use std::sync::LazyLock;

use futures::{stream::FuturesUnordered, StreamExt};
use scraper::{Html, Selector};

static SELECTOR: LazyLock<Selector> = LazyLock::new(|| {
    Selector::parse("html > body > pre > a").unwrap()
});

async fn parse(path: &str) -> eyre::Result<Vec<String>> {
    let response = reqwest::get(format!("https://lofigirl.com/wp-content/uploads/{}", path)).await?;
    let document = response.text().await?;

    let html = Html::parse_document(&document);
    Ok(html.select(&SELECTOR).skip(5).map(|x| String::from(x.attr("href").unwrap())).collect())
}

/// This function basically just scans the entire file server, and returns a list of paths to mp3 files.
/// 
/// It's a bit hacky, and basically works by checking all of the years, then months, and then all of the files.
/// This is done as a way to avoid recursion, since async rust really hates recursive functions.
async fn scan() -> eyre::Result<Vec<String>> {
    let items = parse("").await?;
    
    let years: Vec<u32> = items.iter().filter_map(|x| {
        let year = x.strip_suffix("/")?;
        year.parse().ok()
    }).collect();

    // A little bit of async to run all of the months concurrently.
    let mut futures = FuturesUnordered::new();
    
    for year in years {
        let months = parse(&year.to_string()).await?;
        
        for month in months {
            futures.push(async move {
                let path = format!("{}/{}", year, month);

                let items = parse(&path).await.unwrap();
                let items = items.into_iter().filter_map(|x| {
                    if x.ends_with(".mp3") {
                        Some(format!("{path}{x}"))
                    } else {
                        None
                    }
                }).collect::<Vec<String>>();

                items
            });
        }
    }

    let mut files = Vec::new();
    while let Some(mut result) = futures.next().await {
        files.append(&mut result);
    }

    eyre::Result::Ok(files)
}

pub async fn scrape() -> eyre::Result<()> {
    let files = scan().await?;
    for file in files {
        println!("{}", file);
    }

    Ok(())
}