romannumdemo.gno

  1// Package romannumdemo is a small gnoweb demo of the Roman-numeral converter
  2// provided by the [p/moul/x/daily/romannum](/p/moul/x/daily/romannum/v0)
  3// library: it renders a table of worked examples and interactive
  4// integer→Roman and Roman→integer conversions.
  5//
  6// It contains no conversion logic of its own — everything comes from
  7// romannum.ToRoman and romannum.FromRoman.
  8package romannumdemo
  9
 10import (
 11	"strconv"
 12	"strings"
 13
 14	"gno.land/p/g1magld5ptgzaktqcexxq0pgq5lmdf0kz6re8hlv/md/v0"
 15	"gno.land/p/g1magld5ptgzaktqcexxq0pgq5lmdf0kz6re8hlv/x/daily/romannum/v0"
 16)
 17
 18// examples are the classic milestones shown by the root Render.
 19var examples = []int{1, 4, 9, 14, 40, 49, 90, 400, 900, 1994, 2024, 3888, 3999}
 20
 21// Render drives gnoweb:
 22//   - ""        or "/"          → a table of example conversions
 23//   - "/<n>"                    → integer → Roman
 24//   - "/r/<roman>"              → Roman → integer
 25func Render(path string) string {
 26	arg := strings.Trim(strings.TrimSpace(path), "/")
 27
 28	switch {
 29	case arg == "":
 30		return renderTable()
 31	case strings.HasPrefix(strings.ToLower(arg), "r/"):
 32		return renderFromRoman(arg[2:])
 33	default:
 34		return renderToRoman(arg)
 35	}
 36}
 37
 38func renderToRoman(arg string) string {
 39	n, err := strconv.Atoi(strings.TrimSpace(arg))
 40	if err != nil {
 41		return "# Roman numeral converter\n\nCould not parse " + md.InlineCode(arg) +
 42			"` as an integer.\n\n" + usage()
 43	}
 44	if n < 1 || n > 3999 {
 45		return "# Roman numeral converter\n\n`" + strconv.Itoa(n) +
 46			"` is out of range — Roman numerals here cover **1..3999**.\n\n" + usage()
 47	}
 48	var b strings.Builder
 49	b.WriteString("# " + strconv.Itoa(n) + " → " + romannum.ToRoman(n) + "\n\n")
 50	b.WriteString("| decimal | roman |\n|---:|:---|\n")
 51	b.WriteString("| " + strconv.Itoa(n) + " | **" + romannum.ToRoman(n) + "** |\n\n")
 52	if n > 1 {
 53		b.WriteString("[« " + strconv.Itoa(n-1) + "](/r/moul/x/daily/romannumdemo/v0:" +
 54			strconv.Itoa(n-1) + ") · ")
 55	}
 56	if n < 3999 {
 57		b.WriteString("[" + strconv.Itoa(n+1) + " »](/r/moul/x/daily/romannumdemo/v0:" +
 58			strconv.Itoa(n+1) + ")")
 59	}
 60	b.WriteString("\n\n" + usage())
 61	return b.String()
 62}
 63
 64func renderFromRoman(arg string) string {
 65	arg = strings.TrimSpace(arg)
 66	n, ok := tryFromRoman(arg)
 67	if !ok {
 68		return "# Roman numeral converter\n\n" + md.InlineCode(arg) +
 69			" is not a valid Roman numeral (1..3999).\n\n" + usage()
 70	}
 71	up := strings.ToUpper(arg)
 72	var b strings.Builder
 73	b.WriteString("# " + up + " → " + strconv.Itoa(n) + "\n\n")
 74	b.WriteString("| roman | decimal |\n|:---|---:|\n")
 75	b.WriteString("| **" + up + "** | " + strconv.Itoa(n) + " |\n\n")
 76	b.WriteString(usage())
 77	return b.String()
 78}
 79
 80// tryFromRoman wraps the panic-on-invalid romannum.FromRoman in a panic-free
 81// (value, ok) shape, so the demo can report a friendly error for bad input.
 82func tryFromRoman(s string) (n int, ok bool) {
 83	defer func() {
 84		if recover() != nil {
 85			n, ok = 0, false
 86		}
 87	}()
 88	return romannum.FromRoman(s), true
 89}
 90
 91func renderTable() string {
 92	var b strings.Builder
 93	b.WriteString("# Roman numeral converter\n\n")
 94	b.WriteString("A tiny demo of the [`p/moul/x/daily/romannum`](/p/moul/x/daily/romannum/v0) ")
 95	b.WriteString("library — the classic `ToRoman` / `FromRoman` kata. ")
 96	b.WriteString("Pure and deterministic.\n\n")
 97	b.WriteString("## Examples\n\n")
 98	b.WriteString("| decimal | roman |\n|---:|:---|\n")
 99	for _, n := range examples {
100		b.WriteString("| [" + strconv.Itoa(n) + "](/r/moul/x/daily/romannumdemo/v0:" +
101			strconv.Itoa(n) + ") | " + romannum.ToRoman(n) + " |\n")
102	}
103	b.WriteString("\n" + usage())
104	return b.String()
105}
106
107func usage() string {
108	return "## Try it\n\n" +
109		"- `:/<n>` — integer → Roman, e.g. `:/2024` → " + romannum.ToRoman(2024) + "\n" +
110		"- `:/r/<roman>` — Roman → integer, e.g. `:/r/MMXXIV` → 2024\n"
111}