1 files changed, 167 insertions, 0 deletions
diff --git a/src/gleam_javascript_ffi.mjs b/src/gleam_javascript_ffi.mjs
new file mode 100644
index 0000000..7c14c10
--- /dev/null
+++ b/src/gleam_javascript_ffi.mjs
@@ -0,0 +1,167 @@
+import { Ok, Error } from "./gleam.mjs";
+import {
+  UndefinedType,
+  ObjectType,
+  BooleanType,
+  NumberType,
+  BigIntType,
+  StringType,
+  SymbolType,
+  FunctionType,
+} from "./gleam/javascript.mjs";
+
+export function toArray(list) {
+  return list.toArray();
+}
+
+export function map(thing, fn) {
+  return thing.map(fn);
+}
+
+export function length(thing) {
+  return thing.length;
+}
+
+export function reduce(thing, acc, fn) {
+  return thing.reduce(fn, acc);
+}
+
+export function reduceRight(thing, acc, fn) {
+  return thing.reduceRight(fn, acc);
+}
+
+export function index(thing, index) {
+  return index in thing ? new Ok(thing[index]) : new Error(undefined);
+}
+
+export function object_from_entries(entries) {
+  return Object.fromEntries(entries);
+}
+
+export function type_of(value) {
+  switch (typeof value) {
+    case "undefined":
+      return new UndefinedType();
+    case "object":
+      return new ObjectType();
+    case "boolean":
+      return new BooleanType();
+    case "number":
+      return new NumberType();
+    case "bigint":
+      return new BigIntType();
+    case "string":
+      return new StringType();
+    case "symbol":
+      return new SymbolType();
+    case "function":
+      return new FunctionType();
+    default:
+      throw new globalThis.Error(`Unexpected typeof ${typeof value}`);
+  }
+}
+
+export function get_symbol(name) {
+  return Symbol.for(name);
+}
+
+// A wrapper around a promise to prevent `Promise<Promise<T>>` collapsing into
+// `Promise<T>`.
+class PromiseLayer {
+  constructor(promise) {
+    this.promise = promise;
+  }
+
+  static wrap(value) {
+    return value instanceof Promise ? new PromiseLayer(value) : value;
+  }
+
+  static unwrap(value) {
+    return value instanceof PromiseLayer ? value.promise : value;
+  }
+}
+
+export function newPromise(executor) {
+  return new Promise((resolve) =>
+    executor((value) => {
+      resolve(PromiseLayer.wrap(value));
+    })
+  );
+}
+
+export function resolve(value) {
+  return Promise.resolve(PromiseLayer.wrap(value));
+}
+
+export function then(promise, fn) {
+  return promise.then((value) => fn(PromiseLayer.unwrap(value)));
+}
+
+export function map_promise(promise, fn) {
+  return promise.then((value) =>
+    PromiseLayer.wrap(fn(PromiseLayer.unwrap(value)))
+  );
+}
+
+export function rescue(promise, fn) {
+  return promise.catch((error) => fn(error));
+}
+
+class Reference {
+  constructor(value) {
+    this.value = value;
+  }
+}
+
+export function dereference(reference) {
+  return reference.value;
+}
+
+export function make_reference(value) {
+  return new Reference(value);
+}
+
+export function set_reference(ref, value) {
+  let previous = ref.value;
+  ref.value = value;
+  return previous;
+}
+
+export function reference_equal(a,b) {
+  return a === b
+}
+
+export function all_promises(...promises) {
+  if (promises.length === 1) {
+    return Promise.all(promises[0]);
+  } else {
+    return Promise.all(promises);
+  }
+}
+
+export function race_promises(...promises) {
+  if (promises.length === 1) {
+    return Promise.race(promises[0]);
+  } else {
+    return Promise.race(promises);
+  }
+}
+
+export function map_new() {
+  return new Map();
+}
+
+export function map_set(map, key, value) {
+  return map.set(key, value);
+}
+
+export function map_get(map, key) {
+  if (map.has(key)) {
+    return new Ok(map.get(key));
+  }
+  return new Error(undefined);
+}
+
+export function map_size(map) {
+  return map.size;
+}