Extract CaptureButton; allow non-singletone connections

ui/ops.js

@@ -2,43 +2,39 @@ import initModule from '../libapi.mjs';
 
 /** @typedef {import('../libapi.mjs').Context} Context */
 
-/** This function should be called once user has selected the camera and other operations can begin. */
-export let start;
+const ContextPromise = initModule().then(Module => Module.Context);
 
-let started = new Promise(resolve => {
-  start = resolve;
-});
+export async function connect() {
+  let Context = await ContextPromise;
 
-let queue = (async () => {
-  let { Context } = await initModule();
-  await started;
-  let ctx = await new Context();
-  addEventListener('beforeunload', e => {
-    ctx.delete();
-  });
-  return ctx;
-})();
+  let context = await new Context();
 
-/** Schedules an exclusive async operation on the global context.
- * @template T
- * @param {(ctx: Context) => Promise<T>} op
- * @returns {Promise<T>}
- */
-export function scheduleOp(op) {
-  let caughtRes = queue.then(async ctx => {
-    let resultPromise = op(ctx);
-    try {
-      await resultPromise;
-    } catch {}
-    return {
-      ctx,
-      resultPromise
-    };
-  });
+  let queue = Promise.resolve();
 
-  // Queue should ignore result values as well as errors from singular ops.
-  queue = caughtRes.then(res => res.ctx);
+  /** Schedules an exclusive async operation on the global context.
+   * @template T
+   * @param {(ctx: Context) => Promise<T>} op
+   * @returns {Promise<T>}
+   */
+  function schedule(op) {
+    let res = queue.then(() => op(context));
 
-  // Result should contain the unwrapped value or error.
-  return caughtRes.then(res => res.resultPromise);
+    // Queue should ignore result values as well as errors from singular ops.
+    queue = res.then(
+      () => {},
+      () => {}
+    );
+
+    // Result should contain the unwrapped value or error.
+    return res;
+  }
+
+  return {
+    schedule,
+    disconnect() {
+      context.delete();
+    }
+  };
 }
+
+/** @typedef {ReturnType<typeof connect> extends Promise<infer Connection> ? Connection : never} Connection */