git ssb

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var nest = require('depnest')
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var pull = require('pull-stream')
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var pullCat = require('pull-cat')
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var sort = require('ssb-sort')
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var ref = require('ssb-ref')
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var { map, computed } = require('mutant')
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exports.needs = nest({
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  'sbot.pull.links': 'first',
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  'sbot.async.get': 'first',
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  'lib.obs.pullLookup': 'first',
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  'message.sync.unbox': 'first'
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})
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exports.gives = nest('feed.obs.thread')
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exports.create = function (api) {
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  return nest('feed.obs.thread', thread)
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  function thread (rootId, { branch } = {}) {
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    if (!ref.isLink(rootId)) throw new Error('an id must be specified')
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    var rootMessageStream = pull(
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      pull.values([rootId]),
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      pull.asyncMap((key, cb) => {
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        return api.sbot.async.get(key, (err, value) => cb(err, {key, value}))
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      })
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    )
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    var messageLookup = api.lib.obs.pullLookup(pull(
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      pullCat([
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        rootMessageStream,
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        api.sbot.pull.links({ rel: branch ? 'branch' : 'root', dest: rootId, keys: true, values: true, live: true })
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      ]),
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      unboxIfNeeded()
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    ), 'key')
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    var orderedIds = computed(messageLookup, (lookup) => {
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      var msgs = Object.keys(lookup).map(k => lookup[k])
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      return sort(msgs).map(getKey)
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    })
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    var messages = map(orderedIds, (id) => {
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      return messageLookup.get(id)
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    })
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    var result = {
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      messages,
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      lastId: computed(messages, (messages) => {
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        var branches = sort.heads(messages)
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        if(branches.length <= 1) branches = branches[0]
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        return branches
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      }),
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      rootId: computed(messages, (messages) => {
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        if (branch && messages.length) {
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          return messages[0].value.content.root
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        } else {
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          return rootId
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        }
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      }),
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      branchId: computed(messages, (messages) => {
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        if (branch) return rootId
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      }),
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      previousKey: function (msg) {
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        return PreviousKey(result.messages, msg)
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      },
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      isPrivate: computed(messages, msgs => {
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        if (!msgs[0]) return false
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        return msgs[0].value.private || false
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      }),
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      channel: computed(messages, msgs => {
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        if (!msgs[0]) return undefined
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        return msgs[0].value.content.channel
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      }),
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      recps: computed(messages, msgs => {
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        if (!msgs[0]) return undefined
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        return msgs[0].value.content.recps
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      })
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    }
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    result.sync = messageLookup.sync
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    return result
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  }
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  function unboxIfNeeded () {
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    return pull.map(function (msg) {
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      if (msg.sync || (msg.value && typeof msg.value.content === 'object')) {
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        return msg
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      } else {
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        return api.message.sync.unbox(msg)
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      }
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    })
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  }
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}
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function getKey (msg) {
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  return msg.key
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}
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function PreviousKey (collection, item) {
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  return computed(collection, (c) => {
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    var index = collection.indexOf(item)
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    if (~index) {
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      var previous = c[index - 1]
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      if (previous) {
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        return previous.key
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      }
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    }
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  })
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}
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