LibCMake: Introduce a CMake lexer

Userland/Libraries/LibCMake/Lexer.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/GenericLexer.h>
+#include <AK/Vector.h>
+#include <LibCMake/Token.h>
+
+namespace CMake {
+
+class Lexer : private GenericLexer {
+public:
+    static ErrorOr<Vector<Token>> lex(StringView input);
+
+private:
+    Lexer(StringView input);
+
+    ErrorOr<Vector<Token>> lex_file();
+
+    void skip_whitespace();
+
+    void consume_whitespace_or_comments();
+    void consume_command_invocation();
+    void consume_arguments();
+    void consume_argument();
+    void consume_bracket_argument();
+    void consume_quoted_argument();
+    void consume_unquoted_argument();
+    void consume_comment();
+    void consume_open_paren();
+    void consume_close_paren();
+    void consume_garbage();
+
+    StringView read_bracket_argument();
+    static Vector<VariableReference> parse_variable_references_from_argument(StringView argument_value, Position argument_start);
+
+    Position position() const;
+    void next_line();
+
+    void emit_token(Token::Type, StringView value, Position start, Position end, Optional<ControlKeywordType> = {}, Vector<VariableReference> = {});
+
+    Vector<Token> m_tokens;
+    size_t m_line { 0 };
+    size_t m_string_offset_after_previous_newline { 0 };
+};
+
+}