gsails 0.1.0

Main abstractions for the Sails framework
Documentation 
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use crate::{collections::BTreeMap, MessageId, Vec};
use core::ops::DerefMut;

#[cfg(not(target_arch = "wasm32"))]
fn get_message_id_to_service_route_map(
) -> impl DerefMut<Target = BTreeMap<MessageId, Vec<&'static [u8]>>> {
    use spin::Mutex;

    static MESSAGE_ID_TO_SERVICE_ROUTE: Mutex<BTreeMap<MessageId, Vec<&'static [u8]>>> =
        Mutex::new(BTreeMap::new());

    MESSAGE_ID_TO_SERVICE_ROUTE.lock()
}

#[cfg(target_arch = "wasm32")]
fn get_message_id_to_service_route_map(
) -> impl DerefMut<Target = BTreeMap<MessageId, Vec<&'static [u8]>>> {
    static mut MESSAGE_ID_TO_SERVICE_ROUTE: BTreeMap<MessageId, Vec<&'static [u8]>> =
        BTreeMap::new();

    // SAFETY: only for wasm32 target
    #[allow(static_mut_refs)]
    unsafe {
        &mut MESSAGE_ID_TO_SERVICE_ROUTE
    }
}

pub trait Service {
    type Exposure: Exposure;

    fn expose(self, message_id: MessageId, route: &'static [u8]) -> Self::Exposure;
}

pub trait Exposure {
    fn message_id(&self) -> MessageId;
    fn route(&self) -> &'static [u8];
}

#[derive(Debug, Clone, Copy)]
pub struct ExposureContext {
    message_id: MessageId,
    route: &'static [u8],
}

impl ExposureContext {
    pub fn message_id(&self) -> MessageId {
        self.message_id
    }

    pub fn route(&self) -> &'static [u8] {
        self.route
    }
}

pub(crate) fn exposure_context(message_id: MessageId) -> ExposureContext {
    let map = get_message_id_to_service_route_map();
    let route = map
        .get(&message_id)
        .and_then(|routes| routes.last().copied())
        .unwrap_or_else(|| {
            panic!(
                "Exposure context is not found for message id {:?}",
                message_id
            )
        });
    ExposureContext { message_id, route }
}

pub struct ExposureCallScope {
    message_id: MessageId,
    route: &'static [u8],
}

impl ExposureCallScope {
    pub fn new(exposure: &impl Exposure) -> Self {
        let mut map = get_message_id_to_service_route_map();
        let routes = map.entry(exposure.message_id()).or_default();
        routes.push(exposure.route());
        Self {
            message_id: exposure.message_id(),
            route: exposure.route(),
        }
    }
}

impl Drop for ExposureCallScope {
    fn drop(&mut self) {
        let mut map = get_message_id_to_service_route_map();
        let routes = map
            .get_mut(&self.message_id)
            .unwrap_or_else(|| unreachable!("Entry for message should always exist"));
        let route = routes
            .pop()
            .unwrap_or_else(|| unreachable!("Route should always exist"));
        if route != self.route {
            unreachable!("Route should always match");
        }
        if routes.is_empty() {
            map.remove(&self.message_id);
        }
    }
}