Overleaf/services/web/public/coffee/editor/sharejs/server/socketio.coffee

# This implements the socketio-based network API for ShareJS.
#
# This is the frontend used by the javascript socket implementation.
#
# See documentation for this protocol is in doc/protocol.md
# Tests are in test/socketio.coffee
#
# This code will be removed in a future version of sharejs because socket.io is
# too buggy.

socketio = require 'socket.io'
util = require 'util'
hat = require 'hat'

p = ->#util.debug
i = ->#util.inspect

# Attach the streaming protocol to the supplied http.Server.
#
# Options = {}
exports.attach = (server, createClient, options) ->
  io = socketio.listen server

  io.configure ->
    io.set 'log level', 1
    for option of options
      io.set option, options[option]

  authClient = (handshakeData, callback) ->
    data =
      headers: handshakeData.headers
      remoteAddress: handshakeData.address.address
      secure: handshakeData.secure

    createClient data, (error, client) ->
      if error
        # Its important that we don't pass the error message to the client here - leaving it as null
        # will ensure the client recieves the normal 'not_authorized' message and thus
        # emits 'connect_failed' instead of 'error'
        callback null, false
      else
        handshakeData.client = client
        callback null, true

  io.of('/sjs').authorization(authClient).on 'connection', (socket) ->
    client = socket.handshake.client

    # There seems to be a bug in socket.io where socket.request isn't set sometimes.
    p "New socket connected from #{socket.request.socket.remoteAddress} with id #{socket.id}" if socket.request?

    lastSentDoc = null
    lastReceivedDoc = null

    # Map from docName -> {listener:fn, queue:[msg], busy:bool}
    docState = {}
    closed = false

    # Send a message to the socket.
    # msg _must_ have the doc:DOCNAME property set. We'll remove it if its the same as lastReceivedDoc.
    send = (msg) ->
      if msg.doc == lastSentDoc
        delete msg.doc
      else
        lastSentDoc = msg.doc

      p "Sending #{i msg}"
      socket.json.send msg

    # Open the given document name, at the requested version.
    # callback(error, version)
    open = (docName, version, callback) ->
      callback 'Doc already opened' if docState[docName].listener?
      p "Registering listener on #{docName} by #{socket.id} at #{version}"

      # This passes op events to the client
      docState[docName].listener = listener = (opData) ->
        throw new Error 'Consistency violation - doc listener invalid' unless docState[docName].listener == listener

        p "listener doc:#{docName} opdata:#{i opData} v:#{version}"

        # Skip the op if this socket sent it.
        return if opData.meta?.source == client.id

        opMsg =
          doc: docName
          op: opData.op
          v: opData.v
          meta: opData.meta

        send opMsg
      
      # Tell the socket the doc is open at the requested version
      client.listen docName, version, listener, (error, v) ->
        delete docState[docName].listener if error
        callback error, v

    # Close the named document.
    # callback([error])
    close = (docName, callback) ->
      p "Closing #{docName}"
      listener = docState[docName].listener
      return callback 'Doc already closed' unless listener?

      client.removeListener docName
      docState[docName].listener = null
      callback()

    # Handles messages with any combination of the open:true, create:true and snapshot:null parameters
    handleOpenCreateSnapshot = (query, finished) ->
      docName = query.doc
      msg = doc:docName

      callback = (error) ->
        if error
          close(docName) if msg.open == true
          msg.open = false if query.open == true
          msg.snapshot = null if query.snapshot != undefined
          delete msg.create

          msg.error = error

        send msg
        finished()

      return callback 'No docName specified' unless query.doc?

      if query.create == true
        if typeof query.type != 'string'
          return callback 'create:true requires type specified'

      if query.meta != undefined
        unless typeof query.meta == 'object' and Array.isArray(query.meta) == false
          return callback 'meta must be an object'

      docData = undefined
      # Technically, we don't need a snapshot if the user called create but not open or createSnapshot,
      # but no clients do that yet anyway.
      #
      # It might be nice to add a 'createOrGet()' method to model / db manager. But most
      # of the time clients are opening an existing document rather than creating a new one anyway.
      ###
      model.clientGetSnapshot client, query.doc, (error, data) ->
        maybeCreate = (callback) ->
          if query.create and error is 'Document does not exist'
            model.clientCreate client, docName, query.type, query.meta or {}, callback
          else
            callback error, data

        maybeCreate (error, data) ->
          if query.create
            msg.create = !!error
          if error is 'Document already exists'
            msg.create = false
          else if error and (!msg.create or error isnt 'Document already exists')
            # This is the real final callback, to say an error has occurred.
            return callback error
          else if query.create or query.snapshot is null


          if query.snapshot isnt null
      ###

      # This is implemented with a series of cascading methods for each different type of
      # thing this method can handle. This would be so much nicer with an async library. Welcome to
      # callback hell.

      step1Create = ->
        return step2Snapshot() if query.create != true

        # The document obviously already exists if we have a snapshot.
        if docData
          msg.create = false
          step2Snapshot()
        else
          client.create docName, query.type, query.meta || {}, (error) ->
            if error is 'Document already exists'
              # We've called getSnapshot (-> null), then createClient (-> already exists). Its possible
              # another client has called createClient first.
              client.getSnapshot docName, (error, data) ->
                return callback error if error

                docData = data
                msg.create = false
                step2Snapshot()
            else if error
              callback error
            else
              msg.create = !error
              step2Snapshot()

      # The socket requested a document snapshot
      step2Snapshot = ->
        # Skip inserting a snapshot if the document was just created.
        if query.snapshot != null or msg.create == true
          step3Open()
          return

        if docData
          msg.v = docData.v
          msg.type = docData.type.name unless query.type == docData.type.name
          msg.snapshot = docData.snapshot
        else
          return callback 'Document does not exist'

        step3Open()

      # Attempt to open a document with a given name. Version is optional.
      # callback(opened at version) or callback(null, errormessage)
      step3Open = ->
        return callback() if query.open != true

        # Verify the type matches
        return callback 'Type mismatch' if query.type and docData and query.type != docData.type.name

        open docName, query.v, (error, version) ->
          return callback error if error

          # + Should fail if the type is wrong.

          p "Opened #{docName} at #{version} by #{socket.id}"
          msg.open = true
          msg.v = version
          callback()

      if query.snapshot == null or (query.open == true and query.type)
        client.getSnapshot query.doc, (error, data) ->
          return callback error if error and error != 'Document does not exist'

          docData = data
          step1Create()
      else
        step1Create()

    # The socket closes a document
    handleClose = (query, callback) ->
      close query.doc, (error) ->
        if error
          # An error closing still results in the doc being closed.
          send {doc:query.doc, open:false, error:error}
        else
          send {doc:query.doc, open:false}

        callback()

    # We received an op from the socket
    handleOp = (query, callback) ->
      throw new Error 'No docName specified' unless query.doc?
      throw new Error 'No version specified' unless query.v? or (query.meta?.path? and query.meta?.value?)

      op_data = {v:query.v, op:query.op}
      op_data.meta = query.meta || {}
      op_data.meta.source = socket.id

      client.submitOp query.doc, op_data, (error, appliedVersion) ->
        msg = if error
          p "Sending error to socket: #{error}"
          {doc:query.doc, v:null, error:error}
        else
          {doc:query.doc, v:appliedVersion}

        p "sending #{i msg}"
        send msg
        callback()

    flush = (state) ->
      return if state.busy || state.queue.length == 0
      state.busy = true

      query = state.queue.shift()

      callback = ->
        state.busy = false
        flush state

      p "processing query #{i query}"
      try
        if query.open == false
          handleClose query, callback

        else if query.open != undefined or query.snapshot != undefined or query.create
          # You can open, request a snapshot and create all in the same
          # request. They're all handled together.
          handleOpenCreateSnapshot query, callback

        else if query.op? or query.meta? # The socket is applying an op.
          handleOp query, callback

        else
          util.debug "Unknown message received: #{util.inspect query}"

      catch error
        util.debug error.stack
        # ... And disconnect the socket?
        callback()
    
    # And now the actual message handler.
    messageListener = (query) ->
      p "Server recieved message #{i query}"
      # There seems to be a bug in socket.io where messages are detected
      # after the client disconnects.
      if closed
        console.warn "WARNING: received query from socket after the socket disconnected."
        console.warn socket
        return

      try
        query = JSON.parse query if typeof(query) == 'string'

        if query.doc == null
          lastReceivedDoc = null
          query.doc = hat()
        else if query.doc != undefined
          lastReceivedDoc = query.doc
        else
          throw new Error 'msg.doc missing. Probably the client reconnected without telling us - this is a socket.io bug.' unless lastReceivedDoc
          query.doc = lastReceivedDoc
      catch error
        util.debug error.stack
        return

      docState[query.doc] ||= {listener:null, queue:[], busy:no}
      docState[query.doc].queue.push query
      flush docState[query.doc]

    socket.on 'message', messageListener
    socket.on 'disconnect', ->
      p "socket #{socket.id} disconnected"
      closed = true
      for docName, state of docState
        state.busy = true
        state.queue = []
        client.removeListener docName if state.listener?
      socket.removeListener 'message', messageListener
      docState = {}
  
  server