The Host Contract

IHostApp is how the module reads your data, and IRemoteReplies is how replies from the fediverse get back into it.

IHostApp

bxsclass implements="bxModules.bxactivitypub.contracts.IHostApp" {
    // baseUrl(), findActor(), getObject(), isPublic()
}

Types are "Person" and "Group" for accounts, "post" for posts and, if you reply back, "comment" for comments.

Method	Returns
`baseUrl()`	Your canonical origin, e.g. `"https://example.com"`. Account and post ids are built from it
`findActor( type, name )`	`{ id, name, displayName, summary, avatar, header, url }` or `null`
`getObject( "post", id )`	`{ author, title, summary, content, url, published, tags }` or `null`
`getObject( "comment", id )`	Optional: `{ author, postId, parentId, content, url, published }` or `null`
`isPublic( type, id )`	Whether this account, post or comment may be federated at all

findActor( type, name )

Field
`id`	Your UUID for the account. Keypairs and followers are keyed by it
`name`	The handle, as in `@name@host`
`displayName`	The account's display name
`summary`	The bio, as HTML
`avatar`	Optional absolute URL
`header`	Optional absolute URL for the profile banner. Mastodon crops it to about 3:1
`url`	Optional absolute URL of the account's profile page

getObject( "post", id )

Field
`author`	The Person's `name`
`title`, `summary`	Plain text
`content`	HTML
`url`	The post's own page
`published`	A date. Mastodon files the post under it
`tags`	Optional array of `{ name, url }`, sent as hashtags so posts appear in Mastodon's hashtag timelines on the servers that receive them. Names are reduced to letters, digits and underscores

getObject( "comment", id )

Only needed for replying back. Return null for every comment to never reply back.

Field
`author`	The Person's `name` the comment goes out as
`postId`	Your id of the post it's on
`parentId`	Your id of the comment it answers — `""` for top level
`content`	HTML
`url`, `published`	As for posts

isPublic( type, id )

Checked before every lookup, every time an object is served, and before every delivery. false means the module behaves as if the account, post or comment doesn't exist. Return false for drafts, private content and inactive accounts.

IRemoteReplies (optional)

Implement this too and replies from the fediverse to your public posts reach your app. Without it, the module stays one-way:

bxsclass implements="bxModules.bxactivitypub.contracts.IHostApp,bxModules.bxactivitypub.contracts.IRemoteReplies" {
    // ...
}

Method	Called when
`acceptRemoteReply( postId, parentId, reply )`	A new reply to `postId` arrives. `parentId` is your id of the reply it answers, or `""` for the post. Return your id for it, or `null` to refuse it
`updateRemoteReply( hostId, reply )`	Its author edited it
`deleteRemoteReply( hostId )`	Its author deleted it, or their account

reply is:

plain{
    objectUrl, url,
    author { actorUrl, name, handle, profileUrl, avatarUrl },
    contentHtml, sensitive, summary, published, attachmentCount
}

contentHtml is untrustedIt's HTML from another server. Sanitize it before you store or render it — for example with bx-esapi's sanitizeHTML() and a policy that allows only what you want to show. The module removes the leading mention of your account but does nothing else to it.

Only public replies are passed on. Followers-only replies and direct messages are dropped, and so is anything whose author isn't the account that signed it.
Replies to replies you accepted arrive with parentId set, so threads keep their shape.
sensitive and summary are the author's content warning. attachmentCount is how many images or files were attached — they aren't passed on.
Moderation is yours: store replies as pending, publish them straight away, or anything in between.