use std::error::Error;
use std::fs;
use std::thread;
use std::time::Duration;

use reqwest;
use scraper::{ElementRef, Html, Selector};

fn main() -> Result<(), Box<dyn Error>> {
  let client = reqwest::blocking::Client::new();

  // Get the HTML from the groups list.
  let response = client
    .get("https://tildes.net/groups")
    .header(reqwest::header::USER_AGENT, "Tildes Wiki Sitemap")
    .send()?;
  let body = response.text()?;

  // Parse the HTML.
  let html = Html::parse_document(body.as_str());

  // Create a selector to grab all anchors that link to a group.
  let selector = Selector::parse(".group-list .link-group").unwrap();

  // Get all the group link elements from the HTML.
  let group_links = html.select(&selector).collect::<Vec<ElementRef>>();

  // Create the sitemap with the info.
  let mut sitemap = String::from("# Tildes Wiki Sitemap\n\n");
  sitemap += "Automatically generated by \
  [this program](https://gitlab.com/bauke/tildes-wiki-sitemap). \
  [PM @Bauke](https://tildes.net/user/Bauke/new_message?subject=Tildes%20Wiki%20Sitemap\
  &message=Update%20the%20sitemap%20you%20doofus!) if this page is outdated and \
  you can't run the program yourself.\n\n\
  This page is a temporary placeholder to help wiki contributors navigate. \
  Find this page easily by bookmarking it!\n\n";

  for group_link in group_links {
    // Get the group name without the tilde.
    let group_name = String::from(&group_link.inner_html()[1..]);
    println!("┌ Processing ~{}!", group_name);

    // Get the HTML from the group page.
    let response = client
      .get(format!("https://tildes.net/~{}", group_name).as_str())
      .header(reqwest::header::USER_AGENT, "Tildes Wiki Sitemap")
      .send()?;
    let body = response.text()?;

    // Parse the HTML.
    let html = Html::parse_document(body.as_str());

    // Create a selector to grab all the anchors in the sidebar that lead to a wiki page.
    let selector =
      Selector::parse("#sidebar .nav a[href*=\"/wiki/\"]").unwrap();

    // Get all the wiki URL elements from the HTML.
    let wiki_links = html.select(&selector).collect::<Vec<ElementRef>>();
    let wiki_links_amount = wiki_links.len();

    // Create a selector to grab the group description.
    let selector =
      Selector::parse("#sidebar .group-short-description").unwrap();

    // Get all the wiki URL elements from the HTML.
    let group_description = html.select(&selector).collect::<Vec<ElementRef>>();

    // Add the group as a new header.
    sitemap += format!("## ~{}\n\n", group_name).as_str();

    // If a group description is found, add it to the Markdown.
    if !group_description.is_empty() {
      let description = group_description.first().unwrap().inner_html();
      sitemap += format!("> {}\n\n", description).as_str();
    }

    // If there's no wiki pages, add a little blurb with a link to create one.
    if wiki_links.is_empty() {
      sitemap += format!("There are no wiki pages for ~{} yet, \
      [click here and be the first to create one](https://tildes.net/~{}/wiki/new_page), \
      if you have the necessary permission!\n", group_name, group_name).as_str();
    }

    // Loop over the links and add them in a list.
    for wiki_link in wiki_links {
      let wiki_page_title = wiki_link.inner_html();
      let wiki_page_link = wiki_link.value().attr("href").unwrap_or("");
      sitemap +=
        format!("* [{}]({})\n", wiki_page_title, wiki_page_link).as_str();
    }

    sitemap += "\n";
    println!("└ Processed {} wiki links.", wiki_links_amount);
    thread::sleep(Duration::from_millis(500));
  }

  sitemap = sitemap.trim_end().to_string() + "\n";
  fs::write("./sitemap.md", sitemap)?;
  println!("✓ Done!");
  Ok(())
}