default TCP connect host:port list.
func defaultTCPHosts() []string {
	return []string{
		"datavi.be:443", "fast.com:443",
		"console.aws.amazon.com:443", "console.cloud.google.com:443",
		"captive.apple.com:80", "google.com:443",
	}
}

// newRootCmd builds the cobra root command with its flags bound.
func newRootCmd() *cobra.Command {
	cfg := &config{}
	cmd := &cobra.Command{
		Use:   "rtnetmon",
		Short: "Real-time network monitoring dashboard",
		Long: `rtnetmon is a dual-interface network monitoring dashboard that provides
real-time visibility into network health, packet loss, and latency.`,
		RunE: func(cmd *cobra.Command, _ []string) error {
			return runMonitor(cmd, cfg)
		},
	}
	registerFlags(cmd, cfg)

	return cmd
}

// registerFlags defines and viper-binds the command's flags.
func registerFlags(cmd *cobra.Command, cfg *config) {
	f := cmd.Flags()
	f.StringVar(&cfg.IfaceA, "ifaceA", "gu0", "primary network interface")
	f.StringVar(&cfg.LabelA, "labelA", "gu LAN - VPN outbound", "label for ifaceA")
	f.StringVar(&cfg.IfaceB, "ifaceB", "backhaul0", "secondary network interface")
	f.StringVar(&cfg.LabelB, "labelB", "Cox cable direct", "label for ifaceB")
	f.StringSliceVar(&cfg.Hosts, "hosts", defaultReachabilityHosts(),
		"comma-separated reachability hosts")
	f.StringVar(&cfg.LogFile, "logfile", "/tmp/rtnetmon.log", "path to log file")

	for _, name := range []string{
		"ifaceA", "labelA", "ifaceB", "labelB", "hosts", "logfile",
	} {
		_ = viper.BindPFlag(name, f.Lookup(name))
	}
}

// runMonitor detects the interfaces to monitor, then constructs and runs the
// monitor from cfg.
func runMonitor(cmd *cobra.Command, cfg *config) error {
	monitor.Logf(cfg.LogFile, "Starting rtnetmon")

	specs, err := detectInterfaces(cmd, cfg)
	if err != nil {
		return err
	}

	mon := monitor.NewMonitor(specs, cfg.LogFile)

	for _, host := range cfg.Hosts {
		mon.AddReachabilityHost(host)
	}

	for _, host := range defaultPacketLossHosts() {
		mon.AddPacketLossHost(host)
	}

	for _, host := range defaultTCPHosts() {
		mon.AddTCPHost(host)
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	sig := make(chan os.Signal, 1)
	signal.Notify(sig, os.Interrupt, syscall.SIGTERM)

	go func() {
		s := <-sig
		monitor.Logf(cfg.LogFile, "Signal received: %v", s)
		cancel()
	}()

	return mon.Run(ctx)
}

// detectInterfaces enumerates the host, reads its default routes, and applies
// the platform selection rules to decide which interfaces to monitor.
func detectInterfaces(
	cmd *cobra.Command, cfg *config,
) ([]monitor.IfaceSpec, error) {
	ifaces, err := netdetect.Interfaces()
	if err != nil {
		return nil, err
	}

	routes, err := netdetect.DefaultRoutes()
	if err != nil {
		return nil, err
	}

	flags := netdetect.Flags{
		IfaceA:    cfg.IfaceA,
		LabelA:    cfg.LabelA,
		IfaceB:    cfg.IfaceB,
		LabelB:    cfg.LabelB,
		LabelASet: cmd.Flags().Changed("labelA"),
		LabelBSet: cmd.Flags().Changed("labelB"),
	}

	panes, err := netdetect.Select(runtime.GOOS, ifaces, routes, flags)
	if err != nil {
		return nil, err
	}

	specs := make([]monitor.IfaceSpec, len(panes))
	for i, p := range panes {
		specs[i] = monitor.IfaceSpec{Name: p.Name, Label: p.Label}
	}

	monitor.Logf(cfg.LogFile, "Monitoring %d interface(s)", len(specs))

	return specs, nil
}

// Execute builds the root command and runs it.
func Execute() error {
	return newRootCmd().Execute()
}