yjs/src/Utils.js

/* global Y */
'use strict'

/*
  EventHandler is an helper class for constructing custom types.

  Why: When constructing custom types, you sometimes want your types to work
  synchronous: E.g.
  ``` Synchronous
  mytype.setSomething("yay")
  mytype.getSomething() === "yay"
  ```
  ``` Asynchronous
  mytype.setSomething("yay")
  mytype.getSomething() === undefined
  mytype.waitForSomething().then(function(){
    mytype.getSomething() === "yay"
  })

  The structures usually work asynchronously (you have to wait for the
  database request to finish). EventHandler will help you to make your type
  synchronously.
*/
class EventHandler {
  /*
    onevent: is called when the structure changes.

    Note: "awaiting opertations" is used to denote operations that were
    prematurely called. Events for received operations can not be executed until
    all prematurely called operations were executed ("waiting operations")
  */
  constructor (onevent) {
    this.waiting = []
    this.awaiting = 0
    this.onevent = onevent
    this.eventListeners = []
  }
  /*
    Call this when a new operation arrives. It will be executed right away if
    there are no waiting operations, that you prematurely executed
  */
  receivedOp (op) {
    if (this.awaiting <= 0) {
      this.onevent([op])
    } else {
      this.waiting.push(Y.utils.copyObject(op))
    }
  }
  /*
    You created some operations, and you want the `onevent` function to be
    called right away. Received operations will not be executed untill all
    prematurely called operations are executed
  */
  awaitAndPrematurelyCall (ops) {
    this.awaiting++
    this.onevent(ops)
  }
  /*
    Basic event listener boilerplate...
    TODO: maybe put this in a different type..
  */
  addEventListener (f) {
    this.eventListeners.push(f)
  }
  removeEventListener (f) {
    this.eventListeners = this.eventListeners.filter(function (g) {
      return f !== g
    })
  }
  removeAllEventListeners () {
    this.eventListeners = []
  }
  callEventListeners (event) {
    for (var i in this.eventListeners) {
      try {
        this.eventListeners[i](event)
      } catch (e) {
        console.log('User events must not throw Errors!') // eslint-disable-line
      }
    }
  }
  /*
    Call this when you successfully awaited the execution of n Insert operations
  */
  awaitedInserts (n) {
    var ops = this.waiting.splice(this.waiting.length - n)
    for (var oid = 0; oid < ops.length; oid++) {
      var op = ops[oid]
      for (var i = this.waiting.length - 1; i >= 0; i--) {
        let w = this.waiting[i]
        if (Y.utils.compareIds(op.left, w.id)) {
          // include the effect of op in w
          w.right = op.id
          // exclude the effect of w in op
          op.left = w.left
        } else if (Y.utils.compareIds(op.right, w.id)) {
          // similar..
          w.left = op.id
          op.right = w.right
        }
      }
    }
    this._tryCallEvents()
  }
  /*
    Call this when you successfully awaited the execution of n Delete operations
  */
  awaitedDeletes (n, newLeft) {
    var ops = this.waiting.splice(this.waiting.length - n)
    for (var j in ops) {
      var del = ops[j]
      if (newLeft != null) {
        for (var i in this.waiting) {
          let w = this.waiting[i]
          // We will just care about w.left
          if (Y.utils.compareIds(del.target, w.left)) {
            del.left = newLeft
          }
        }
      }
    }
    this._tryCallEvents()
  }
  /* (private)
    Try to execute the events for the waiting operations
  */
  _tryCallEvents () {
    this.awaiting--
    if (this.awaiting <= 0 && this.waiting.length > 0) {
      var events = this.waiting
      this.waiting = []
      this.onevent(events)
    }
  }
}
Y.utils.EventHandler = EventHandler

/*
  A wrapper for the definition of a custom type.
  Every custom type must have three properties:

  * createType
    - Defines the model of a newly created custom type and returns the type
  * initType
    - Given a model, creates a custom type
  * class
    - the constructor of the custom type (e.g. in order to inherit from a type)
*/
class CustomType { // eslint-disable-line
  constructor (def) {
    if (def.createType == null ||
      def.initType == null ||
      def.class == null
    ) {
      throw new Error('Custom type was not initialized correctly!')
    }
    this.createType = def.createType
    this.initType = def.initType
    this.class = def.class
  }
}
Y.utils.CustomType = CustomType

/*
  Make a flat copy of an object
  (just copy properties)
*/
function copyObject (o) {
  var c = {}
  for (var key in o) {
    c[key] = o[key]
  }
  return c
}
Y.utils.copyObject = copyObject

/*
  Defines a smaller relation on Id's
*/
function smaller (a, b) {
  return a[0] < b[0] || (a[0] === b[0] && a[1] < b[1])
}
Y.utils.smaller = smaller

function compareIds (id1, id2) {
  if (id1 == null || id2 == null) {
    if (id1 == null && id2 == null) {
      return true
    }
    return false
  }
  if (id1[0] === id2[0] && id1[1] === id2[1]) {
    return true
  } else {
    return false
  }
}
Y.utils.compareIds = compareIds