//! Plumbing shared by g1t services that run on Workers.
//!
//! Services talk to each other over service bindings with a small JSON
//! protocol: `POST /rpc/<method>` with the method's arguments as the body,
//! answered with the method's return value.
use serde::Serialize;
use serde::de::DeserializeOwned;
use worker::{Date, Fetcher, Headers, Method, Request, RequestInit, Response, Result};
/// The current time in milliseconds since the epoch.
pub fn now_ms() -> u64 {
Date::now().as_millis()
}
/// The method name of an RPC request, or `None` if it is not one.
pub fn rpc_method(request: &Request) -> Option<String> {
if request.method() != Method::Post {
return None;
}
request
.path()
.strip_prefix("/rpc/")
.map(|method| method.to_owned())
}
/// Deserializes a method's arguments.
pub fn args<A: DeserializeOwned>(body: serde_json::Value) -> Result<A> {
serde_json::from_value(body)
.map_err(|error| worker::Error::RustError(format!("bad arguments: {error}")))
}
/// Serializes a method's return value as the response body.
pub fn reply<R: Serialize>(value: &R) -> Result<Response> {
Response::from_json(value)
}
/// Calls `method` on another service through its binding.
pub async fn call<A: Serialize, R: DeserializeOwned>(
service: &Fetcher,
method: &str,
arguments: &A,
) -> Result<R> {
let headers = Headers::new();
headers.set("content-type", "application/json")?;
let mut init = RequestInit::new();
init.with_method(Method::Post)
.with_headers(headers)
.with_body(Some(serde_json::to_string(arguments)?.into()));
// The hostname is ignored; a service binding always reaches its service.
let request = Request::new_with_init(&format!("https://service/rpc/{method}"), &init)?;
let mut response = service.fetch_request(request).await?;
if response.status_code() != 200 {
return Err(worker::Error::RustError(format!(
"{method} failed with status {}: {}",
response.status_code(),
response.text().await.unwrap_or_default()
)));
}
response.json().await
}
/// Helpers for bindings that workers-rs has no typed wrapper for, such as
/// Artifacts and Email Sending. Values cross the boundary as JSON.
pub mod js {
use std::fmt;
use serde::Serialize;
use serde::de::DeserializeOwned;
use worker::js_sys::{Array, Function, JSON, Promise, Reflect};
use worker::wasm_bindgen::{JsCast, JsValue};
use worker::wasm_bindgen_futures::JsFuture;
use worker::{Env, Error, Result};
/// An exception thrown by JavaScript, with its `code` if it had one.
#[derive(Debug)]
pub struct Thrown {
pub code: Option<String>,
pub message: String,
}
impl Thrown {
fn from_value(value: JsValue) -> Self {
let property = |name: &str| {
Reflect::get(&value, &name.into())
.ok()
.and_then(|property| property.as_string())
};
Thrown {
code: property("code"),
message: property("message").unwrap_or_else(|| format!("{value:?}")),
}
}
pub fn is(&self, code: &str) -> bool {
self.code.as_deref() == Some(code)
}
}
impl fmt::Display for Thrown {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.code {
Some(code) => write!(f, "{code}: {}", self.message),
None => f.write_str(&self.message),
}
}
}
impl From<Thrown> for Error {
fn from(thrown: Thrown) -> Self {
Error::RustError(thrown.to_string())
}
}
/// The binding called `name`, as a raw JavaScript value.
pub fn binding(env: &Env, name: &str) -> Result<JsValue> {
let value = Reflect::get(env.as_ref(), &name.into()).map_err(Thrown::from_value)?;
if value.is_undefined() {
return Err(Error::RustError(format!(
"binding {name} is not configured"
)));
}
Ok(value)
}
/// Reads a property of a JavaScript object.
pub fn get(target: &JsValue, name: &str) -> JsValue {
Reflect::get(target, &name.into()).unwrap_or(JsValue::UNDEFINED)
}
/// Sets a property on an object.
pub fn set(target: &JsValue, name: &str, value: &JsValue) {
let _ = Reflect::set(target, &name.into(), value);
}
pub fn to_js<T: Serialize>(value: &T) -> Result<JsValue> {
Ok(JSON::parse(&serde_json::to_string(value)?).map_err(Thrown::from_value)?)
}
pub fn from_js<T: DeserializeOwned>(value: &JsValue) -> Result<T> {
let text = if value.is_undefined() {
None
} else {
JSON::stringify(value)
.map_err(Thrown::from_value)?
.as_string()
};
let text = text.as_deref().unwrap_or("null");
serde_json::from_str(text).map_err(|error| {
// Say what arrived; a bare serde error is useless in a log.
let seen: String = text.chars().take(300).collect();
Error::RustError(format!(
"unexpected value from JavaScript ({error}): {seen}"
))
})
}
/// Calls `target[method](...args)` and awaits the result if it is a
/// thenable. `method` may be a name or a symbol.
pub async fn call_key(
target: &JsValue,
method: &JsValue,
args: &[JsValue],
) -> std::result::Result<JsValue, Thrown> {
let function: Function = Reflect::get(target, method)
.map_err(Thrown::from_value)?
.dyn_into()
.map_err(|_| Thrown {
code: None,
message: format!("{method:?} is not a function"),
})?;
let arguments: Array = args.iter().collect();
// An RPC stub treats every property access as a remote method, so
// `function.apply(...)` would be sent over the wire as a call to
// "apply". Reflect.apply invokes the function without touching it.
let returned = Reflect::apply(&function, target, &arguments).map_err(Thrown::from_value)?;
// Worker RPC returns its own thenable rather than a Promise, so
// resolve whatever came back instead of testing its type.
JsFuture::from(Promise::resolve(&returned))
.await
.map_err(Thrown::from_value)
}
/// Calls `target.method(...args)`; see [`call_key`].
pub async fn call(
target: &JsValue,
method: &str,
args: &[JsValue],
) -> std::result::Result<JsValue, Thrown> {
call_key(target, &method.into(), args).await
}
}