//! Parsing for `/~<group>`.

use scraper::Html;

use crate::{
  regexes::GROUP_SUBSCRIBERS_RE,
  selectors::{
    GROUP_DESCRIPTION, GROUP_NAME, GROUP_SUBSCRIBERS, GROUP_SUB_GROUP_LINKS,
    GROUP_WIKI_LINKS,
  },
  utilities::{
    extract_anchor_values, parse_regex_match, select_first_element_text,
  },
  ParseError,
};

/// A group's information.
#[derive(Debug)]
pub struct Group {
  /// The group description.
  pub description: Option<String>,

  /// The group name, including leading tilde.
  pub name: String,

  /// Names of sub-groups.
  pub sub_groups: Vec<String>,

  /// The amount of subscribers.
  pub subscribers: i32,

  /// Links to wiki pages.
  pub wiki_links: Vec<GroupWikiLink>,
}

/// A group's wiki link.
#[derive(Debug)]
pub struct GroupWikiLink {
  /// The name of the wiki page.
  pub name: String,

  /// The URL to the wiki page.
  pub url: String,
}

impl Group {
  /// Parses a [`Group`] from a [`scraper::Html`] tree.
  pub fn from_html(html: &Html) -> Result<Self, ParseError> {
    let description =
      select_first_element_text(html.root_element(), &GROUP_DESCRIPTION);

    let name = select_first_element_text(html.root_element(), &GROUP_NAME)
      .ok_or(ParseError::MissingExpectedHtml)?;

    let subscribers = parse_regex_match(
      GROUP_SUBSCRIBERS_RE
        .captures_iter(
          &select_first_element_text(html.root_element(), &GROUP_SUBSCRIBERS)
            .ok_or(ParseError::MissingExpectedHtml)?,
        )
        .next()
        .ok_or(ParseError::MissingExpectedHtml)?
        .name("count"),
    )
    .ok_or(ParseError::MissingExpectedHtml)?;

    let sub_groups = html
      .select(&GROUP_SUB_GROUP_LINKS)
      .map(|element| Ok(extract_anchor_values(element)?.0))
      .collect::<Result<_, _>>()?;

    let wiki_links = html
      .select(&GROUP_WIKI_LINKS)
      .map(|element| {
        let (name, url) = extract_anchor_values(element)?;
        Ok(GroupWikiLink { name, url })
      })
      .collect::<Result<_, _>>()?;

    Ok(Self {
      description,
      name,
      sub_groups,
      subscribers,
      wiki_links,
    })
  }
}