use reqwest::{blocking::Client, cookie::Jar};
use std::{env, error::Error, fs, path::PathBuf, sync::Arc};

const BASE_URL: &str = "https://adventofcode.com";

#[macro_export]
macro_rules! input {
    () => {{
        let stem = std::path::Path::new(file!())
            .file_stem()
            .unwrap()
            .to_string_lossy();
        let (year, day) = stem.split_once('-').unwrap();
        $crate::get_day(year, day).unwrap()
    }};
}

pub fn get_day(year: &str, day: &str) -> Result<String, Box<dyn Error>> {
    let path = PathBuf::from(format!("input/{year}/day{day}.txt"));
    fs::create_dir_all(path.parent().unwrap())?;

    if let Ok(input) = fs::read_to_string(&path) {
        Ok(input)
    } else {
        // get session token
        let file = fs::read_to_string(".env").unwrap_or(String::new());
        let session = file
            .lines()
            .filter_map(|line| line.split_once('='))
            .map(|(key, value)| (key.to_string(), value.to_string()))
            .chain(env::vars())
            .find_map(|(k, v)| (k == "SESSION").then_some(v))
            .ok_or(
                "SESSION environment variable not set, retrieve it from https://adventofcode.com",
            )?;

        // create session cookie
        let cookie = format!("session={session}");

        // setup client
        let jar = Arc::new(Jar::default());
        jar.add_cookie_str(&cookie, &BASE_URL.parse()?);
        let client = Client::builder().cookie_provider(jar).build()?;

        // download until day fails
        let url = format!("{BASE_URL}/{year}/day/{day}/input");
        let text = client.get(url).send()?.text()?;
        fs::create_dir_all(path.parent().unwrap())?;
        fs::write(path, &text)?;

        Ok(text)
    }
}