git ssb

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var pull = require('pull-stream')
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var multicb = require('multicb')
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var cat = require('pull-cat')
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var u = require('./util')
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module.exports = About
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function About(app, myId, follows) {
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  this.app = app
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  this.myId = myId
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  this.follows = follows
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}
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About.prototype.createAboutOpStream = function (id) {
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  return pull(
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    this.app.sbot.links({dest: id, rel: 'about', values: true, reverse: true, private: true, meta: false}),
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    this.app.unboxMessages(),
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    pull.map(function (msg) {
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      var c = msg.value.content
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      if (typeof c !== 'object' || c === null) return []
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      return Object.keys(c).filter(function (key) {
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        return key !== 'about'
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          && key !== 'type'
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          && key !== 'recps'
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          && key !== 'reason'
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      }).map(function (key) {
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        var value = c[key]
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        return {
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          id: msg.key,
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          author: msg.value.author,
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          timestamp: msg.value.timestamp,
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          prop: key,
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          value: value,
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          remove: value && value.remove,
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        }
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      })
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    }),
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    pull.flatten()
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  )
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}
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About.prototype.createAboutStreams = function (id) {
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  var ops = this.createAboutOpStream(id)
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  var scalars = {/* author: {prop: value} */}
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  var sets = {/* author: {prop: {link}} */}
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  var setsDone = multicb({pluck: 1, spread: true})
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  setsDone()(null, pull.values([]))
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  return {
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    scalars: pull(
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      ops,
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      pull.unique(function (op) {
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        return op.author + '-' + op.prop + '-'
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      }),
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      pull.filter(function (op) {
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        return !op.remove
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      })
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    ),
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    sets: u.readNext(setsDone)
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  }
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}
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function computeTopAbout(aboutByFeed) {
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  var propValueCounts = {/* prop: {value: count} */}
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  var topValues = {/* prop: value */}
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  var topValueCounts = {/* prop: count */}
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  for (var feed in aboutByFeed) {
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    var feedAbout = aboutByFeed[feed]
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    for (var prop in feedAbout) {
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      var value = feedAbout[prop]
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      var valueCounts = propValueCounts[prop] || (propValueCounts[prop] = {})
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      var count = (valueCounts[value] || 0) + 1
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      valueCounts[value] = count
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      if (count > (topValueCounts[prop] || 0)) {
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        topValueCounts[prop] = count
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        topValues[prop] = value
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      }
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    }
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  }
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  return topValues
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}
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About.prototype.get = function (dest, cb) {
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  if (dest[0] === '@') return this.getSocial(dest, cb)
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  return this.getCausal(dest, cb)
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}
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function copy(obj) {
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  if (obj === null || typeof obj !== 'object') return obj
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  var o = {}
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  for (var k in obj) o[k] = obj[k]
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  return o
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}
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function premapAbout(msg) {
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  var value = {
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    about: {},
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    mentions: {},
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    branches: {},
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    sources: {},
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    ts: msg.ts
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  }
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  var c = msg.value.content
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  if (!c) return value
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  if (c.branch) {
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    msg.branches.map(function (id) {
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      value.branches[id] = true
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    })
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  }
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  if (!c.about && c.root) return value
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  value.about = {}
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  var author = msg.value.author
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  var source = {id: msg.key, seq: msg.value.sequence}
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  for (var k in c) switch(k) {
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    case 'type':
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    case 'about':
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    case 'branch':
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      break
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    case 'recps':
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      // get recps from root message only
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      if (!c.root && !c.about) {
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        value.recps = {}
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        u.toLinkArray(c.recps).forEach(function (link) {
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          value.recps[link.link] = link
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        })
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      }
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      break
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    case 'mentions':
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      value.mentions = {}
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      u.toLinkArray(c.mentions).map(function (link) {
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        value.mentions[link.link] = link
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      })
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      break
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    case 'image':
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      var link = u.toLink(c.image)
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      if (!link) break
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      value.about.image = link.link
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      value.about.imageLink = link
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      var sources = value.sources.image || (value.sources.image = [])
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      sources[author] = source
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      break
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    case 'attendee':
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      var attendee = u.linkDest(c.attendee)
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      if (attendee && attendee === author) {
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        // TODO: allow users adding other users as attendees?
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        var attendeeLink = copy(u.toLink(c.attendee))
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        attendeeLink.source = msg.key
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        value.attending = {}
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        value.attending[attendee] = attendeeLink.remove ? null : attendeeLink }
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      break
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    default:
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      // TODO: handle arrays
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      value.about[k] = c[k]
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      var sources = value.sources[k] || (value.sources[k] = {})
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      sources[author] = source
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  }
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  return value
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}
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function reduceAbout(values, lastValue) {
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  var newValue = {
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    about: {},
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    mentions: {},
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    branches: {},
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    sources: {}
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  }
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  values.sort(compareByTs).concat(lastValue).forEach(function (value) {
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    if (!value) return
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    if (value.ts) {
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      if (!newValue.ts || value.ts > newValue.ts) {
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        newValue.ts = value.ts
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      }
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    }
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    if (value.attending) {
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      var attending = newValue.attending || (newValue.attending = {})
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      for (var k in value.attending) {
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        attending[k] = value.attending[k]
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      }
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    }
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    if (value.mentions) for (var k in value.mentions) {
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      newValue.mentions[k] = value.mentions[k]
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    }
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    if (value.branches) for (var k in value.branches) {
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      newValue.branches[k] = value.branches[k]
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    }
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    if (value.recps) {
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      // note: zero recps is still private. truthy recps indicates private
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      var recps = newValue.recps || (newValue.recps = {})
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      for (var k in value.recps) {
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        newValue.recps[k] = value.recps[k]
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      }
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    }
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    if (value.about) for (var k in value.about) {
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      // TODO: use merge heuristics
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      newValue.about[k] = value.about[k]
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      if (lastValue && lastValue.about[k]) {
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        if (value === lastValue) {
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          newValue.sources[k] = lastValue.sources[k]
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        } else {
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          // message setting a property resets the property's sources from branches
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        }
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      } else {
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        var newSources = newValue.sources[k] || (newValue.sources[k] = {})
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        var sources = value.sources[k]
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        for (var feed in sources) {
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          if (newSources[feed] && newSources[feed].seq > sources[feed].seq) {
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            // assume causal order in user's own feed.
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            // this condition shouldn't be reached if messages are in feed order
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            console.error('skip', k, feed, sources[feed].id, newSources[feed].id)
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            continue
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          }
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          newSources[feed] = sources[feed]
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        }
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      }
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    }
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  })
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  return newValue
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}
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function postmapAbout(value) {
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  var about = {
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    ts: value.ts,
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    _sources: {}
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  }
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  for (var k in value.sources) {
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    var propSources = about._sources[k] = []
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    for (var feed in value.sources[k]) {
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      propSources.push(value.sources[k][feed].id)
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    }
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  }
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  if (value.mentions) {
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    about.mentions = []
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    for (var k in value.mentions) {
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      about.mentions.push(value.mentions[k])
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    }
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  }
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  if (value.attending) {
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    about.attendee = []
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    for (var k in value.attending) {
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      var link = value.attending[k]
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      if (link) about.attendee.push(link)
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    }
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  }
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  if (value.branches) about.branch = Object.keys(value.branches)
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  if (value.recps) {
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    about.recps = []
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    for (var k in value.recps) {
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      about.recps.push(value.recps[k])
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    }
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  }
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  if (value.about) for (var k in value.about) {
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    about[k] = value.about[k]
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  }
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  return about
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}
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function compareByTs(a, b) {
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  return a.ts - b.ts
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}
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About.prototype.getCausal = function (dest, cb) {
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  if (!this.app.sbot.links) return pull.error(new Error('missing sbot.links'))
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  var self = this
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  var backlinks = {}
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  var seen = {}
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  var queue = []
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  var aboutAtMsgs = {}
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  var now = Date.now()
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  function enqueue(msg) {
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    if (!seen[msg.key]) {
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      seen[msg.key] = true
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      queue.push(msg)
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    }
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  }
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  function isMsgIdDone(id) {
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    return !!aboutAtMsgs[id]
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  }
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  function isMsgReady(msg) {
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    return msg.branches.every(isMsgIdDone)
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  }
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  function dequeue() {
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    var msg = queue.filter(isMsgReady).sort(compareByTs)[0]
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    if (!msg) return console.error('thread error'), queue.shift()
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    var i = queue.indexOf(msg)
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    queue.splice(i, 1)
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    return msg
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  }
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  pull(
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    cat([
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      dest[0] === '%' && self.app.pullGetMsg(dest),
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      self.app.sbot.links({
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        rel: 'about',
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        dest: dest,
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        values: true,
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        private: true,
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        meta: false
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      }),
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      self.app.sbot.links({
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        rel: 'root',
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        dest: dest,
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        values: true,
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        private: true,
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        meta: false
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      })
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    ]),
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    pull.unique('key'),
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    self.app.unboxMessages(),
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    pull.drain(function (msg) {
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      var c = msg.value.content
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      if (!c) return
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      msg = {
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        key: msg.key,
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        ts: Math.min(now,
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          Number(msg.timestamp) || Infinity,
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          Number(msg.value.timestamp || c.timestamp) || Infinity),
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        value: msg.value,
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        branches: u.toLinkArray(c.branch).map(u.linkDest)
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      }
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      if (!msg.branches.length) {
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        enqueue(msg)
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      } else msg.branches.forEach(function (id) {
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        var linksToMsg = backlinks[id] || (backlinks[id] = [])
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        linksToMsg.push(msg)
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      })
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    }, function (err) {
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      if (err) return cb(err)
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      while (queue.length) {
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        var msg = dequeue()
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        var abouts = msg.branches.map(function (id) { return aboutAtMsgs[id] })
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        aboutAtMsgs[msg.key] = reduceAbout(abouts, premapAbout(msg))
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        var linksToMsg = backlinks[msg.key]
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        if (linksToMsg) linksToMsg.forEach(enqueue)
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      }
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      var headAbouts = []
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      var headIds = []
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      for (var id in aboutAtMsgs) {
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        if (backlinks[id]) continue
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        headIds.push(id)
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        headAbouts.push(aboutAtMsgs[id])
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      }
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      headAbouts.sort(compareByTs)
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      var about = postmapAbout(reduceAbout(headAbouts))
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      about.branch = headIds
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      cb(null, about)
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    })
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  )
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}
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function getValue(obj) {
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  return obj.value
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}
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About.prototype.getSocial = function (dest, cb) {
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  var self = this
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  var myAbout = []
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  var aboutByFeed = {}
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  var aboutByFeedFollowed = {}
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  if (!this.app.sbot.links) return cb(new Error('missing sbot.links'))
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  this.follows.getFollows(this.myId, function (err, follows) {
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    if (err) return cb(err)
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    pull(
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      cat([
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        dest[0] === '%' && self.app.pullGetMsg(dest),
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        self.app.sbot.links({
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          rel: 'about',
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          dest: dest,
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          values: true,
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          private: true,
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          meta: false
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        })
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      ]),
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      self.app.unboxMessages(),
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      pull.drain(function (msg) {
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        var author = msg.value.author
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        var c = msg.value.content
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        if (!c) return
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        if (msg.key === dest && c.type === 'about') {
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          // don't describe an about message with itself
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          return
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        }
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        var about = author === self.myId ? myAbout :
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          follows[author] ?
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            aboutByFeedFollowed[author] || (aboutByFeedFollowed[author] = {}) :
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            aboutByFeed[author] || (aboutByFeed[author] = {})
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        if (c.name) about.name = c.name
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        if (c.title) about.title = c.title
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        if (c.image) {
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          about.image = u.linkDest(c.image)
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          about.imageLink = u.toLink(c.image)
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        }
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        if (c.description) about.description = c.description
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        if (c.publicWebHosting) about.publicWebHosting = c.publicWebHosting
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      }, function (err) {
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        if (err) return cb(err)
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        var destAbout = aboutByFeedFollowed[dest] || aboutByFeed[dest]
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        // bias the author's choices by giving them an extra vote
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        if (destAbout) {
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          if (follows[dest]) aboutByFeedFollowed._author = destAbout
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          else aboutByFeed._author = destAbout
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        }
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        var about = {}
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        var followedAbout = computeTopAbout(aboutByFeedFollowed)
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        var topAbout = computeTopAbout(aboutByFeed)
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        for (var k in topAbout) about[k] = topAbout[k]
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        // prefer followed feeds' choices
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        for (var k in followedAbout) about[k] = followedAbout[k]
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        // if we follow the destination/author feed, prefer its choices
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        if (follows[dest]) for (var k in destAbout) about[k] = destAbout[k]
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        // always prefer own choices
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        for (var k in myAbout) about[k] = myAbout[k]
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        cb(null, about)
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      })
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    )
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  })
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}
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