R/utils-selenium.R

In villegar/scrappy: A Simple Web Scraper

#' Click the element
#'
#' @param element HTML element.
#'
#' @return Returns the status of the action.
#' @keywords internal
click_element <- function(element) {
  tryCatch(
    {
      element$clickElement()
      TRUE
    },
    warning = function(w) {
      FALSE
    },
    error = function(e) {
      FALSE
    },
    finally = {
    }
  )
}

#' Inject a snippet of JavaScript
#'
#' Inject a snippet of JavaScript into the page for execution in the context
#' of the currently selected frame. The executed script is assumed to be
#' synchronous and the result of evaluating the script is returned to the
#' client. The script argument defines the script to execute in the form of a
#' function body.
#'
#' @param client \code{RSelenium} client.
#' @param script String with the JavaScript to be executed.
#' @param args List of arguments for the `script`.
#'
#' @return Returns the status of the action.
#' @keywords internal
execute_script <- function(client, script, args) {
  tryCatch(
    {
      client$executeScript(script, args)
      TRUE
    },
    warning = function(w) {
      FALSE
    },
    error = function(e) {
      FALSE
    },
    finally = {
    }
  )
}

#' Search for an element on the page
#'
#' Search for an element on the page, starting from the document root.
#'
#' @param client \code{RSelenium} client.
#' @param using String with "css" or "xpath".
#' @param value String with css tag or xpath.
#'
#' @return The located element will be returned as an object of `webElement`
#'     class.
#' @keywords internal
find_element <- function(client, using, value) {
  tryCatch(
    {
      suppressMessages({
        client$findElement(using = using, value = value)
      })
    },
    warning = function(w) {
      return(NA)
    },
    error = function(e) {
      return(NA)
    }
  )
}

#' Search for an element on the page and click it
#'
#' Search for an element on the page, starting from the document root.
#'
#' @param client \code{RSelenium} client.
#' @param using String with "css" or "xpath".
#' @param value String with css tag or xpath.
#'
#' @return The located element will be returned as an object of `webElement`
#'     class.
#' @keywords internal
find_and_click <- function(client, using, value) {
  tryCatch(
    {
      suppressMessages({
        client$findElement(using = using, value = value)$clickElement()
      })
    },
    warning = function(w) {
      return(NA)
    },
    error = function(e) {
      return(NA)
    }
  )
}

#' Search for multiple elements on the page
#'
#' Search for multiple elements on the page, starting from the document root.
#'
#' @param client \code{RSelenium} client.
#' @param using String with "css" or "xpath".
#' @param value String with css tag or xpath.
#'
#' @return The located elements will be returned as an list of objects of
#'     `WebElement` class.
#' @keywords internal
find_elements <- function(client, using, value) {
  tryCatch(
    {
      suppressMessages({
        client$findElements(using = using, value = value)
      })
    },
    warning = function(w) {
      return(NULL)
    },
    error = function(e) {
      return(NULL)
    }
  )
}


#' Navigate to a given url
#'
#' @param client \code{RSelenium} client.
#' @param url String with a URL.
#'
#' @return Returns the status of the action.
#' @keywords internal
navigate <- function(client, url) {
  tryCatch(
    {
      client$navigate(url)
      TRUE
    },
    warning = function(w) {
      FALSE
    },
    error = function(e) {
      FALSE
    },
    finally = {
    }
  )
}

#' Random wait time
#'
#' @param sleep Integer with number of seconds to use as pause between actions
#'     on the web page.
#'
#' @keywords internal
random_wait <- function(sleep = 1) {
  Sys.sleep(sample(seq(0, sleep, by = 0.1), 1))
}