use std::sync::LazyLock;

use askama::Template;
use askama_web::WebTemplate;
use pulldown_cmark::{Event, Options, Parser, Tag, html};

static README_HTML: LazyLock<String> = LazyLock::new(|| {
    let events: Vec<_> = Parser::new_ext(
        include_str!("../../README.md"),
        Options::ENABLE_TABLES | Options::ENABLE_STRIKETHROUGH | Options::ENABLE_TASKLISTS,
    )
    .collect();
    let anchored = events.iter().enumerate().map(|(index, event)| {
        if let Event::Start(Tag::Heading(level, None, _)) = event {
            let title: String = events[index + 1..]
                .iter()
                .take_while(|event| !matches!(event, Event::End(Tag::Heading(..))))
                .filter_map(|event| match event {
                    Event::Text(text) | Event::Code(text) => Some(text.as_ref()),
                    _ => None,
                })
                .collect();
            let slug: String = title
                .to_lowercase()
                .chars()
                .filter(|character| {
                    character.is_alphanumeric() || *character == '-' || character.is_whitespace()
                })
                .collect();
            let slug = slug.split_whitespace().collect::<Vec<_>>().join("-");
            return Event::Html(format!("<{level} id=\"{slug}\">").into());
        }
        event.clone()
    });
    let mut rendered = String::new();
    html::push_html(&mut rendered, anchored);
    rendered
});

#[derive(Template, WebTemplate)]
#[template(path = "home.html")]
pub struct HomePage {
    readme: &'static str,
}

pub async fn home_page() -> HomePage {
    HomePage {
        readme: &README_HTML,
    }
}