diff --git a/src/lib/cli.cpp b/src/lib/cli.cpp
index 32047f7..a9ca296 100644
--- a/src/lib/cli.cpp
+++ b/src/lib/cli.cpp
@@ -13,13 +13,12 @@
 // version 3 along with this program.
 // If not, see https://www.gnu.org/licenses/agpl-3.0.en.html
 
-#include "cli.h++"
-
 #include <string>
 #include <vector>
 #include <map>
 
-#include "error.h++"
+#include "cli.hpp"
+#include "error.hpp"
 
 namespace CLI {
     Flag::Flag() {
diff --git a/src/lib/cli.h++ b/src/lib/cli.h++
index 93f3ee9..25e79e7 100644
--- a/src/lib/cli.h++
+++ b/src/lib/cli.h++
@@ -19,7 +19,7 @@
 #include <vector>
 #include <map>
 
-#include "error.h++"
+#include "error.hpp"
 
 namespace CLI {
 
diff --git a/src/lib/cli.hpp b/src/lib/cli.hpp
new file mode 100644
index 0000000..25e79e7
--- /dev/null
+++ b/src/lib/cli.hpp
@@ -0,0 +1,94 @@
+// Copyright 2022, FOSS-VG Developers and Contributers
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, version 3.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// version 3 along with this program.
+// If not, see https://www.gnu.org/licenses/agpl-3.0.en.html
+
+#pragma once
+
+#include <string>
+#include <vector>
+#include <map>
+
+#include "error.hpp"
+
+namespace CLI {
+
+    struct Flag {
+        char shortName;
+        std::string longName;
+        // used for automatic usage generation
+        std::string description;
+
+        bool present;
+
+        Flag();
+        Flag(char shortName, std::string longName, std::string description);
+    };
+
+    struct Option {
+        char shortName;
+        std::string longName;
+        // used for automatic usage generation
+        std::string description;
+        std::string placeholder; // the "COUNT" in "ping [-c <COUNT>] <HOST>"
+
+        bool present;
+        std::string value;
+
+        Option();
+        Option(char shortName, std::string longName, std::string placeholder, std::string description);
+    };
+
+    struct Argument {
+        // used for automatic usage generation
+        std::string description;
+        std::string placeholder; // the "HOST" in "ping [-c <COUNT>] <HOST>"
+
+        bool present;
+        std::string value;
+
+        Argument();
+        Argument(std::string placeholder, std::string description);
+    };
+
+    class ArgumentsParser {
+        private:
+            std::map<char, Flag*> flagsByShortName;
+            std::map<std::string, Flag*> flagsByLongName;
+            std::map<char, Option*> optionsByShortName;
+            std::map<std::string, Option*> optionsByLongName;
+            std::vector<Argument> arguments;
+            std::string description;
+            std::string additionalInfo;
+
+        public:
+            std::string programName;
+            bool wrongUsage;
+            std::vector<std::string> wrongUsageMessages;
+
+            // using int here bc that's how main() is defined
+            ArgumentsParser(int argc, const char* const argv[], std::vector<Flag> flags, std::vector<Option> options, std::vector<Argument> arguments);
+            ArgumentsParser(int argc, const char* const argv[], std::vector<Flag> flags, std::vector<Option> options, std::vector<Argument> arguments, std::string description);
+            ArgumentsParser(int argc, const char* const argv[], std::vector<Flag> flags, std::vector<Option> options, std::vector<Argument> arguments, std::string description, std::string additionalInfo);
+            ~ArgumentsParser();
+
+            ErrorOr<bool> getFlag(char shortName);
+            ErrorOr<bool> getFlag(std::string longName);
+            ErrorOr<std::string> getArgument(std::vector<CLI::Argument>::size_type position);
+            ErrorOr<std::string> getOption(char shortName);
+            ErrorOr<std::string> getOption(std::string longName);
+
+            std::string getUsage();
+    };
+
+}
diff --git a/src/lib/error.h++ b/src/lib/error.hpp
similarity index 100%
rename from src/lib/error.h++
rename to src/lib/error.hpp
diff --git a/src/lib/javacompat.cpp b/src/lib/javacompat.cpp
index 5d9ca08..6fa26b7 100644
--- a/src/lib/javacompat.cpp
+++ b/src/lib/javacompat.cpp
@@ -15,8 +15,8 @@
 
 #include <tinyutf8/tinyutf8.h>
 #include <string>
-#include "error.h++"
-#include "javacompat.h++"
+#include "error.hpp"
+#include "javacompat.hpp"
 #include "../../.endianness"
 
 #ifdef FOSSVG_ENDIAN_BIG_WORD
diff --git a/src/lib/javacompat.h++ b/src/lib/javacompat.hpp
similarity index 97%
rename from src/lib/javacompat.h++
rename to src/lib/javacompat.hpp
index 5e9c7c3..0e1ccbe 100644
--- a/src/lib/javacompat.h++
+++ b/src/lib/javacompat.hpp
@@ -13,9 +13,9 @@
 //version 3 along with this program.
 //If not, see https://www.gnu.org/licenses/agpl-3.0.en.html
 
-#include <tinyutf8/tinyutf8.h>
-#include "error.h++"
 #include <vector>
+#include <tinyutf8/tinyutf8.h>
+#include "error.hpp"
 
 namespace JavaCompat {
     ErrorOr<tiny_utf8::string> importJavaString(uint8_t data[], uint16_t size);
diff --git a/src/lib/nbt.cpp b/src/lib/nbt.cpp
index adc2473..427c109 100644
--- a/src/lib/nbt.cpp
+++ b/src/lib/nbt.cpp
@@ -19,9 +19,9 @@
 #include <tinyutf8/tinyutf8.h>
 #include <iostream>
 
-#include "nbt.h++"
-#include "error.h++"
-#include "javacompat.h++"
+#include "nbt.hpp"
+#include "error.hpp"
+#include "javacompat.hpp"
 
 
 #include "../../.endianness"
@@ -156,7 +156,7 @@ namespace NBT {
             if(dataSize > 0xFFFF){
                 return ErrorOr<tiny_utf8::string>(true, ErrorCodes::OVERRUN);
             }
-            
+
             ErrorOr<tiny_utf8::string> output = JavaCompat::importJavaString(data+currentPosition, (uint16_t) dataSize);
             if(output.isError){
                 return ErrorOr<tiny_utf8::string>(true, output.errorCode);
diff --git a/src/lib/nbt.h++ b/src/lib/nbt.hpp
similarity index 99%
rename from src/lib/nbt.h++
rename to src/lib/nbt.hpp
index 2b29151..6eca6db 100644
--- a/src/lib/nbt.h++
+++ b/src/lib/nbt.hpp
@@ -37,8 +37,8 @@
 #pragma once
 #include <cstdint>
 #include <vector>
-#include "error.h++"
 #include <tinyutf8/tinyutf8.h>
+#include "error.hpp"
 
 namespace NBT {
     namespace helper {
diff --git a/src/test/assert.h++ b/src/test/assert.hpp
similarity index 100%
rename from src/test/assert.h++
rename to src/test/assert.hpp
diff --git a/src/test/cli_argument_parser.cpp b/src/test/cli_argument_parser.cpp
index e4cd3fc..c58ae32 100644
--- a/src/test/cli_argument_parser.cpp
+++ b/src/test/cli_argument_parser.cpp
@@ -16,10 +16,10 @@
 #include <string>
 #include <iostream>
 #include <vector>
-#include "assert.h++"
-#include "../lib/error.h++"
+#include "assert.hpp"
+#include "../lib/error.hpp"
 
-#include "../lib/cli.h++"
+#include "../lib/cli.hpp"
 
 int main() {
     std::cout << "################################################################################" << std::endl;
diff --git a/src/test/javacompat.cpp b/src/test/javacompat.cpp
index e8c08e9..7ddda95 100644
--- a/src/test/javacompat.cpp
+++ b/src/test/javacompat.cpp
@@ -13,12 +13,12 @@
 // version 3 along with this program.
 // If not, see https://www.gnu.org/licenses/agpl-3.0.en.html
 
-#include "assert.h++"
-#include "../lib/javacompat.h++"
 #include <iostream>
 #include <tinyutf8/tinyutf8.h>
 #include <fstream>
 #include <vector>
+#include "assert.hpp"
+#include "../lib/javacompat.hpp"
 
 
 int main(){
diff --git a/src/test/nbt_helpers.cpp b/src/test/nbt_helpers.cpp
index edcb82e..803bfd5 100644
--- a/src/test/nbt_helpers.cpp
+++ b/src/test/nbt_helpers.cpp
@@ -18,11 +18,11 @@
 #include <vector>
 #include <fstream>
 
-#include "assert.h++"
+#include "assert.hpp"
 
-#include "../lib/nbt.h++"
-#include "../lib/error.h++"
-#include "../lib/javacompat.h++"
+#include "../lib/nbt.hpp"
+#include "../lib/error.hpp"
+#include "../lib/javacompat.hpp"
 
 int main(){
     std::cout << "################################################################################" << std::endl;
diff --git a/src/test/nbt_writestring_failure_mode.cpp b/src/test/nbt_writestring_failure_mode.cpp
index 68c0307..93b7d09 100644
--- a/src/test/nbt_writestring_failure_mode.cpp
+++ b/src/test/nbt_writestring_failure_mode.cpp
@@ -1,9 +1,9 @@
 #include <string>
 #include <vector>
 #include <iostream>
-#include "../lib/nbt.h++"
-#include "../lib/error.h++"
-#include "../lib/javacompat.h++"
+#include "../lib/nbt.hpp"
+#include "../lib/error.hpp"
+#include "../lib/javacompat.hpp"
 
 int main() {
     std::cout << "================================================================================" << std::endl;
diff --git a/src/tools/dumpnbt.cpp b/src/tools/dumpnbt.cpp
index 0540282..eed0487 100644
--- a/src/tools/dumpnbt.cpp
+++ b/src/tools/dumpnbt.cpp
@@ -13,7 +13,7 @@
 // version 3 along with this program.
 // If not, see https://www.gnu.org/licenses/agpl-3.0.en.html
 
-#include "../lib/nbt.h++"
+#include "../lib/nbt.hpp"
 
 int main(int argc, char* argv[]) {
     return 0;
diff --git a/src/tools/hexnet.cpp b/src/tools/hexnet.cpp
index 3676841..9e43aa9 100644
--- a/src/tools/hexnet.cpp
+++ b/src/tools/hexnet.cpp
@@ -23,8 +23,8 @@
 #include <mutex>
 #include <csignal>
 
-#include "../lib/error.h++"
-#include "../lib/cli.h++"
+#include "../lib/error.hpp"
+#include "../lib/cli.hpp"
 
 #define EXIT_SUCCESS 0
 #define EXIT_RUNTIME 1