Add cli input handler

Also check for directories
Also add a small help

cli.js

@@ -1,10 +1,16 @@
-import { readFile, writeFile } from 'node:fs/promises';
+#!/usr/bin/env node
+
+import { readFile, writeFile, stat } from 'node:fs/promises';
+import { argv, exit } from 'node:process';
 import { convert } from './magic.js';
 
 async function reader(path) {
     try {
+        const preFlighCheck = await stat(path);
+        const isUsable = preFlighCheck.isFile() && !preFlighCheck.isDirectory()
+        if (!isUsable)
+            return "";
         const contents = await readFile(path, { encoding: 'utf8' });
-        //   console.log(contents)
         return contents;
     } catch (err) {
         console.error(err.message);
@@ -13,6 +19,10 @@ async function reader(path){
 
 async function writer(path, content) {
     try {
+        const preFlighCheck = await stat(path);
+        const isUsable = preFlighCheck.isFile() && !preFlighCheck.isDirectory()
+        if (!isUsable)
+            return;
         await writeFile(path, content, { encoding: 'utf8' });
     } catch (err) {
         console.error(err.message);
@@ -22,15 +32,34 @@ async function writer(path, content){
 
 function convertForConsole(convertFunction) {
     return async function (filePath) {
-        const sourceFile = await reader("./systemd-unit.conf");
+        const sourceFile = await reader(filePath);
         const converted = convertFunction(sourceFile);
         await writer("./init.conf", converted.result)
     }
 }
 
-async function setup(){
+async function setup(input, output) {
     const convertFunction = convertForConsole(convert)
-    convertFunction();
+    convertFunction(input);
 }
 
-setup();
+const [, , input, output] = argv;
+
+// print process.argv
+// argv.forEach((val, index) => {
+//   console.log(`${index}: ${val}`);
+// });
+// exit(0);
+if (input === "-h" || input === '--help' || argv.length < 3) {
+    console.info(`
+Convert systemd service unit to openrc
+
+    usage: 
+cli.js <input-systemd-unit> <output-init-file> 
+
+    example: 
+cli.js systemd.unit init.conf
+`)
+    exit();
+}
+setup(input, output);