//! Who is asking: the session cookie resolved to an account, as an axum
//! extractor every page handler takes.

use super::{csrf_token, mac_equal, session_value, SESSION_COOKIE};
use crate::db::{self, accounts::Account};
use crate::Shared;
use axum::extract::FromRequestParts;
use axum::http::request::Parts;
use axum::http::{header, HeaderMap};
use std::convert::Infallible;

#[derive(Clone, Debug)]
pub struct ViewerAccount {
    pub account: Account,
    /// The cookie value, which CSRF tokens are bound to.
    pub session: String,
    pub csrf: String,
    /// Unread notifications, for the header.
    pub unread: i64,
}

/// The signed-in account, if any. Never fails: anonymous is a valid viewer.
#[derive(Clone, Debug, Default)]
pub struct Viewer(pub Option<ViewerAccount>);

impl Viewer {
    pub fn account(&self) -> Option<&Account> {
        self.0.as_ref().map(|v| &v.account)
    }

    pub fn signed_in(&self) -> bool {
        self.0.is_some()
    }

    pub fn is_admin(&self) -> bool {
        self.account().is_some_and(|a| a.is_admin)
    }

    pub fn csrf(&self) -> &str {
        self.0.as_ref().map(|v| v.csrf.as_str()).unwrap_or("")
    }

    /// Whether a submitted CSRF token belongs to this session.
    pub fn csrf_ok(&self, token: &str) -> bool {
        self.0.as_ref().is_some_and(|v| mac_equal(&v.csrf, token))
    }
}

/// The value of a named cookie in the request.
pub fn cookie(headers: &HeaderMap, name: &str) -> Option<String> {
    headers.get_all(header::COOKIE).iter().filter_map(|v| v.to_str().ok()).flat_map(|line| line.split(';')).find_map(|kv| {
        let (k, v) = kv.trim().split_once('=')?;
        (k == name).then(|| v.trim().to_string())
    })
}

/// Resolve a session cookie value to its account.
pub async fn resolve(app: &Shared, value: &str) -> Option<ViewerAccount> {
    let (username, mac) = value.rsplit_once('.')?;
    let account = db::accounts::account_by_name(&app.db, username).await.ok()??;
    if account.banned {
        return None;
    }
    let expected = session_value(&app.cookie_key, &account.username, &account.session_salt);
    let (_, expected_mac) = expected.rsplit_once('.')?;
    if !mac_equal(expected_mac, mac) {
        return None;
    }
    let csrf = csrf_token(&app.cookie_key, &expected);
    let unread = db::notify::unread(&app.db, account.id).await.unwrap_or(0);
    Some(ViewerAccount { account, session: expected, csrf, unread })
}

impl FromRequestParts<Shared> for Viewer {
    type Rejection = Infallible;

    async fn from_request_parts(parts: &mut Parts, app: &Shared) -> Result<Viewer, Infallible> {
        let Some(value) = cookie(&parts.headers, SESSION_COOKIE) else { return Ok(Viewer(None)) };
        let viewer = resolve(app, &value).await;
        if let Some(v) = &viewer {
            let pool = app.db.clone();
            let id = v.account.id;
            tokio::spawn(async move {
                let _ = db::accounts::touch_seen(&pool, id).await;
            });
        }
        Ok(Viewer(viewer))
    }
}