git ssb

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var cont = require('cont')
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var util = require('./util')
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var Queue = require('./queue')
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var ssbKeys = require('ssb-keys')
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function isFunction (f) {
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  return 'function' === typeof f
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}
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function isObject (o) {
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  return (
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    o && 'object' === typeof o
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    && !Buffer.isBuffer(o)
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    && !Array.isArray(o)
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  )
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}
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module.exports = function (ssb, keys) {
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  if(!ssb.add)
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    throw new Error('*must* install feeds on this ssb instance')
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  var queue = Queue(function (msg, prev, cb) {
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    if(prev) next(prev)
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    else
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      ssb.getLatest(keys.id, function (_, prev) { next(prev) })
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    function next (prev) {
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      ssb.add(
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        util.create(
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          keys, null, msg,
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          prev && prev.value,
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          prev && prev.key
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        ),
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        cb
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      )
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    }
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  })
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  var publish =
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    cont(function (type, message, cb) {
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      // argument variations
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      if (isFunction(message))    { cb = message; message = type } // add(msgObj, cbFn)
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      else if (isObject(message)) { message.type = type } // add(typeStr, mgObj, cbFn)
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      else                        { message = { type: type, value: message } } // add(typeStr, msgStr, cbFn)
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      var err = util.isInvalidContent(message)
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      if(err) return cb(err)
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      queue(message, cb)
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      return this
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    })
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  return {
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    id: keys.id,
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    keys: keys,
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    add: publish,
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    publish: publish
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  }
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}
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