1 files changed, 21 insertions, 13 deletions

diff --git a/src/flags.rs b/src/flags.rs
index 91acf3a..9432b8f 100644
--- a/src/flags.rs
+++ b/src/flags.rs
@@ -5,7 +5,7 @@ pub struct Flags {
   pub arg_count: usize
 }
 
-pub fn parse(args: &[String]) -> Flags {
+pub fn parse(args: &[String]) -> Option<Flags> {
   let mut flags = Flags { 
     help: false, 
     version: false,
@@ -17,15 +17,21 @@ pub fn parse(args: &[String]) -> Flags {
     flags.arg_count += 1;
     if arg.starts_with("--") {
       let flag = &arg[2..];
-      check_flag(&flag, &mut flags);
+      if !set_flag(&flag, &mut flags) {
+        eprintln!("Invalid argument: {}", arg);
+        return None
+      }
     } else {
       let flag = &arg[1..];
       for char in flag.chars() {
-        check_flag(&char.to_string(), &mut flags);
+        if !set_flag(&char.to_string(), &mut flags) {
+            eprintln!("Invalid argument: {}", arg);
+            return None
+        }
       }
     }
   }
-  flags
+  Some(flags)
 }
 
 fn is_arg(arg: &str) -> bool {
@@ -36,16 +42,18 @@ const HELP_FLAG:              &str = "help h";
 const VERSION_FLAG:           &str = "version v";
 const DONT_PERSIST:           &str = "d";
 
-fn check_flag(arg: &str, flags: &mut Flags) {
+fn set_flag(arg: &str, flags: &mut Flags) -> bool {
   if has_flag_set(&arg, HELP_FLAG) {
-    flags.help = true
-  }
-  if has_flag_set(&arg, VERSION_FLAG) {
-    flags.version = true
-  }
-  if has_flag_set(&arg, DONT_PERSIST) {
-    flags.dont_persist = true
+    flags.help = true;
+    return true
+  } else if has_flag_set(&arg, VERSION_FLAG) {
+    flags.version = true;
+    return true
+  } else if has_flag_set(&arg, DONT_PERSIST) {
+    flags.dont_persist = true;
+    return true
   }
+  false
 }
 
 fn has_flag_set(arg: &str, check: &str) -> bool {
@@ -55,4 +63,4 @@ fn has_flag_set(arg: &str, check: &str) -> bool {
     }
   }
   return false
-}
\ No newline at end of file
+}