Add a js implementation of wasm-ext. (#1454)

* Squashed commit of the following:

commit 8d11f27165aecb6275c6a435e36d4fc38193b601
Author: Ashley Ruglys <ashley.ruglys@gmail.com>
Date:   Thu Feb 13 16:27:26 2020 +0100

    Fix implementation

commit 8f60187bcc3b57069eb8bd7ac530d9da3da4176e
Author: Ashley Ruglys <ashley.ruglys@gmail.com>
Date:   Thu Feb 13 12:38:35 2020 +0100

    Add implementation

commit 445fadea709c930b83b4f7905c030bb29c776eed
Author: Ashley Ruglys <ashley.ruglys@gmail.com>
Date:   Wed Feb 12 16:45:31 2020 +0100

    Use different features on different targets

commit e5d47c19fc06b96bad16f433a1526ecf4d9ce99b
Author: Ashley Ruglys <ashley.ruglys@gmail.com>
Date:   Mon Feb 10 13:23:50 2020 +0100

    Use ring on native

commit 8def133f8230885535765f8e244162cdb8901a34
Author: Ashley Ruglys <ashley.ruglys@gmail.com>
Date:   Fri Feb 7 14:46:52 2020 +0100

    Use the sha2 crate for sha512 hashing

commit 268880d2ed6510a0339d70184d7ad88f3efb39c4
Author: Ashley <ashley.ruglys@gmail.com>
Date:   Fri Feb 7 01:25:29 2020 +0100

    Fix documentation

commit 9769bc5242972c2c74e9b5e36960ca2513ddbb33
Author: Ashley <ashley.ruglys@gmail.com>
Date:   Fri Feb 7 01:17:20 2020 +0100

    Switch snow resolver to default

commit ac22537385ff81b274aec14a8c6f47a0b59606ce
Author: Ashley <ashley.ruglys@gmail.com>
Date:   Thu Feb 6 20:34:50 2020 +0100

    hmm...

* Feature gate

* Rename -> websocket_transport

* Update transports/wasm-ext/Cargo.toml

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update transports/wasm-ext/src/lib.rs

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

transports/wasm-ext/Cargo.toml

@@ -16,3 +16,6 @@ libp2p-core = { version = "0.16.0", path = "../../core" }
 parity-send-wrapper = "0.1.0"
 wasm-bindgen = "0.2.42"
 wasm-bindgen-futures = "0.4.4"
+
+[features]
+websocket = []

transports/wasm-ext/src/lib.rs

@@ -72,7 +72,7 @@ pub mod ffi {
         #[wasm_bindgen(method, catch)]
         pub fn listen_on(this: &Transport, multiaddr: &str) -> Result<js_sys::Iterator, JsValue>;
 
-        /// Returns a `Readable​Stream​` that .
+        /// Returns a `Readable​Stream​`.
         #[wasm_bindgen(method, getter)]
         pub fn read(this: &Connection) -> js_sys::Iterator;
 
@@ -123,6 +123,13 @@ pub mod ffi {
         #[wasm_bindgen(method, getter)]
         pub fn local_addr(this: &ConnectionEvent) -> String;
     }
+
+    #[cfg(feature = "websocket")]
+    #[wasm_bindgen(module = "/src/websockets.js")]
+    extern "C" {
+        /// Returns a `Transport` implemented using websockets.
+        pub fn websocket_transport() -> Transport;
+    }
 }
 
 /// Implementation of `Transport` whose implementation is handled by some FFI.

transports/wasm-ext/src/websockets.js

@@ -0,0 +1,152 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+export const websocket_transport = () => {
+	return {
+		dial: dial,
+		listen_on: (addr) => {
+			let err = new Error("Listening on WebSockets is not possible from within a browser");
+			err.name = "NotSupportedError";
+			throw err;
+		},
+	};
+}
+
+/// Turns a string multiaddress into a WebSockets string URL.
+// TODO: support dns addresses as well
+const multiaddr_to_ws = (addr) => {
+	let parsed = addr.match(/^\/(ip4|ip6|dns4|dns6)\/(.*?)\/tcp\/(.*?)\/(ws|wss|x-parity-ws\/(.*)|x-parity-wss\/(.*))$/);
+	let proto = 'wss';
+	if (parsed[4] == 'ws' || parsed[4] == 'x-parity-ws') {
+		proto = 'ws';
+	}
+	let url = decodeURIComponent(parsed[5] || parsed[6] || '');
+	if (parsed != null) {
+		if (parsed[1] == 'ip6') {
+			return proto + "://[" + parsed[2] + "]:" + parsed[3] + url;
+		} else {
+			return proto + "://" + parsed[2] + ":" + parsed[3] + url;
+		}
+	}
+
+	let err = new Error("Address not supported: " + addr);
+	err.name = "NotSupportedError";
+	throw err;
+}
+
+// Attempt to dial a multiaddress.
+const dial = (addr) => {
+	let ws = new WebSocket(multiaddr_to_ws(addr));
+	let reader = read_queue();
+
+	return new Promise((resolve, reject) => {
+		// TODO: handle ws.onerror properly after dialing has happened
+		ws.onerror = (ev) => reject(ev);
+		ws.onmessage = (ev) => reader.inject_blob(ev.data);
+		ws.onclose = () => reader.inject_eof();
+		ws.onopen = () => resolve({
+			read: (function*() { while(ws.readyState == 1) { yield reader.next(); } })(),
+			write: (data) => {
+				if (ws.readyState == 1) {
+					ws.send(data);
+					return promise_when_ws_finished(ws);
+				} else {
+					return Promise.reject("WebSocket is closed");
+				}
+			},
+			shutdown: () => {},
+			close: () => ws.close()
+		});
+	});
+}
+
+// Takes a WebSocket object and returns a Promise that resolves when bufferedAmount is 0.
+const promise_when_ws_finished = (ws) => {
+	if (ws.bufferedAmount == 0) {
+		return Promise.resolve();
+	}
+
+	return new Promise((resolve, reject) => {
+		setTimeout(function check() {
+			if (ws.bufferedAmount == 0) {
+				resolve();
+			} else {
+				setTimeout(check, 100);
+			}
+		}, 2);
+	})
+}
+
+// Creates a queue reading system.
+const read_queue = () => {
+	// State of the queue.
+	let state = {
+		// Array of promises resolving to `ArrayBuffer`s, that haven't been transmitted back with
+		// `next` yet.
+		queue: new Array(),
+		// If `resolve` isn't null, it is a "resolve" function of a promise that has already been
+		// returned by `next`. It should be called with some data.
+		resolve: null,
+	};
+
+	return {
+		// Inserts a new Blob in the queue.
+		inject_blob: (blob) => {
+			if (state.resolve != null) {
+				var resolve = state.resolve;
+				state.resolve = null;
+
+				var reader = new FileReader();
+				reader.addEventListener("loadend", () => resolve(reader.result));
+				reader.readAsArrayBuffer(blob);
+			} else {
+				state.queue.push(new Promise((resolve, reject) => {
+					var reader = new FileReader();
+					reader.addEventListener("loadend", () => resolve(reader.result));
+					reader.readAsArrayBuffer(blob);
+				}));
+			}
+		},
+
+		// Inserts an EOF message in the queue.
+		inject_eof: () => {
+			if (state.resolve != null) {
+				var resolve = state.resolve;
+				state.resolve = null;
+				resolve(null);
+			} else {
+				state.queue.push(Promise.resolve(null));
+			}
+		},
+
+		// Returns a Promise that yields the next entry as an ArrayBuffer.
+		next: () => {
+			if (state.queue.length != 0) {
+				return state.queue.shift(0);
+			} else {
+				if (state.resolve !== null)
+					throw "Internal error: already have a pending promise";
+				return new Promise((resolve, reject) => {
+					state.resolve = resolve;
+				});
+			}
+		}
+	};
+};