kappa-views.js

// ------------------ KV ------------------ 

// API:
//         - put
//         - get
// EVENTS:
//         - new value for key listened to

// id view
// requires 'msg.links' being populated to point to old version
// TODO: how is 'version' encapulated/known-about here?
//       A: it's just an opaque identifier (umkv already works this way)
db.view.kv(function (msg, next) {
  var ops = []
  if (!msg.id) return next()
  ops.push({
    key: msg.id,
    links: msg.links
  })
  else next(null, ops)
})

// content hash view
var sha = require('sha.js')
db.view.kv(function (msg, next) {
  var ops = []
  var hash = sha('sha256').update(JSON.stringify(msg)).digest('hex')
  ops.push({ key: hash, links: [] })
  next(null, ops)
})


// ------------------ REFS ------------------ 

// API:
//         - read(refId)  -> ReadableStream
// EVENTS:
//         - new item added to ref id listened to

// changeset backrefs
db.view.refs(function (msg, next) {
  var ops = []
  if (msg.changeset) ops.push({ src: msg.changeset, dst: msg.id })
  next(null, ops)
})

// ways backrefs
db.view.refs(function (msg, next) {
  var ops = []
  if (msg.type === 'way') {
    msg.refs.forEach(function (ref) {
      ops.push({
        src: ref,
        dst: msg.id
      })
    })
  }
  next(null, ops)
})


// ------------------ LIST ------------------ 

// API:
//      - read(lt, gt)  -> ReadableStream
//      - (maybe some kind of pagination)
// EVENTS:
//         - new item added to range listened to

// by type
db.view.ascendingList(function (msg, next) {
  var ops = []
  ops.push(msg.type)
  next(null, ops)
})


// ------------------ SPATIAL ------------------ 

// API:
//      - query(bbox)  -> ReadableStream
// EVENTS:
//         - new item added to bbox listened to

// lat/lon spatial
db.view.spatial(function (msg, next) {
  if (msg.lat && msg.lon) next(null, { lat: msg.lat, lon: msg.lon })
  else next(null, [])
})



//----------------------------

// cabal: messages by channel
db.view.ascendingList(function (msg, next) {
  if (msg.type !== 'chat/text') return next()
  var ops = []
  ops.push(msg.channel + '!' + msg.timestamp)
  next(null, ops)
})

// cabal: latest nick
// not shown: 'links' field needs to be written @ publish time, so it can be
// used by the view here
db.view.kv(function (msg, next) {
  if (msg.type !== 'chat/about') return next()
  ops.push({
    key: msg.id,
    links: msg.links
  })
  next(null, ops)
})