boydog-server.js

const path = require("path")
const ShareDB = require("sharedb")
const WebSocket = require("ws")
const WebSocketJSONStream = require("@teamwork/websocket-json-stream")
const backend = new ShareDB()
const connection = backend.connect()

// Boydog back-end scope
let refScope = {} // Scope reference
let docScope = {} // ShareDB docs

const _iterate = (root, path = "") => {
  // TODO: Add support for reading non-leaf elements, these should reply with JSON.stringify(path)
  Object.entries(root).forEach((e) => {
    if (Object.prototype.toString.call(e[1]) === "[object Object]") {
      return _iterate(e[1], `${path}>${e[0]}`)
    } else if (Object.prototype.toString.call(e[1]) === "[object Array]") {
      return _iterate({ ...e[1] }, `${path}>${e[0]}`)
    } else {
      // This is a leaf
      const fullPath = `${path}>${e[0]}`.substr(1)
      if (docScope[fullPath] !== undefined) return // If document is already created, bailout

      docScope[fullPath] = ((selector) => {
        // Get document or create it if needed
        const doc = connection.get("boydog", selector)
        doc.fetch(function (err) {
          if (err) throw err
          if (doc.type === null) {
            // Document doesn't exist. Create it.
            docScope[fullPath]._latestValue = String(e[1])
            doc.create({ content: String(e[1]) })
            console.log("New document created:", fullPath)

            // Subscribe after an OP so that we know the latest value
            docScope[fullPath].subscribe((err) => {
              if (err) throw err
              docScope[fullPath].on("op", (op, source) => {
                docScope[fullPath].fetch((err) => {
                  if (err) throw err
                  docScope[fullPath]._latestValue = docScope[fullPath].data.content // The latest value is saved inside docScope too
                })
              })
            })

            // Define getter so that the latest value can be obtained from the server
            Object.defineProperty(root, e[0], {
              // TODO: Define set function, currently the user is not able to set a new scope value from the server
              set: (v) => {
                v = String(v)
                if (v === docScope[fullPath]._latestValue) return

                // TODO: Submit only needed changes. This code works but briefly erases the content from all clients and submits the new content. This sometimes causes the user's caret going to the beginning of the input.
                docScope[fullPath].submitOp(
                  [{ p: ["content", 0], sd: docScope[fullPath]._latestValue }], // Delete old content on its entirety
                  (err) => {
                    if (err) throw err
                    docScope[fullPath].submitOp(
                      [{ p: ["content", 0], si: v }], // Add new value
                      (err) => {
                        if (err) throw err
                      }
                    )
                  }
                )
              },
              get: () => {
                return docScope[fullPath]._latestValue
              },
            })
          }
        })
        return doc
      })(fullPath)
    }
  })
}

const init = (scope, server) => {
  refScope = scope

  //Add "/boydog-client" as an express Express route
  server._events.request.get("/boydog-client", function (req, res) {
    return res.sendFile(path.join(__dirname, "boydog-client.bundle.js"))
  })

  // Connect any incoming WebSocket connection to ShareDB
  const wss = new WebSocket.Server({ server })
  wss.on("connection", (ws) => {
    backend.listen(new WebSocketJSONStream(ws))
  })

  _iterate(scope)
}

const refresh = () => {
  _iterate(refScope)
}

module.exports = { init, refresh }