ssb-artefact

An ssb-server plugin for creating, reading and updating artefacts in scuttlebutt

Modules

• ssb-artefact

Artefact

An artefact is a media file that is stored using ssb.

   A   (the root message)
   |
   B   (an edit after A)
  / \
 C   D (two concurrent edits after B)

Because there might be multiple offline edits to an artefact which didn't know bout one-another, it's possible for divergence to happen: C and D wont know about each other.

An artefact is an Object which maps the key of each latest edit to the state it perceives the artefact to be in:

// artefact for the example above
{
  key: MessageId, // artefactId supplied, the root message of the artefact
  states: [
    { head: C, state: stateC },
    { head: D, state: stateD },
  ]
}

and the state is an Object which looks like the following for the four different artefact types:

{
  // fields for all types
  type: String,
  blob: Blob,
  createdAt: EdtfDateString

  title: String,
  description: String,

  identifier: String,
  licence: String,
  rights: String,
  source: String,

  language: String,
  translation: String

  authors: {
    [FeedId]: [
      { start: Integer, end: Integer }
    ]
  }

  recps: Recps,
  tombstone: Tombstone

  // additional fields for video and audio types only
  duration: Integer
  transcription: String
}

API

server.artefact.create(type, artefactBlob, details, cb)

Creates a new artefact record and describes details you'd like to set on it

• type String - describes the type of artefact
  • Only accepts photo, video or audio
• artefactBlob Blob - the blob object for the artefact media
• details Object - allows you to specify additional fields depending on the type of artefact. See example below
• cb Function - a callback with signature (err, artefactId)

The expected form of details:

{
  // fields for all types
  recps: [ FeedId, ...],           // can only be set in create

  authors: {
    add: [FeedId, ALL_AUTHORS],
    remove: [FeedId, ALL_AUTHORS] // NOTE: not available on create
  }

  title: { set: String },
  description: { set: String },

  createdAt: { set: EdtfDateString },

  identifier: { set: String },
  licence: { set: String },
  rights: { set: String },
  source: { set: String },

  language: { set: String },
  translation: { set: String },

  tombstone: { set: Tombstone },

  // additional fields for video and audio types only
  duration: { set: Integer },
  transcription: { set: String }
}

• type Tombstone is either null OR an Object of shape:

  {
    date: UnixTime,  // an Integer indicating microseconds from 1st Jan 1970, can be negative!
    reason: String   // (optional)
  }

• recps is a special scuttlebutt property, short for "recipients". Adding this means the artefact will automatically be encrypted so only the FeedId and GroupId listed in the recps Array will be able to read this artefact.

• type EdtfDateString is an edtf date string field. See edtf for more details.

• authors contains two arrays (add, remove) for adding and removing authors to the set. Authors are of the form feedId or *:

  • FeedId - updates from this author will be valid
  • * - updates by all authors will be valid
  • NOTE: authors are valid until they are removed from the set. When this feedId, it overrides all authors until it is removed
  • Any updates that arent from a valid author are classed as invalid and wont be returned when using the get method

Note: All of these fields are optional

server.artefact.get(artefactId, cb)

Gets an artefact record by its artefactId

• artefactId String - the cypherlink for the artefact (the msgId of the root message for the artefact)
• cb Function - a callback with signature (err, artefact)

All fields will be returned, but if no value has been set/added for that field, the value will be null

server.artefact.update(artefactId, details, cb)

Gets an artefact record by its artefactId

• artefactId String - the cypherlink for the artefact (the msgId of the root message for the artefact)
• details Object - same as in artefact.create except recps is set for you based on what the first message was
• cb Function - a callback with signature (err)

All fields will be returned, but if no value has been set/added for that field, the value will be null