1 files changed, 133 insertions, 0 deletions
diff --git a/src/client-runtime.ffi.mjs b/src/client-runtime.ffi.mjs
new file mode 100644
index 0000000..13e3906
--- /dev/null
+++ b/src/client-runtime.ffi.mjs
@@ -0,0 +1,133 @@
+import { ElementNotFound, NotABrowser } from "./lustre.mjs";
+import { Dispatch, Shutdown } from "./lustre/runtime.mjs";
+import { morph } from "./vdom.ffi.mjs";
+import { Ok, Error, isEqual } from "./gleam.mjs";
+
+export class LustreClientApplication {
+  #root = null;
+  #queue = [];
+  #effects = [];
+  #didUpdate = false;
+
+  #model = null;
+  #update = null;
+  #view = null;
+
+  static start(flags, selector, init, update, view) {
+    if (!is_browser()) return new Error(new NotABrowser());
+    const root =
+      selector instanceof HTMLElement
+        ? selector
+        : document.querySelector(selector);
+    if (!root) return new Error(new ElementNotFound());
+    const app = new LustreClientApplication(init(flags), update, view, root);
+
+    return new Ok((msg) => app.send(msg));
+  }
+
+  constructor([model, effects], update, view, root = document.body) {
+    this.#model = model;
+    this.#update = update;
+    this.#view = view;
+    this.#root = root;
+    this.#effects = effects.all.toArray();
+    this.#didUpdate = true;
+
+    window.requestAnimationFrame(() => this.#tick());
+  }
+
+  send(action) {
+    switch (true) {
+      case action instanceof Dispatch: {
+        this.#queue.push(action[0]);
+        this.#tick();
+
+        return;
+      }
+
+      case action instanceof Shutdown: {
+        this.#shutdown();
+        return;
+      }
+
+      default:
+        return;
+    }
+  }
+
+  emit(event, data) {
+    this.#root.dispatchEvent(
+      new CustomEvent(event, {
+        bubbles: true,
+        detail: data,
+        composed: true,
+      })
+    );
+  }
+
+  #tick() {
+    this.#flush_queue();
+
+    if (this.#didUpdate) {
+      const vdom = this.#view(this.#model);
+
+      this.#didUpdate = false;
+      this.#root = morph(this.#root, vdom, (msg) => {
+        this.send(new Dispatch(msg));
+      });
+    }
+  }
+
+  #flush_queue(iterations = 0) {
+    while (this.#queue.length) {
+      const [next, effects] = this.#update(this.#model, this.#queue.shift());
+
+      this.#model = next;
+      this.#didUpdate ||= isEqual(this.#model, next);
+      this.#effects = this.#effects.concat(effects.all.toArray());
+    }
+
+    while (this.#effects.length) {
+      this.#effects.shift()(
+        (msg) => this.send(new Dispatch(msg)),
+        (event, data) => this.emit(event, data)
+      );
+    }
+
+    if (this.#queue.length) {
+      if (iterations < 5) {
+        this.#flush_queue(++iterations);
+      } else {
+        window.requestAnimationFrame(() => this.#tick());
+      }
+    }
+  }
+
+  #shutdown() {
+    this.#root.remove();
+    this.#root = null;
+    this.#model = null;
+    this.#queue = [];
+    this.#effects = [];
+    this.#didUpdate = false;
+    this.#update = () => {};
+    this.#view = () => {};
+  }
+}
+
+export const start = (app, selector, flags) =>
+  LustreClientApplication.start(
+    flags,
+    selector,
+    app.init,
+    app.update,
+    app.view
+  );
+
+// UTILS -----------------------------------------------------------------------
+
+export const is_browser = () => window && window.document;
+export const is_registered = (name) =>
+  is_browser() && !!window.customElements.get(name);
+export const prevent_default = (event) => event.preventDefault();
+export const stop_propagation = (event) => event.stopPropagation();