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/*
This file is part of the Toolforge Rust tutorial

Copyright 2021 Kunal Mehta and contributors

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#[macro_use]
extern crate rocket;

use anyhow::Result;
use mysql_async::prelude::*;
use rocket::http::Status;
use rocket_dyn_templates::Template;
use serde::Serialize;

/// The context needed to render the "index.html" template
#[derive(Serialize)]
struct IndexTemplate {
    /// The title variable
    title: String,
}

/// The context needed to render the "error.html" template
#[derive(Serialize)]
struct ErrorTemplate {
    /// The error message
    error: String,
}

/// Handle all GET requests for the "/" route. We return either a `Template`
/// instance, or a `Template` instance with a specific HTTP status code.
#[get("/")]
async fn index() -> Result<Template, (Status, Template)> {
    match get_latest_edit().await {
        // Got the title, render the "index" template
        Ok(title) => Ok(Template::render("index", IndexTemplate { title })),
        // Some error occurred when trying to query MySQL, render the "error"
        // template with a HTTP 500 status code
        Err(err) => Err((
            Status::InternalServerError,
            Template::render(
                "error",
                ErrorTemplate {
                    error: err.to_string(),
                },
            ),
        )),
    }
}

/// Get the latest edit via the enwiki database replica
async fn get_latest_edit() -> Result<String> {
    // Read from ~/replica.my.cnf and build a connection URL
    let db_url = toolforge::connection_info!("enwiki_p", WEB)?.to_string();
    // Create a new database connection pool. We intentionally do not use
    // Rocket's connection pooling facilities as Toolforge policy requires that
    // we do not hold connections open while not in use. So we open the
    // connection when we need to make a query and then immediately close it.
    let pool = mysql_async::Pool::new(db_url.as_str());
    // Open a connection and make a query
    let mut conn = pool.get_conn().await?;
    let resp: Option<String> = conn
        .query_first(
            r#"
SELECT
  rc_title
FROM
  recentchanges
WHERE
  rc_namespace = 0
ORDER BY
  rc_timestamp DESC
LIMIT
  1"#,
        )
        .await?;
    // Close the connections and pool (optional, this would happen
    // automatically when the variables are dropped)
    drop(conn);
    pool.disconnect().await?;
    // This unwrap is safe because we can assume that 1 row will always be returned
    Ok(resp.unwrap())
}

#[launch]
fn rocket() -> _ {
    rocket::build()
        .mount("/", routes![index])
        .attach(Template::fairing())
}