timecapsule.gno

  1// Package timecapsule is a public guestbook where every message is sealed
  2// until a future block height, then permanently unlocked for anyone to read.
  3package timecapsule
  4
  5import (
  6	"strconv"
  7	"strings"
  8
  9	"chain"
 10	"chain/markdown"
 11	"chain/runtime"
 12
 13	"gno.land/p/g1magld5ptgzaktqcexxq0pgq5lmdf0kz6re8hlv/kit/store/v0"
 14	"gno.land/p/nt/markdown/sanitize/v0"
 15)
 16
 17// capsule carries no id field: the id belongs to the store, which hands it
 18// back on lookup and iteration.
 19type capsule struct {
 20	author       address
 21	message      string
 22	createdAt    int64
 23	unlockHeight int64
 24}
 25
 26// capsules assigns the capsule ids. v0 kept its own nextID plus an idKey()
 27// that called strings.Repeat WITHOUT the length guard the other realms had, so
 28// at the 10^12th capsule it did not mis-sort, it panicked: Repeat rejects a
 29// negative count, and the realm would have stopped accepting Leave calls. The
 30// store key is 8 fixed bytes with no width to outgrow.
 31var capsules = store.Named("capsule")
 32
 33const (
 34	maxDelayBlocks int64 = 1_000_000
 35	maxMessageLen  int   = 500
 36)
 37
 38// Leave seals a new message that stays hidden until `delayBlocks` blocks
 39// from now, then becomes publicly readable forever. Returns the capsule id.
 40func Leave(cur realm, message string, delayBlocks int64) int64 {
 41	if !cur.Previous().IsUserCall() {
 42		panic("only direct user calls can leave a capsule")
 43	}
 44
 45	message = strings.TrimSpace(message)
 46	if strings.TrimSpace(markdown.StripBidiAndZeroWidth(message)) == "" {
 47		panic("message must not be empty")
 48	}
 49	if len(message) > maxMessageLen {
 50		panic("message too long")
 51	}
 52	if delayBlocks <= 0 || delayBlocks > maxDelayBlocks {
 53		panic("delayBlocks out of range")
 54	}
 55
 56	now := runtime.ChainHeight()
 57	c := &capsule{
 58		author:       cur.Previous().Address(),
 59		message:      message,
 60		createdAt:    now,
 61		unlockHeight: now + delayBlocks,
 62	}
 63	id := capsules.Add(c)
 64
 65	chain.Emit("CapsuleSealed",
 66		"id", id.String(),
 67		"unlockHeight", strconv.FormatInt(c.unlockHeight, 10),
 68	)
 69	return int64(id)
 70}
 71
 72func Render(path string) string {
 73	switch {
 74	case path == "":
 75		return renderHome()
 76	case path == "sealed":
 77		return renderSealed()
 78	case strings.HasPrefix(path, "capsule/"):
 79		return renderCapsule(strings.TrimPrefix(path, "capsule/"))
 80	default:
 81		return "> [!WARNING]\n> Path not found\n"
 82	}
 83}
 84
 85func renderHome() string {
 86	now := runtime.ChainHeight()
 87
 88	revealed := 0
 89	sealed := 0
 90	capsules.Each(func(_ store.ID, value any) {
 91		if value.(*capsule).unlockHeight <= now {
 92			revealed++
 93		} else {
 94			sealed++
 95		}
 96	})
 97
 98	var out strings.Builder
 99	out.WriteString("# ⏳ Time Capsule Guestbook\n\n")
100	out.WriteString("Leave a message for the future. It stays sealed until its unlock block height, then anyone can read it — call `Leave(message, delayBlocks)`.\n\n")
101	out.WriteString(strconv.Itoa(revealed+sealed) + " capsule(s) total · " +
102		strconv.Itoa(revealed) + " unlocked · " + strconv.Itoa(sealed) + " still sealed")
103	if sealed > 0 {
104		out.WriteString(" (see [sealed](sealed))")
105	}
106	out.WriteString(".\n\n## Unlocked messages\n\n")
107
108	if revealed == 0 {
109		out.WriteString("_None yet. Be the first to leave one that will open later._\n")
110		return out.String()
111	}
112
113	capsules.Each(func(id store.ID, value any) {
114		c := value.(*capsule)
115		if c.unlockHeight <= now {
116			out.WriteString(renderEntry(id, c))
117		}
118	})
119	return out.String()
120}
121
122func renderSealed() string {
123	now := runtime.ChainHeight()
124
125	var out strings.Builder
126	out.WriteString("# Sealed Capsules\n\n")
127
128	found := false
129	capsules.Each(func(id store.ID, value any) {
130		c := value.(*capsule)
131		if c.unlockHeight > now {
132			found = true
133			out.WriteString("- capsule [#" + id.String() + "](capsule/" +
134				id.String() + ") by `" + c.author.String() +
135				"` — unlocks at block " + strconv.FormatInt(c.unlockHeight, 10) +
136				" (" + strconv.FormatInt(c.unlockHeight-now, 10) + " blocks left)\n")
137		}
138	})
139	if !found {
140		out.WriteString("_No sealed capsules right now._\n")
141	}
142	return out.String()
143}
144
145func renderCapsule(idStr string) string {
146	id, ok := store.ParseID(idStr)
147	if !ok {
148		return "> [!WARNING]\n> Invalid capsule id\n"
149	}
150	v, ok := capsules.Get(id)
151	if !ok {
152		return "> [!WARNING]\n> Capsule not found\n"
153	}
154	c := v.(*capsule)
155	now := runtime.ChainHeight()
156
157	var out strings.Builder
158	out.WriteString("# Capsule #" + id.String() + "\n\n")
159	out.WriteString("Sealed by `" + c.author.String() + "` at block " + strconv.FormatInt(c.createdAt, 10) + ".\n\n")
160
161	if c.unlockHeight > now {
162		out.WriteString("\U0001f512 Still sealed. Unlocks at block " + strconv.FormatInt(c.unlockHeight, 10) +
163			" (" + strconv.FormatInt(c.unlockHeight-now, 10) + " blocks left).\n")
164		return out.String()
165	}
166
167	out.WriteString("\U0001f513 Unlocked at block " + strconv.FormatInt(c.unlockHeight, 10) + ":\n\n> " +
168		sanitize.InlineText(c.message) + "\n")
169	return out.String()
170}
171
172func renderEntry(id store.ID, c *capsule) string {
173	return "- **#" + id.String() + "** by `" + c.author.String() +
174		"` (sealed at block " + strconv.FormatInt(c.createdAt, 10) +
175		", opened at block " + strconv.FormatInt(c.unlockHeight, 10) + "):\n  > " +
176		sanitize.InlineText(c.message) + "\n\n"
177}