git ssb

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var ref = require('ssb-ref')
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var ssbKeys = require('ssb-keys')
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exports.initial = function () {
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  return {
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    validated: 0,
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    queued: 0,
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    queue: [],
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    feeds: {},
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    error: null
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  }
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}
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exports.checkInvalidCheap = function (state, msg) {
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  //the message is just invalid
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  if(!ref.isFeedId(msg.author))
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    return new Error('invalid message: must have author')
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  //state is id, sequence, timestamp
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  if(state) {
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    //the message is possibly a fork, but only if the signature is valid.
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    if(msg.sequence != state.sequence + 1)
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      return new Error('invalid message: expected sequence ' + (state.sequence + 1) + ' but got:'+ msg.sequence + 'in state:'+JSON.stringify(state))
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    if(msg.timestamp <= state.ts)
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      return new Error('invalid message: timestamp not increasing')
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    if(msg.previous != state.id)
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      return new Error('invalid message: expected different previous message')
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    //and check type, and length, and some other stuff. finaly check the signature.
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  }
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  else {
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    if(msg.previous !== null)
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      return new Error('initial message must have previous: null')
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    if(msg.sequence !== 1)
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      return new Error('initial message must have sequence: 1')
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    if('number' !== typeof msg.timestamp)
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      return new Error('initial message must have timestamp')
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  }
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}
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exports.checkInvalid = function (state, msg) {
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  var err = exports.checkInvalidCheap(state, msg)
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  if(err) return err
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  if(!ssbKeys.verifyObj({public: msg.author.substring(1)}, msg))
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    return new Error('invalid signature')
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  return false //not invalid
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}
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/*
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{
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  //an array of messages which have been validated, but not written to the database yet.
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  valid: [],
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  //a map of information needed to know if something should be appeneded to the valid queue.
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  feeds: {
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    <feed>: {id, sequence, ts}
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  },
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  error: null
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}
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*/
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exports.queue = function (state, msg) {
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  var err
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  if(state.error = exports.checkInvalidCheap(flatState(state.feeds[msg.author]), msg))
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    return state
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  state.feeds[msg.author] = state.feeds[msg.author] || {
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    id: null, sequence: null, timestamp: null, queue: []
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  }
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  state.queued += 1
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  state.feeds[msg.author].queue.push(msg)
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  return state
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}
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function flatState (fstate) {
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  if(!fstate) return null
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  if(fstate.queue.length) {
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    var last = fstate.queue[fstate.queue.length - 1]
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    return {
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      id: exports.id(last),
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      timestamp: last.timestamp,
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      sequence: last.sequence
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    }
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  }
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  else
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    return fstate
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}
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exports.append = function (state, msg) {
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  if(state.error = exports.checkInvalid(flatState(state.feeds[msg.author]), msg))
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    return state
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  else if(state.feeds[msg.author]) {
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    var a = state.feeds[msg.author]
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    a.id = exports.id(msg)
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    a.sequence = msg.sequence
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    a.timestamp = msg.timestamp
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    var q = state.feeds[msg.author].queue
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    state.validated += q.length
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    state.queued -= q.length
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    while(q.length)
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      state.queue.push(q.shift())
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  }
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  else {
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    state.feeds[msg.author] = {id: exports.id(msg), sequence: msg.sequence, timestamp: msg.timestamp, queue: []}
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  }
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  state.queue.push(msg)
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  state.validated += 1
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  return state
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}
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exports.validate = function (state, feed) {
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  if(!state.feeds[feed] || !state.feeds[feed].queue.length) {
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    return state
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  }
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  var msg = state.feeds[feed].queue.pop()
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  state.queued -= 1
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  return exports.append(state, msg)
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}
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//pass in your own timestamp, so it's completely deterministic
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exports.create = function (keys, hmac_key, state, content, timestamp) {
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  state = flatState(state)
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  return ssbKeys.signObj(keys, hmac_key, {
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    previous: state ? state.id : null,
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    sequence: state ? state.sequence + 1 : 1,
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    author: keys.id,
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    timestamp: timestamp,
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    hash: 'sha256',
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    content: content,
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  })
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}
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exports.id = function (msg) {
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  return '%'+ssbKeys.hash(JSON.stringify(msg, null, 2))
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}
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exports.appendNew = function (state, hmac_key, keys, content, timestamp) {
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  var msg = exports.create(keys, hmac_key, state.feeds[keys.id], content, timestamp)
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  state = exports.append(state, msg)
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  return state
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}
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