git ssb

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const nest = require('depnest')
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const { h, Array: MutantArray, resolve, computed } = require('mutant')
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const Scroller = require('mutant-scroll')
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const pull = require('pull-stream')
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const Next = require('pull-next')
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const get = require('lodash/get')
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const clone = require('lodash/cloneDeep')
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exports.gives = nest('app.page.blogIndex')
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exports.needs = nest({
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  'app.html.blogCard': 'first',
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  'app.html.topNav': 'first',
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  'app.html.sideNav': 'first',
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  'blog.sync.isBlog': 'first',
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  'sbot.pull.stream': 'first',
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  'sbot.obs.connection': 'first',
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  'history.sync.push': 'first',
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  'keys.sync.id': 'first',
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  'contact.obs.followers': 'first',
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  'channel.obs.isSubscribedTo': 'first',
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  'message.sync.isBlocked': 'first',
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  'translations.sync.strings': 'first',
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  'unread.sync.isUnread': 'first'
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})
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exports.create = (api) => {
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  var blogsCache = MutantArray()
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  return nest('app.page.blogIndex', function (location) {
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    // location here can expected to be: { page: 'blogIndex', filter: 'All' }
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    const { page, filter = 'All' } = location
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    var strings = api.translations.sync.strings()
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    blogsCache.clear()
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    var blogs = Scroller({
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      classList: ['content'],
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      prepend: [
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        api.app.html.topNav(location),
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        // Filters()
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      ],
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      streamToTop: Source({ reverse: false, live: true, old: false, limit: 20 }, api, filter),
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      streamToBottom: Source({ reverse: true, live: false, limit: 20 }, api, filter),
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      updateTop: update,
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      updateBottom: update,
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      store: blogsCache,
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      render
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    })
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    // HACK
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    blogs.insertBefore(Filters(), blogs.querySelector('.content'))
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    function Filters () {
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      const goTo = (loc) => () => api.history.sync.push(loc)
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      return h('Filters', [
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        h('span -filter', {
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          className: filter === 'All' ? '-active' : '',
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          'ev-click': goTo({ page, filter: 'All' })
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        }, 'All'),
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        h('span', '|'),
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        h('span -filter', {
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          className: filter === 'Subscriptions' ? '-active' : '',
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          'ev-click': goTo({ page, filter: 'Subscriptions' })
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        }, 'Subscriptions'),
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        h('span', '|'),
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        h('span -filter', {
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          className: filter === 'Friends' ? '-active' : '',
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          'ev-click': goTo({ page, filter: 'Friends' })
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        }, 'Friends')
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      ])
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    }
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    return h('Page -blogIndex', { title: strings.home }, [
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      api.app.html.sideNav(location),
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      blogs
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    ])
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  })
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  function Source (opts, api, filter) {
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    const commonOpts = {
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      query: [{
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        $filter: {
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          value: {
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            content: {
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              type: 'blog'
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            },
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            timestamp: { $gt: 0, $lt: undefined }
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          }
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        }
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      }]
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    }
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    const myId = api.keys.sync.id()
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    const { followers } = api.contact.obs
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    const filterbyFriends = (msg) => {
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      if (filter !== 'Friends') return true
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      const feed = msg.value.author
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      const theirFollowers = followers(feed)
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      const youFollowThem = computed(theirFollowers, followers => followers.includes(myId))
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      return resolve(youFollowThem)
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    }
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    const filterBySubscription = (msg) => {
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      if (filter !== 'Subscriptions') return true
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      if (!msg.value.content.hasOwnProperty('channel')) {
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        return false
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      }
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      const channel = msg.value.content.channel
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      return resolve(api.channel.obs.isSubscribedTo(channel))
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    }
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    return pull(
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      StepperStream(
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        (options) => api.sbot.pull.stream(sbot => sbot.query.read(options)),
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        Object.assign(commonOpts, opts)
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      ),
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      pull.filter(api.blog.sync.isBlog), // isBlog or Plog?
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      pull.filter(filterBySubscription),
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      pull.filter(filterbyFriends),
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      // pull.filter(msg => !msg.value.content.root), // show only root messages
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      pull.filter(msg => !api.message.sync.isBlocked(msg)) // this is already in feed.pull.type
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    )
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  }
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  function update (soFar, newBlog) {
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    soFar.transaction(() => {
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      var object = newBlog // Value(newBlog)
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      const index = indexOf(soFar, (blog) => newBlog.key === resolve(blog).key)
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      // if blog already in cache, not needed again
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      if (index >= 0) return
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      const justOlderPosition = indexOf(soFar, (msg) => newBlog.value.timestamp > resolve(msg).value.timestamp)
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      if (justOlderPosition > -1) {
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        soFar.insert(object, justOlderPosition)
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      } else {
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        soFar.push(object)
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      }
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    })
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  }
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  function render (blog) {
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    const { recps, channel } = blog.value.content
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    var onClick
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    if (channel && !recps) { onClick = (ev) => api.history.sync.push(Object.assign({}, blog, { page: 'blogShow' })) }
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    return api.app.html.blogCard(blog, { onClick })
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  }
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}
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function indexOf (array, fn) {
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  for (var i = 0; i < array.getLength(); i++) {
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    if (fn(array.get(i))) {
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      return i
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    }
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  }
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  return -1
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}
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// this is needed because muxrpc doesn't do back-pressure yet
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// this is a modified pull-next-step for ssb-query
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function StepperStream (createStream, _opts) {
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  var opts = clone(_opts)
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  var last = null
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  var count = -1
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  return Next(() => {
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    if (last) {
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      if (count === 0) return
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      // mix: not sure which case this ends stream for
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      //
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      var value = get(last, ['value', 'timestamp'])
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      if (value == null) return
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      if (opts.reverse) {
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        opts.query[0].$filter.value.timestamp.$lt = value
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      } else {
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        opts.query[0].$filter.value.timestamp.$gt = value
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      }
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      last = null
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    }
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    return pull(
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      createStream(clone(opts)),
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      pull.through(
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        (msg) => {
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          count++
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          if (!msg.sync) {
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            last = msg
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          }
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        },
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        (err) => {
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          // retry on errors...
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          if (err) {
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            count = -1
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            return count
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          }
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          // end stream if there were no results
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          if (last == null) last = {}
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        }
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      )
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    )
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  })
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}
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