use std::rc::Rc;

use actix_session::SessionExt;
use actix_utils::future::{ready, Ready};
use actix_web::{
    body::MessageBody,
    cookie::time::{format_description::well_known::Rfc3339, OffsetDateTime},
    dev::{Service, ServiceRequest, ServiceResponse, Transform},
    Error, HttpMessage as _, Result,
};
use futures_core::future::LocalBoxFuture;

use crate::{
    config::{Configuration, IdentityMiddlewareBuilder},
    identity::IdentityInner,
    Identity,
};

/// Identity management middleware.
///
/// ```no_run
/// use actix_web::{cookie::Key, App, HttpServer};
/// use actix_session::storage::RedisSessionStore;
/// use actix_identity::{Identity, IdentityMiddleware};
/// use actix_session::{Session, SessionMiddleware};
///
/// #[actix_web::main]
/// async fn main() {
///     let secret_key = Key::generate();
///     let redis_store = RedisSessionStore::new("redis://127.0.0.1:6379").await.unwrap();
///
///     HttpServer::new(move || {
///        App::new()
///            // Install the identity framework first.
///            .wrap(IdentityMiddleware::default())
///            // The identity system is built on top of sessions.
///            // You must install the session middleware to leverage `actix-identity`.
///            .wrap(SessionMiddleware::new(redis_store.clone(), secret_key.clone()))
///     })
/// # ;
/// }
/// ```
#[derive(Default, Clone)]
pub struct IdentityMiddleware {
    configuration: Rc<Configuration>,
}

impl IdentityMiddleware {
    pub(crate) fn new(configuration: Configuration) -> Self {
        Self {
            configuration: Rc::new(configuration),
        }
    }

    /// A fluent API to configure [`IdentityMiddleware`].
    pub fn builder() -> IdentityMiddlewareBuilder {
        IdentityMiddlewareBuilder::new()
    }
}

impl<S, B> Transform<S, ServiceRequest> for IdentityMiddleware
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
    S::Future: 'static,
    B: MessageBody + 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Transform = InnerIdentityMiddleware<S>;
    type InitError = ();
    type Future = Ready<Result<Self::Transform, Self::InitError>>;

    fn new_transform(&self, service: S) -> Self::Future {
        ready(Ok(InnerIdentityMiddleware {
            service: Rc::new(service),
            configuration: Rc::clone(&self.configuration),
        }))
    }
}

#[doc(hidden)]
pub struct InnerIdentityMiddleware<S> {
    service: Rc<S>,
    configuration: Rc<Configuration>,
}

impl<S> Clone for InnerIdentityMiddleware<S> {
    fn clone(&self) -> Self {
        Self {
            service: Rc::clone(&self.service),
            configuration: Rc::clone(&self.configuration),
        }
    }
}

impl<S, B> Service<ServiceRequest> for InnerIdentityMiddleware<S>
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
    S::Future: 'static,
    B: MessageBody + 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;

    actix_service::forward_ready!(service);

    fn call(&self, req: ServiceRequest) -> Self::Future {
        let srv = Rc::clone(&self.service);
        let configuration = Rc::clone(&self.configuration);
        Box::pin(async move {
            let identity_inner = IdentityInner {
                session: req.get_session(),
                logout_behaviour: configuration.on_logout.clone(),
                is_login_deadline_enabled: configuration.login_deadline.is_some(),
                is_visit_deadline_enabled: configuration.visit_deadline.is_some(),
            };
            req.extensions_mut().insert(identity_inner);
            enforce_policies(&req, &configuration);
            srv.call(req).await
        })
    }
}

// easier to scan with returns where they are
// especially if the function body were to evolve in the future
#[allow(clippy::needless_return)]
fn enforce_policies(req: &ServiceRequest, configuration: &Configuration) {
    let must_extract_identity =
        configuration.login_deadline.is_some() || configuration.visit_deadline.is_some();

    if !must_extract_identity {
        return;
    }

    let identity = match Identity::extract(&req.extensions()) {
        Ok(identity) => identity,
        Err(err) => {
            tracing::debug!(
                error.display = %err,
                error.debug = ?err,
                "Failed to extract an `Identity` from the incoming request."
            );
            return;
        }
    };

    if let Some(login_deadline) = configuration.login_deadline {
        if matches!(
            enforce_login_deadline(&identity, login_deadline),
            PolicyDecision::LogOut
        ) {
            identity.logout();
            return;
        }
    }

    if let Some(visit_deadline) = configuration.visit_deadline {
        if matches!(
            enforce_visit_deadline(&identity, visit_deadline),
            PolicyDecision::LogOut
        ) {
            identity.logout();
            return;
        } else if let Err(err) = identity.set_last_visited_at() {
            tracing::warn!(
                error.display = %err,
                error.debug = ?err,
                "Failed to set the last visited timestamp on `Identity` for an incoming request."
            );
        }
    }
}

fn enforce_login_deadline(
    identity: &Identity,
    login_deadline: std::time::Duration,
) -> PolicyDecision {
    match identity.logged_at() {
        Ok(None) => {
            tracing::info!(
                "Login deadline is enabled, but there is no login timestamp in the session \
                state attached to the incoming request. Logging the user out."
            );
            PolicyDecision::LogOut
        }
        Err(err) => {
            tracing::info!(
                error.display = %err,
                error.debug = ?err,
                "Login deadline is enabled but we failed to extract the login timestamp from the \
                session state attached to the incoming request. Logging the user out."
            );
            PolicyDecision::LogOut
        }
        Ok(Some(logged_in_at)) => {
            let elapsed = OffsetDateTime::now_utc() - logged_in_at;
            if elapsed > login_deadline {
                tracing::info!(
                    user.logged_in_at = %logged_in_at.format(&Rfc3339).unwrap_or_default(),
                    identity.login_deadline_seconds = login_deadline.as_secs(),
                    identity.elapsed_since_login_seconds = elapsed.whole_seconds(),
                    "Login deadline is enabled and too much time has passed since the user logged \
                    in. Logging the user out."
                );
                PolicyDecision::LogOut
            } else {
                PolicyDecision::StayLoggedIn
            }
        }
    }
}

fn enforce_visit_deadline(
    identity: &Identity,
    visit_deadline: std::time::Duration,
) -> PolicyDecision {
    match identity.last_visited_at() {
        Ok(None) => {
            tracing::info!(
                "Last visit deadline is enabled, but there is no last visit timestamp in the \
                session state attached to the incoming request. Logging the user out."
            );
            PolicyDecision::LogOut
        }
        Err(err) => {
            tracing::info!(
                error.display = %err,
                error.debug = ?err,
                "Last visit deadline is enabled but we failed to extract the last visit timestamp \
                from the session state attached to the incoming request. Logging the user out."
            );
            PolicyDecision::LogOut
        }
        Ok(Some(last_visited_at)) => {
            let elapsed = OffsetDateTime::now_utc() - last_visited_at;
            if elapsed > visit_deadline {
                tracing::info!(
                    user.last_visited_at = %last_visited_at.format(&Rfc3339).unwrap_or_default(),
                    identity.visit_deadline_seconds = visit_deadline.as_secs(),
                    identity.elapsed_since_last_visit_seconds = elapsed.whole_seconds(),
                    "Last visit deadline is enabled and too much time has passed since the last \
                    time the user visited. Logging the user out."
                );
                PolicyDecision::LogOut
            } else {
                PolicyDecision::StayLoggedIn
            }
        }
    }
}

enum PolicyDecision {
    StayLoggedIn,
    LogOut,
}