guestbook.gno

  1// Package guestbook is a public, on-chain guestbook realm for gno.land.
  2//
  3// Anyone can sign the guestbook with a short message via the Sign crossing
  4// function. Every entry records the caller's address, the message, and the
  5// block height at which it was signed. Render lists all entries newest-first
  6// as a Markdown table.
  7//
  8// v1 renders through [p/moul/kit/ui](/p/moul/kit/ui/v0) instead of the
  9// hand-rolled shortAddr and escapeCell helpers v0 carried. The escaping is the
 10// substantive change: v0 replaced four characters, while ui.Cell also strips
 11// bidi and zero-width characters, which a message can otherwise use to reorder
 12// how the rest of the row reads.
 13package guestbook
 14
 15import (
 16	"strconv"
 17	"strings"
 18
 19	"chain"
 20	"chain/markdown"
 21	"chain/runtime"
 22
 23	"gno.land/p/moul/kit/store/v0"
 24	"gno.land/p/moul/kit/ui/v0"
 25)
 26
 27// Entry is a single signed guestbook line. It carries no ID field: the id
 28// belongs to the store, which hands it back on lookup and iteration.
 29type Entry struct {
 30	Author  string // bech32 address of the signer
 31	Message string // the message left by the signer
 32	Height  int64  // block height at which the entry was signed
 33}
 34
 35const maxMessageLen = 280
 36
 37// entries assigns the sequence numbers. v1 kept its own count plus a seqKey()
 38// that zero-padded to width 16, the widest of the six hand-rolled variants in
 39// this repo and still a ceiling; the store key has none.
 40var entries = store.Named("guestbook: entry")
 41
 42// Sign appends a new entry to the guestbook attributed to the immediate caller.
 43//
 44// It is a crossing function (gno 0.9 interrealm convention): callers invoke it
 45// as Sign(cross(cur), "hello"). The cur.IsCurrent() guard is the authentication
 46// primitive — without it a stale/forged realm value could spoof the author.
 47func Sign(cur realm, message string) {
 48	if !cur.IsCurrent() {
 49		panic("guestbook: spoofed realm; Sign must be called via cross(cur)")
 50	}
 51
 52	author := cur.Previous().Address().String()
 53	id, e := addEntry(author, message, runtime.ChainHeight())
 54
 55	chain.Emit("Signed",
 56		"id", id.String(),
 57		"author", e.Author,
 58		"height", strconv.FormatInt(e.Height, 10),
 59	)
 60}
 61
 62// addEntry validates the message and appends an entry. Non-crossing internal
 63// helper so the append/validation logic is unit-testable without a realm frame.
 64// Panics (aborting the tx, reverting state) on an invalid message.
 65func addEntry(author, message string, height int64) (store.ID, *Entry) {
 66	msg := strings.TrimSpace(message)
 67	if strings.TrimSpace(markdown.StripBidiAndZeroWidth(msg)) == "" {
 68		panic("guestbook: message must not be empty")
 69	}
 70	if len(msg) > maxMessageLen {
 71		panic("guestbook: message too long (max " + strconv.Itoa(maxMessageLen) + " bytes)")
 72	}
 73
 74	e := &Entry{
 75		Author:  author,
 76		Message: msg,
 77		Height:  height,
 78	}
 79	return entries.Add(e), e
 80}
 81
 82// Count returns the total number of signatures. Read-only, non-crossing.
 83func Count() int {
 84	return entries.Len()
 85}
 86
 87// Render lists every entry newest-first as a Markdown table plus a total count.
 88func Render(path string) string {
 89	if entries.Len() == 0 {
 90		return "# Guestbook\n\n" + ui.Empty("No one has signed yet. Be the first!")
 91	}
 92
 93	t := ui.NewTable("#", "Who", "Message", "Height")
 94	// Ids ascend with signing, so reverse iteration is newest-first.
 95	entries.EachReverse(func(id store.ID, v any) {
 96		e := v.(*Entry)
 97		t.Row(
 98			id.String(),
 99			ui.AddrOf(e.Author),
100			ui.Cell(e.Message),
101			strconv.FormatInt(e.Height, 10),
102		)
103	})
104
105	return "# Guestbook\n\n**Total signatures:** " + strconv.Itoa(entries.Len()) + "\n\n" + t.String()
106}