#!/usr/bin/env Rscript

# Author: Lucas

library(rvest)
library(stringi)
library(textclean)


#' Clean a html formatted wikipedia page. 
#' Nodes of interest from the DOM are extracted and then cleaned from all html
#' tags and annotations.
#' 
#' @param html Url linking to a wikipedia webpage or a html formatted document.
#' @return Plaintext document containing only the maintext of the give wikipedia page.
cleanHtml <- function(html) {
  
  # 1. read data from url or html-formatted text
  # 2 .extract nodes containing main information (ignore infoboxes, list of literature, ...)
  # 3. collapse vektors into a single one
  # 4. remove html tags
  # 5.  - remove annotations ([123]) and trim whitespace
  #     - remove whitespace after newline
  #     - remove whitespace before punctuation
  #     - replace multiple newlines with single newline
  result <- read_html(html) %>%
    html_nodes(css="h3:nth-child(13) , h4 , p+ h3 , p") %>%
    stri_flatten(collapse = " ") %>%
    replace_html() %>%
    gsub("\\[\\d*\\]", "", .) %>%
    gsub("  +", " ", .) %>%
    gsub("\n ", "\n", .) %>%
    gsub(" *([.!?:,'’])", "\\1", .) %>%
    gsub("\n *\n+", "\n", .) %>%
    sub(" ", "", .)
}