1 files changed, 58 insertions, 0 deletions
diff --git a/src/reCAPTCHA.ts b/src/reCAPTCHA.ts
new file mode 100644
index 0000000..51a6350
--- /dev/null
+++ b/src/reCAPTCHA.ts
@@ -0,0 +1,58 @@
+// handles dynamic reCAPTCHA loading
+
+const loadHandler = "onRecaptchaLoad";
+const script = `https://www.google.com/recaptcha/api.js?onload=${loadHandler}`;
+
+export default class ReCaptchaLoader {
+	/**
+	 * asynchronously injects reCAPTCHA and resolves once fully loaded
+	 *
+	 * @return {Promise<Object>} the grecaptcha inferface
+	 */
+	static load () {
+		return new Promise((resolve, reject) => {
+			if (Reflect.has(self, "grecaptcha")) {
+				// we already have it loaded: reset it
+				this.instance.reset();
+				return resolve(this.instance);
+			}
+
+			let el: HTMLScriptElement|null = document.querySelector(`script[src="${script}"]`);
+
+			if (el) {
+				// already loading: don't attempt another load
+				return;
+			} else {
+				el = document.createElement("script");
+				el.type = "text/javascript";
+				el.async = true;
+				el.src = script;
+			}
+
+			// create a load handler:
+			Reflect.set(self, loadHandler, () => {
+				resolve(this.instance);
+				Reflect.deleteProperty(self, loadHandler);
+			});
+
+			// attach the handlers:
+			el.addEventListener("error", reject);
+			el.addEventListener("abort", reject);
+			// no listener for "load": we rely on reCAPTCHA to self-report loading
+
+			// inject the tag and begin loading
+			document.head.appendChild(el);
+		});
+	}
+
+	/**
+	 * checks whether reCAPTCHA is ready to use
+	 */
+	static get isReady () {
+		return Reflect.has(self, "grecaptcha");
+	}
+
+	static get instance () {
+		return this.isReady ? Reflect.get(self, "grecaptcha"): null;
+	}
+}