LibCMake: Introduce a CMake lexer

Userland/Libraries/LibCMake/Token.h

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/StringView.h>
+#include <AK/Vector.h>
+
+namespace CMake {
+
+struct Position {
+    size_t line { 0 };
+    size_t column { 0 };
+};
+
+struct VariableReference {
+    StringView value;
+    Position start;
+    Position end;
+};
+
+enum class ControlKeywordType {
+    If,
+    ElseIf,
+    Else,
+    EndIf,
+    ForEach,
+    EndForEach,
+    While,
+    EndWhile,
+    Break,
+    Continue,
+    Macro,
+    EndMacro,
+    Function,
+    EndFunction,
+};
+
+struct Token {
+    enum class Type {
+        BracketComment,
+        LineComment,
+        Identifier,
+        ControlKeyword,
+        OpenParen,
+        CloseParen,
+        BracketArgument,
+        QuotedArgument,
+        UnquotedArgument,
+        Garbage,
+
+        // These are elements inside argument tokens
+        VariableReference,
+    };
+
+    Type type;
+    StringView value;
+
+    Position start;
+    Position end;
+
+    // Type-specific
+    Optional<ControlKeywordType> control_keyword {};
+    Vector<VariableReference> variable_references {};
+};
+
+static constexpr StringView to_string(Token::Type type)
+{
+    switch (type) {
+    case Token::Type::BracketComment:
+        return "BracketComment"sv;
+    case Token::Type::LineComment:
+        return "LineComment"sv;
+    case Token::Type::Identifier:
+        return "Identifier"sv;
+    case Token::Type::ControlKeyword:
+        return "ControlKeyword"sv;
+    case Token::Type::OpenParen:
+        return "OpenParen"sv;
+    case Token::Type::CloseParen:
+        return "CloseParen"sv;
+    case Token::Type::BracketArgument:
+        return "BracketArgument"sv;
+    case Token::Type::QuotedArgument:
+        return "QuotedArgument"sv;
+    case Token::Type::UnquotedArgument:
+        return "UnquotedArgument"sv;
+    case Token::Type::Garbage:
+        return "Garbage"sv;
+    case Token::Type::VariableReference:
+        return "VariableReference"sv;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
+Optional<ControlKeywordType> control_keyword_from_string(StringView value);
+
+}