Switch from unwrap() to expect()

src/main.rs

@@ -1,5 +1,8 @@
+use std::collections::HashSet;
 use std::env;
 
+use rand::RngCore;
+
 fn main() {
     // Take in two command line arguments, one i32 and one optional String
     let args: Vec<String> = env::args().collect();
@@ -18,15 +21,17 @@ fn main() {
     // Disallowed_chars is an optional argument
     let disallowed_chars: Option<&String> = args.get(2);
 
-    let mut allowed_chars: String = String::from("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890-=`~!@#$%^&*()_+[]\\{}|;':,./<>?");
+    let allowed_chars: String = String::from("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890-=`~!@#$%^&*()_+[]\\{}|;':,./<>?");
+
+    let mut allowed_chars_set: HashSet<char> = allowed_chars.chars().collect();
 
     // Remove disallowed characters from allowed_characters if disallowed_chars is specified
     if let Some(disallowed_chars) = disallowed_chars {
         for disallowed_char in disallowed_chars.chars() {
-            allowed_chars = allowed_chars.replace(disallowed_char, "");
+            allowed_chars_set.remove(&disallowed_char);
         }
 
-        if allowed_chars.len() == 0 { // Make sure there are still characters left to use
+        if allowed_chars_set.len() == 0 { // Make sure there are still characters left to use
             println!("Error: You have disallowed all characters");
             println!("The allowed character set includes: abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890-=`~!@#$%^&*()_+[]\\{{}}|;':,./<>?");
             return;
@@ -34,13 +39,14 @@ fn main() {
     }
 
     if let Some(new_password_length) = new_password_length { // Unwrap Option in i32
+        let mut rng = rand::thread_rng();
         // Generate a random string of length n
         let mut new_password = String::new();
         for _ in 0..new_password_length {
             new_password.push(
-                allowed_chars.chars()
+                *allowed_chars_set.iter()
-                    .nth(rand::random::<usize>() % allowed_chars.len())
+                    .nth(rng.next_u32() as usize % allowed_chars_set.len())
-                    .unwrap()
+                    .expect("Error: Invalid index")
             );
         }