use handlebars::Handlebars;
use serde::Serialize;
use serde_json::json;
use std::sync::Arc;
use std::time::SystemTime;
use warp::{Filter, Rejection};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Build template registry
    let mut hbs = Handlebars::new();
    hbs.register_template_file("base", "templates/base.hbs")?;
    hbs.register_template_file("index", "templates/index.hbs")?;
    let hbs = Arc::new(hbs);

    // Build routes
    let routes = index_filter(hbs.clone())
        .or(evals_list())
        .or(warp::fs::dir("static"));

    // Start server
    warp::serve(routes).run(([127, 0, 0, 1], 8080)).await;

    // Done
    Ok(())
}

fn index_filter(
    hbs: Arc<Handlebars<'static>>,
) -> impl Filter<Extract = (impl warp::Reply,), Error = Rejection> + Clone {
    warp::get()
        .and(warp::path::end())
        .map(move || render("index", hbs.clone(), json!({"year", year().unwrap()})))
}

fn evals_list() -> impl Filter<Extract = (&'static str,), Error = Rejection> + Clone {
    warp::get()
        .and(warp::path("evals"))
        .and(warp::path::end())
        .map(|| "evals here")
}

fn render<T>(template: &str, hbs: Arc<Handlebars>, value: T) -> impl warp::Reply
where
    T: Serialize,
{
    let render = hbs
        .render(template, &value)
        .unwrap_or_else(|err| err.to_string());
    warp::reply::html(render)
}

const UNIX_YEAR: u64 = 31556926;

fn year() -> Result<u64, Box<dyn std::error::Error>> {
    let date = SystemTime::now()
        .duration_since(SystemTime::UNIX_EPOCH)?
        .as_secs();
    Ok(date / UNIX_YEAR)
}