require(rvest)
require(openxlsx)


spr_books <- read.xlsx("Free+English+textbooks.xlsx")

dl_dir <- "Downloads"

if (!dir.exists(dl_dir)) dir.create(dl_dir)

for (i in 1:nrow(spr_books)) {
  
  pkg_dir <- spr_books[i, "English.Package.Name"]
  
  dest_dir <- paste0(dl_dir, "/", pkg_dir, "/")
  
  if (!dir.exists(dest_dir)) dir.create(dest_dir)
  
  url1 <- spr_books[i, "OpenURL"]
  
  webpage <- read_html(url1)
  
  link <- 
  webpage %>% 
    html_nodes(".test-bookpdf-link") %>% html_attr('href')
  
  book_name <- paste0(dest_dir, gsub("/", "-", spr_books[i, "Book.Title"]), ".pdf")
  
  if (!file.exists(book_name))
    download.file(paste0("https://link.springer.com", link[1]), book_name, mode="wb")
  
  cat(paste("#", i, " ", spr_books[i, "Book.Title"]), sep = "\n")

}