should be it

external/duckdb/extension/autocomplete/include/parser/peg_parser.hpp

@@ -0,0 +1,66 @@
+
+#pragma once
+#include "duckdb/common/case_insensitive_map.hpp"
+#include "duckdb/common/string_map_set.hpp"
+
+namespace duckdb {
+enum class PEGRuleType {
+	LITERAL,   // literal rule ('Keyword'i)
+	REFERENCE, // reference to another rule (Rule)
+	OPTIONAL,  // optional rule (Rule?)
+	OR,        // or rule (Rule1 / Rule2)
+	REPEAT     // repeat rule (Rule1*
+};
+
+enum class PEGTokenType {
+	LITERAL,       // literal token ('Keyword'i)
+	REFERENCE,     // reference token (Rule)
+	OPERATOR,      // operator token (/ or )
+	FUNCTION_CALL, // start of function call (i.e. Function(...))
+	REGEX          // regular expression ([ \t\n\r] or <[a-z_]i[a-z0-9_]i>)
+};
+
+struct PEGToken {
+	PEGTokenType type;
+	string_t text;
+};
+
+struct PEGRule {
+	string_map_t<idx_t> parameters;
+	vector<PEGToken> tokens;
+
+	void Clear() {
+		parameters.clear();
+		tokens.clear();
+	}
+};
+
+struct PEGParser {
+public:
+	void ParseRules(const char *grammar);
+	void AddRule(string_t rule_name, PEGRule rule);
+
+	case_insensitive_map_t<PEGRule> rules;
+};
+
+enum class PEGParseState {
+	RULE_NAME,      // Rule name
+	RULE_SEPARATOR, // look for <-
+	RULE_DEFINITION // part of rule definition
+};
+
+inline bool IsPEGOperator(char c) {
+	switch (c) {
+	case '/':
+	case '?':
+	case '(':
+	case ')':
+	case '*':
+	case '!':
+		return true;
+	default:
+		return false;
+	}
+}
+
+} // namespace duckdb