Add settings configuration, not using it yet

options/options.js

@@ -0,0 +1,60 @@
+/*
+Store the currently selected settings using browser.storage.local.
+*/
+function storeSettings() {
+
+  function getSince() {
+    const proxy_scheme = document.querySelector("#proxy_scheme");
+    return proxy_scheme.value;
+  }
+
+  function getTypes() {
+    let proxy_value = [];
+    const textboxes = document.querySelectorAll(".proxy-options [type=text]");
+    for (let item of textboxes) {
+      if (item.checked) {
+        proxy_value.push(item.getAttribute("value"));
+      }
+    }
+    return proxy_value;
+  }
+
+  const proxy_scheme = getSince();
+  const proxy_value = getTypes();
+  browser.storage.local.set({
+    proxy_scheme,
+    proxy_value
+  });
+}
+
+/*
+Update the options UI with the settings values retrieved from storage,
+or the default settings if the stored settings are empty.
+*/
+function updateUI(restoredSettings) {
+  const selectList = document.querySelector("#proxy_scheme");
+  selectList.value = restoredSettings.proxy_scheme;
+
+  const textboxes = document.querySelectorAll(".proxy-options [type=text]");
+  for (let item of textboxes) {
+    if (restoredSettings.proxy_value.indexOf(item.getAttribute("value")) != -1) {
+      item.value = restoredSettings.proxy_value.indexOf(item.getAttribute("value"));
+    }
+  }
+}
+
+function onError(e) {
+  console.error(e);
+}
+
+/*
+On opening the options page, fetch stored settings and update the UI with them.
+*/
+const gettingStoredSettings = browser.storage.local.get();
+gettingStoredSettings.then(updateUI, onError);
+
+/*
+On clicking the save button, save the currently selected settings.
+*/
+const saveButton = document.querySelector("#save-button");
+saveButton.addEventListener("click", storeSettings);