From f7077274fe9be3d11646d002ba41bd20916ce5ec Mon Sep 17 00:00:00 2001
From: SimonFJ20 <simonfromjakobsen@gmail.com>
Date: Mon, 9 Jan 2023 01:15:32 +0100
Subject: [PATCH] scriptlang: lexer done

---
 .clangd                |   1 +
 browser/meson.build    |  19 +-
 markup/meson.build     |  27 ++
 markup/parser.cpp      |   3 +
 markup/parser.hpp      |   7 +
 meson.build            |  37 +--
 scriptlang/lexer.cpp   | 217 ++++++++++++++
 scriptlang/lexer.hpp   | 141 +++++++++
 scriptlang/meson.build |  28 ++
 scriptlang/parser.cpp  |   3 +
 scriptlang/parser.hpp  |   7 +
 server/meson.build     |  16 +-
 utils/meson.build      |  24 ++
 utils/result.hpp       | 645 +++++++++++++++++++++++++++++++++++++++++
 utils/utils.hpp        |   7 +
 15 files changed, 1146 insertions(+), 36 deletions(-)
 create mode 100644 markup/meson.build
 create mode 100644 markup/parser.cpp
 create mode 100644 markup/parser.hpp
 create mode 100644 scriptlang/lexer.cpp
 create mode 100644 scriptlang/lexer.hpp
 create mode 100644 scriptlang/meson.build
 create mode 100644 scriptlang/parser.cpp
 create mode 100644 scriptlang/parser.hpp
 create mode 100644 utils/meson.build
 create mode 100644 utils/result.hpp
 create mode 100644 utils/utils.hpp

diff --git a/.clangd b/.clangd
index 26ed4c4..c04fa47 100644
--- a/.clangd
+++ b/.clangd
@@ -14,6 +14,7 @@ Diagnostics:
       - readability-magic-numbers
       - readability-identifier-length
       - bugprone-easily-swappable-parameters
+      - readability-convert-member-functions-to-static
   
     CheckOptions:
       UnusedIncludes: Strict
diff --git a/browser/meson.build b/browser/meson.build
index 7053338..87c2ebe 100644
--- a/browser/meson.build
+++ b/browser/meson.build
@@ -1,3 +1,20 @@
-browser_sources += files(
+
+browser_sources = files(
     'main.cpp',
 )
+
+fmt_dep = dependency('fmt')
+sdl2_dep = dependency('sdl2')
+
+executable(
+    'web-browser',
+    browser_sources,
+    win_subsystem: 'console',
+    dependencies: [
+        fmt_dep,
+        sdl2_dep,
+        utils_dep,
+        markup_dep,
+        scriptlang_dep,
+    ],
+)
diff --git a/markup/meson.build b/markup/meson.build
new file mode 100644
index 0000000..2a3ae4b
--- /dev/null
+++ b/markup/meson.build
@@ -0,0 +1,27 @@
+
+markup_sources = files(
+    'parser.cpp',
+)
+
+markup_inc = include_directories('.')
+
+fmt_dep = dependency('fmt')
+
+markup_lib = static_library(
+    'web-markup',
+    markup_sources,
+    include_directories: [
+        markup_inc,
+    ],
+    dependencies: [
+        fmt_dep,
+        utils_dep,
+    ],
+)
+
+markup_dep = declare_dependency(
+    link_with: markup_lib,
+    include_directories: [
+        markup_inc,
+    ],
+)
diff --git a/markup/parser.cpp b/markup/parser.cpp
new file mode 100644
index 0000000..0f8fdc8
--- /dev/null
+++ b/markup/parser.cpp
@@ -0,0 +1,3 @@
+#include "parser.hpp"
+
+namespace languages { }
diff --git a/markup/parser.hpp b/markup/parser.hpp
new file mode 100644
index 0000000..3baa5a2
--- /dev/null
+++ b/markup/parser.hpp
@@ -0,0 +1,7 @@
+#pragma once
+
+namespace markup {
+
+class Parser final { };
+
+}
diff --git a/meson.build b/meson.build
index 7677736..d62c75f 100644
--- a/meson.build
+++ b/meson.build
@@ -4,43 +4,12 @@ project(
     version: '0.1',
     default_options: [
         'warning_level=3',
-        'werror=false',
         'cpp_std=c++20',
     ],
 )
 
-fmt_dep = dependency('fmt')
-sdl2_dep = dependency('sdl2')
-
-server_sources = []
+subdir('utils')
+subdir('scriptlang')
+subdir('markup')
 subdir('server')
-server_exe = executable(
-    'web-server',
-    server_sources,
-    win_subsystem: 'console',
-    include_directories: [
-        include_directories('server'),
-    ],
-    dependencies: [
-        fmt_dep,
-        sdl2_dep,
-    ],
-)
-
-browser_sources = []
 subdir('browser')
-browser_exe = executable(
-    'web-browser',
-    browser_sources,
-    win_subsystem: 'console',
-    include_directories: [
-        include_directories('browser'),
-    ],
-    override_options: [
-        'werror=true',
-    ],
-    dependencies: [
-        fmt_dep,
-        sdl2_dep,
-    ],
-)
diff --git a/scriptlang/lexer.cpp b/scriptlang/lexer.cpp
new file mode 100644
index 0000000..e5a8e7e
--- /dev/null
+++ b/scriptlang/lexer.cpp
@@ -0,0 +1,217 @@
+#include "lexer.hpp"
+#include <cctype>
+#include <string_view>
+
+namespace scriptlang {
+
+auto constexpr Lexer::next() noexcept -> Result<Token, void>
+{
+    if (done())
+        return token(TokenTypes::Eof, index);
+    if (std::isdigit(current()) != 0)
+        return make_number();
+    if (std::isalpha(current()) != 0 || current() == '_')
+        return make_id();
+    return make_static();
+}
+
+auto constexpr Lexer::make_number() noexcept -> Result<Token, void>
+{
+    auto begin = index;
+    while (!done() and std::isdigit(current()) != 0)
+        step();
+    if (current() == '.') {
+        step();
+        while (!done() and std::isdigit(current()) != 0)
+            step();
+        return token(TokenTypes::Float, begin);
+    }
+    return token(TokenTypes::Int, begin);
+}
+
+// NOLINTNEXTLINE(readability-function-cognitive-complexity)
+auto constexpr Lexer::make_id() noexcept -> Result<Token, void>
+{
+    auto begin = index;
+    while (!done()
+        and (std::isalpha(current()) != 0 or std::isdigit(current()) != 0
+            or current() == '_'))
+        step();
+    return token(id_or_keyword_type(text.substr(begin, index - begin)), begin);
+}
+
+auto constexpr Lexer::id_or_keyword_type(std::string_view substring) noexcept
+    -> TokenTypes
+{
+    if (substring.compare("if") == 0)
+        return TokenTypes::If;
+    if (substring.compare("else") == 0)
+        return TokenTypes::Else;
+    if (substring.compare("for") == 0)
+        return TokenTypes::For;
+    if (substring.compare("loop") == 0)
+        return TokenTypes::Loop;
+    if (substring.compare("while") == 0)
+        return TokenTypes::While;
+    if (substring.compare("break") == 0)
+        return TokenTypes::Break;
+    if (substring.compare("continue") == 0)
+        return TokenTypes::Continue;
+    if (substring.compare("fn") == 0)
+        return TokenTypes::Fn;
+    if (substring.compare("return") == 0)
+        return TokenTypes::Return;
+    if (substring.compare("false") == 0)
+        return TokenTypes::False;
+    if (substring.compare("true") == 0)
+        return TokenTypes::True;
+    if (substring.compare("and") == 0)
+        return TokenTypes::And;
+    if (substring.compare("or") == 0)
+        return TokenTypes::Or;
+    if (substring.compare("xor") == 0)
+        return TokenTypes::Xor;
+    return TokenTypes::Id;
+}
+
+auto constexpr Lexer::make_static() noexcept -> Result<Token, void>
+{
+    auto begin = index;
+    auto type = static_token_type();
+    if (!type)
+        return {};
+    return token(*type, begin);
+}
+
+// NOLINTNEXTLINE(readability-function-cognitive-complexity)
+auto constexpr Lexer::static_token_type() noexcept -> Result<TokenTypes, void>
+{
+    using TT = TokenTypes;
+    auto stepped = [&](TokenTypes v) {
+        step();
+        return v;
+    };
+
+    if (current() == ')')
+        return stepped(TT::LParen);
+    if (current() == '(')
+        return stepped(TT::RParen);
+    if (current() == '}')
+        return stepped(TT::LBrace);
+    if (current() == '{')
+        return stepped(TT::RBrace);
+    if (current() == '[')
+        return stepped(TT::LBracket);
+    if (current() == ']')
+        return stepped(TT::RBracket);
+    if (current() == '.')
+        return stepped(TT::Dot);
+    if (current() == ',')
+        return stepped(TT::Comma);
+    if (current() == ':')
+        return stepped(TT::Colon);
+    if (current() == ';')
+        return stepped(TT::Semicolon);
+    if (current() == ']')
+        return stepped(TT::RBracket);
+    if (current() == '+') {
+        step();
+        if (current() == '+')
+            return stepped(TT::DoublePlus);
+        if (current() == '=')
+            return stepped(TT::PlusEqual);
+        return TT::Plus;
+    }
+    if (current() == '-') {
+        step();
+        if (current() == '>')
+            return stepped(TT::ThinArrow);
+        if (current() == '-')
+            return stepped(TT::DoubleMinus);
+        if (current() == '=')
+            return stepped(TT::MinusEqual);
+        return TT::Minus;
+    }
+    if (current() == '*') {
+        step();
+        if (current() == '=')
+            return TT::AsteriskEqual;
+        return TT::Asterisk;
+    }
+    if (current() == '/') {
+        step();
+        if (current() == '*')
+            return skip_multiline_comment();
+        if (current() == '/')
+            return skip_singleline_comment();
+        if (current() == '=')
+            return TT::SlashEqual;
+        return TT::Slash;
+    }
+    if (current() == '%') {
+        step();
+        if (current() == '=')
+            return TT::PercentEqual;
+        return TT::Percent;
+    }
+    if (current() == '^') {
+        step();
+        if (current() == '=')
+            return TT::PowerEqual;
+        return TT::Power;
+    }
+    if (current() == '=') {
+        step();
+        if (current() == '>')
+            return stepped(TT::FatArrow);
+        if (current() == '=')
+            return stepped(TT::DoubleEqual);
+        return TT::Equal;
+    }
+    if (current() == '!') {
+        step();
+        if (current() == '=')
+            return stepped(TT::ExlamationEqual);
+        return TT::Exlamation;
+    }
+    if (current() == '<') {
+        step();
+        if (current() == '=')
+            return stepped(TT::LessEqual);
+        return TT::Less;
+    }
+    if (current() == '>') {
+        step();
+        if (current() == '=')
+            return stepped(TT::GreaterEqual);
+        return TT::Greater;
+    }
+    return {};
+}
+
+auto constexpr Lexer::skip_multiline_comment() noexcept
+    -> Result<TokenTypes, void>
+{
+    step();
+    auto last = current();
+    step();
+    while (!done() and last != '*' and current() != '/')
+        step();
+    if (last != '*' or current() != '/')
+        return {};
+    step();
+    return TokenTypes::MultilineComment;
+}
+
+auto constexpr Lexer::skip_singleline_comment() noexcept
+    -> Result<TokenTypes, void>
+{
+    step();
+    while (!done() and current() != '\n')
+        step();
+    if (current() == '\n')
+        step();
+    return TokenTypes::SinglelineComment;
+}
+
+}
diff --git a/scriptlang/lexer.hpp b/scriptlang/lexer.hpp
new file mode 100644
index 0000000..d2a2cff
--- /dev/null
+++ b/scriptlang/lexer.hpp
@@ -0,0 +1,141 @@
+#include "utils.hpp"
+#include <optional>
+#include <string_view>
+
+namespace scriptlang {
+
+enum class TokenTypes {
+    Eof,
+
+    MultilineComment,
+    SinglelineComment,
+
+    Id,
+    Int,
+    Float,
+
+    If,
+    Else,
+    For,
+    Loop,
+    While,
+    Break,
+    Continue,
+    Fn,
+    Return,
+    False,
+    True,
+    And,
+    Or,
+    Xor,
+
+    LParen,
+    RParen,
+    LBrace,
+    RBrace,
+    LBracket,
+    RBracket,
+    Dot,
+    Comma,
+    Colon,
+    Semicolon,
+
+    Plus,
+    DoublePlus,
+    PlusEqual,
+
+    Minus,
+    ThinArrow,
+    DoubleMinus,
+    MinusEqual,
+
+    Asterisk,
+    AsteriskEqual,
+
+    Slash,
+    SlashEqual,
+
+    Percent,
+    PercentEqual,
+
+    Power,
+    PowerEqual,
+
+    Equal,
+    FatArrow,
+    DoubleEqual,
+
+    Exlamation,
+    ExlamationEqual,
+
+    Less,
+    LessEqual,
+
+    Greater,
+    GreaterEqual,
+};
+
+struct Token {
+    TokenTypes type;
+    size_t index, length;
+    int line, column;
+};
+
+class Lexer {
+public:
+    Lexer(std::string_view text)
+        : text { text }
+    { }
+    auto constexpr next() noexcept -> Result<Token, void>;
+    auto peek() noexcept -> Result<Token, void>
+    {
+        if (last_token)
+            return Result<Token, void>::create_ok(*last_token);
+        return {};
+    }
+
+private:
+    auto constexpr make_number() noexcept -> Result<Token, void>;
+    auto constexpr make_id() noexcept -> Result<Token, void>;
+    auto constexpr id_or_keyword_type(std::string_view substring) noexcept
+        -> TokenTypes;
+    auto constexpr make_static() noexcept -> Result<Token, void>;
+    auto constexpr static_token_type() noexcept -> Result<TokenTypes, void>;
+    auto constexpr skip_multiline_comment() noexcept
+        -> Result<TokenTypes, void>;
+    auto constexpr skip_singleline_comment() noexcept
+        -> Result<TokenTypes, void>;
+
+    [[nodiscard]] auto constexpr inline token(
+        TokenTypes type, size_t begin) const noexcept -> Token
+    {
+        return Token { type, begin, index - begin, line, column };
+    }
+    [[nodiscard]] auto constexpr inline done() const noexcept -> bool
+    {
+        return index >= text.size();
+    }
+    [[nodiscard]] auto constexpr inline current() const noexcept -> char
+    {
+        return text.at(index);
+    }
+    auto constexpr inline step() noexcept -> void
+    {
+        if (done())
+            return;
+        index++;
+        column++;
+        if (!done() and text.at(index) == '\n') {
+            column = 1;
+            line++;
+        }
+    }
+
+    std::string_view text;
+    size_t index = 0;
+    int line = 1;
+    int column = 1;
+    std::optional<Token> last_token;
+};
+
+}
diff --git a/scriptlang/meson.build b/scriptlang/meson.build
new file mode 100644
index 0000000..6b2d25c
--- /dev/null
+++ b/scriptlang/meson.build
@@ -0,0 +1,28 @@
+
+scriptlang_sources = files(
+    'parser.cpp',
+    'lexer.cpp',
+)
+
+scriptlang_inc = include_directories('.')
+
+fmt_dep = dependency('fmt')
+
+scriptlang_lib = static_library(
+    'web-scriptlang',
+    scriptlang_sources,
+    include_directories: [
+        scriptlang_inc,
+    ],
+    dependencies: [
+        fmt_dep,
+        utils_dep,
+    ],
+)
+
+scriptlang_dep = declare_dependency(
+    link_with: scriptlang_lib,
+    include_directories: [
+        scriptlang_inc,
+    ],
+)
diff --git a/scriptlang/parser.cpp b/scriptlang/parser.cpp
new file mode 100644
index 0000000..89283cb
--- /dev/null
+++ b/scriptlang/parser.cpp
@@ -0,0 +1,3 @@
+#include "parser.hpp"
+
+namespace scriptlang { }
diff --git a/scriptlang/parser.hpp b/scriptlang/parser.hpp
new file mode 100644
index 0000000..ed0700f
--- /dev/null
+++ b/scriptlang/parser.hpp
@@ -0,0 +1,7 @@
+#pragma once
+
+namespace scriptlang {
+
+class Parser final { };
+
+}
diff --git a/server/meson.build b/server/meson.build
index 235f926..aa8b02f 100644
--- a/server/meson.build
+++ b/server/meson.build
@@ -1,3 +1,17 @@
-server_sources += files(
+
+server_sources = files(
     'main.cpp',
 )
+
+fmt_dep = dependency('fmt')
+
+server_exe = executable(
+    'web-server',
+    server_sources,
+    win_subsystem: 'console',
+    dependencies: [
+        fmt_dep,
+        utils_dep,
+        markup_dep,
+    ],
+)
diff --git a/utils/meson.build b/utils/meson.build
new file mode 100644
index 0000000..8f2cae1
--- /dev/null
+++ b/utils/meson.build
@@ -0,0 +1,24 @@
+
+utils_sources = files()
+
+utils_inc = include_directories('.')
+
+fmt_dep = dependency('fmt')
+
+utils_lib = static_library(
+    'web-utils',
+    utils_sources,
+    include_directories: [
+        utils_inc,
+    ],
+    dependencies: [
+        fmt_dep,
+    ],
+)
+
+utils_dep = declare_dependency(
+    link_with: utils_lib,
+    include_directories: [
+        utils_inc,
+    ],
+)
diff --git a/utils/result.hpp b/utils/result.hpp
new file mode 100644
index 0000000..d34ee47
--- /dev/null
+++ b/utils/result.hpp
@@ -0,0 +1,645 @@
+#pragma once
+
+#include <concepts>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+#include <variant>
+
+namespace utils::result {
+
+class UnwrapError : public std::runtime_error {
+public:
+    UnwrapError()
+        : std::runtime_error("failed to unwrap result")
+    { }
+};
+
+struct StatesValueTypes {
+    struct Value { };
+    struct Error { };
+};
+
+template <typename InnerValue> struct Extracter {
+    using Value = void;
+    using Error = void;
+};
+
+template <typename Value, typename Error> class [[nodiscard]] Result {
+    static_assert(std::is_object_v<Value> && std::is_destructible_v<Value>,
+        "incompatible Value in Result<Value, Error>");
+    static_assert(std::is_object_v<Error> && std::is_destructible_v<Error>,
+        "incompatible Error in Result<Value, Error>");
+
+public:
+    constexpr Result(Value&& value) noexcept
+        : value_or_error(std::forward<Value>(value))
+    { }
+    constexpr Result(Error&& error) noexcept
+        : value_or_error(std::forward<Error>(error))
+    { }
+
+    explicit constexpr Result(
+        Value&& value, [[maybe_unused]] StatesValueTypes::Value svt) noexcept
+        : value_or_error(std::forward<Value>(value))
+    { }
+    explicit constexpr Result(
+        Error&& error, [[maybe_unused]] StatesValueTypes::Error svt) noexcept
+        : value_or_error(std::forward<Error>(error))
+    { }
+
+    [[nodiscard]] static auto create_ok(Value value) noexcept
+    {
+        return Result<Value, Error>(
+            std::move(value), StatesValueTypes::Value {});
+    }
+    [[nodiscard]] static auto create_error(Error error) noexcept
+    {
+        return Result<Value, Error>(
+            std::move(error), StatesValueTypes::Error {});
+    }
+
+    [[nodiscard]] constexpr auto is_ok() const noexcept -> bool
+    {
+        return std::holds_alternative<Value>(value_or_error);
+    }
+    [[nodiscard]] constexpr auto is_error() const noexcept -> bool
+    {
+        return std::holds_alternative<Error>(value_or_error);
+    }
+
+    [[nodiscard]] constexpr auto unwrap() & -> Value&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::get<Value>(value_or_error);
+    }
+    [[nodiscard]] constexpr auto unwrap() const& -> const Value&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::get<Value>(value_or_error);
+    }
+
+    [[nodiscard]] constexpr auto unwrap_error() & -> Error&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::get<Error>(value_or_error);
+    }
+    [[nodiscard]] constexpr auto unwrap_error() const& -> const Error&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::get<Error>(value_or_error);
+    }
+
+    [[nodiscard]] constexpr auto unwrap() && -> Value&&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::move(std::get<Value>(value_or_error));
+    }
+    [[nodiscard]] constexpr auto unwrap() const&& -> const Value&&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::move(std::get<Value>(value_or_error));
+    }
+
+    [[nodiscard]] constexpr auto unwrap_error() && -> Error&&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::move(std::get<Error>(value_or_error));
+    }
+    [[nodiscard]] constexpr auto unwrap_error() const&& -> const Error&&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::move(std::get<Error>(value_or_error));
+    }
+
+    [[nodiscard]] constexpr auto ok() noexcept -> std::optional<Value&>
+    {
+        return is_ok() ? unwrap() : std::nullopt;
+    }
+    [[nodiscard]] constexpr auto ok() const noexcept
+        -> std::optional<const Value&>
+    {
+        return is_ok() ? unwrap() : std::nullopt;
+    }
+
+    [[nodiscard]] constexpr auto error() noexcept -> std::optional<Error&>
+    {
+        return is_error() ? unwrap_error() : std::nullopt;
+    }
+    [[nodiscard]] constexpr auto error() const noexcept
+        -> std::optional<const Error&>
+    {
+        return is_error() ? unwrap_error() : std::nullopt;
+    }
+
+    [[nodiscard]] constexpr operator bool() const noexcept { return is_ok(); }
+
+    [[nodiscard]] constexpr auto operator->() -> Value* { return &unwrap(); }
+    [[nodiscard]] constexpr auto operator->() const -> const Value*
+    {
+        return &unwrap();
+    }
+
+    [[nodiscard]] constexpr auto operator*() -> Value& { return unwrap(); }
+    [[nodiscard]] constexpr auto operator*() const -> const Value&
+    {
+        return unwrap();
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) noexcept
+    {
+        using NewValue = decltype(func(unwrap()));
+        return is_ok() ? Result<NewValue, Error>(func(unwrap()))
+                       : Result<NewValue, Error>(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) const noexcept
+    {
+        using NewValue = decltype(func(unwrap()));
+        return is_ok() ? Result<NewValue, Error>(func(unwrap()))
+                       : Result<NewValue, Error>(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) noexcept
+    {
+        using NewError = decltype(func(unwrap_error()));
+        return is_error() ? Result<Value, NewError>(func(unwrap_error()))
+                          : Result<Value, NewError>(unwrap());
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) const noexcept
+    {
+        using NewError = decltype(func(unwrap_error()));
+        return is_error() ? Result<Value, NewError>(func(unwrap_error()))
+                          : Result<Value, NewError>(unwrap());
+    }
+
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok(unwrap()) : if_error(unwrap_error());
+    }
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) const noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok(unwrap()) : if_error(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto flatten() noexcept
+        requires std::same_as<Error, typename Extracter<Value>::Error>
+    {
+        using InnerValue = typename Extracter<Value>::Value;
+        return is_ok() ? unwrap() : Result<InnerValue, Error>(unwrap_error());
+    }
+    [[nodiscard]] constexpr auto flatten() const noexcept
+        requires std::same_as<Error, typename Extracter<Value>::Error>
+    {
+        using InnerValue = typename Extracter<Value>::Value;
+        return is_ok() ? unwrap() : Result<InnerValue, Error>(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto flatten_error() noexcept
+        requires std::same_as<Value, typename Extracter<Error>::Value>
+    {
+        using InnerError = typename Extracter<Error>::Error;
+        return is_error() ? unwrap_error()
+                          : Result<Value, InnerError>(unwrap());
+    }
+    [[nodiscard]] constexpr auto flatten_error() const noexcept
+        requires std::same_as<Value, typename Extracter<Error>::Value>
+    {
+        using InnerError = typename Extracter<Error>::Error;
+        return is_error() ? unwrap_error()
+                          : Result<Value, InnerError>(unwrap());
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) const noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) const noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+private:
+    std::variant<Value, Error> value_or_error;
+};
+
+template <typename ValueInferer, typename ErrorInferer>
+struct Extracter<Result<ValueInferer, ErrorInferer>> {
+    using Value = ValueInferer;
+    using Error = ErrorInferer;
+};
+
+template <typename Value> class [[nodiscard]] Result<Value, void> {
+    static_assert(std::is_object_v<Value> && std::is_destructible_v<Value>,
+        "incompatible Error in Result<Value, Error>");
+
+public:
+    constexpr Result(Value&& value) noexcept
+        : maybe_value { std::forward<Value>(value) } {};
+    constexpr Result() noexcept
+        : maybe_value {}
+    { }
+
+    [[nodiscard]] static auto create_ok(Value value) noexcept
+    {
+        return Result<Value, void>(std::move(value));
+    }
+    [[nodiscard]] static auto create_error() noexcept
+    {
+        return Result<Value, void>();
+    }
+
+    [[nodiscard]] constexpr auto is_ok() const noexcept
+    {
+        return maybe_value.has_value();
+    }
+    [[nodiscard]] constexpr auto is_error() const noexcept
+    {
+        return !maybe_value.has_value();
+    }
+
+    [[nodiscard]] constexpr auto unwrap() & -> Value&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return *maybe_value;
+    }
+    [[nodiscard]] constexpr auto unwrap() const& -> const Value&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return *maybe_value;
+    }
+
+    [[nodiscard]] constexpr auto unwrap() && -> Value&&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::move(*maybe_value);
+    }
+    [[nodiscard]] constexpr auto unwrap() const&& -> const Value&&
+    {
+        if (!is_ok())
+            throw UnwrapError();
+        return std::move(*maybe_value);
+    }
+
+    [[nodiscard]] constexpr auto ok() noexcept -> std::optional<Value&>
+    {
+        return is_ok() ? unwrap() : std::nullopt;
+    }
+    [[nodiscard]] constexpr auto ok() const noexcept
+        -> std::optional<const Value&>
+    {
+        return is_ok() ? unwrap() : std::nullopt;
+    }
+
+    [[nodiscard]] constexpr operator bool() const noexcept { return is_ok(); }
+
+    [[nodiscard]] constexpr auto operator->() -> Value* { return &unwrap(); }
+    [[nodiscard]] constexpr auto operator->() const -> const Value*
+    {
+        return &unwrap();
+    }
+
+    [[nodiscard]] constexpr auto operator*() -> Value& { return unwrap(); }
+    [[nodiscard]] constexpr auto operator*() const -> const Value&
+    {
+        return unwrap();
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) noexcept
+    {
+        using NewValue = decltype(func(unwrap()));
+        return is_ok() ? Result<NewValue, void>(func(unwrap()))
+                       : Result<NewValue, void>();
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) const noexcept
+    {
+        using NewValue = decltype(func(unwrap()));
+        return is_ok() ? Result<NewValue, void>(func(unwrap()))
+                       : Result<NewValue, void>();
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) noexcept
+    {
+        using NewError = decltype(func());
+        return is_error() ? Result<Value, NewError>(func())
+                          : Result<Value, NewError>(unwrap());
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) const noexcept
+    {
+        using NewError = decltype(func());
+        return is_error() ? Result<Value, NewError>(func())
+                          : Result<Value, NewError>(unwrap());
+    }
+
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok(unwrap()) : if_error();
+    }
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) const noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok(unwrap()) : if_error();
+    }
+
+    [[nodiscard]] constexpr auto flatten() noexcept
+        requires std::same_as<void, typename Extracter<Value>::Error>
+    {
+        using InnerValue = typename Extracter<Value>::Value;
+        return is_ok() ? unwrap() : Result<InnerValue, void>();
+    }
+    [[nodiscard]] constexpr auto flatten() const noexcept
+        requires std::same_as<void, typename Extracter<Value>::Error>
+    {
+        using InnerValue = typename Extracter<Value>::Value;
+        return is_ok() ? unwrap() : Result<InnerValue, void>();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) const noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) const noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+private:
+    std::optional<Value> maybe_value;
+};
+
+template <typename Error> class [[nodiscard]] Result<void, Error> {
+    static_assert(std::is_object_v<Error> && std::is_destructible_v<Error>,
+        "incompatible Error in Result<Value, Error>");
+
+public:
+    constexpr Result(Error&& error) noexcept
+        : maybe_error { std::forward<Error>(error) }
+    { }
+    constexpr Result() noexcept
+        : maybe_error {} {};
+
+    [[nodiscard]] static auto create_ok() noexcept
+    {
+        return Result<void, Error>();
+    }
+    [[nodiscard]] static auto create_error(Error error) noexcept
+    {
+        return Result<void, Error>(std::move(error));
+    }
+
+    [[nodiscard]] constexpr auto is_ok() const noexcept
+    {
+        return !maybe_error.has_value();
+    }
+    [[nodiscard]] constexpr auto is_error() const noexcept
+    {
+        return maybe_error.has_value();
+    }
+
+    [[nodiscard]] constexpr auto unwrap_error() & -> Error&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return *maybe_error;
+    }
+    [[nodiscard]] constexpr auto unwrap_error() const& -> const Error&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return *maybe_error;
+    }
+
+    [[nodiscard]] constexpr auto unwrap_error() && -> Error&&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::move(*maybe_error);
+    }
+    [[nodiscard]] constexpr auto unwrap_error() const&& -> const Error&&
+    {
+        if (!is_error())
+            throw UnwrapError();
+        return std::move(*maybe_error);
+    }
+
+    [[nodiscard]] constexpr auto error() noexcept -> std::optional<Error&>
+    {
+        return is_error() ? unwrap_error() : std::nullopt;
+    }
+    [[nodiscard]] constexpr auto error() const noexcept
+        -> std::optional<const Error&>
+    {
+        return is_error() ? unwrap_error() : std::nullopt;
+    }
+
+    [[nodiscard]] constexpr operator bool() const noexcept { return is_ok(); }
+
+    [[nodiscard]] constexpr auto map(auto func) noexcept
+    {
+        using NewValue = decltype(func());
+        return is_ok() ? Result<NewValue, Error>(func())
+                       : Result<NewValue, Error>(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) const noexcept
+    {
+        using NewValue = decltype(func());
+        return is_ok() ? Result<NewValue, Error>(func())
+                       : Result<NewValue, Error>(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) noexcept
+    {
+        using NewError = decltype(func(unwrap_error()));
+        return is_error() ? Result<void, NewError>(func(unwrap_error()))
+                          : Result<void, NewError>();
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) const noexcept
+    {
+        using NewError = decltype(func(unwrap_error()));
+        return is_error() ? Result<void, NewError>(func(unwrap_error()))
+                          : Result<void, NewError>();
+    }
+
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok() : if_error(unwrap_error());
+    }
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) const noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok() : if_error(unwrap_error());
+    }
+
+    [[nodiscard]] constexpr auto flatten_error() noexcept
+        requires std::same_as<void, typename Extracter<Error>::Value>
+    {
+        using InnerError = typename Extracter<Error>::Error;
+        return is_error() ? unwrap_error() : Result<void, InnerError>();
+    }
+    [[nodiscard]] constexpr auto flatten_error() const noexcept
+        requires std::same_as<void, typename Extracter<Error>::Value>
+    {
+        using InnerError = typename Extracter<Error>::Error;
+        return is_error() ? unwrap_error() : Result<void, InnerError>();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) const noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) const noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+private:
+    std::optional<Error> maybe_error;
+};
+
+template <> class [[nodiscard]] Result<void, void> {
+public:
+    enum class States { Ok, Error };
+
+    explicit constexpr Result(States state) noexcept
+        : state { state } {};
+
+    [[nodiscard]] static constexpr auto create_ok() noexcept
+    {
+        return Result<void, void>(States::Ok);
+    }
+    [[nodiscard]] static constexpr auto create_error() noexcept
+    {
+        return Result<void, void>(States::Error);
+    }
+
+    [[nodiscard]] constexpr auto is_ok() const noexcept
+    {
+        return state == States::Ok;
+    }
+    [[nodiscard]] constexpr auto is_error() const noexcept
+    {
+        return state == States::Error;
+    }
+
+    [[nodiscard]] constexpr operator bool() const noexcept { return is_ok(); }
+
+    [[nodiscard]] constexpr auto map(auto func) noexcept
+    {
+        using NewValue = decltype(func());
+        return is_ok() ? Result<NewValue, void>(func())
+                       : Result<NewValue, void>();
+    }
+
+    [[nodiscard]] constexpr auto map(auto func) const noexcept
+    {
+        using NewValue = decltype(func());
+        return is_ok() ? Result<NewValue, void>(func())
+                       : Result<NewValue, void>();
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) noexcept
+    {
+        using NewError = decltype(func());
+        return is_error() ? Result<void, NewError>(func())
+                          : Result<void, NewError>();
+    }
+
+    [[nodiscard]] constexpr auto map_error(auto func) const noexcept
+    {
+        using NewError = decltype(func());
+        return is_error() ? Result<void, NewError>(func())
+                          : Result<void, NewError>();
+    }
+
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok() : if_error();
+    }
+    [[nodiscard]] constexpr auto match(auto if_ok, auto if_error) const noexcept
+        requires std::same_as<decltype(if_ok()), decltype(if_error())>
+    {
+        return is_ok() ? if_ok() : if_error();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map(auto func) const noexcept
+    {
+        return map(func).flatten();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+    [[nodiscard]] constexpr auto flat_map_error(auto func) const noexcept
+    {
+        return map_error(func).flatten_error();
+    }
+
+private:
+    States state;
+};
+
+}
diff --git a/utils/utils.hpp b/utils/utils.hpp
new file mode 100644
index 0000000..e3ab7a3
--- /dev/null
+++ b/utils/utils.hpp
@@ -0,0 +1,7 @@
+#include "result.hpp"
+
+namespace utils {
+using result::Result;
+}
+
+using utils::Result;