gno.land/p/moul/reactions/v0

The engine behind an embeddable reaction block: pages, tallies, a closed emoji palette, and the markdown that shows them. No realm state, no chain reads, no authority decisions. The realm on top owns all three.

Live realm: gno.land/r/moul/reactions/v0.

The model

A Board maps a page key to a Page. A page holds exactly three things:

There is no text field anywhere. That is what makes the whole thing runnable with no moderation: reactions come from a closed set of six, so there is nothing to take down.

 1b := reactions.NewBoard()
 2b.React("gno.land/r/moul/home", caller, reactions.KeyFire, height) // false if rejected
 3b.Unreact("gno.land/r/moul/home", caller)                          // false if there was none
 4
 5p := b.Page("gno.land/r/moul/home") // nil when untouched, and nil is safe to use
 6p.Count(reactions.KeyFire)          // 1
 7p.Total()                           // addresses reacting, not clicks
 8p.Of(caller)                        // "fire", or "" for none
 9key, who, height := p.Last()
10
11md := reactions.Block(realmPath, page, p) // the whole widget

Every Page read is nil-safe and answers as if the page were empty, so a host realm renders the block without ever checking whether the page exists.

Three decisions worth knowing before you use it

A reaction key is an ASCII name, not a glyph. "up", not 👍. A name survives a URL query parameter, an avl key and a markdown escaper with no encoding question anywhere, and the palette can change a glyph without rewriting stored state. Emoji(key) is the presentation half.

No glyph in the palette uses U+FE0F or a zero-width joiner. The link title goes through ui.Inline, which strips exactly those, so a glyph needing a variation selector would come out the other side as its monochrome form. ❤️ is the casualty; heart is 💜, a codepoint that is colour on its own. Pinned by TestEmojiSurviveTheEscaper.

Unreact does not rewind the last-reaction line. It records an event that happened, and recomputing it would mean walking every address on the page, so Page.Last keeps naming a reaction nobody holds any more.

What is shown is a separate decision, and Summary makes it: a page whose reactors have all left renders as empty, not as a withdrawn reaction. Gating on the last key alone would print "last 👍 by g1… · 0 reactions" above an empty strip, which contradicts itself. TestSummaryGoesEmptyWhenEveryoneLeaves pins the pair.

Page keys

A page key is a package path, and ValidPage is what bounds this package's exposure: at least one /, no empty element, and only lowercase ASCII letters, digits, ., -, _, : and /, up to MaxPageLen bytes. That excludes every character a markdown escaper exists for, plus every byte above ASCII, so a stored key can never be a bidi run, a zero-width joiner or an image.

: is in the set so a host realm can key one block per article on the path it already serves: gno.land/r/you/blog:hello-world.

This package only ever puts a key in a URL. A realm that shows the key as text escapes it there; ValidPage and ui.Inline protect against different mistakes.

Not to be confused with

r/moul/x/daily/reactions is an older, unrelated experiment: a single self-contained board with its own "topics", no embedding, and no way for a reader to change or remove a reaction. Nothing is shared between the two.

Part of moul/gno-contracts — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

Dependency graph:

⚠️ Disclaimer: provided as-is, without warranty; not security-audited. Full disclaimer: DISCLAIMER.