main.rs

use std::io;

use actix_web::{
    body::BoxBody,
    dev::ServiceResponse,
    get,
    http::{header::ContentType, StatusCode},
    middleware::{ErrorHandlerResponse, ErrorHandlers},
    web, App, HttpResponse, HttpServer, Responder, Result,
};
use actix_web_lab::respond::Html;
use handlebars::{DirectorySourceOptions, Handlebars};
use serde_json::json;

#[get("/")]
async fn index(hb: web::Data<Handlebars<'_>>) -> impl Responder {
    let data = json!({
        "name": "Handlebars"
    });
    let body = hb.render("index", &data).unwrap();

    Html(body)
}

#[get("/{user}/{data}")]
async fn user(hb: web::Data<Handlebars<'_>>, path: web::Path<(String, String)>) -> impl Responder {
    let info = path.into_inner();
    let data = json!({
        "user": info.0,
        "data": info.1
    });
    let body = hb.render("user", &data).unwrap();

    Html(body)
}

#[actix_web::main]
async fn main() -> io::Result<()> {
    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));

    // Handlebars uses a repository for the compiled templates. This object must be
    // shared between the application threads, and is therefore passed to the
    // Application Builder as an atomic reference-counted pointer.
    let mut handlebars = Handlebars::new();
    handlebars
        .register_templates_directory(
            "./templates",
            DirectorySourceOptions {
                tpl_extension: ".html".to_owned(),
                hidden: false,
                temporary: false,
            },
        )
        .unwrap();
    let handlebars_ref = web::Data::new(handlebars);

    HttpServer::new(move || {
        App::new()
            .wrap(error_handlers())
            .app_data(handlebars_ref.clone())
            .service(index)
            .service(user)
    })
    .workers(2)
    .bind(("127.0.0.1", 8080))?
    .run()
    .await
}

// Custom error handlers, to return HTML responses when an error occurs.
fn error_handlers() -> ErrorHandlers<BoxBody> {
    ErrorHandlers::new().handler(StatusCode::NOT_FOUND, not_found)
}

// Error handler for a 404 Page not found error.
fn not_found<B>(res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<BoxBody>> {
    let response = get_error_response(&res, "Page not found");
    Ok(ErrorHandlerResponse::Response(ServiceResponse::new(
        res.into_parts().0,
        response.map_into_left_body(),
    )))
}

// Generic error handler.
fn get_error_response<B>(res: &ServiceResponse<B>, error: &str) -> HttpResponse<BoxBody> {
    let request = res.request();

    // Provide a fallback to a simple plain text response in case an error occurs during the
    // rendering of the error page.
    let fallback = |err: &str| {
        HttpResponse::build(res.status())
            .content_type(ContentType::plaintext())
            .body(err.to_string())
    };

    let hb = request
        .app_data::<web::Data<Handlebars>>()
        .map(|t| t.get_ref());
    match hb {
        Some(hb) => {
            let data = json!({
                "error": error,
                "status_code": res.status().as_str()
            });
            let body = hb.render("error", &data);

            match body {
                Ok(body) => HttpResponse::build(res.status())
                    .content_type(ContentType::html())
                    .body(body),
                Err(_) => fallback(error),
            }
        }
        None => fallback(error),
    }
}