go_subnetter/cmd/subnetter/main.go

package main

import (
	"bytes"
	"errors"
	`fmt`
	"io"
	"log"
	"net"
	"net/netip"
	"os"
	"strings"

	"go4.org/netipx"
	"subnetter/netsplit"
	`subnetter/version`

	"github.com/jessevdk/go-flags"
	"r00t2.io/sysutils/paths"
)

func main() {

	var err error
	var b []byte
	var pfx *net.IPNet
	var resPfx *netip.Prefix
	var origPfx netip.Prefix
	var splitter netsplit.NetSplitter
	var cmnArgs common
	var nets []*netip.Prefix
	var remaining *netipx.IPSet
	var buf *bytes.Buffer
	var res *netsplit.StructuredResults
	var noStrict bool
	var strictErr error
	var splitErr = new(netsplit.SplitErr)
	var parser = flags.NewParser(args, flags.Default)

	if _, err = parser.Parse(); err != nil {
		switch flagsErr := err.(type) {
		case *flags.Error:
			switch flagsErr.Type {
			case flags.ErrHelp, flags.ErrCommandRequired, flags.ErrRequired: // These print their relevant messages by themselves.
				return
			default:
				log.Panicln(err)
			}
		default:
			log.Panicln(err)
		}
	}

	if version.Ver, err = version.Version(); err != nil {
		log.Panicln(err)
	}

	// If args.Version or args.DetailVersion are true, just print them and exit.
	if args.DetailVersion || args.Version {
		if args.Version {
			fmt.Println(version.Ver.Short())
			return
		} else if args.DetailVersion {
			fmt.Println(version.Ver.Detail())
			return
		}
	}

	switch parser.Active.Name {
	case "table":
		buf = new(bytes.Buffer)
		if err = tblTpl.ExecuteTemplate(buf, "table.tpl", args.Table.tableOpts); err != nil {
			log.Panicln(err)
		}
		os.Stdout.Write(buf.Bytes())
		return
	case "parse":
		if strings.TrimSpace(args.Parse.InFile) == "-" {
			buf = new(bytes.Buffer)
			if _, err = io.Copy(buf, os.Stdin); err != nil {
				log.Panicln(err)
			}
			b = buf.Bytes()
		} else {
			if err = paths.RealPath(&args.Parse.InFile); err != nil {
				log.Panicln(err)
			}
			if b, err = os.ReadFile(args.Parse.InFile); err != nil {
				log.Panicln(err)
			}
		}
		if res, err = netsplit.Parse(b); err != nil {
			log.Panicln(err)
		}
		if resPfx, nets, remaining, splitter, err = res.Uncontain(); err != nil {
			log.Panicln(err)
		}
		if resPfx != nil {
			origPfx = *resPfx
		}
		pfx = netipx.PrefixIPNet(origPfx.Masked())
		cmnArgs = common{
			outputOpts:    args.Parse.outputOpts,
			AllowReserved: args.Parse.AllowReserved,
			AllowHostNet:  args.Parse.AllowHostNet,
		}
		if err = printNets(&origPfx, pfx, nets, remaining, &cmnArgs, res.GetSplitter()); err != nil {
			log.Panicln(err)
		}
		return
	default:
		// Actually subnet (and print results).
		/*
			A netsplit.NetSplitter is needed, along with:
				* prefix
				* verbosity
				* disable showing remaining
				* formatter
			These are all handily-dandily enclosed in a `common` struct type.
		*/
		switch parser.Active.Name {
		case "split-hosts":
			if err = validate.Struct(args.SplitHost); err != nil {
				log.Panicln(err)
			}
			cmnArgs = args.SplitHost.common
			splitter = &netsplit.HostSplitter{
				NumberHosts:  args.SplitHost.Hosts,
				Strict:       args.SplitHost.Strict,
				BaseSplitter: new(netsplit.BaseSplitter),
			}
			noStrict = !args.SplitHost.Strict
			strictErr = netsplit.ErrBadNumHosts
		case "split-nets":
			if err = validate.Struct(args.SplitSubnets); err != nil {
				log.Panicln(err)
			}
			cmnArgs = args.SplitSubnets.common
			splitter = &netsplit.SubnetSplitter{
				Strict:        args.SplitSubnets.Strict,
				NumberSubnets: args.SplitSubnets.NumNets,
				BaseSplitter:  new(netsplit.BaseSplitter),
			}
			noStrict = !args.SplitSubnets.Strict
			strictErr = netsplit.ErrNoNetSpace
		case "split-cidr":
			if err = validate.Struct(args.SplitCIDR); err != nil {
				log.Panicln(err)
			}
			cmnArgs = args.SplitCIDR.common
			splitter = &netsplit.CIDRSplitter{
				PrefixLength: args.SplitCIDR.Prefix,
				BaseSplitter: new(netsplit.BaseSplitter),
			}
		case "vlsm":
			if err = validate.Struct(args.VLSM); err != nil {
				log.Panicln(err)
			}
			cmnArgs = args.VLSM.common
			splitter = &netsplit.VLSMSplitter{
				Ascending:     args.VLSM.Asc,
				PrefixLengths: args.VLSM.Sizes,
				BaseSplitter:  new(netsplit.BaseSplitter),
			}
		}
		if origPfx, err = netip.ParsePrefix(cmnArgs.Network.Network); err != nil {
			log.Panicln(err)
		}
		// This can be a direct conversion. We have to make sure we mask off the host bits to avoid errors, though.
		/*
			if _, pfx, err = net.ParseCIDR(cmnArgs.network.network); err != nil {
				log.Panicln(err)
			}
		*/
		pfx = netipx.PrefixIPNet(origPfx.Masked())
		splitter.SetParent(*pfx)
		if nets, remaining, err = splitter.Split(); err != nil {
			if errors.As(err, &splitErr) {
				if noStrict && errors.Is(splitErr.Wrapped, strictErr) {
					err = nil
				} else {
					printSplitErr(splitErr)
					os.Exit(1)
				}
			} else {
				log.Panicln(err)
			}
		}
		if err = printNets(&origPfx, pfx, nets, remaining, &cmnArgs, splitter); err != nil {
			log.Panicln(err)
		}
	}

}