git ssb

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const pull = require('pull-stream')
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exports.manifest = {
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  read: 'source',
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  countStream: 'source',
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  feedLikesMsgStream: 'source',
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  get: 'async'
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}
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exports.init = function (ssb) {
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  return {
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    read,
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    feedLikesMsgStream: function ({ feedId, msgId }) {
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      let value = false
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      let sync = false
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      return pull(
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        ssb.backlinks.read({
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          live: true,
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          query: [{
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            $filter: {
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              dest: msgId,
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              value: {
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                author: feedId,
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                content: { type: 'vote', vote: { link: msgId } }
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              }
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            }
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          }]
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        }),
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        pull.map((msg) => {
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          if (msg.sync) {
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            sync = true
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            return value
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          }
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          const vote = msg.value.content.vote
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          if (vote) {
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            value = vote.value > 0
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            if (sync) return value
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          }
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          return null
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        }),
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        pull.filter(present)
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      )
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    },
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    get: function ({ dest }, cb) {
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      const ids = new Set()
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      pull(
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        read({ dest }),
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        pull.drain(msg => {
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          const author = msg.value.author
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          const vote = msg.value.content.vote
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          if (vote) {
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            if (vote.value > 0) {
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              ids.add(author)
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            } else {
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              ids.delete(author)
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            }
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          }
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        }, (err) => {
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          if (err) return cb(err)
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          cb(null, Array.from(ids))
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        })
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      )
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    },
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    countStream: function ({ dest }) {
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      const ids = new Set()
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      let sync = false
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      return pull(
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        read({ dest, live: true }),
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        pull.map(msg => {
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          if (msg.sync) {
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            sync = true
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            return ids.size
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          }
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          const author = msg.value.author
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          const vote = msg.value.content.vote
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          if (vote) {
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            if (vote.value > 0) {
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              ids.add(author)
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            } else {
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              ids.delete(author)
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            }
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          }
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          if (sync) {
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            return ids.size
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          }
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          return null
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        }),
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        pull.filter(present)
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      )
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    }
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  }
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  function read ({
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    reverse = false,
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    limit = null,
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    live = null,
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    dest = null
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  }) {
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    return pull(
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      ssb.backlinks.read({
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        reverse,
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        live,
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        limit,
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        query: [{
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          $filter: {
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            dest,
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            value: { content: { type: 'vote', vote: { link: dest } } }
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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 present (value) {
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  return value != null
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}
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