Add streaming method generation (untested)

usdpl-back/Cargo.toml

@@ -19,7 +19,7 @@ usdpl-core = { version = "0.11", path = "../usdpl-core"}
 log = "0.4"
 
 # gRPC/protobuf
-nrpc = "0.6"
+nrpc = { version = "0.10", path = "../../nRPC/nrpc", default-features = false, features = [ "server-send" ] }
 async-lock = "2.7"
 prost = "0.11"
 

usdpl-build/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-nrpc-build = { version = "0.7", path = "../../nRPC/nrpc-build" }
+nrpc-build = { version = "0.10", path = "../../nRPC/nrpc-build" }
 prost-build = "0.11"
 prost-types = "0.11"
 

usdpl-build/src/front/service_generator.rs

@@ -35,6 +35,9 @@ fn generate_service_methods(
 
         let mut input_params = Vec::with_capacity(input_type.field.len());
         let mut params_to_fields = Vec::with_capacity(input_type.field.len());
+
+        match (method.client_streaming, method.server_streaming) {
+            (false, false) => {
                 for field in &input_type.field {
                     //let param_name = quote::format_ident!("val{}", i.to_string());
                     let type_enum = ProtobufType::from_field(field, &service.name, false);
@@ -97,6 +100,138 @@ fn generate_service_methods(
                         }
                     }
                 });
+            },
+            (true, false) => {
+                // many -> 1
+                gen_methods.push(quote::quote! {
+                    #[wasm_bindgen]
+                    pub async fn #method_name(&self, generator: js_sys::Function) -> Option<#method_output> {
+
+                        // function into Rust futures Stream
+                        let stream = Box::new(::usdpl_front::wasm::JsFunctionStream::<#method_input>::from_function(generator));
+
+                        match self.service.#method_name(stream).await {
+                            Ok(x) => {
+                                let x2: #method_output_as_in = x.into();
+                                Some(x2.into_wasm())
+                            },
+                            Err(e) => {
+                                // log error
+                                log::error!("service:{}|method:{}|error:{}", self.service.descriptor(), #method_name_str, e);
+                                None
+                            }
+                        }
+                    }
+                });
+            },
+            (false, true) => {
+                // 1 -> many
+                for field in &input_type.field {
+                    //let param_name = quote::format_ident!("val{}", i.to_string());
+                    let type_enum = ProtobufType::from_field(field, &service.name, false);
+                    //let rs_type_name = type_enum.to_tokens();
+                    let js_type_name = type_enum.to_wasm_tokens();
+                    let rs_type_name = type_enum.to_tokens();
+                    let field_name = quote::format_ident!(
+                        "{}",
+                        field
+                            .name
+                            .as_ref()
+                            .expect("Protobuf message field needs a name")
+                    );
+                    input_params.push(quote::quote! {
+                        #field_name: #js_type_name,
+                    });
+                    params_to_fields.push(quote::quote! {
+                        #field_name: #rs_type_name::from_wasm(#field_name.into()),//: #field_name,
+                    });
+                }
+                let params_to_fields_transformer = if input_type.field.len() == 1 {
+                    let field_name = quote::format_ident!(
+                        "{}",
+                        input_type.field[0]
+                            .name
+                            .as_ref()
+                            .expect("Protobuf message field needs a name")
+                    );
+                    quote::quote! {
+                        let val = #method_input::from_wasm(#field_name.into());
+                    }
+                } else if input_type.field.is_empty() {
+                    quote::quote! {
+                        let val = #method_input {};
+                    }
+                } else {
+                    quote::quote! {
+                        let val = #method_input {
+                            #(#params_to_fields)*
+                        };
+                    }
+                };
+
+                gen_methods.push(quote::quote! {
+                    #[wasm_bindgen]
+                    pub async fn #method_name(&self, #(#input_params)*, callback: js_sys::Function) {
+
+                        #params_to_fields_transformer
+
+                        match self.service.#method_name(val.into()).await {
+                            Ok(x) => {
+                                while let Some(next_result) = x.next().await {
+                                    match next_result {
+                                        Err(e) => {
+                                            log::error!("service:{}|method:{}|error:{}", self.service.descriptor(), #method_name_str, e);
+                                        },
+                                        Ok(item) => {
+                                            callback.call1(JsValue::undefined(), item.into_wasm_streamable());
+                                        }
+                                    }
+                                }
+                            },
+                            Err(e) => {
+                                // log error
+                                log::error!("service:{}|method:{}|error:{}", self.service.descriptor(), #method_name_str, e);
+                            }
+                        }
+                    }
+                });
+            },
+            (true, true) => {
+                // many -> many
+                gen_methods.push(quote::quote! {
+                    #[wasm_bindgen]
+                    pub async fn #method_name(&self, generator: js_sys::Function, callback: js_sys::Function) -> Option<#method_output> {
+
+                        // function into Rust futures Stream
+                        let stream = Box::new(::usdpl_front::wasm::JsFunctionStream::<#method_input>::from_function(generator));
+
+                        match self.service.#method_name(stream).await {
+                            Ok(x) => {
+                                while let Some(next_result) = x.next().await {
+                                    match next_result {
+                                        Err(e) => {
+                                            log::error!("service:{}|method:{}|error:{}", self.service.descriptor(), #method_name_str, e);
+                                        },
+                                        Ok(item) => {
+                                            callback.call1(JsValue::undefined(), item.into_wasm_streamable());
+                                        }
+                                    }
+                                }
+                            },
+                            Err(e) => {
+                                // log error
+                                log::error!("service:{}|method:{}|error:{}", self.service.descriptor(), #method_name_str, e);
+                                None
+                            }
+                        }
+                    }
+                });
+            },
+        }
+
+
+
+
     }
     quote::quote! {
         #(#gen_methods)*
@@ -198,6 +333,7 @@ fn generate_wasm_struct_interop(
             .as_ref()
             .expect("Protobuf message needs a name")
     );
+    let js_map_name = quote::format_ident!("{}", "js_map");
     let mut gen_fields = Vec::with_capacity(descriptor.field.len());
     let mut gen_into_fields = Vec::with_capacity(descriptor.field.len());
     let mut gen_from_fields = Vec::with_capacity(descriptor.field.len());
@@ -288,17 +424,21 @@ fn generate_wasm_struct_interop(
     } else if descriptor.field.len() == 1 {
         let field = &descriptor.field[0];
         //dbg!(descriptor, field);
-        let field_name = quote::format_ident!(
-            "{}",
-            field
+        let field_name_str = field
             .name
             .as_ref()
-                .expect("Protobuf message field needs a name")
+            .expect("Protobuf message field needs a name");
+        let field_name = quote::format_ident!(
+            "{}",
+            field_name_str
         );
         let type_enum = ProtobufType::from_field(field, service, is_known_map(field, known_maps));
         let type_name = type_enum.to_tokens();
         let wasm_type_name = type_enum.to_wasm_tokens();
 
+        let into_wasm_streamable = quote::quote!{self.into_wasm_streamable()};
+        let from_wasm_streamable = quote::quote!{#type_name::from_wasm_streamable(js)};
+
         quote::quote! {
             pub type #msg_name = #type_name;
             pub type #msg_name_wasm = #wasm_type_name;
@@ -320,22 +460,41 @@ fn generate_wasm_struct_interop(
                 }
             }
 
+            impl ::usdpl_front::wasm::FromWasmStreamableType for #msg_name {
+                fn from_wasm_streamable(js: JsValue) -> Result<Self, ::usdpl_front::wasm::WasmStreamableConversionError> {
+                    #from_wasm_streamable
+                }
+            }
+
+            impl ::usdpl_front::wasm::IntoWasmStreamableType for #msg_name {
+                fn into_wasm_streamable(self) -> JsValue {
+                    #into_wasm_streamable
+                }
+            }
+
             #(#gen_nested_types)*
 
             #(#gen_enums)*
         }
     } else {
+        let mut gen_into_wasm_streamable_fields = Vec::with_capacity(descriptor.field.len());
+        let mut gen_from_wasm_streamable_fields = Vec::with_capacity(descriptor.field.len());
+
         for field in &descriptor.field {
-            let field_name = quote::format_ident!(
-                "{}",
-                field
+            let field_name_str = field
                 .name
                 .as_ref()
-                    .expect("Protobuf message field needs a name")
+                .expect("Protobuf message field needs a name");
+            let field_name = quote::format_ident!(
+                "{}",
+                field_name_str
             );
             let type_enum =
                 ProtobufType::from_field(field, service, is_known_map(field, known_maps));
             let type_name = type_enum.to_tokens();
+
+            let into_wasm_streamable = type_enum.to_into_wasm_streamable(field_name_str, &js_map_name);
+            let from_wasm_streamable = type_enum.to_from_wasm_streamable(field_name_str, &js_map_name);
             //let wasm_type_name = type_enum.to_wasm_tokens();
             gen_fields.push(quote::quote! {
                 pub #field_name: #type_name,
@@ -347,6 +506,9 @@ fn generate_wasm_struct_interop(
             gen_from_fields.push(quote::quote! {
                 #field_name: <_>::from(other.#field_name),
             });
+
+            gen_into_wasm_streamable_fields.push(into_wasm_streamable);
+            gen_from_wasm_streamable_fields.push(from_wasm_streamable);
         }
 
         let wasm_attribute_maybe =
@@ -399,6 +561,23 @@ fn generate_wasm_struct_interop(
                 }
             }
 
+            impl ::usdpl_front::wasm::FromWasmStreamableType for #msg_name {
+                fn from_wasm_streamable(js: JsValue) -> Result<Self, ::usdpl_front::wasm::WasmStreamableConversionError> {
+                    let #js_map_name = js_sys::Map::from(js);
+                    Ok(Self {
+                        #(#gen_from_wasm_streamable_fields)*
+                    })
+                }
+            }
+
+            impl ::usdpl_front::wasm::IntoWasmStreamableType for #msg_name {
+                fn into_wasm_streamable(self) -> JsValue {
+                    let #js_map_name = js_sys::Map::new();
+                    #(#gen_into_wasm_streamable_fields)*
+                    #js_map_name.into()
+                }
+            }
+
             #(#gen_nested_types)*
 
             #(#gen_enums)*
@@ -551,6 +730,18 @@ impl ProtobufType {
             }
         }
     }
+
+    fn to_into_wasm_streamable(&self, field_name: &str, js_map_name: &syn::Ident) -> proc_macro2::TokenStream {
+        //let type_tokens = self.to_tokens();
+        //let field_ident = quote::format_ident!("{}", field_name);
+        quote::quote!{#js_map_name.set(#field_name.into(), self.field_ident);}
+    }
+
+    fn to_from_wasm_streamable(&self, field_name: &str, js_map_name: &syn::Ident) -> proc_macro2::TokenStream {
+        let type_tokens = self.to_tokens();
+        //let field_ident = quote::format_ident!("{}", field_name);
+        quote::quote!{#field_name: #type_tokens::from_wasm_streamable(#js_map_name.get(#field_name.into()))?,}
+    }
 }
 
 fn generate_wasm_enum_interop(
@@ -815,8 +1006,10 @@ impl IServiceGenerator for WasmServiceGenerator {
                 use usdpl_front::_helpers::wasm_bindgen_futures;
                 use usdpl_front::_helpers::js_sys;
                 use usdpl_front::_helpers::log;
-
-                use ::nrpc::ClientService;
+                use usdpl_front::_helpers::futures;
+                use usdpl_front::_helpers::futures::StreamExt;
+                use usdpl_front::_helpers::nrpc::ClientService;
+                use usdpl_front::wasm::{IntoWasmStreamableType, FromWasmStreamableType};
 
                 use usdpl_front::wasm::*;
 

usdpl-front/Cargo.toml

@@ -20,7 +20,7 @@ encrypt = ["usdpl-core/encrypt", "obfstr", "hex"]
 [dependencies]
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.4"
-gloo-net = { version = "0.2", features = ["websocket"] }
+gloo-net = { version = "0.3", features = ["websocket"] }
 futures = "0.3"
 console_log = { version = "1.0", optional = true, features = ["color"] }
 
@@ -45,7 +45,7 @@ async-channel = "1.8"
 obfstr = { version = "0.3", optional = true }
 hex = { version = "0.4", optional = true }
 
-nrpc = { version = "0.7", path = "../../nRPC/nrpc" }
+nrpc = { version = "0.10", path = "../../nRPC/nrpc", default-features = false}
 usdpl-core = { version = "0.11", path = "../usdpl-core" }
 prost = "0.11"
 log = "0.4"

usdpl-front/src/client_handler.rs

@@ -1,8 +1,8 @@
 use std::sync::atomic::{AtomicU64, Ordering};
 
-use futures::{SinkExt, StreamExt};
-use gloo_net::websocket::{futures::WebSocket, Message};
-use nrpc::{ClientHandler, ServiceError, _helpers::async_trait, _helpers::bytes};
+use futures::{SinkExt, StreamExt, future::{select, Either}};
+use gloo_net::websocket::{futures::WebSocket, Message, State};
+use nrpc::{ClientHandler, ServiceError, ServiceClientStream, _helpers::async_trait, _helpers::bytes};
 use wasm_bindgen_futures::spawn_local;
 
 static LAST_ID: AtomicU64 = AtomicU64::new(0);
@@ -13,24 +13,104 @@ pub struct WebSocketHandler {
     port: u16,
 }
 
-async fn send_recv_ws(url: String, input: bytes::Bytes) -> Result<Vec<u8>, String> {
-    let mut ws = WebSocket::open(&url).map_err(|e| e.to_string())?;
-    ws.send(Message::Bytes(input.into()))
-        .await
-        .map_err(|e| e.to_string())?;
+async fn send_recv_ws<'a>(tx: async_channel::Sender<Result<bytes::Bytes, String>>, url: String, mut input: ServiceClientStream<'a, bytes::Bytes>) {
+    let ws = match WebSocket::open(&url).map_err(|e| e.to_string()) {
+        Ok(x) => x,
+        Err(e) => {
+            tx.send(Err(e.to_string())).await.unwrap_or(());
+            return;
+        }
+    };
 
-    read_next_incoming(ws).await
-}
-
-async fn read_next_incoming(mut ws: WebSocket) -> Result<Vec<u8>, String> {
-    if let Some(msg) = ws.next().await {
-        match msg.map_err(|e| e.to_string())? {
-            Message::Bytes(b) => Ok(b),
-            Message::Text(_) => Err("Message::Text not allowed".into()),
+    let (mut input_done, mut output_done) = (false, false);
+    let mut last_ws_state = ws.state();
+    let (mut ws_sink, mut ws_stream) = ws.split();
+    let (mut left, mut right) = (input.next(), ws_stream.next());
+    while let State::Open = last_ws_state {
+        if !input_done && !output_done {
+            match select(left, right).await {
+                Either::Left((next, outstanding)) => {
+                    if let Some(next) = next {
+                        match next {
+                            Ok(next) => {
+                                if let Err(e) = ws_sink.send(Message::Bytes(next.into())).await {
+                                    tx.send(Err(e.to_string())).await.unwrap_or(());
+                                }
+                            },
+                            Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(())
                         }
                     } else {
-        Err("No response received".into())
+                        input_done = true;
                     }
+                    right = outstanding;
+                    left = input.next();
+                },
+                Either::Right((response, outstanding)) => {
+                    if let Some(next) = response {
+                        match next {
+                            Ok(Message::Bytes(b)) => tx.send(Ok(b.into())).await.unwrap_or(()),
+                            Ok(_) => tx.send(Err("Message::Text not allowed".into())).await.unwrap_or(()),
+                            Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(()),
+                        }
+                    } else {
+                        output_done = true;
+                    }
+                    left = outstanding;
+                    let ws = ws_stream.reunite(ws_sink).unwrap();
+                    last_ws_state = ws.state();
+                    (ws_sink, ws_stream) = ws.split();
+                    right = ws_stream.next();
+                }
+            }
+        } else if input_done {
+            if let Some(next) = right.await {
+                match next {
+                    Ok(Message::Bytes(b)) => tx.send(Ok(b.into())).await.unwrap_or(()),
+                    Ok(_) => tx.send(Err("Message::Text not allowed".into())).await.unwrap_or(()),
+                    Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(()),
+                }
+            } else {
+                output_done = true;
+            }
+            //left = outstanding;
+            let ws = ws_stream.reunite(ws_sink).unwrap();
+            last_ws_state = ws.state();
+            (ws_sink, ws_stream) = ws.split();
+            right = ws_stream.next();
+        } else {
+
+        }
+    }
+    /*spawn_local(async move {
+        while let State::Open = ws.state() {
+            if let Some(next) = input.next().await {
+                match next {
+                    Ok(next) => {
+                        if let Err(e) = ws.send(Message::Bytes(next.into())).await {
+                            tx2.send(Err(e.to_string())).await.unwrap_or(());
+                        }
+                    },
+                    Err(e) => tx2.send(Err(e.to_string())).await.unwrap_or(())
+                }
+            } else {
+                break;
+            }
+        }
+    });
+
+    spawn_local(async move {
+        while let State::Open = ws.state() {
+            if let Some(next) = ws.next().await {
+                match next {
+                    Ok(Message::Bytes(b)) => tx.send(Ok(b.into())).await.unwrap_or(()),
+                    Ok(_) => tx.send(Err("Message::Text not allowed".into())).await.unwrap_or(()),
+                    Err(e) => tx.send(Err(e.to_string())).await.unwrap_or(()),
+                }
+            } else {
+                break;
+            }
+        }
+    });*/
 }
 
 #[derive(Debug)]
@@ -44,6 +124,8 @@ impl std::fmt::Display for ErrorStr {
 
 impl std::error::Error for ErrorStr {}
 
+const CHANNEL_BOUND: usize = 4;
+
 impl WebSocketHandler {
     /// Instantiate the web socket client for connecting on the specified port
     pub fn new(port: u16) -> Self {
@@ -51,32 +133,25 @@ impl WebSocketHandler {
     }
 }
 
-#[async_trait::async_trait]
-impl ClientHandler for WebSocketHandler {
-    async fn call(
+#[async_trait::async_trait(?Send)]
+impl ClientHandler<'static> for WebSocketHandler {
+    async fn call<'a: 'static>(
         &self,
         package: &str,
         service: &str,
         method: &str,
-        input: bytes::Bytes,
-        output: &mut bytes::BytesMut,
-    ) -> Result<(), ServiceError> {
+        input: ServiceClientStream<'a, bytes::Bytes>,
+    ) -> Result<ServiceClientStream<'a, bytes::Bytes>, ServiceError> {
         let id = LAST_ID.fetch_add(1, Ordering::SeqCst);
         let url = format!(
             "ws://usdpl-ws-{}.localhost:{}/{}.{}/{}",
             id, self.port, package, service, method,
         );
-        let (tx, rx) = async_channel::bounded(1);
-        spawn_local(async move {
-            tx.send(send_recv_ws(url, input).await).await.unwrap_or(());
-        });
+        let (tx, rx) = async_channel::bounded(CHANNEL_BOUND);
+        spawn_local(send_recv_ws(tx, url, input));
 
-        output.extend_from_slice(
-            &rx.recv()
-                .await
-                .map_err(|e| ServiceError::Method(Box::new(e)))?
-                .map_err(|e| ServiceError::Method(Box::new(ErrorStr(e))))?,
-        );
-        Ok(())
+        Ok(Box::new(rx.map(|buf_result: Result<bytes::Bytes, String>| buf_result
+            .map(|buf| bytes::Bytes::from(buf))
+            .map_err(|e| ServiceError::Method(Box::new(ErrorStr(e)))))))
     }
 }

usdpl-front/src/convert.rs

@@ -38,3 +38,11 @@ pub(crate) fn js_to_primitive(val: JsValue) -> Primitive {
 pub(crate) fn str_to_js<S: std::string::ToString>(s: S) -> JsString {
     s.to_string().into()
 }
+
+pub(crate) fn js_to_str(js: JsValue) -> String {
+    if let Some(s) = js.as_string() {
+        s
+    } else {
+        format!("{:?}", js)
+    }
+}

usdpl-front/src/lib.rs

@@ -23,6 +23,8 @@ pub mod _helpers {
     pub use wasm_bindgen;
     pub use wasm_bindgen_futures;
     pub use log;
+    pub use futures;
+    pub use nrpc;
 }
 
 use std::sync::atomic::{AtomicU64, Ordering};

usdpl-front/src/wasm/js_function_stream.rs

@@ -0,0 +1,74 @@
+use core::pin::Pin;
+use core::future::Future;
+
+use futures::{Stream, task::{Poll, Context}};
+use wasm_bindgen_futures::JsFuture;
+use wasm_bindgen::JsValue;
+use js_sys::{Function, Promise};
+
+use nrpc::ServiceError;
+use super::FromWasmStreamableType;
+use crate::convert::js_to_str;
+
+/// futures::Stream wrapper for a JS async function that generates a new T-like value every call
+pub struct JsFunctionStream<T: FromWasmStreamableType + Unpin + 'static> {
+    function: Function,
+    promise: Option<JsFuture>,
+    _idc: std::marker::PhantomData<T>,
+}
+
+impl <T: FromWasmStreamableType + Unpin + 'static> JsFunctionStream<T> {
+    /// Construct the function stream wrapper
+    pub fn from_function(f: Function) -> Self {
+        Self {
+            function: f,
+            promise: None,
+            _idc: std::marker::PhantomData::default(),
+        }
+    }
+}
+
+impl <T: FromWasmStreamableType  + Unpin + 'static> Stream for JsFunctionStream<T> {
+    type Item = Result<T, ServiceError>;
+
+    fn poll_next(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>
+    ) -> Poll<Option<Self::Item>> {
+        // this is horrible, I'm sorry
+        let js_poll = if let Some(mut promise) = self.promise.take() {
+            let mut pin = Pin::new(&mut promise);
+            JsFuture::poll(pin.as_mut(), cx)
+        } else {
+            let function_result = match self.function.call0(&JsValue::undefined()) {
+                Ok(x) => x,
+                Err(e) => return Poll::Ready(Some(Err(ServiceError::Method(s_to_err(format!("JS function call error: {}", js_to_str(e)))))))
+            };
+
+            let js_promise = Promise::from(function_result);
+            let mut js_future = JsFuture::from(js_promise);
+            let mut pin = Pin::new(&mut js_future);
+            let poll = JsFuture::poll(pin.as_mut(), cx);
+            self.promise = Some(js_future);
+            poll
+        };
+        js_poll.map(|t| match t {
+            Ok(t) => {
+                if t.is_null() || t.is_undefined() {
+                    None
+                } else {
+                    Some(T::from_wasm_streamable(t).map_err(|e| ServiceError::Method(s_to_err(format!("JS type conversion error: {}", e)))))
+                }
+            },
+            Err(e) => Some(Err(ServiceError::Method(s_to_err(format!("JS function promise error: {}", js_to_str(e))))))
+        })
+    }
+}
+
+fn s_to_err(s: String) -> Box<(dyn std::error::Error + Send + Sync + 'static)> {
+    s.into()
+}
+
+fn _check_service_stream<T: FromWasmStreamableType  + Unpin + 'static>(js_stream: JsFunctionStream<T>) {
+    let _: nrpc::ServiceClientStream<'static, T> = Box::new(js_stream);
+}

usdpl-front/src/wasm/mod.rs

@@ -1,7 +1,11 @@
 //! WASM <-> Rust interop utilities
 mod arrays;
+mod js_function_stream;
 mod maps;
+mod streaming;
 mod trivials;
 mod wasm_traits;
 
+pub use js_function_stream::JsFunctionStream;
 pub use wasm_traits::*;
+pub use streaming::*;

usdpl-front/src/wasm/streaming.rs

@@ -0,0 +1,189 @@
+use wasm_bindgen::JsValue;
+
+/// Convert Rust type to WASM-compatible type involved in nRPC streaming
+pub trait IntoWasmStreamableType {
+    /// Required method
+    fn into_wasm_streamable(self) -> JsValue;
+}
+
+#[derive(Debug)]
+/// Conversion error from FromWasmStreamableType
+pub enum WasmStreamableConversionError {
+    /// JSValue underlying type is incorrect
+    UnexpectedType {
+        /// Expected Javascript type
+        expected: JsType,
+        /// Actual Javascript type
+        got: JsType,
+    },
+}
+
+impl core::fmt::Display for WasmStreamableConversionError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::UnexpectedType { expected, got } => write!(f, "Unexpected type {}, expected {}", expected, got),
+        }
+    }
+}
+
+impl std::error::Error for WasmStreamableConversionError {}
+
+/// Approximation of all possible JS types detectable through Wasm
+#[allow(missing_docs)]
+#[derive(Debug)]
+pub enum JsType {
+    Number,
+    String,
+    Bool,
+    Array,
+    BigInt,
+    Function,
+    Symbol,
+    Undefined,
+    Null,
+    Object,
+    Unknown,
+}
+
+impl core::fmt::Display for JsType {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Number => write!(f, "number"),
+            Self::String => write!(f, "string"),
+            Self::Bool => write!(f, "boolean"),
+            Self::Array => write!(f, "array"),
+            Self::BigInt => write!(f, "bigint"),
+            Self::Function => write!(f, "function"),
+            Self::Symbol => write!(f, "symbol"),
+            Self::Undefined => write!(f, "undefined"),
+            Self::Null => write!(f, "null"),
+            Self::Object => write!(f, "object"),
+            Self::Unknown => write!(f, "<unknown>"),
+        }
+    }
+}
+
+impl JsType {
+    fn guess(js: &JsValue) -> JsType {
+        if js.as_f64().is_some() {
+            Self::Number
+        } else if js.as_string().is_some() {
+            Self::String
+        } else if js.as_bool().is_some() {
+            Self::Bool
+        } else if js.is_array() {
+            Self::Array
+        } else if js.is_bigint() {
+            Self::BigInt
+        } else if js.is_function() {
+            Self::Function
+        } else if js.is_symbol() {
+            Self::Symbol
+        } else if js.is_undefined() {
+            Self::Undefined
+        } else if js.is_null() {
+            Self::Null
+        } else if js.is_object() {
+            Self::Object
+        } else {
+            Self::Unknown
+        }
+    }
+}
+
+/// Convert WASM-compatible type involved in nRPC streaming to Rust-centric type
+pub trait FromWasmStreamableType: Sized {
+    /// Required method
+    fn from_wasm_streamable(js: JsValue) -> Result<Self, WasmStreamableConversionError>;
+}
+
+macro_rules! trivial_convert_number {
+    ($ty: ty) => {
+        impl FromWasmStreamableType for $ty {
+            fn from_wasm_streamable(js: JsValue) -> Result<Self, WasmStreamableConversionError> {
+                if let Some(num) = js.as_f64() {
+                    Ok(num as $ty)
+                } else {
+                    Err(WasmStreamableConversionError::UnexpectedType {
+                        expected: JsType::Number,
+                        got: JsType::guess(&js),
+                    })
+                }
+            }
+        }
+
+        impl IntoWasmStreamableType for $ty {
+            fn into_wasm_streamable(self) -> JsValue {
+                self.into()
+            }
+        }
+    };
+}
+
+trivial_convert_number! { f64 }
+trivial_convert_number! { f32 }
+
+trivial_convert_number! { isize }
+trivial_convert_number! { usize }
+
+trivial_convert_number! { i8 }
+trivial_convert_number! { i16 }
+trivial_convert_number! { i32 }
+trivial_convert_number! { i64 }
+trivial_convert_number! { i128 }
+
+trivial_convert_number! { u8 }
+trivial_convert_number! { u16 }
+trivial_convert_number! { u32 }
+trivial_convert_number! { u64 }
+trivial_convert_number! { u128 }
+
+impl FromWasmStreamableType for String {
+    fn from_wasm_streamable(js: JsValue) -> Result<Self, WasmStreamableConversionError> {
+        if let Some(s) = js.as_string() {
+            Ok(s)
+        } else {
+            Err(WasmStreamableConversionError::UnexpectedType {
+                expected: JsType::String,
+                got: JsType::guess(&js),
+            })
+        }
+    }
+}
+
+impl IntoWasmStreamableType for String {
+    fn into_wasm_streamable(self) -> JsValue {
+        self.into()
+    }
+}
+
+impl FromWasmStreamableType for bool {
+    fn from_wasm_streamable(js: JsValue) -> Result<Self, WasmStreamableConversionError> {
+        if let Some(b) = js.as_bool() {
+            Ok(b)
+        } else {
+            Err(WasmStreamableConversionError::UnexpectedType {
+                expected: JsType::Bool,
+                got: JsType::guess(&js),
+            })
+        }
+    }
+}
+
+impl IntoWasmStreamableType for bool {
+    fn into_wasm_streamable(self) -> JsValue {
+        self.into()
+    }
+}
+
+impl FromWasmStreamableType for () {
+    fn from_wasm_streamable(_js: JsValue) -> Result<Self, WasmStreamableConversionError> {
+        Ok(())
+    }
+}
+
+impl IntoWasmStreamableType for () {
+    fn into_wasm_streamable(self) -> JsValue {
+        JsValue::undefined()
+    }
+}