git ssb

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var pull = require('pull-stream')
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var pullPushable = require('pull-pushable')
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var pullNext = require('pull-next')
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var SortedArray = require('sorted-array-functions')
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module.exports = FeedSummary
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function FeedSummary (source, windowSize, cb) {
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  var last = null
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  var returned = false
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  var done = false
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  return pullNext(() => {
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    if (!done) {
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      var next = {reverse: true, limit: windowSize || 1000, live: false}
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      if (last) {
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        next.lt = last.timestamp || last.value.sequence
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      }
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      var pushable = pullPushable()
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      pull(
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        source(next),
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        pull.collect((err, values) => {
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          if (err) throw err
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          if (!values.length) {
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            done = true
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          } else {
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            groupMessages(values).forEach(v => pushable.push(v))
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            last = values[values.length - 1]
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          }
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          pushable.end()
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          if (!returned) cb && cb()
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          returned = true
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        })
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      )
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    }
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    return pushable
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  })
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}
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function groupMessages (messages, filter) {
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  var follows = {}
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  var messageUpdates = {}
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  reverseForEach(messages, function (msg) {
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    if (!msg.value) return
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    var c = msg.value.content
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    if (c.type === 'contact') {
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      updateContact(msg, follows)
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    } else if (c.type === 'vote') {
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      if (c.vote && c.vote.link) {
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        // only show digs of posts added in the current window
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        // and only for the main post
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        const group = messageUpdates[c.vote.link]
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        if (group) {
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          if (c.vote.value > 0) {
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            group.lastUpdateType = 'dig'
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            group.digs.add(msg.value.author)
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            group.updated = msg.timestamp
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          } else {
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            group.digs.delete(msg.value.author)
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            if (group.lastUpdateType === 'dig' && !group.digs.size && !group.replies.length) {
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              group.lastUpdateType = 'reply'
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            }
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          }
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        }
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      }
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    } else {
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      if (c.root) {
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        const group = ensureMessage(c.root, messageUpdates)
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        group.lastUpdateType = 'reply'
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        group.repliesFrom.add(msg.value.author)
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        //SortedArray.add(group.replies, msg, compareUserTimestamp)
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        group.replies.push(msg)
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        group.channel = group.channel || msg.value.content.channel
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        group.updated = msg.timestamp
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      } else {
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        const group = ensureMessage(msg.key, messageUpdates)
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        group.lastUpdateType = 'post'
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        group.updated = msg.timestamp
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        group.author = msg.value.author
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        group.channel = msg.value.content.channel
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        group.message = msg
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      }
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    }
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  })
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  var result = []
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  Object.keys(follows).forEach((key) => {
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    SortedArray.add(result, follows[key], compareUpdated)
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  })
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  Object.keys(messageUpdates).forEach((key) => {
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    SortedArray.add(result, messageUpdates[key], compareUpdated)
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  })
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  return result
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}
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function compareUserTimestamp (a, b) {
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  return a.value.timestamp - b.value.timestamp
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}
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function compareUpdated (a, b) {
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  return b.updated - a.updated
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}
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function reverseForEach (items, fn) {
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  var i = items.length - 1
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  var start = Date.now()
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  nextBatch()
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  function nextBatch () {
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    while (i >= 0 && Date.now() - start < 10) {
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      fn(items[i], i)
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      i -= 1
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    }
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    if (i > 0) {
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      setImmediate(nextBatch)
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    }
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  }
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}
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function updateContact (msg, groups) {
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  var c = msg.value.content
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  var id = msg.value.author
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  var group = groups[id]
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  if (c.contact) {
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    if (c.following) {
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      if (!group) {
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        group = groups[id] = {
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          type: 'follow',
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          lastUpdateType: null,
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          contacts: new Set(),
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          updated: 0,
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          author: id,
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          id: id
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        }
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      }
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      group.contacts.add(c.contact)
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      group.updated = msg.timestamp
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    } else {
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      if (group) {
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        group.contacts.delete(c.contact)
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        if (!group.contacts.size) {
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          delete groups[id]
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        }
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      }
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    }
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  }
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}
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function ensureMessage (id, groups) {
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  var group = groups[id]
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  if (!group) {
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    group = groups[id] = {
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      type: 'message',
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      repliesFrom: new Set(),
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      replies: [],
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      message: null,
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      messageId: id,
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      digs: new Set(),
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      updated: 0
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    }
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  }
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  return group
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}
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