Added server address input validation.

public/_locales/en/messages.json

@@ -400,9 +400,12 @@
         "message": "SponsorBlock Server Address"
     },
     "customServerAddressDescription": {
-        "message": "The address SponsorBlock uses to make calls to the server.\nIt must be formatted https://domain with no trailing forward slash (/).\nUnless you have your own server instance, this should not be changed."
+        "message": "The address SponsorBlock uses to make calls to the server.\nUnless you have your own server instance, this should not be changed."
     },
     "saveCustomServerAddress": {
         "message": "Save"
+    },
+    "customAddressError": {
+        "message": "This address is not in the right form. Make sure you have http:// or https:// at the begining and no slashes or sub-folders at the end."
     }
 }

public/options/options.html

@@ -41,7 +41,7 @@
 			<br/>
 			<br/>
 	
-			<div option-type="text-change" sync-option="invidiousInstances">
+			<div option-type="private-text-change" sync-option="invidiousInstances">
 				<div class="option-button trigger-button">
 					__MSG_addInvidiousInstance__
 				</div>

src/options.ts

@@ -63,6 +63,20 @@ async function init() {
                 textInput.value = Config.config[textChangeOption];
 
                 setButton.addEventListener("click", () => {
+                    // See if anything extra must be done
+                    switch (textChangeOption) {
+                        case "serverAddress":
+                            let result = validateServerAddress(textInput.value);
+
+                            if (result !== null) {
+                                textInput.value = result;
+                            } else {
+                                return;
+                            }
+
+                            break;
+                    }
+
                     Config.config[textChangeOption] = textInput.value;
                 });
     
@@ -325,3 +339,27 @@ function activatePrivateTextChange(element: HTMLElement) {
 
     element.querySelector(".option-hidden-section").classList.remove("hidden");
 }
+
+/**
+ * Validates the value used for the database server address.
+ * Returns null and alerts the user if there is an issue.
+ * 
+ * @param input Input server address
+ */
+function validateServerAddress(input: string): string {
+    // Trim the last slash if needed
+    if (input.endsWith("/")) {
+        input = input.substring(0, input.length - 1);
+    }
+
+    // Isn't HTTP protocol or has extra slashes
+    if ((!input.startsWith("https://") && !input.startsWith("http://")) 
+        || input.replace("://", "").includes("/")) {
+
+        alert(chrome.i18n.getMessage("customAddressError"));
+
+        return null;
+    }
+
+    return input;
+}