event_stream.js

var copy = require('shallow-copy')
var xtend = require('xtend')
var Color = require('color')

module.exports = EventStream

EventStream.validEvent = validEvent

function EventStream () {
  if (!(this instanceof EventStream)) return new EventStream()
  this.events = []
}

EventStream.prototype.push = function push (event) {
  var value = this.events.push(event)
  return value
}

EventStream.prototype.pop = function pop () {
  var value = this.events.pop()
  return value
}

EventStream.prototype.toJSON = function toJSON () {
  var self = this
  var lastType
  this.normalized = this.events.map(createEvent)
  this.normalized.forEach(processPath)

  return this.normalized.reduce(
    reduce,
    []
  )

  function createEvent (event) {
    var args = copy(event.args)
    if (args) {
      ;['stroke', 'fill'].forEach(function setRgb (key) {
        if (args[key]) args[key] = Color(args[key]).rgbaString()
      })
    }
    return {
      type: event.type,
      id: event.id,
      args: args,
      layout: event.layout,
      pathId: event.path ? event.path.id : undefined
    }
  }

  function processPath (event) {
    if (event.pathId) {
      var path = self.normalized.filter(findById)[0]
      if (path) {
        event.deleted = true
        path.args = xtend(path.args, event.args)
        path.deleted = event.type === 'delete'
      }
    }

    function findById (e) {
      return e.id === event.pathId
    }
  }

  function reduce (result, event) {
    if (event.type === 'style' && lastType === 'style') result.pop()
    if (validEvent(event)) {
      lastType = event.type
      result.push(
        ['type', 'args', 'layout'].reduce(copyEvent, {})
      )
      return result
    }

    function copyEvent (result, key) {
      if (event[key]) {
        result[key] = event[key]
      }
      return result
    }
    return result
  }
}

function validEvent (event) {
  if (event.deleted) return false

  if (event.type === 'text') {
    return !!event.args.value
  }

  if (event.type === 'path') {
    return !!event.args.d.match(/a|l/i)
  }

  return Object.keys(event.args || {}).length +
  Object.keys(event.layout || {}).length > 0
}