1 files changed, 87 insertions, 0 deletions
diff --git a/toolkit/components/satchel/FormScenarios.sys.mjs b/toolkit/components/satchel/FormScenarios.sys.mjs
new file mode 100644
index 0000000000..505b5443ec
--- /dev/null
+++ b/toolkit/components/satchel/FormScenarios.sys.mjs
@@ -0,0 +1,87 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { FormLikeFactory } from "resource://gre/modules/FormLikeFactory.sys.mjs";
+import { SignUpFormRuleset } from "resource://gre/modules/SignUpFormRuleset.sys.mjs";
+import { FirefoxRelayUtils } from "resource://gre/modules/FirefoxRelayUtils.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+export class FormScenarios {
+  /**
+   * Caches the scores when running the SignUpFormRuleset against a form
+   */
+  static #cachedSignUpFormScore = new WeakMap();
+
+  /**
+   * Detect usage scenarios of the form.
+   *
+   * @param {object} options named options
+   * @param {HTMLInputElement} [options.input] where current focus is
+   * @param {FormLike} [options.form]
+   *
+   * @returns {Array<string>} detected scenario names
+   */
+  static detect({ input, form }) {
+    const scenarios = {};
+
+    if (!FormScenarios.signupDetectionEnabled) {
+      return scenarios;
+    }
+
+    // Running simple heuristics first, because running the SignUpFormRuleset is expensive
+    if (
+      input &&
+      // At the moment Relay integration is the only interested party in "sign up form",
+      // so we optimize a bit by checking if it's enabled or not.
+      FirefoxRelayUtils.isRelayInterestedField(input)
+    ) {
+      form ??= FormLikeFactory.findRootForField(input);
+
+      scenarios.signUpForm = FormScenarios.#isProbablyASignUpForm(form);
+    }
+
+    return scenarios;
+  }
+
+  /**
+   * Determine if the form is a sign-up form.
+   * This is done by running the rules of the Fathom SignUpFormRuleset against the form and calucating a score between 0 and 1.
+   * It's considered a sign-up form, if the score is higher than the confidence threshold (default=0.75)
+   *
+   * @param {HTMLFormElement} formElement
+   * @returns {boolean} returns true if the calculcated score is higher than the confidenceThreshold
+   */
+  static #isProbablyASignUpForm(formElement) {
+    let score = FormScenarios.#cachedSignUpFormScore.get(formElement);
+    if (!score) {
+      TelemetryStopwatch.start("PWMGR_SIGNUP_FORM_DETECTION_MS");
+      try {
+        const { rules, type } = SignUpFormRuleset;
+        const results = rules.against(formElement);
+        score = results.get(formElement).scoreFor(type);
+        TelemetryStopwatch.finish("PWMGR_SIGNUP_FORM_DETECTION_MS");
+      } finally {
+        if (TelemetryStopwatch.running("PWMGR_SIGNUP_FORM_DETECTION_MS")) {
+          TelemetryStopwatch.cancel("PWMGR_SIGNUP_FORM_DETECTION_MS");
+        }
+      }
+      FormScenarios.#cachedSignUpFormScore.set(formElement, score);
+    }
+
+    const threshold = FormScenarios.signupDetectionConfidenceThreshold;
+    return score > threshold;
+  }
+}
+XPCOMUtils.defineLazyPreferenceGetter(
+  FormScenarios,
+  "signupDetectionConfidenceThreshold",
+  "signon.signupDetection.confidenceThreshold",
+  "0.75"
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  FormScenarios,
+  "signupDetectionEnabled",
+  "signon.signupDetection.enabled",
+  true
+);