fbpack: User-friendly Facebook-scraping

search_fb <- function(x, remDr,
                      type=c("all", "users", "pages", "places",
                             "groups", "apps", "events"),
                      number_of_results=5, attributes, ...){
  # Search on Facebook for a given character string.
  # Type can be specified, default to user
  # location, workplace, education are for type="user"
  # number_of_results is the maximum number of returned links
  # a character vector with length number_of_results, containing links.
 

  #
  # Function to find out wether the user logged in already
  #
  # wait_for_user_login <- function(remDr){
  #   startime <- Sys.time()
  #   login_done <- list()
  #   while(length(login_done)==0 | Sys.time()-startime < 5){
  #       tryCatch({login_done <- remDr$findElement(using = 'css selector',
  #                  "div._4r_y")},
  #           error = function(e){NULL},
  #           warning=function(w){NULL})
  #       }
  #   return(remDr)
  # }

  #
  # open facebook, log in
  #

  # remDr <- remoteDriver$new(...)
  # # open browser
  # remDr$open()
  # remDr$setImplicitWaitTimeout(5000)
  # remDr$setTimeout("page load", 10000)
  # # navigate to facebook.com
  # remDr$navigate("http://www.facebook.com")

  # # log in
  # # tryCatch needed if something fails
  # tryCatch({
  #   if(!missing(login_name) & !missing(login_password)){
  #     webElem <- remDr$findElement(using = 'xpath', "//*/input[@id = 'email']")
  #     webElem$sendKeysToElement(list(login_name, key="tab"))
  #     webElem <- remDr$findElement(using = 'xpath', "//*/input[@id = 'pass']")
  #     webElem$sendKeysToElement(list(login_password, key="enter"))
  #   }},
  #   error=function(e){message(e)},
  #   warning=function(w){message(w)},
  #   finally=function(){remDr$close()})
  
  # remDr <- wait_for_user_login(remDr)
  #
  # navigate to search page, enter query if necessary
  #
  remDr$navigate(paste0("https://www.facebook.com/search/results/?q=",
                        x,
                        "&type=",
                        ifelse(length(type)==1, type, "users")))
  type <- ifelse(length(type)==1, type, "users")
  
  # check if there are any results
  result_elements <- remDr$findElements("css selector",
                                        "div._6a._6b._5d-4")
  Sys.sleep(0.5)
  
  if(!length(result_elements)){
    found_entities <- NA
  } else {
    

    attribute_names <- unlist(sapply(
                         remDr$findElements("css selector", "label._41dd"),
                         function(x){x$getElementText()}))

    # if type=="user" and other attributes are given, fill them in:
    if(type[1]=="users" & !missing(attributes)){
  
      inp_flds <- expression(
        input_fields <- tryCatch({remDr$findElements("css selector",
                                                     "input._58al")},
          warning = function(w){paste0("Warning:\n", w, "\n Continuing search.")},
          error   = function(e){paste0("Error:\n", e, "\n Continuing search.")}))
      
      search_filters <- intersect(attribute_names, names(attributes))
      for(i in 1:length(search_filters)){
        input_field <- eval(inp_flds)[[which(attribute_names == search_filters[i])]]
        tryCatch({
          try(input_field$sendKeysToElement(list(attributes[[search_filters[i]]])))
          Sys.sleep(0.5)
          # choose first suggestion
          input_field$sendKeysToElement(list(key="down_arrow"))
          Sys.sleep(0.5)
          input_field$sendKeysToElement(list(key="up_arrow"))
          Sys.sleep(0.5)
          input_field$sendKeysToElement(list(key="tab"))
          Sys.sleep(0.5)},
          warning=function(w){paste0(search_filters[i], " may not be used.\n", w)},
          error=function(e){paste0(search_filters[i], " may not be used.\n", e)
                            remDr$close()})
      }
    }


      # # location:
      # if(!missing(location)){
      #   location_input <- eval(inp_flds)[[1]]
      #   tryCatch({ #location_input <- remDr$findElement("xpath",
      #               #       "//*/input[@data-reactid = '.a1.1:$lo.1.0.0']")
      #     #"placeholder",
      #      #                           "Type the name of a town or region.")
      #   try(location_input$sendKeysToElement(list(location)))
      #   # wait 0.5s for drop-down suggestions
      #   },
      #     warning= function(w){warning(paste0("Location may not be used,",
      #       " continuing search anyhow.\n\tWarning: ", w))},
      #     error  = function(e){warning(paste0("An error occured at location",
      #       " input. Continuing search anyhow.\n\tThis is the original error",
      #       " message: ", e))})
      # }
  
      # # education:
      # if(!missing(education)){
      #   education_input <- eval(inp_flds)[[3]]
      #   tryCatch({#education_input <- remDr$findElement("xpath",
      #              #        "//*/input[@data-reactid = '.a1.1:$ed.1.0.0']")
      #     # "placeholder", "Type the name of a university or a school.")
      #   try(education_input$sendKeysToElement(list(education)))
      #   # wait 0.5s for drop-down suggestions
      #   Sys.sleep(.5)
      #   # choose first suggestion
      #   education_input$sendKeysToElement(list(key="down_arrow"))
      #   Sys.sleep(0.5)
      #   education_input$sendKeysToElement(list(key="up_arrow"))
      #   Sys.sleep(0.5)
      #   education_input$sendKeysToElement(list(key="tab"))
      #   Sys.sleep(0.5)},
      #     warning= function(w){warning(paste0("Education may not be used,",
      #       " continuing search anyhow.\n\tWarning: ", w))},
      #     error  = function(e){warning(paste0("An error occured at education",
      #       " input. Continuing search anyhow.\n\tThis is the original error",
      #       " message: ", e))})
      # }
  
      # # workplace:
      # if(!missing(workplace)){
      #   workplace_input <- eval(inp_flds)[[2]]
      #   tryCatch({#workplace_input <- remDr$findElement("xpath",
      #              #        "//*/input[@data-reactid = '.a1.1:$wk.1.0.0']")
      #     #"placeholder", "Type the name of a company.")
      #   try(workplace_input$sendKeysToElement(list(workplace)))
      #   # wait 0.5s for drop-down suggestions, cannot get around it... :(
      #     # TODO: evaluate suggestions
      #   Sys.sleep(.5)
      #   # choose first suggestion
      #   workplace_input$sendKeysToElement(list(key="down_arrow"))
      #   Sys.sleep(0.5)
      #   workplace_input$sendKeysToElement(list(key="up_arrow"))
      #   Sys.sleep(0.5)
      #   workplace_input$sendKeysToElement(list(key="tab"))
      #   Sys.sleep(0.5)},
      #     warning= function(w){warning(paste0("workplace may not be used,",
      #       " continuing search anyhow.\n\tWarning: ", w))},
      #     error  = function(e){warning(paste0("An error occured at workplace",
      #       " input. Continuing search anyhow.\n\tThis is the original error",
      #       " message: ", e))})
      # }


    #
    # Collect results
    #
  
    found_entities <- NULL
    while(length(found_entities) < number_of_results){
      # collect links
      results <- remDr$findElements("css selector", "a._8o._8s.lfloat._ohe")
      found_entities_tmp <- unlist(
        sapply(results, function(element){
          element$getElementAttribute("href")
        }))
      # sanity check:
      if(length(results) < length(found_entities_tmp)){
          warning("There may be more links than found entities!")
        }
  
      # tmp must be longer than the collector:
      found_entities_tmp <- found_entities_tmp[!grepl("l.php",
                                               found_entities_tmp)]
      if(length(found_entities_tmp) <= length(found_entities)){
        break
        } else {
        found_entities <- c(found_entities, found_entities_tmp)
                            
        # scroll page only if necessary
        if(length(found_entities) < number_of_results){
          for(i in 1:30){
            tryCatch({remDr$executeScript("window.scrollBy(0,2000)")},
                     error = function(e){warning(paste0("An error occured when",
                       "scrolled:\n", e))},
                     warning=function(w){warning(paste0("Warning when scrolling:\n",
                       w))})
             }
           }         
        }
     } # ending while cycle 
   } # ending case when there are results
    #}
  # Log out, close browser
  #
  # tryCatch({
  #   log_out_element <- remDr$findElement(using = "id",
  #                        value = "pageLoginAnchor")
  #   log_out_element$clickElement()

  #   log_out_form <- remDr$findElements(using = "class name",
  #                        value = "_54nc")
  #   log_out_form <- log_out_form[[length(log_out_form)-2]]
  #   log_out_form$clickElement()},
  #   error=function(e){warning(paste0("Error:\n", e))
  #                     return(found_entities[1:number_of_results])
  #                     remDr$close()},
  #   warning=function(w){warning(paste0("Warning:\n", w))
  #                     return(found_entities[1:number_of_results])
  #                     remDr$close()})
  # close remote_driver, write data, clear everything and close R
  # remDr$close()

  #
  # Return data
  #

  return(found_entities=found_entities[1:number_of_results],
         remote_driver=remDr)
}