git ssb

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var nest = require('depnest')
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var {Value, computed} = require('mutant')
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var pull = require('pull-stream')
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var ref = require('ssb-ref')
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exports.needs = nest({
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  'sbot.pull.stream': 'first'
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})
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exports.gives = nest({
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  'contact.obs': ['following', 'followers', 'blocking', 'blockers'],
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  'sbot.hook.publish': true
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})
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exports.create = function (api) {
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  var cacheLoading = false
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  var cache = {}
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  var sync = Value(false)
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  return nest({
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    'contact.obs': {
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      following: (id) => values(get(id), 'following', true),
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      followers: (id) => values(get(id), 'followers', true),
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      blocking: (id) => values(get(id), 'blocking', true),
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      blockers: (id) => values(get(id), 'blockers', true),
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    },
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    'sbot.hook.publish': function (msg) {
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      if (isContact(msg)) {
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        // HACK: make interface more responsive when sbot is busy
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        var source = msg.value.author
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        var dest = msg.value.content.contact
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        if (typeof msg.value.content.following === 'boolean') {
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          update(source, {
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            following: {
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              [dest]: [msg.value.content]
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            }
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          })
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          update(dest, {
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            followers: {
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              [source]: [msg.value.content]
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            }
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          })
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        }
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        if (typeof msg.value.content.blocking === 'boolean') {
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          update(source, {
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            blocking: {
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              [dest]: [msg.value.content]
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            }
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          })
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          update(dest, {
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            blockers: {
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              [source]: [msg.value.content]
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            }
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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 values (state, key, compare) {
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    var obs = computed([state, key, compare], getIds)
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    obs.sync = sync
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    return obs
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  }
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  function loadCache () {
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    pull(
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      api.sbot.pull.stream(sbot => sbot.contacts.stream({live: true})),
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      pull.drain(item => {
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        for (var target in item) {
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          if (ref.isFeed(target)) update(target, item[target])
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        }
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        if (!sync()) {
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          sync.set(true)
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        }
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      })
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    )
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  }
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  function update (id, values) {
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    // values = { following, followers, blocking, blockedBy, ... }
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    var state = get(id)
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    var lastState = state()
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    var changed = false
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    for (var key in values) {
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      var valuesForKey = lastState[key] = lastState[key] || {}
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      for (var dest in values[key]) {
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        var value = values[key][dest]
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        if (!valuesForKey[dest] || value[1] > valuesForKey[dest][1] || !values[1] || !valuesForKey[dest[1]]) {
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          valuesForKey[dest] = value
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          changed = true
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        }
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      }
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    }
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    if (changed) {
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      state.set(lastState)
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    }
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  }
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  function get (id) {
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    if (!ref.isFeed(id)) throw new Error('Contact state requires an id!')
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    if (!cacheLoading) {
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      cacheLoading = true
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      loadCache()
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    }
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    if (!cache[id]) {
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      cache[id] = Value({})
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    }
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    return cache[id]
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  }
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}
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function getIds (state, key, compare) {
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  var result = new Set()
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  if (state[key]) {
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    for (var dest in state[key]) {
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      if (state[key][dest][0] === compare) {
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        result.add(dest)
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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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function isContact (msg) {
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  return msg.value && msg.value.content && msg.value.content.type === 'contact'
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}
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