git ssb

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var pull = require('pull-stream')
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var computed = require('mutant/computed')
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var MutantPullReduce = require('mutant-pull-reduce')
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var nest = require('depnest')
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var throttle = require('mutant/throttle')
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exports.needs = nest({
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  'sbot.pull.userFeed': 'first'
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})
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exports.gives = nest({
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  'channel.obs': ['subscribed']
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})
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exports.create = function (api) {
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  var cache = {}
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  return nest({
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    'channel.obs': {subscribed}
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  })
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  function subscribed (userId) {
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    if (cache[userId]) {
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      return cache[userId]
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    } else {
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      var stream = pull(
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        api.sbot.pull.userFeed({id: userId, live: true}),
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        pull.filter((msg) => {
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          return !msg.value || msg.value.content.type === 'channel'
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        })
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      )
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      var result = MutantPullReduce(stream, (result, msg) => {
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        var c = msg.value.content
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        if (typeof c.channel === 'string' && c.channel) {
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          var channel = c.channel.trim()
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          if (channel) {
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            if (typeof c.subscribed === 'boolean') {
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              if (c.subscribed) {
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                result.add(channel)
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              } else {
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                result.delete(channel)
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              }
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            }
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          }
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        }
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        return result
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      }, {
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        startValue: new Set(),
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        nextTick: true
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      })
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      var instance = throttle(result, 2000)
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      instance.sync = result.sync
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      instance.has = function (value) {
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        return computed(instance, x => x.has(value))
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      }
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      cache[userId] = instance
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      return instance
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    }
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  }
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}
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