feat: add wasm-gc support for timer, event loop, and time

src/internal/event_loop/event_loop.wasm-gc.mbt

@@ -0,0 +1,36 @@
+// Copyright 2025 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+///|
+let _ignore_unused_import : Unit = {
+  ignore(@c_buffer.unimplemented)
+  ignore(@fd_util.unimplemented)
+  ignore(@os_string.unimplemented)
+  ignore(@os_error.unimplemented)
+  ignore(@time.ms_since_epoch)
+}
+
+///|
+pub fn reschedule() -> Unit {
+  guard !@coroutine.no_more_work() else {  }
+  @coroutine.reschedule()
+  // Instead of looping blockingly until there is no ready task,
+  // we only perform one round of scheduling here
+  // (i.e., only those tasks already ready when `reschedule` is called are run).
+  // Remaining tasks are delayed until the next event loop iteration,
+  // so that those blocking jobs got a chance to execute instead of starving.
+  if @coroutine.has_immediately_ready_task() {
+    ignore(wasm_set_timeout(0, reschedule))
+  }
+}

src/internal/event_loop/moon.pkg

@@ -36,6 +36,7 @@ options(
     "cancel_before_submit_test.mbt": [ "native" ],
     "event_loop.js.mbt": [ "js" ],
     "event_loop.mbt": [ "native" ],
+    "event_loop.wasm-gc.mbt": [ "wasm-gc" ],
     "fs.mbt": [ "native" ],
     "io.mbt": [ "native" ],
     "io_unix.mbt": [ "native" ],
@@ -49,8 +50,10 @@ options(
     "process_windows.mbt": [ "native" ],
     "stdio.mbt": [ "native" ],
     "thread_pool.mbt": [ "native" ],
+    "timer.js.mbt": [ "js" ],
     "timer.mbt": [ "native" ],
-    "unimplemented.mbt": [ "wasm", "wasm-gc" ],
+    "timer.wasm-gc.mbt": [ "wasm-gc" ],
+    "unimplemented.mbt": [ "wasm" ],
     "worker_wbtest.mbt": [ "native", "js" ],
   },
 )

src/internal/event_loop/timer.wasm-gc.mbt

@@ -0,0 +1,36 @@
+// Copyright 2025 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+///|
+#external
+type Timer
+
+///|
+fn wasm_set_timeout(duration : Int, f : () -> Unit) -> Timer = "moonbitlang_async_timer" "set_timeout"
+
+///|
+fn wasm_clear_timeout(timer : Timer) = "moonbitlang_async_timer" "clear_timeout"
+
+///|
+pub fn Timer::new(duration : Int, f : () -> Unit) -> Timer {
+  wasm_set_timeout(duration, () => {
+    f()
+    reschedule()
+  })
+}
+
+///|
+pub fn Timer::cancel(self : Timer) -> Unit {
+  wasm_clear_timeout(self)
+}

src/internal/event_loop/wasm-gc-imports.js

@@ -0,0 +1,15 @@
+// Import objects for moonbitlang/async wasm-gc timer, event loop, and time modules.
+// When loading the compiled wasm-gc module, merge these into the import object:
+//
+//   import { moonbitlang_async_timer, moonbitlang_async_time } from "./wasm-gc-imports.js";
+//   const imports = { ...otherImports, moonbitlang_async_timer, moonbitlang_async_time };
+//   const { instance } = await WebAssembly.instantiateStreaming(fetch("module.wasm"), imports);
+
+export const moonbitlang_async_timer = {
+  set_timeout: (duration, f) => setTimeout(f, duration),
+  clear_timeout: (timer) => clearTimeout(timer),
+};
+
+export const moonbitlang_async_time = {
+  date_now: () => Date.now(),
+};

src/internal/time/time.mbt

@@ -62,7 +62,34 @@ pub fn ms_since_epoch() -> Int64 {
 }
 
 ///|
-#cfg(any(target="wasm", target="wasm-gc"))
+#cfg(target="wasm-gc")
+fn wasm_gc_date_now() -> Double = "moonbitlang_async_time" "date_now"
+
+///|
+/// Get the current wall-clock time in milliseconds.
+///
+/// This is the time source used by the async runtime. It is intended for
+/// computing elapsed time by subtraction. The value can jump forwards or
+/// backwards if the system clock is adjusted, so do not assume monotonicity.
+///
+/// Platform notes:
+/// - Unix/macOS: `gettimeofday()` (Unix epoch)
+/// - Windows: `GetSystemTimeAsFileTime()` (FILETIME epoch, 1601)
+/// - JavaScript/wasm-gc: `Date.now()` (Unix epoch)
+///
+/// # Example
+/// ```mbt check
+/// test {
+///   let _ : Int64 = ms_since_epoch()
+/// }
+/// ```
+#cfg(target="wasm-gc")
+pub fn ms_since_epoch() -> Int64 {
+  wasm_gc_date_now().to_int64()
+}
+
+///|
+#cfg(target="wasm")
 pub fn ms_since_epoch() -> Int64 {
   abort("unimplemented")
 }