git ssb

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var nest = require('depnest')
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var ref = require('ssb-ref')
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var MutantPullReduce = require('mutant-pull-reduce')
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var SortedArray = require('sorted-array-functions')
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var { computed } = require('mutant')
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exports.needs = nest({
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  'message.sync.unbox': 'first',
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  'sbot.pull.backlinks': 'first'
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})
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exports.gives = nest({
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  'sbot.hook.publish': true,
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  'message.obs.likes': true
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})
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exports.create = function (api) {
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  var activeLikes = new Set()
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  return nest({
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    'sbot.hook.publish': (msg) => {
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      if (!(msg && msg.value && msg.value.content)) return
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      if (typeof msg.value.content === 'string') {
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        msg = api.message.sync.unbox(msg)
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        if (!msg) return
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      }
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      var c = msg.value.content
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      if (c.type !== 'vote') return
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      if (!c.vote || !c.vote.link) return
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      activeLikes.forEach((likes) => {
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        if (likes.id === c.vote.link) {
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          likes.push({
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            dest: c.vote.link,
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            id: msg.key,
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            expression: c.vote.expression,
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            value: c.vote.value,
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            timestamp: msg.value.timestamp,
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            author: msg.value.author
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          })
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        }
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      })
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    },
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    'message.obs.likes': (id) => {
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      if (!ref.isLink(id)) throw new Error('an id must be specified')
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      var obs = get(id)
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      obs.id = id
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      return computed(obs, getLikes, {
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        // allow manual append for simulated realtime
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        onListen: () => activeLikes.add(obs),
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        onUnlisten: () => activeLikes.delete(obs)
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      })
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    }
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  })
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  function get (id) {
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    var likes = MutantPullReduce(api.sbot.pull.backlinks({
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      live: true,
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      query: [
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        {$filter: {
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          dest: id,
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          value: {
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            content: {
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              type: 'vote',
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              vote: { link: id }
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            }
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          }
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        }},
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        {$map: {
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          dest: 'dest',
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          id: 'key',
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          expression: ['value', 'content', 'vote', 'expression'],
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          value: ['value', 'content', 'vote', 'value'],
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          timestamp: 'timestamp',
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          author: ['value', 'author']
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        }}
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      ]
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    }), (result, msg) => {
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      if (!result[msg.author]) {
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        result[msg.author] = []
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      }
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      SortedArray.add(result[msg.author], msg, mostRecent)
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      return result
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    }, {
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      startValue: []
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    })
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    return likes
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  }
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}
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function getLikes (likes) {
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  return Object.keys(likes).reduce((result, id) => {
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    if (likes[id][0].value) {
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      result.push(id)
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    }
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    return result
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  }, [])
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}
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function mostRecent (a, b) {
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  return b.timestamp - a.timestamp
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}
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