save key-by-key

key-saving.js

// - Request saves on a key-by-key basis
//
// - After the operation, record whether keys are now persisted 
//   or whether they errored out 
// 
// - Store keys in a workflow:
//   _requestedKeys -> requested, but not in flight or successfully saved
//   _pendingKeys   -> keys whose save is in flight now 
//   _successKeys   -> keys whose save was successful 
//   _errorKeys     -> keys whose save errored 

{
  // note this field name as will-save 
  // and request a save if there isn't one already
  requestSave: function(fieldName) {
    this._requestedKeys.push(fieldName)
    if(this._pendingKeys.length == 0) {
      // if it's already saving, hold your horses
      this.enqueueSave()
    }
  },
  
  // mark currently-requested keys as pending 
  // fire the save 
  _save: function() {
    this._pendingKeys = this._requestedKeys 
    this._requestedKeys = [] 
    this.doSave().then(function() {
      // after a success, mark pending keys as successful
      // - clear pending 
      // - clear errors 
      // TODO: after a timeout, clear success keys 
      this._successKeys = this._pendingKeys
      this._pendingKeys = []
      this._errorKeys = []
      // if there were requests during this save, 
      // allow them to have their chance
      if(this._requestedKeys.length) { 
        this.enqueueSave() 
      }
    }).catch(function(jqXHR)) {
      // after an error:
      // since these werent successfully saved, 
      // they should still be considered as requested for the next save 
      // (their new values weren't persisted)
      this._requestedKeys = this._requestedKeys.concat(this._pendingKeys)
      this._errorKeys = this._pendingKeys
    }
  },
  
  // for displaying key-level status, 
  // figure out where this key is in the process
  statusForKey: function(key) {
    if(this._successKeys.indexOf(key) != -1) {
      return 'success'
    } else if (this._pendingKeys.indexOf(key) != -1 || this._requestedKeys.indexOf(key) != -1) {
      return 'pending'
    } else if (this._errorKeys.indexOf(key) != -1) {
      return 'error'
    } else {
      return null
    }
  }
}