xo-reader2: + ExpectSymbolSsm + SyntaxStateMachine.on_parsed_symbol

xo-reader2/include/xo/reader2/DExpectSymbolSsm.hpp

@@ -0,0 +1,91 @@
+/* file DExpectSymbolSsm.hpp
+ *
+ * author: Roland Conybeare, Aug 2024
+ */
+
+#pragma once
+
+#include "ParserStateMachine.hpp"
+//#include "SyntaxStateMachine.hpp"
+#include "syntaxstatetype.hpp"
+#include <xo/facet/obj.hpp>
+
+namespace xo {
+    namespace scm {
+        /** @class DExpectSymbolSsm
+         *  @brief state machine to expect + capture a symbol
+         *
+         *  For example:
+         *  -  lhs in a define-expression
+         **/
+        class DExpectSymbolSsm {
+        public:
+            using DArena = xo::mm::DArena;
+
+        public:
+            DExpectSymbolSsm();
+
+            /** create instance using memory from @p parser_mm **/
+            static DExpectSymbolSsm * make(DArena & parser_mm);
+
+            /** start nested parser expecting a symbol,
+             *  on top of parser state machine @p p_psm.
+             *  On success will deliver symbol by invoking
+             *    .on_symbol(sym, p_psm)
+             *  to the state machine on top of the stack
+             *  as of when this start() method invoked
+             **/
+            static void start(DArena & parser_mm,
+                              ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming token @p tk,
+             *  with overall parser state in @p p_psm
+             **/
+            static void on_symbol_token(const Token & tk,
+                                        ParserStateMachine * p_psm);
+
+            /** @defgroup scm-expectsymbol-ssm-facet syntaxstatemachine facet methods **/
+            ///@{
+
+            /** identifies the ssm implemented here **/
+            syntaxstatetype ssm_type() const noexcept;
+
+            /** text describing expected/allowed input to this ssm in current state.
+             *  Intended to drive error mesages
+             **/
+            std::string_view get_expect_str() const noexcept;
+
+            /** update state for this syntax on incoming token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_def_token(const Token & tk,
+                              ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_if_token(const Token & tk,
+                             ParserStateMachine * p_psm);
+
+            /** update state for this syntax after parsing a symbol @p sym;
+             *  overall parser state in @p p_psm.
+             *
+             *  NOTE:
+             *  might not be obvious that this is unreachable.
+             *  DExpectSymbolSsm converts a symbol token,
+             *  and delivers it to parent ssm using this entry point.
+             *  This method would only be called if consecutive
+             *  DExpectSymbolSsm instances on parser stack;
+             *  which scenario never occurs in Schematika syntax
+             **/
+            void on_parsed_symbol(std::string_view sym,
+                                  ParserStateMachine * p_psm);
+
+
+            ///@}
+
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DExpectSymbolSsm.hpp */