// Copyright 2023 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <Parsers/TokenIterator.h>


namespace DB
{

UnmatchedParentheses checkUnmatchedParentheses(TokenIterator begin, Token * last)
{
    /// We have just two kind of parentheses: () and [].
    UnmatchedParentheses stack;

    for (TokenIterator it = begin; it.isValid() && &it.get() <= last; ++it)
    {
        if (it->type == TokenType::OpeningRoundBracket || it->type == TokenType::OpeningSquareBracket)
        {
            stack.push_back(*it);
        }
        else if (it->type == TokenType::ClosingRoundBracket || it->type == TokenType::ClosingSquareBracket)
        {
            if (stack.empty())
            {
                /// Excessive closing bracket.
                stack.push_back(*it);
                return stack;
            }
            else if (
                (stack.back().type == TokenType::OpeningRoundBracket && it->type == TokenType::ClosingRoundBracket)
                || (stack.back().type == TokenType::OpeningSquareBracket
                    && it->type == TokenType::ClosingSquareBracket))
            {
                /// Valid match.
                stack.pop_back();
            }
            else
            {
                /// Closing bracket type doesn't match opening bracket type.
                stack.push_back(*it);
                return stack;
            }
        }
    }

    /// If stack is not empty, we have unclosed brackets.
    return stack;
}

} // namespace DB