go_subnetter/cmd/subnetter/consts.go

package main

import (
	`embed`
	"strings"
	`text/template`

	"github.com/go-playground/validator/v10"
)

var (
	args     = new(Args)
	validate = validator.New(validator.WithRequiredStructEnabled())
)

const (
	/*
		fixedPad is a fixed "surrounding" pad always present (as minimum), even for values max len on columns.
		*Must* be positive even, as <fixed left pad> and <fixed right pad> == fixedPad/2.
	*/
	fixedPad int = 2
	/*
		padChars is what fills the pads in table cells.
		At the *LEAST*, a cell will be "<fixedPad/2 * padChars><str><fixedPad/2 * padChars>"
	*/
	padChars string = " "
)

var (
	//go:embed "_tpl"
	tplDir embed.FS
	tblTpl *template.Template = template.Must(template.New("").Funcs(
		template.FuncMap{
			"bold":     tplFmtBold,
			"legacy4":  tplTableLegacy4,
			"mask4":    tplTableMasks4,
			"notes":    tplTableNotes,
			"prefixes": tplTablePrefixes,
		},
	).ParseFS(tplDir, "_tpl/*.tpl"))
)

var (
	// Primarily output formatting stuff in this block.
	sectSepCnt = 48
	// sectFmts contains a lookup of map[<is plain>][]string{<level 1>, <level 2>, <level 3>}
	sectFmts map[bool][]string = map[bool][]string{
		true: []string{
			strings.Repeat("=", sectSepCnt),
			strings.Repeat("-", sectSepCnt),
			strings.Repeat(".", sectSepCnt),
		},
		false: []string{
			strings.Repeat("━", sectSepCnt),
			strings.Repeat("─", sectSepCnt),
			strings.Repeat("╍", sectSepCnt),
		},
	}
	// tblFmts contains a lookup of map[<is plain>]*tableFormatter.
	tblFmts map[bool]*tableFormatter = map[bool]*tableFormatter{
		// Plaintext/ASCII-only
		true: &tableFormatter{
			TopLeftHdr:      "*", // Or _
			TopFillHdr:      "*", // ""
			TopColSepHdr:    "*", // ""
			TopRightHdr:     "*", // ""
			ColSepHdr:       "|",
			BottomLeftHdr:   "*", // Or +
			BottomFillHdr:   "*", // Or -
			BottomColSepHdr: "*", // Or +
			BottomRightHdr:  "*", // ""
			Left:            "|",
			Fill:            "-",
			LineColSep:      "|",
			LineLeft:        "|",
			LineRight:       "|",
			ColSep:          "|",
			Right:           "|",
			LastLeft:        "+",
			LastFill:        "-",
			LastSep:         "-",
			LastRight:       "+",
			SuppressLineSep: true,
			NoUpperTitle:    false,
			NoBoldTitle:     true,
		},
		// Unicode/UTF-8
		// https://en.wikipedia.org/wiki/Box-drawing_characters
		false: &tableFormatter{
			TopLeftHdr:      "┏",
			TopFillHdr:      "━",
			TopColSepHdr:    "┳",
			TopRightHdr:     "┓",
			ColSepHdr:       "┃",
			BottomLeftHdr:   "┣",
			BottomFillHdr:   "━",
			BottomColSepHdr: "╇",
			BottomRightHdr:  "┫",
			Left:            "┃",
			Fill:            "─",
			LineColSep:      "┼",
			LineLeft:        "┠",
			LineRight:       "┨",
			ColSep:          "│",
			Right:           "┃",
			LastLeft:        "┗",
			LastFill:        "━",
			LastSep:         "┷",
			LastRight:       "┛",
			SuppressLineSep: false,
			NoUpperTitle:    true,
			NoBoldTitle:     false,
		},
	}
)

var (
	// netNotes is keyed first on IP/inet family version (4/6) and then the prefix size.
	netNotes map[uint8]map[uint8]string = map[uint8]map[uint8]string{
		4: map[uint8]string{
			32: "Host route/single host",
			31: "PTP link",
			30: "PTP (legacy/compatibility)",
			29: "Smallest multi-host network size possible",
			28: "Typical/common size for small LANs/VLANs",
			27: "Typical/common size for small LANs/VLANs",
			26: "Typical/common size for small LANs/VLANs",
			25: "Typical/common size for large LANs/VLANs",
			24: "Typical/common size for large LANs/VLANs",
			22: "Typical/common size for smaller business networks",
			21: "Typical/common size for larger business networks, smaller ISPs",
			20: "Typical/common size for larger business networks, smaller ISPs",
			19: "Typical/common size for enterprise business networks, larger ISPs",
			18: "Typical/common size for enterprise business networks, larger ISPs",
			17: "Typical/common size for enterprise business networks, larger ISPs",
			8:  "Largest IANA block allocation size possible",
			0:  "Entire IPv4 Internet address prefix; commonly used to indicate default route",
		},
		6: map[uint8]string{
			128: "Host route/single host, single endpoints, and loopback (::1/128 explicitly)",
			127: "Point-to-Point link (inter-router)",
			64:  "Single LAN; default prefix size for SLAAC",
			60:  "Some (very limited) 6rd networks",
			56:  "Minimum end site assignment (RFC 6177)",
			48:  "Typical/common assignment for larger sites",
			36:  "Possible future LIR \"extra-small\" allocation",
			32:  "\"Minimal\" LIR allocation",
			28:  "\"Medium\" LIR allocation",
			24:  "\"Large\" LIR allocation",
			20:  "\"Extra-large\" LIR allocation",
			12:  "RIR allocation from IANA",
			0:   "Entire IPv6 Internet address prefix; commonly used to represent default route",
		},
	}
)