Sketched rough parser code construction including some SQL AST classes.

core/SqlParser.h

@@ -0,0 +1,72 @@
+#ifndef SQLPARSER_H
+#define SQLPARSER_H
+
+#include "SqlLexer.h"
+#include <memory>
+#include <optional>
+
+enum class Keyword {
+	NotAKeyword,
+	As,
+	By,
+	Delete,
+	From,
+	Group,
+	Insert,
+	Order,
+	Select,
+	Update,
+	Where,
+
+};
+
+namespace SqlAst {
+
+	class Select;
+	class SelectList;
+
+}
+// The parsing works by calling functions that know either a global part
+// or a smaller specific part and is thus recursive. At certain points a function parsing something specific
+// will reach a point where it is in a valid terminal state and it encounters something that cannot be a continuation
+// of what it is parsing and thus returns succesfully or it is in a non terminal state and encounters something unexpected
+// In both cases it will return hoping that one of the functions above can continue (and recover from the error if needed)
+
+class SqlParser
+{
+public:
+	explicit SqlParser(SqlLexer &lexer);
+
+	void parse();
+
+	/** Checks to see if the next token is the expected keyword.
+	 *
+	 * If it is the token is consumed and the function returns true.
+	 * Otherwise false is returned
+	 */
+	std::optional<SqlToken> expectKeyword(Keyword kw);
+	std::optional<SqlToken> expectSymbol();
+	std::optional<SqlToken> expectToken(BasicTokenType tt);
+
+	/** If the next token is Keyword kw consume it otherwise do nothing.
+	 * In some cases the return value is unimportant as the keyword is completely optional
+	 * in other cases the optional keywords presence might force the next token to be something specific
+	 *
+	 * \return true if the token was found
+	 */
+	bool consumeOptionalKeyword(Keyword kw);
+private:
+
+	//using TokenStack = std::stack<SqlToken>;
+
+	//TokenStack tokenStack;
+
+	SqlLexer &lexer;
+
+	//bool try_reduce(SqkToken token);
+
+
+};
+
+
+#endif // SQLPARSER_H