gno.land/r/moul/x/daily/romannumdemo/v0⧉

1// Package romannumdemo is a small gnoweb demo of the Roman-numeral converter2// provided by the [p/moul/x/daily/romannum](/p/moul/x/daily/romannum/v0)3// library: it renders a table of worked examples and interactive4// integer→Roman and Roman→integer conversions.5//6// It contains no conversion logic of its own — everything comes from7// romannum.ToRoman and romannum.FromRoman.8package romannumdemo910import (11	"strconv"12	"strings"1314	"gno.land/p/moul/x/daily/romannum/v0"15)1617// examples are the classic milestones shown by the root Render.18var examples = []int{1, 4, 9, 14, 40, 49, 90, 400, 900, 1994, 2024, 3888, 3999}1920// Render drives gnoweb:21//   - ""        or "/"          → a table of example conversions22//   - "/<n>"                    → integer → Roman23//   - "/r/<roman>"              → Roman → integer24func Render(path string) string {25	arg := strings.Trim(strings.TrimSpace(path), "/")2627	switch {28	case arg == "":29		return renderTable()30	case strings.HasPrefix(strings.ToLower(arg), "r/"):31		return renderFromRoman(arg[2:])32	default:33		return renderToRoman(arg)34	}35}3637func renderToRoman(arg string) string {38	n, err := strconv.Atoi(strings.TrimSpace(arg))39	if err != nil {40		return "# Roman numeral converter\n\nCould not parse `" + arg +41			"` as an integer.\n\n" + usage()42	}43	if n < 1 || n > 3999 {44		return "# Roman numeral converter\n\n`" + strconv.Itoa(n) +45			"` is out of range — Roman numerals here cover **1..3999**.\n\n" + usage()46	}47	var b strings.Builder48	b.WriteString("# " + strconv.Itoa(n) + " → " + romannum.ToRoman(n) + "\n\n")49	b.WriteString("| decimal | roman |\n|---:|:---|\n")50	b.WriteString("| " + strconv.Itoa(n) + " | **" + romannum.ToRoman(n) + "** |\n\n")51	if n > 1 {52		b.WriteString("[« " + strconv.Itoa(n-1) + "](/r/moul/x/daily/romannumdemo/v0:" +53			strconv.Itoa(n-1) + ") · ")54	}55	if n < 3999 {56		b.WriteString("[" + strconv.Itoa(n+1) + " »](/r/moul/x/daily/romannumdemo/v0:" +57			strconv.Itoa(n+1) + ")")58	}59	b.WriteString("\n\n" + usage())60	return b.String()61}6263func renderFromRoman(arg string) string {64	arg = strings.TrimSpace(arg)65	n, ok := tryFromRoman(arg)66	if !ok {67		return "# Roman numeral converter\n\n`" + arg +68			"` is not a valid Roman numeral (1..3999).\n\n" + usage()69	}70	up := strings.ToUpper(arg)71	var b strings.Builder72	b.WriteString("# " + up + " → " + strconv.Itoa(n) + "\n\n")73	b.WriteString("| roman | decimal |\n|:---|---:|\n")74	b.WriteString("| **" + up + "** | " + strconv.Itoa(n) + " |\n\n")75	b.WriteString(usage())76	return b.String()77}7879// tryFromRoman wraps the panic-on-invalid romannum.FromRoman in a panic-free80// (value, ok) shape, so the demo can report a friendly error for bad input.81func tryFromRoman(s string) (n int, ok bool) {82	defer func() {83		if recover() != nil {84			n, ok = 0, false85		}86	}()87	return romannum.FromRoman(s), true88}8990func renderTable() string {91	var b strings.Builder92	b.WriteString("# Roman numeral converter\n\n")93	b.WriteString("A tiny demo of the [`p/moul/x/daily/romannum`](/p/moul/x/daily/romannum/v0) ")94	b.WriteString("library — the classic `ToRoman` / `FromRoman` kata. ")95	b.WriteString("Pure and deterministic.\n\n")96	b.WriteString("## Examples\n\n")97	b.WriteString("| decimal | roman |\n|---:|:---|\n")98	for _, n := range examples {99		b.WriteString("| [" + strconv.Itoa(n) + "](/r/moul/x/daily/romannumdemo/v0:" +100			strconv.Itoa(n) + ") | " + romannum.ToRoman(n) + " |\n")101	}102	b.WriteString("\n" + usage())103	return b.String()104}105106func usage() string {107	return "## Try it\n\n" +108		"- `:/<n>` — integer → Roman, e.g. `:/2024` → " + romannum.ToRoman(2024) + "\n" +109		"- `:/r/<roman>` — Roman → integer, e.g. `:/r/MMXXIV` → 2024\n"110}111