tparser:

#' @rdname getTimeline
#' @export
#'
#' @title
#' Returns up to 3,200 recent tweets from a given user
#'
#' @description
#' \code{getTimeline} connects to the REST API of Twitter and returns up to
#' 3,200 recent tweets sent by these user. If the total number of tweets sent
#' by this user is less than 3,200 tweets, it will return all tweets.
#'
#' @author
#' Pablo Barbera \email{pablo.barbera@@nyu.edu}
#'
#' @param filename file where tweets will be stored (in json format)
#'
#' @param n number of tweets to be downloaded (maximum is 3,200)
#'
#' @param screen_name user name of the Twitter user for which his/her tweets
#' will be downloaded
#'
#' @param id id of Twitter user for which his/her tweets will be downloaded
#' (Use either of these two arguments)
#'
#' @param oauth_folder folder where OAuth tokens are stored.
#'
#' @param since_id id of the oldest tweet to be downloaded. Useful if, for
#' example, we're only interested in getting tweets sent after a certain
#' date.
#'
#' @param trim_user if "true", downloaded tweets will include user object
#' embedded. If "false", only tweet information will be downloaded.
#'
#' @param sleep numeric, number of seconds between API calls. Higher number
#' will increase reliability of API calls; lower number will increase speed.
#'
#' @param verbose If TRUE, provides additional output in console about API
#' rate limits
#'
#' @examples \dontrun{
#' ## Download recent tweets by user "p_barbera"
#'  friends <- getTimeline(screen_name="p_barbera", oauth_folder="oauth")
#' }
#'

getTimeline <- function(filename, n=3200, oauth_folder="~/credentials", screen_name=NULL,
                        id=NULL, since_id=NULL, trim_user="true", sleep=.5, verbose=FALSE){

  ## create list of credentials
  creds <- list.files(oauth_folder, full.names=T)
  ## open a random credential
  cr <- sample(creds, 1)
  if (verbose) message(cr)
  load(cr)
  ## while rate limit is 0, open a new one
  limit <- getLimitTimeline(my_oauth)
  if (verbose) message(limit, " hits left")
  while (limit==0){
    cr <- sample(creds, 1)
    if (verbose) message(cr)
    load(cr)
    Sys.sleep(sleep)
    # sleep for 5 minutes if limit rate is less than 100
    rate.limit <- getLimitRate(my_oauth)
    if (rate.limit<100){
      Sys.sleep(300)
    }
    limit <- getLimitTimeline(my_oauth)
    if (verbose) message(limit, " hits left")
  }
  ## url to call
  url <- "https://api.twitter.com/1.1/statuses/user_timeline.json"

  ## first API call
  if (!is.null(screen_name)){
    params <- list(screen_name = screen_name, count=200, trim_user=trim_user)
  }
  if (!is.null(id)){
    params <- list(id=id, count=200, trim_user=trim_user)
  }
  if (!is.null(since_id)){
    params[["since_id"]] <- since_id
  }
  query <- lapply(params, function(x) URLencode(as.character(x)))

  # preparing OAuth token for httr
  options("httr_oauth_cache"=FALSE)
  app <- httr::oauth_app("twitter", key = my_oauth$consumerKey,
                         secret = my_oauth$consumerSecret)
  credentials <- list(oauth_token = my_oauth$oauthKey, oauth_token_secret = my_oauth$oauthSecret)
  twitter_token <- httr::Token1.0$new(endpoint = NULL, params = list(as_header = TRUE),
                                      app = app, credentials = credentials)

  # first query
  url.data <- httr::GET(url, query = query, httr::config(token = twitter_token))
  Sys.sleep(sleep)
  ## one API call less
  limit <- limit - 1
  ## changing oauth token if we hit the limit
  if (verbose) message(limit, " hits left")
  cr_old <- cr
  while (limit==0){
    cr <- sample(creds, 1)
    if (verbose) message(cr)
    load(cr)
    Sys.sleep(sleep)
    # sleep for 5 minutes if limit rate is less than 100
    rate.limit <- getLimitRate(my_oauth)
    if (rate.limit<100){
      Sys.sleep(300)
    }
    limit <- getLimitTimeline(my_oauth)
    if (verbose) message(limit, " hits left")
  }
  if (cr != cr_old) {
    app <- httr::oauth_app("twitter", key = my_oauth$consumerKey,
                           secret = my_oauth$consumerSecret)
    credentials <- list(oauth_token = my_oauth$oauthKey, oauth_token_secret = my_oauth$oauthSecret)
    twitter_token <- httr::Token1.0$new(endpoint = NULL, params = list(as_header = TRUE),
                                        app = app, credentials = credentials)
  }
  ## trying to parse JSON data
  ## json.data <- fromJSON(url.data, unexpected.escape = "skip")
  json.data <- httr::content(url.data)
  if (length(json.data$error)!=0){
    message(url.data)
    stop("error! Last cursor: ", cursor)
  }
  ## writing to disk
  conn <- file(filename, "a")
  ret <- lapply(json.data, function(x) writeLines(jsonlite::toJSON(x, null="null"), con=conn, useBytes=TRUE))
  close(conn)
  ## max_id
  tweets <- length(json.data)
  max_id <- json.data[[tweets]]$id_str
  message(tweets, " tweets. Max id: ", max_id)
  max_id_old <- "none"
  if (is.null(since_id)) {since_id <- 1}

  while (tweets < n & max_id != max_id_old &
         as.numeric(max_id) > as.numeric(since_id)){
    max_id_old <- max_id
    if (!is.null(screen_name)){
      params <- list(screen_name = screen_name, count=200, max_id=max_id,
                     trim_user=trim_user)
    }
    if (!is.null(id)){
      params <- list(id=id, count=200, max_id=max_id, trim_user=trim_user)
    }
    if (!is.null(since_id) && since_id != 1 ){
      params[['since_id']] <- since_id
    }
    query <- lapply(params, function(x) URLencode(as.character(x)))
    url.data <- httr::GET(url, query = query, httr::config(token = twitter_token))
    Sys.sleep(sleep)
    ## one API call less
    limit <- limit - 1
    ## changing oauth token if we hit the limit
    message(limit, " hits left")
    cr_old <- cr
    while (limit==0){
      cr <- sample(creds, 1)
      message(cr)
      load(cr)
      Sys.sleep(sleep)
      # sleep for 5 minutes if limit rate is less than 100
      rate.limit <- getLimitRate(my_oauth)
      if (rate.limit<100){
        Sys.sleep(300)
      }
      limit <- getLimitTimeline(my_oauth)
      message(limit, " hits left")
    }
    if (cr != cr_old) {
      app <- httr::oauth_app("twitter", key = my_oauth$consumerKey,
                             secret = my_oauth$consumerSecret)
      credentials <- list(oauth_token = my_oauth$oauthKey, oauth_token_secret = my_oauth$oauthSecret)
      twitter_token <- httr::Token1.0$new(endpoint = NULL, params = list(as_header = TRUE),
                                          app = app, credentials = credentials)
    }
    ## trying to parse JSON data
    ## json.data <- fromJSON(url.data, unexpected.escape = "skip")
    json.data <- httr::content(url.data)
    if (length(json.data$error)!=0){
      message(url.data)
      stop("error! Last cursor: ", cursor)
    }
    ## writing to disk
    conn <- file(filename, "a")
    ret <- lapply(json.data, function(x) writeLines(jsonlite::toJSON(x, null="null"), con=conn, useBytes=TRUE))
    close(conn)
    ## max_id
    tweets <- tweets + length(json.data)
    max_id <- json.data[[length(json.data)]]$id_str
    message(tweets, " tweets. Max id: ", max_id)
    return(max_id)
  }
}


getLimitTimeline <- function(my_oauth){
  url <- "https://api.twitter.com/1.1/application/rate_limit_status.json"
  params <- list(resources = "statuses,application")
  response <- my_oauth$OAuthRequest(URL=url, params=params, method="GET",
                                    cainfo=system.file("CurlSSL", "cacert.pem", package = "RCurl"))
  return(unlist(rjson::fromJSON(response)$resources$statuses$`/statuses/user_timeline`[['remaining']]))

}