add filters download and updating

scripts/filters.js

@@ -0,0 +1,79 @@
+/* filters.js
+Manage filters.
+*/
+
+/* Select the most appropriate filter based on a URL.
+
+@param {string} URL the current URL
+*/
+export async function select(URL = window.location.href) {}
+
+/* Update all filters or just one.
+
+@param {string} URL the URL to update
+@return {boolean} the state
+*/
+export async function update(URL) {
+  console.log("Updating…");
+  // Import the updater.
+  const secretariat = await import(
+    chrome.runtime.getURL("scripts/secretariat.js")
+  );
+  const net = await import(chrome.runtime.getURL("scripts/net.js"));
+
+  // Apparently, JS doesn't have a native queueing system, but it might best work here.
+  class Queue {
+    constructor() {
+      this.elements = [];
+    }
+
+    enqueue(element) {
+      this.elements.push(element);
+    }
+
+    dequeue() {
+      return this.elements.shift();
+    }
+
+    isEmpty() {
+      return this.elements.length <= 0;
+    }
+  }
+
+  // Create a queue of the filters.
+  let filters = new Queue();
+
+  async function download(URL) {
+    let filter = await fetch(URL);
+
+    // Return the filter.
+    return filter;
+  }
+
+  if (URL) {
+    // Check if the URL is in a valid protocol
+    if (URL.includes(`://`)) {
+      // Append that to the queue.
+      filters.enqueue(URL);
+    }
+  } else {
+    // Add every item to the queue based on what was loaded first.
+    if ((await Promise.all([secretariat.read(`filters`, -1)]))[0]) {
+      Object.keys(
+        (await Promise.all([secretariat.read(`filters`, -1)]))[0],
+      ).every((filter_URL) => {
+        if (filter_URL.includes(`://`)) {
+          filters.enqueue(filter_URL);
+        }
+      });
+    }
+  }
+
+  while (!filters.isEmpty()) {
+    let filter_URL = filters.dequeue();
+    let filter = await net.download(filter_URL);
+
+    // Write the filter to storage.
+    secretariat.write(["filters", filter_URL], filter, -1);
+  }
+}