diff --git a/CMakeLists.txt b/CMakeLists.txt
index 39aa735..5540b7e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,7 @@
 cmake_minimum_required(VERSION 3.31.2)
 
+include(FetchContent)
+
 set(BUILD_SHARED_LIBS OFF CACHE BOOL "Link libraries statically")
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "CNU|Clang")
@@ -12,8 +14,17 @@ if(MSVC)
 	set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 endif()
 
+
 #add_subdirectory("thirdparty/lib")
 
+FetchContent_Declare(
+    cxxopts
+    GIT_REPOSITORY https://github.com/jarro2783/cxxopts.git
+    GIT_TAG "v3.3.1"
+)
+
+FetchContent_MakeAvailable(cxxopts)
+
 project(oxygen LANGUAGES CXX)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
@@ -27,9 +38,16 @@ add_executable(oxygen "${MY_SOURCES}")
 target_compile_definitions("${CMAKE_PROJECT_NAME}" PUBLIC RESOURCE_PATH="${CMAKE_CURRENT_SOURCE_DIR}/resources/")
 #target_compile_definitions("${CMAKE_PROJECT_NAME}" PUBLIC RESOURCE_PATH="./resources/")
 
+# ----- Preprocessor -----
+if(include_dump_args_flag)
+    target_compile_definitions("${CMAKE_PROJECT_NAME}" PRIVATE DBG_OXY_DUMP_ARGS=1)
+endif()
+
 target_include_directories(oxygen PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/include/")
 #target_link_libraries(oxygen PRIVATE lib)
 
+target_link_libraries(oxygen PRIVATE cxxopts::cxxopts)
+
 # ----- LLVM ------
 find_package(LLVM REQUIRED CONFIG)
 
diff --git a/README.md b/README.md
index b4c9636..8c45857 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,3 @@
-
 # Oxygen
 
 A frankenstein compiler of C-like languages (C/C++) and Rust with its borrow system, using LLVM as backend.
@@ -11,21 +10,27 @@ A frankenstein compiler of C-like languages (C/C++) and Rust with its borrow sys
 The project rely on CMake and LLVM, specifically, CMake 3.31.2, LLVM 19 respectively.
 It also uses C++ 23 standartd.
 
-## Installation
+Other dependencies are downloaded using CMake.
+
+## Building
 
 First, ensure you have CMake, LLVM and any sutable C++ compiler installed.
 Then clone repo and run CMake
 
 ```bash
-  git clone ...
-  cd oxygen
   mkdir build/
   cd build
   cmake ..
   make
 ```
-    
+
 ## Usage/Examples
 
-Well, as the compiler in earliest stage of development, there aren't much of an example to give,
+The compiler accepts input file, as well as output file with `-o` flag.
+Warnings can be ignored using `--Wignore` or produce errors instead, with `--Werror` flags.
+
+If defined `DBG_OXY_DUMP_ARGS` in source, or `-Dinclude_dump_args_flag=1` in CMake via shell,
+the `-dArgs` flag will be availabe, to dump options structure.
+
+The compiler in earliest stage of development, so there aren't much of an example to give,
 nor what syntax or features it implies
diff --git a/include/Args/CompilerOptions.hpp b/include/Args/CompilerOptions.hpp
new file mode 100644
index 0000000..5b8a82f
--- /dev/null
+++ b/include/Args/CompilerOptions.hpp
@@ -0,0 +1,69 @@
+#pragma once
+
+#include "Diagnostic/DiagnosticLevel.hpp"
+#include "Diagnostic/DiagnosticsEngine.hpp"
+#include <iostream>
+#include <string>
+#include <cxxopts.hpp>
+
+struct CompilerOptions {
+    bool werror = false;    // Produce errors instead of warnings
+    bool wignore = false;   // Disable all warnings
+
+    std::string inputFile;
+    std::string outputFile = "a.out";
+
+    int context = 1;
+
+    /* -=-=-=- DEBUG -=-=-=- */
+    bool dumpArgs = false;
+};
+
+CompilerOptions parseArguments(int argc, char** argv) {
+    CompilerOptions opts;
+
+    cxxopts::Options options(argv[0], "Oxygen compiler");
+    options.positional_help("input file").show_positional_help();
+
+    options.add_options()
+        ("h,help", "Print help")
+
+        ("Wignore", "Disable all warnings", cxxopts::value<bool>(opts.wignore))
+        ("Werror", "Produce errors instead of warnings", cxxopts::value<bool>(opts.werror))
+
+        ("o", "Output file", cxxopts::value<std::string>(opts.outputFile))
+        ("input", "Input file", cxxopts::value<std::string>(opts.inputFile))
+
+        ("context", "Lines of context around diagnostic", cxxopts::value<int>(opts.context)->default_value("1"))
+
+#ifdef DBG_OXY_DUMP_ARGS
+        ("dArgs", "Dumps parsed arguments to standard output", cxxopts::value<bool>(opts.dumpArgs))
+#endif
+; // options.add_options()
+
+
+    options.parse_positional({"input"});
+
+    auto result = options.parse(argc, argv);
+
+    if (result.count("help")) {
+        std::cout << options.help() << "\n";
+        exit(0);
+    }
+
+    if (!result.count("input")) {
+        std::cerr << "No input file provded. Use --help\n";
+        exit(1);
+    }
+
+    if(opts.dumpArgs) {
+        std::cout << "PARSED ARGS:\n";
+        std::cout << "  Wignore -> " << opts.wignore << "\n";
+        std::cout << "  Werror -> " << opts.werror << "\n";
+        std::cout << "  output -> " << opts.outputFile << "\n";
+        std::cout << "  input -> " << opts.inputFile << "\n";
+        std::cout << "  context -> " << opts.context << "\n";
+    }
+
+    return opts;
+}
diff --git a/include/Diagnostic/Colors.hpp b/include/Diagnostic/Colors.hpp
new file mode 100644
index 0000000..d7defdf
--- /dev/null
+++ b/include/Diagnostic/Colors.hpp
@@ -0,0 +1,13 @@
+#pragma once
+
+namespace Colors {
+    constexpr const char* Reset = "\033[0m";
+    constexpr const char* Red = "\033[31m";
+    constexpr const char* Yellow = "\033[33m";
+    constexpr const char* Blue = "\033[34m";
+    constexpr const char* Cyan = "\033[36m";
+    constexpr const char* Gray = "\033[90m";
+
+    constexpr const char* Bold = "\033[1m";
+    constexpr const char* Underline = "\033[4m";
+}
diff --git a/include/Diagnostic/Diagnostic.hpp b/include/Diagnostic/Diagnostic.hpp
new file mode 100644
index 0000000..0b6979d
--- /dev/null
+++ b/include/Diagnostic/Diagnostic.hpp
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "Diagnostic/DiagnosticLevel.hpp"
+#include "Diagnostic/SourceLocation.hpp"
+#include "Diagnostic/DiagnosticNote.hpp"
+#include <string>
+#include <vector>
+
+struct Diagnostic {
+    DiagnosticLevel level;
+    SourceLocation loc;
+    std::string message;
+    std::string suggestion;
+    int length = 1;
+    std::vector<DiagnosticNote> notes;
+};
diff --git a/include/Diagnostic/DiagnosticLevel.hpp b/include/Diagnostic/DiagnosticLevel.hpp
new file mode 100644
index 0000000..9a986e9
--- /dev/null
+++ b/include/Diagnostic/DiagnosticLevel.hpp
@@ -0,0 +1,7 @@
+#pragma once
+
+enum class DiagnosticLevel {
+    Info,
+    Warning,
+    Error
+};
diff --git a/include/Diagnostic/DiagnosticNote.hpp b/include/Diagnostic/DiagnosticNote.hpp
new file mode 100644
index 0000000..edb2da7
--- /dev/null
+++ b/include/Diagnostic/DiagnosticNote.hpp
@@ -0,0 +1,10 @@
+#pragma once
+
+#include "Diagnostic/SourceLocation.hpp"
+#include <string>
+
+struct DiagnosticNote {
+    SourceLocation loc;
+    int length = 1;
+    std::string message;
+};
diff --git a/include/Diagnostic/DiagnosticsEngine.hpp b/include/Diagnostic/DiagnosticsEngine.hpp
new file mode 100644
index 0000000..c968599
--- /dev/null
+++ b/include/Diagnostic/DiagnosticsEngine.hpp
@@ -0,0 +1,196 @@
+#pragma once
+
+#include <algorithm>
+#include <iomanip>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include "Diagnostic/Diagnostic.hpp"
+#include "Diagnostic/SourceManager.hpp"
+#include "Diagnostic/DiagnosticLevel.hpp"
+#include "Diagnostic/SourceLocation.hpp"
+#include "Diagnostic/Colors.hpp"
+
+class DiagnosticsEngine {
+public:
+    DiagnosticsEngine(SourceManager& sm, int contextLines = 1, bool ignoreWarnings = false, bool warningsAreErrors = false)
+        : srcMgr(sm), context(contextLines), ignoreWarnings(ignoreWarnings), warningsAsErrors(warningsAreErrors) {}
+
+    void report(const Diagnostic& d) {
+        if (d.level == DiagnosticLevel::Warning && ignoreWarnings)
+            return;
+
+        Diagnostic newD;
+        if (d.level == DiagnosticLevel::Warning && warningsAsErrors) {
+            newD.loc = d.loc;
+            newD.level = DiagnosticLevel::Error;
+            newD.length = d.length;
+            newD.message = d.message;
+            newD.notes = d.notes;
+            newD.suggestion = d.suggestion;
+        } else {
+            newD = d;
+        }
+
+        diags.push_back(newD);
+        printDiagnostic(newD);
+    }
+
+    bool hasErrors() const {
+        for (auto &d : diags) {
+            if (d.level == DiagnosticLevel::Error)
+                return true;
+        }
+        return false;
+    }
+
+    void setContext(int ctx) { context = ctx; }
+
+private:
+    SourceManager& srcMgr;
+    int context;
+    std::vector<Diagnostic> diags;
+    bool ignoreWarnings = false;
+    bool warningsAsErrors = false;
+
+    static std::string expandTabs(const std::string& s, unsigned tabSize = 4) {
+        std::string out;
+        out.reserve(s.size());
+        unsigned col = 0;
+        for (char ch : s) {
+            if (ch == '\t') {
+                unsigned spaces = tabSize - (col % tabSize);
+                out.append(spaces, ' ');
+                col += spaces;
+            } else {
+                out.push_back(ch);
+                ++col;
+            }
+        }
+        return out;
+    }
+
+    static const char* levelToString(DiagnosticLevel level) {
+        switch (level) {
+            case DiagnosticLevel::Info: return "note";
+            case DiagnosticLevel::Warning: return "warning";
+            case DiagnosticLevel::Error: return "error";
+        }
+        return "";
+    }
+
+    static const char* levelColor(DiagnosticLevel level) {
+        switch (level) {
+            case DiagnosticLevel::Info: return Colors::Blue;
+            case DiagnosticLevel::Warning: return Colors::Yellow;
+            case DiagnosticLevel::Error: return Colors::Red;
+        }
+        return "";
+    }
+
+    void printDiagnostic(const Diagnostic& d) {
+        // header -> file:line:column: <level>: <message>
+        std::ostringstream header;
+        header << d.loc.file << ":" << d.loc.line << ":" << d.loc.column << ": ";
+
+        std::string lev = levelToString(d.level);
+        const char* color = levelColor(d.level);
+
+        std::cerr << color << header.str() << lev << ": " << Colors::Bold << d.message << Colors::Reset << "\n";
+
+        if (!d.suggestion.empty()) {
+            std::cerr << Colors::Gray << "  hint: " << Colors::Reset << d.suggestion << "\n";
+        }
+
+        printSourceSnippet(d.loc, d.length);
+
+        for(const auto &note : d.notes) {
+            std::ostringstream noteHeader;
+            noteHeader << note.loc.file << ":" << note.loc.line << ":" << note.loc.column << ": ";
+            std::cerr << Colors::Cyan << noteHeader.str() << "note: " << Colors::Reset << note.message << "\n";
+            printSourceSnippet(note.loc, note.length);
+        }
+    }
+
+    void printSourceSnippet(const SourceLocation& loc, int length) {
+        const auto& lines = srcMgr.getLines(loc.fileId);
+        if(lines.empty()) {
+            std::cerr << Colors::Gray << "  (source not available)\n" << Colors::Reset;
+            return;
+        }
+
+        int totalLines = (int)lines.size();
+        int lineIdx = std::max(1, loc.line);
+        if (lineIdx > totalLines) {
+            std::cerr << Colors::Gray << "  (location outside file: line " << loc.line << " > " << totalLines << ")\n" << Colors::Reset;
+            return;
+        }
+
+        int start = std::max(1, loc.line - context);
+        int end = std::min(totalLines, loc.line + context);
+
+        int width = 1;
+        int maxLine = end;
+        while(maxLine >= 10) { maxLine /= 10; ++width; }
+
+        for (int L = start; L <= end; ++L) {
+            std::string rawLine = lines[L - 1];
+            std::string expanded = expandTabs(rawLine);
+
+            std::ostringstream gutter;
+            if (L == loc.line) {
+                gutter << Colors::Red << ">" << Colors::Reset << " ";
+            } else {
+                gutter << "  ";
+            }
+
+            std::ostringstream ln;
+            ln << std::setw(width) << L;
+
+            std::cerr << gutter.str() << Colors::Gray << ln.str() << " | " << Colors::Reset;
+            //std::cerr << expanded << "\n";
+
+            if (L == loc.line) {
+                int col = std::max(1, loc.column);
+
+                int lineLen = (int)expanded.size();
+                int startCol = std::min(col, lineLen + 1);
+                int maxAvail = std::max(0, lineLen - (startCol - 1));
+                int caretCount = (length > 0) ? std::min(length, std::max(1, maxAvail)) : 1;
+
+                int prefixLen = (startCol > 1) ? startCol - 1 : 0;
+                if (prefixLen > expanded.size()) prefixLen = expanded.size();
+
+                int errorLen = 0;
+                if (prefixLen < expanded.size()) {
+                    errorLen = std::min((int)(expanded.size() - prefixLen), caretCount);
+                }
+
+                if (errorLen > 0) {
+                    std::cerr << expanded.substr(0, prefixLen) 
+                              << Colors::Bold << Colors::Red 
+                              << expanded.substr(prefixLen, errorLen) 
+                              << Colors::Reset 
+                              << expanded.substr(prefixLen + errorLen) << "\n";
+                } else {
+                    std::cerr << expanded << "\n";
+                }
+
+                std::ostringstream prefixSpaces;
+                prefixSpaces << "  " << std::string(width, ' ') << " | ";
+
+                std::cerr << prefixSpaces.str();
+
+                if (startCol > 1)
+                    std::cerr << std::string(startCol - 1, ' ');
+
+                std::cerr << Colors::Red << "^";
+                for (int i = 1; i < caretCount; ++i) std::cerr << "~";
+                std::cerr << Colors::Reset << "\n";
+            } else {
+                std::cerr << expanded << "\n";
+            }
+        }
+    }
+};
diff --git a/include/Diagnostic/SourceLocation.hpp b/include/Diagnostic/SourceLocation.hpp
new file mode 100644
index 0000000..d9cfa99
--- /dev/null
+++ b/include/Diagnostic/SourceLocation.hpp
@@ -0,0 +1,10 @@
+#pragma once
+
+#include <string>
+
+struct SourceLocation {
+    std::string file;
+    int fileId = -1;
+    int line;
+    int column;
+};
diff --git a/include/Diagnostic/SourceManager.hpp b/include/Diagnostic/SourceManager.hpp
new file mode 100644
index 0000000..31e53d5
--- /dev/null
+++ b/include/Diagnostic/SourceManager.hpp
@@ -0,0 +1,71 @@
+#pragma once
+
+#include <fstream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+class SourceManager {
+public:
+    struct FileInfo {
+        std::string path;
+        std::vector<std::string> lines;
+        std::string content;
+    };
+
+    int loadFile(const std::string& path) {
+        if (fileIDs.count(path)) {
+            return fileIDs[path];
+        }
+
+        std::ifstream ifs(path);
+        if (!ifs) return -1;
+
+        FileInfo info;
+        info.path = path;
+
+        std::ostringstream ss;
+        ss << ifs.rdbuf();
+        info.content = ss.str();
+
+        std::string line;
+        std::istringstream ls(info.content);
+        while (std::getline(ls, line)) {
+            info.lines.push_back(line);
+        }
+
+        int id = nextID++;
+        files[id] = std::move(info);
+
+        return id;
+    }
+
+    const FileInfo* getFile(int fileID) const {
+        auto it = files.find(fileID);
+        return (it == files.end() ? nullptr : &it->second);
+    }
+
+    const std::vector<std::string>& getLines(int fileID) const {
+        static const std::vector<std::string> empty;
+        auto it = files.find(fileID);
+        return it != files.end() ? it->second.lines : empty;
+    }
+
+    const std::string& getContent(int fileID) const {
+        static const std::string empty;
+        auto it = files.find(fileID);
+        return it != files.end() ? it->second.content : empty;
+    }
+
+    bool exists(int fileID) const {
+        auto it = files.find(fileID);
+        return it != files.end();
+    }
+
+private:
+    int nextID = 1;
+    std::map<int, FileInfo> files;
+    std::map<std::string, int> fileIDs;
+};
diff --git a/src/main.cpp b/src/main.cpp
index d1af452..fe611de 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,6 +1,48 @@
-#include <print>
+#include "Args/CompilerOptions.hpp"
+#include "Diagnostic/Diagnostic.hpp"
+#include "Diagnostic/DiagnosticLevel.hpp"
+#include "Diagnostic/DiagnosticsEngine.hpp"
+#include "Diagnostic/SourceManager.hpp"
 
-int main()
-{
-	std::println("hello, world!");
+int main(int argc, char** argv) {
+    CompilerOptions opts = parseArguments(argc, argv);
+    SourceManager sm;
+    DiagnosticsEngine diag(sm, opts.context, opts.wignore, opts.werror);
+
+    auto mainId = sm.loadFile(opts.inputFile);
+
+    if (!sm.exists(mainId)) {
+        Diagnostic d;
+        d.level = DiagnosticLevel::Error;
+        d.loc = { opts.inputFile, 1, 1 };
+        d.message = "cannot open input file";
+        d.length = 6;
+        d.suggestion = "make sure file exists and you have permissions to read it";
+        diag.report(d);
+        return 1;
+    }
+
+    {
+        Diagnostic w;
+        w.level = DiagnosticLevel::Warning;
+        w.loc = { opts.inputFile, mainId, 1, 8 };
+        w.message = "unable to resolve 'std.io'";
+        w.length = 6;
+        w.suggestion = "is it spelled corectly?";
+        diag.report(w);
+    }
+
+    {
+        Diagnostic d;
+        d.level = DiagnosticLevel::Error;
+        d.loc = { opts.inputFile, mainId, 4, 5 };
+        d.message = "Unexpected identifier 'println'";
+        d.length = 7;
+        d.suggestion = "check if it is defined, or module is imported";
+
+        d.notes.push_back({ { opts.inputFile, mainId, 1, 8 }, 6, "this unresovled import might contain identifier" });
+        diag.report(d);
+    }
+
+    return 0;
 }
diff --git a/test.oxy b/test.oxy
new file mode 100644
index 0000000..d4bd96b
--- /dev/null
+++ b/test.oxy
@@ -0,0 +1,7 @@
+import std.io;
+
+func int main() {
+    println("hello, world");
+
+    return 0;
+}