remote-trait-object 0.4.2

use super::export_import::*;
use super::*;
use crate::raw_exchange::HandleToExchange;
use serde::de::{Deserialize, Deserializer};
use serde::ser::{Serialize, Serializer};
use std::cell::RefCell;
use std::marker::PhantomData;
use std::sync::Arc;

/// Some data format traverses over data **twice**, first for size estimation and second for real encoding.
/// Thus we use prepare secondary phase `Exported`.
enum ExportEntry {
    ReadyToExport(Skeleton),
    Exported(HandleToExchange),
}

/// A special wrapper of _skeleton_, used to export a service object.
///
/// You can make any smart pointer of a trait object into a `ServiceToExport`
/// as far as the trait is a subtrait of [`Service`] and marked with the macro [`service`].
///
/// The only way to actually export a `ServiceToExport` is either
/// 1. Returning it while handling a method in another service
/// 2. Passing as an argument in a remote call
///
/// `ServiceToExport` is a compatible type with [`ServiceToImport`] and [`ServiceRef`]
/// You can import a proxy object by putting one of those two types on the same place in the client side.
/// See [Service Compatibility] section
///
/// `ServiceToExport` is a wrapper of [`Skeleton`] that hides the detail exchange process.
/// However you don't have to know what [`Skeleton`] is, unless you're going to perform [raw export and import].
///
/// **NOTE**: it implements [`Serialize`], but you must **NEVER** try to serialize it.
/// It has a side effect of registering the service object in the context,
/// and so should be called only by `remote-trait-object`'s internal process.
/**
## Example
```
use remote_trait_object::*;
use std::sync::Arc;
use parking_lot::RwLock;

#[service(no_proxy)]
pub trait Hello: Service {
    fn hello(&self) -> Vec<ServiceToExport<dyn Hello>>;
}

struct A;
impl Service for A {}
impl Hello for A {
    fn hello(&self) -> Vec<ServiceToExport<dyn Hello>> {
        // Export by return
        vec![
            ServiceToExport::new(Box::new(A) as Box<dyn Hello>),
            ServiceToExport::new(Arc::new(A) as Arc<dyn Hello>),
            ServiceToExport::new(Arc::new(RwLock::new(A)) as Arc<RwLock<dyn Hello>>),
        ]
    }
}
```
**/
/// [`service`]: attr.service.html
/// [Service compatibility]: ./index.html#service_compatibility
/// [raw export and import]: raw_exchange/index.html
pub struct ServiceToExport<T: ?Sized + Service> {
    service: RefCell<ExportEntry>,
    _marker: PhantomData<T>,
}

impl<T: ?Sized + Service> ServiceToExport<T> {
    /// Creates a new instance from a smart pointer of a service object.
    pub fn new(service: impl IntoSkeleton<T>) -> Self {
        Self {
            service: RefCell::new(ExportEntry::ReadyToExport(service.into_skeleton())),
            _marker: PhantomData,
        }
    }

    pub(crate) fn get_raw_export(self) -> Skeleton {
        match self.service.into_inner() {
            ExportEntry::ReadyToExport(s) => s,
            _ => panic!(),
        }
    }
}

/// A special wrapper of _handle_, used to import a service.
///
/// You can make an instance of this into any smart pointer of a trait object
/// as far as the trait is a subtrait of [`Service`] and marked with the macro [`service`].
///
/// The only way to actually import a `ServiceToImport` is either
/// 1. Receiving it as a return value, in a remote call
/// 2. Receiving as an argument while a method in handling another service
///
/// `ServiceToImport` is a compatible type with [`ServiceToExport`] and [`ServiceRef`]
/// You can export a service object by putting one of those two types on the same place on the server side.
/// See [Service Compatibility] section for more.
///
/// `ServiceToImport` is a wrapper of [`HandleToExchange`] that hides the detail exchange process.
/// However you don't have to know what [`HandleToExchange`] is, unless you're going to perform [raw export and import].
///
/// **NOTE**: it implements [`Deserialize`], but you must **NEVER** try to deserialize it.
/// It has a side effect of registering the handle in the context,
/// and so should be called only by `remote-trait-object`'s internal process.
/**
## Example
```
use remote_trait_object::*;
use std::sync::Arc;
use parking_lot::RwLock;

#[service(no_skeleton)]
pub trait Hello: Service {
    fn hello(&self) -> Vec<ServiceToImport<dyn Hello>>;
}

fn do_some_imports(x: Box<dyn Hello>) {
    let mut v = x.hello();
    let a: Box<dyn Hello> = v.pop().unwrap().into_proxy();
    let b: Arc<dyn Hello> = v.pop().unwrap().into_proxy();
    let c: Arc<RwLock<dyn Hello>> = v.pop().unwrap().into_proxy();
}
```
**/
/// [`service`]: attr.service.html
/// [Service compatibility]: ./index.html#service_compatibility
/// [raw export and import]: raw_exchange/index.html
pub struct ServiceToImport<T: ?Sized + Service> {
    handle: HandleToExchange,
    port: Weak<dyn Port>,
    _marker: PhantomData<T>,
}

impl<T: ?Sized + Service> ServiceToImport<T> {
    /// Converts itself into a smart pointer of the trait, which is a _proxy object_.
    pub fn into_proxy<P: ImportProxy<T>>(self) -> P {
        P::import_proxy(self.port, self.handle)
    }

    /// Casts into another `ServiceToImport` with a different service trait.
    ///
    /// If the target trait is not compatible with the original one, it returns `Err`.
    ///
    /// See [Service Compatiblity] section for more.
    ///
    /// [Service compatiblity]: ./index.html#service_compatibility
    pub fn cast_service<U: ?Sized + Service>(self) -> Result<ServiceToImport<U>, ()> {
        // TODO: Check the compatibility between traits using IDL
        Ok(ServiceToImport {
            handle: self.handle,
            port: self.port,
            _marker: PhantomData,
        })
    }

    /// Casts into another `ServiceToImport` with a different service trait, without check.
    ///
    /// If the target trait is not compatible with the original one, any method call of the proxy object imported with this
    /// will cause a serious error.
    ///
    /// See [Service Compatiblity] section for more.
    ///
    /// [Service compatiblity]: ./index.html#service_compatibility
    pub fn cast_service_without_compatibility_check<U: ?Sized + Service>(self) -> ServiceToImport<U> {
        ServiceToImport {
            handle: self.handle,
            port: self.port,
            _marker: PhantomData,
        }
    }

    pub(crate) fn from_raw_import(handle: HandleToExchange, port: Weak<dyn Port>) -> Self {
        Self {
            handle,
            port,
            _marker: PhantomData,
        }
    }
}

/// A union of [`ServiceToExport`] and [`ServiceToImport`]
///
/// **In most case, you will mostly use only this struct to export and import services.**
///
/// This is needed when you want to export and import a service via another service,
/// but using a common single trait as a channel.
///
/// Suppose you want to export `Box<dyn Pizza>` by returning it in another service's method, `fn order_pizza()`.
/// One way of doing this is defining two traits, one for export and one for import.
/// Crate that wants to implement & export a `PizzaStore` and export `Pizza` will have following code
/**
```
use remote_trait_object::*;

#[service]
pub trait Pizza: Service {}

#[service(no_proxy)]
pub trait PizzaStore: Service {
    fn order_pizza(&self) -> ServiceToExport<dyn Pizza>;
}
```

On the other hand, crate that wants to import & remotely call a `PizzaStore` and import `Pizza` will have following code

```
use remote_trait_object::*;

#[service]
pub trait Pizza: Service {}

#[service(no_skeleton)]
pub trait PizzaStore: Service {
    fn order_pizza(&self) -> ServiceToImport<dyn Pizza>;
}
```
**/
/// This works perfectly fine, by returning `ServiceToExport::new(..)` in the former and
/// calling `ServiceToImport::into_remote(the_return_value)` in the latter,
/// because the two `PizzaStore`s are compatible since [`ServiceToImport`] and [`ServiceToExport`] are compatible.
///
/// However, suppose the case where the two parties may have a common dependent crate which would have defined such a common service trait,
/// or even the case where the two parties are in the same crate.
/// It becomes somewhat bothersome to have both duplicated traits only because of [`ServiceToExport`] and [`ServiceToImport`].
///
/// `ServiceRef` is for such purpose. Instead of denoting both [`ServiceToExport`] and [`ServiceToImport`] for two separate traits, just use
/// a single common trait with those two types replaced with `ServiceRef` in the very same place.
///
/// The above two traits now become a single trait.
/**
```
use remote_trait_object::*;

#[service]
pub trait Pizza: Service {}

#[service]
pub trait PizzaStore: Service {
    fn order_pizza(&self) -> ServiceRef<dyn Pizza>;
}
```
**/
/// And this `PizzaStore` can be both
/// - implemented and exported - you will be using `Import` variant for an argument, and `Export` variant for the return value.
/// - imported and locally invoked - you will be using `Export` variant for an argument, and `Import` variant for the return value.
///
/// ## Example
/**
```ignore
// EXPORTER SIDE
impl PizzaStore for SomeType {
    fn order_pizza(&self) -> ServiceRef<dyn Pizza> {
        ServiceRef::create_export(Box::new(SomePizza) as Box<dyn Pizza>)
    }
}

// IMPORTER SIDE
let store: Box<dyn PizzaStore> = some_store();
let pizza: Box<dyn Pizza> = store.order_pizza().unwrap_import().into_proxy();
```
**/
pub enum ServiceRef<T: ?Sized + Service> {
    Export(ServiceToExport<T>),
    Import(ServiceToImport<T>),
}

impl<T: ?Sized + Service> ServiceRef<T> {
    /// Creates an `Export` variant from a smart pointer of a service object.
    ///
    /// It simply `ServiceRef::Export(ServiceToExport::new(service))`.
    pub fn create_export(service: impl IntoSkeleton<T>) -> Self {
        ServiceRef::Export(ServiceToExport::new(service))
    }

    /// Unwraps as an `Import` variant.
    ///
    /// It panics if it is `Export`.
    pub fn unwrap_import(self) -> ServiceToImport<T> {
        match self {
            ServiceRef::Import(x) => x,
            _ => panic!("You can import ony imported ServiceRef"),
        }
    }
}

/// This manages thread-local pointer of the port, which will be used in serialization of
/// service objects wrapped in the S* pointers. Cuttently it is the only way to deliver the port
/// within the de/serialization context.
/// TODO: check that serde doens't spawn a thread while serializing.
pub(crate) mod port_thread_local {
    use super::*;
    use std::cell::RefCell;

    // TODO
    // If a service call another service, this PORT setting might be stacked (at most twice).
    // We check that the consistency of stacking for an assertion purpose.
    // However it might be costly considering the frequency of this operations,
    // so please replace this with unchecking logic
    // after the library becomes stabilized.
    thread_local!(static PORT: RefCell<Vec<Weak<dyn Port>>> = RefCell::new(Vec::new()));

    pub fn set_port(port: Weak<dyn Port>) {
        PORT.with(|k| {
            k.try_borrow_mut().unwrap().push(port);
            assert!(k.borrow().len() <= 2);
        })
    }

    pub fn get_port() -> Weak<dyn Port> {
        PORT.with(|k| k.borrow().last().unwrap().clone())
    }

    pub fn remove_port() {
        PORT.with(|k| {
            k.try_borrow_mut().unwrap().pop().unwrap();
        })
    }
}

impl<T: ?Sized + Service> Serialize for ServiceToExport<T> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer, {
        let error = "You must not de/serialize ServiceRef by yourself. If you not, this is a bug.";
        let (handle, have_to_replace) = match &*self.service.borrow() {
            ExportEntry::ReadyToExport(service) => {
                debug_assert_eq!(Arc::strong_count(&service.raw), 1);
                (port_thread_local::get_port().upgrade().expect(error).register_service(Arc::clone(&service.raw)), true)
            }
            ExportEntry::Exported(handle) => (*handle, false),
        };
        if have_to_replace {
            *self.service.borrow_mut() = ExportEntry::Exported(handle)
        }
        handle.serialize(serializer)
    }
}

impl<'de, T: ?Sized + Service> Deserialize<'de> for ServiceToImport<T> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>, {
        let handle = HandleToExchange::deserialize(deserializer)?;
        Ok(ServiceToImport {
            handle,
            port: port_thread_local::get_port(),
            _marker: std::marker::PhantomData,
        })
    }
}

impl<T: ?Sized + Service> Serialize for ServiceRef<T> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer, {
        match self {
            ServiceRef::Export(x) => x.serialize(serializer),
            ServiceRef::Import(_) => panic!(
                "If you want to re-export an imported object, first completely import it with `into_proxy()` and make it into `ServiceToExport`."
            ),
        }
    }
}

impl<'de, T: ?Sized + Service> Deserialize<'de> for ServiceRef<T> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>, {
        Ok(ServiceRef::Import(ServiceToImport::deserialize(deserializer)?))
    }
}

#[cfg(test)]
mod tests {
    mod serialize_test {
        use super::super::ServiceRef;
        use crate::macro_env::*;
        use crate::packet::*;
        use crate::port::Port;
        use crate::service::ServiceObjectId;
        use crate::*;
        use std::sync::atomic::{AtomicU32, Ordering};
        use std::sync::{Arc, Weak};

        #[derive(Debug)]
        pub struct MockPort {
            count: AtomicU32,
        }

        impl Port for MockPort {
            fn call(&self, _packet: PacketView) -> Packet {
                unimplemented!()
            }

            fn register_service(&self, _service_object: Arc<dyn Dispatch>) -> HandleToExchange {
                self.count.fetch_add(1, Ordering::SeqCst);
                HandleToExchange(123)
            }

            fn delete_request(&self, _id: ServiceObjectId) {
                unimplemented!()
            }
        }

        trait Foo: Service {}

        struct FooImpl;
        impl Foo for FooImpl {}
        impl Service for FooImpl {}
        impl Dispatch for FooImpl {
            fn dispatch_and_call(&self, _method: MethodId, _args: &[u8]) -> Vec<u8> {
                unimplemented!()
            }
        }

        impl IntoSkeleton<dyn Foo> for Arc<dyn Foo> {
            fn into_skeleton(self) -> crate::macro_env::Skeleton {
                crate::macro_env::create_skeleton(Arc::new(FooImpl))
            }
        }

        /// This test checks SArc<dyn Test> is serialized as HandleToExchange or not
        #[test]
        fn test_serialize() {
            let port = Arc::new(MockPort {
                count: AtomicU32::new(0),
            });
            let weak_port = Arc::downgrade(&port) as Weak<dyn Port>;
            super::super::port_thread_local::set_port(weak_port);

            {
                let foo_arc: Arc<dyn Foo> = Arc::new(FooImpl);
                let foo_sarc = ServiceRef::create_export(foo_arc.clone());
                let bytes = serde_json::to_vec(&foo_sarc).unwrap();
                let handle_to_exchange: HandleToExchange = serde_json::from_slice(&bytes).unwrap();
                assert_eq!(handle_to_exchange.0, 123);
                assert_eq!(port.count.load(Ordering::SeqCst), 1);
            }

            {
                let foo_arc: Arc<dyn Foo> = Arc::new(FooImpl);
                let foo_sarc = ServiceRef::create_export(foo_arc.clone());
                let bytes = serde_cbor::to_vec(&foo_sarc).unwrap();
                let handle_to_exchange: HandleToExchange = serde_cbor::from_slice(&bytes).unwrap();
                assert_eq!(handle_to_exchange.0, 123);
                assert_eq!(port.count.load(Ordering::SeqCst), 2);
            }

            {
                let foo_arc: Arc<dyn Foo> = Arc::new(FooImpl);
                let foo_sarc = ServiceRef::create_export(foo_arc.clone());
                let bytes = bincode::serialize(&foo_sarc).unwrap();
                let handle_to_exchange: HandleToExchange = bincode::deserialize(&bytes).unwrap();
                assert_eq!(handle_to_exchange.0, 123);
                assert_eq!(port.count.load(Ordering::SeqCst), 3);
            }
        }
    }

    mod deserialize_test {
        use super::super::ServiceRef;
        use crate::port::Port;
        use crate::{raw_exchange::*, Service};
        use std::sync::Weak;

        trait Foo: Service {
            fn get_handle_to_exchange(&self) -> HandleToExchange;
        }
        struct FooImpl {
            handle_to_exchange: HandleToExchange,
        }
        impl Foo for FooImpl {
            fn get_handle_to_exchange(&self) -> HandleToExchange {
                self.handle_to_exchange
            }
        }
        impl Service for FooImpl {}
        impl ImportProxy<dyn Foo> for Box<dyn Foo> {
            fn import_proxy(_port: Weak<dyn Port>, handle: HandleToExchange) -> Box<dyn Foo> {
                Box::new(FooImpl {
                    handle_to_exchange: handle,
                })
            }
        }

        #[test]
        fn test_deserialize() {
            super::super::port_thread_local::set_port(crate::port::null_weak_port());

            {
                let handle_to_exchange = HandleToExchange(32);
                let serialized_handle = serde_cbor::to_vec(&handle_to_exchange).unwrap();
                let dyn_foo: ServiceRef<dyn Foo> = serde_cbor::from_slice(&serialized_handle).unwrap();
                assert_eq!(dyn_foo.unwrap_import().into_proxy::<Box<dyn Foo>>().get_handle_to_exchange().0, 32);
            }

            {
                let handle_to_exchange = HandleToExchange(2);
                let serialized_handle = serde_cbor::to_vec(&handle_to_exchange).unwrap();
                let dyn_foo: ServiceRef<dyn Foo> = serde_cbor::from_slice(&serialized_handle).unwrap();
                assert_eq!(dyn_foo.unwrap_import().into_proxy::<Box<dyn Foo>>().get_handle_to_exchange().0, 2);
            }
        }
    }
}