git ssb

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'use strict'
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var pull      = require('pull-stream')
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var pl        = require('pull-level')
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var Live      = require('pull-live')
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var paramap   = require('pull-paramap')
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var u         = require('./util')
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var stdopts   = u.options
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var Format    = u.formatStream
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var msgFmt    = u.format
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var timestamp = require('monotonic-timestamp')
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module.exports = function (db, flumedb) {
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  var logDB = db.sublevel('log')
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  db.pre(function (op, add, _batch) {
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    var msg = op.value
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    var id = op.key
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    // index by sequence number
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    var localtime = op.timestamp = timestamp()
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    add({
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      key: localtime, value: id,
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      type: 'put', prefix: logDB
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    })
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  })
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  function Limit (fn) {
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    return function (opts) {
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      if(opts && opts.limit && opts.limit > 0) {
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        var limit = opts.limit
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        var read = fn(opts)
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        return function (abort, cb) {
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          if(limit--) return read(abort, function (err, data) {
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            if(data && data.sync) limit ++
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            cb(err, data)
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          })
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          else read(true, cb)
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        }
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      }
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      else
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        return fn(opts)
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    }
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  }
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  db.createLogStream = Limit(Live(function (opts) {
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    opts = stdopts(opts)
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    var keys = opts.keys; delete opts.keys
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    var values = opts.values; delete opts.values
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    return pull(
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      pl.old(logDB, stdopts(opts)),
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      //lookup2(keys, values, 'timestamp')
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      paramap(function (data, cb) {
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        if(values == false) return cb(null, {key:data.value})
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        var key = data.value
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        var seq = data.key
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        db.get(key, function (err, value) {
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          if (err) cb(err)
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          else cb(null, msgFmt(keys, values, {key: key, value: value, timestamp: seq}))
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        })
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      })
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    )
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  }, function (opts) {
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    return pl.live(db, stdopts(opts))
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  }))
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  if(flumedb) {
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    var prog = {current: 0, start: 0, target: 0}
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    function one (opts, cb) {
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      pull(
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        db.createLogStream(opts),
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        pull.collect(function (err, ary) {
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          cb(err, ary[ary.length - 1])
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        })
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      )
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    }
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    one({reverse: true, limit: 1}, function (err, last) {
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      if(!last) ready() //empty legacy database.
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      else {
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        flumedb.since.once(function (v) {
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          if(v === -1) {
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            load(null)
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          }
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          else flumedb.get(v, function (err, data) {
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            if(err) throw err
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            if(data.timestamp < last.timestamp) {
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              load(data.timestamp)
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            }
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            else ready()
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          })
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        })
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      }
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      function load(since) {
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        // fast track for more accurate progress
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        flumedb.progress.migration = prog
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        var c = 0
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        pull(
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          pl.old(logDB, {values: false}),
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          pull.drain(function () {
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            c++
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          }, function () {
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            prog.target = c
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            migrate()
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          })
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        )
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        function migrate () {
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          // actual upgrade
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          pull(
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            db.createLogStream({gt: since}),
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            paramap(function (data, cb) {
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              prog.current += 1
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              flumedb.append(data, cb)
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            }, 32),
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            pull.drain(null, ready)
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          )
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        }
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      }
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      function ready () {
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        flumedb.ready.set(true)
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      }
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    })
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  }
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}
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