refactor(cli): improve argument parsing and update special characters

- Enhance CLI handling in main.cpp with better error messages, default length as size_t, and proper option validation
- Simplify special characters in passwdgen.cpp to a safer, common subset

src/main.cpp

@@ -7,38 +7,42 @@
 #include <string>
 
 int main(int argc, char *argv[]) {
-    int passwordLength = 0;
+    std::string progname(argv[0]);
+    size_t passwordLength = 32;
     bool punc = false;
 
-    if (argc < 1) {
-        std::cout << random_string(32, false) << std::endl;
-        return 0;
-    }
-    for (int i = 1; i < argc; ++i) {
+    int i = 1;
+    while (i < argc) {
         std::string arg = argv[i];
-        if ((arg == "-h") || (arg == "--help")) {
-            show_usage(argv[0]);
+        if (arg == "-h" || arg == "--help") {
+            show_usage(progname);
             return 0;
-        }
-        if (arg == "-p") {
+        } else if (arg == "-p" || arg == "--punctuation") {
             punc = true;
-        } else if ((arg == "-l") || (arg == "--length")) {
-            if (not argv[i +1]) {
-                std::cerr << "Specify a password length" << std::endl;
+            ++i;
+        } else if (arg == "-l" || arg == "--length") {
+            if (++i >= argc) {
+                std::cerr << progname << ": error: option requires an argument -- " << arg << std::endl;
+                show_usage(progname);
                 return 1;
             }
-            std::string passwordLengthStr = argv[i + 1];
             try {
-                passwordLength = std::stoi(passwordLengthStr);
-            } catch ([[maybe_unused]] const std::invalid_argument& e){
-                std::cerr << "Length must be a valid integer" << std::endl;
+                int tmp = std::stoi(argv[i]);
+                if (tmp < 1) {
+                    std::cerr << progname << ": invalid argument '" << argv[i] << "' for option " << arg << ": value too small" << std::endl;
                     return 1;
                 }
+                passwordLength = static_cast<size_t>(tmp);
+            } catch (const std::exception& e) {
+                std::cerr << progname << ": invalid argument '" << argv[i] << "' for option " << arg << ": " << e.what() << std::endl;
+                return 1;
             }
+            ++i;
+        } else {
+            std::cerr << progname << ": unrecognized option '" << arg << "'" << std::endl;
+            show_usage(progname);
+            return 1;
         }
-
-    if (passwordLength == 0) {
-        passwordLength = 32;
     }
     std::string password = random_string(passwordLength, punc);
     std::cout << password << std::endl;

src/passwdgen.cpp

@@ -6,7 +6,7 @@
 std::string random_string(std::size_t length, bool punc) {
     std::string CHARACTERS;
     std::string ALPHANUM = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
-    const std::string SPECIALS = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~";
+    const std::string SPECIALS = "!@#$%^&*()_+-=[]{}|;:,./?";
 
     if (punc) {
         CHARACTERS = ALPHANUM.append(SPECIALS);