#include "SqlParser.h"
#include "SqlAstSelect.h"
#include <stdexcept>
#include <unordered_map>

using namespace SqlAst;

Keyword isKeyword(const QString &symbol)
{
	static std::unordered_map<std::string, Keyword> lookup_map = {
		{ "as",     Keyword::As },
		{ "by",     Keyword::By },
		{ "delete", Keyword::Delete },
		{ "from",   Keyword::From },
		{ "group",  Keyword::Group },
		{ "insert", Keyword::Insert },
		{ "order",  Keyword::Order },
		{ "select", Keyword::Select },
		{ "update", Keyword::Update },
		{ "where",  Keyword::Where }
	};

	auto res = lookup_map.find(symbol.toLower().toUtf8().data());
	if (res != lookup_map.end())
		return res->second;

	return Keyword::NotAKeyword;
}


SqlParser::SqlParser(SqlLexer &lexer)
	: lexer(lexer)
{

}

std::shared_ptr<SqlAst::Node> SqlParser::parse()
{
	// Basic algo:
	// LOOP
	//   GET token
	//   IF NOT try_reduce(token)
	//   THEN SHIFT
	// END LOOP
	std::shared_ptr<SqlAst::Node> result;
	while (true) {
		SqlToken token = lexer.nextBasicToken();
		if (token.ok) {
			if (token.tokenType == BasicTokenType::Symbol) {
				Keyword kw = isKeyword(token.out);
				switch (kw) {
				case Keyword::Select:
					parseSelect(*this);
					break;

				case Keyword::NotAKeyword:
				default:
					// unexpected
					break;
				}
			}
			else if (token.tokenType == BasicTokenType::End) {
				// Are we at the top level?
				return result;
			}
		}
		else {
			// error during lexical analysis, need to recover
			throw std::runtime_error("Unrecognized input");
		}
	}
}




//bool try_reduce(SqkToken token)
//{
//	// what state are we in? what are we expecting

//}