refactored domain processing code

lib/utils.js

@@ -1,3 +1,8 @@
+import { once } from "events";
+import { createReadStream } from "fs";
+import { basename } from "path";
+import { createInterface } from "readline";
+
 /**
  * Sleeps for a specified amount of time.
  * @param {number} [ms=350] The amount of time in ms.
@@ -6,9 +11,47 @@ export const sleep = (ms = 350) =>
   new Promise((resolve) => setTimeout(resolve, ms));
 
 /**
- * Truncates an array to the specified size.
- * @param {any[]} arr The array to be truncated.
- * @param {number} size The size to which the array will be truncated.
- * @returns {any[]}
+ * Checks if the value is a valid domain.
+ * @param {string} value The value to be checked.
  */
-export const truncateArray = (arr, size) => arr.slice(0, size);
+export const isValidDomain = (value) =>
+  /^(?!-)[A-Za-z0-9-]+([\-\.]{1}[a-z0-9]+)*\.[A-Za-z]{2,6}$/.test(value);
+
+/**
+ * Checks if the value is a comment.
+ * @param {string} value The value to be checked.
+ */
+export const isComment = (value) =>
+  value.startsWith("#") ||
+  value.startsWith("//") ||
+  value.startsWith("!") ||
+  value.startsWith("/*") ||
+  value.startsWith("*/");
+
+/**
+ * @callback onLine
+ * @param {string} line The current line.
+ * @param {ReturnType<createInterface>} rl The readline interface.
+ */
+
+/**
+ * Asynchronously reads a file line by line.
+ * @param {string} filePath The path to the file.
+ * @param {onLine} onLine The callback executed on each line read.
+ */
+export const readFile = async (filePath, onLine) => {
+  try {
+    const rl = createInterface({
+      input: createReadStream(filePath),
+      crlfDelay: Infinity,
+    });
+
+    rl.on("line", (line) => onLine(line, rl));
+
+    await once(rl, "close");
+  } catch (err) {
+    console.error(
+      `Error occurred while reading ${basename(filePath)} - ${err.toString()}`
+    );
+  }
+};