meses-messaging/src/classes/PreviousMessageListQuery.js

Meses messaging SDK in JavaScript

class PreviousMessageListQuery {
  constructor(service, conversationName, next) {
    this._service = service
    this._conversationName = conversationName
    this._next = next
    this._reachEnd = false
  }

  /**
   * Load some message items ordered by messageId (timestamp)
   * 
   * @param  {Number} items - number of items to load
   * @return {Promise} array of messages if fulfilled.
   */
  load(items) {
    if (this._reachEnd)
      return new Promise(function(resolve, reject) { resolve([]) })

    const service = this._service
    const conversationName = this._conversationName
    const next = this._next

    return new Promise(function(resolve, reject) {
      service.getMessages(conversationName, next, items)
        .then(result => { 
          if (result.nextMessageId == null)
            this._reachEnd = true

          this._next = result.nextMessageId
          resolve(result.messages) 
        })
        .catch(err => reject(err))
    }.bind(this))
  }

  /**
   * Predicate for checking whether the query can load more message
   * 
   * @return {Boolean} TRUE if query can load more message
   */
  hasMore() { return !this._reachEnd }
}

export default PreviousMessageListQuery