//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="RegexInterpreter"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using StgSharp.RegularAnalysis.Abstraction;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Threading.Tasks;

namespace StgSharp.RegularAnalysis.TextRegex
{
    public class RegexInterpreter
    {

        private AbstractSyntaxTree<RegexAstNode, RegexElementLabel> _tree = new();

        private CompileStack<RegexAstNode, RegexElementLabel> _stack = new();

        public AbstractSyntaxTree<RegexAstNode, RegexElementLabel> Analyze(
                                                                   string regex
        )
        {
            RegexTokenReader reader = new RegexTokenReader(regex);
            TokenParser<RegexElementLabel, RegexElementLabel> lexer = reader.Pipe(() => new RegexTokenParser());

            while (lexer.TryReadToken(out Token<RegexElementLabel> token))
            {
                if ((token.Flag & RegexElementLabel.SEQUENCE) != 0)
                {
                    // char or charset
                    _stack.PushOperand(new RegexAstNode(token));
                } else if ((token.Flag & RegexElementLabel.GROUP_BEGIN) != 0)
                {
                    _stack.IncreaseDepth(0);
                } else if ((token.Flag & RegexElementLabel.GROUP_END) != 0)
                {
                    // TODO: close all nodes here
                    while (_stack.TryPopOperator(out RegexAstNode? op))
                    {
                        ProcessOperator(op);
                    }
                    if (_stack.OperandInDepthCount != 1) {
                        throw new InvalidOperationException();
                    }
                    _stack.DecreaseDepth();
                } else if ((token.Flag & RegexElementLabel.OPERATOR) != 0) { }
            }
        }

        private void ProcessOperator(
                     RegexAstNode op
        )
        {
            if (op.EqualityTypeConvert == RegexElementLabel.CONCAT)
            {
                if (_stack.TryPopOperand(out RegexAstNode? _1) &&
                    _stack.TryPopOperand(out RegexAstNode? _2))
                {
                    if (RegexAstNode.TryMergeUnit(_2, _1, out RegexAstNode? _3))
                    {
                        _stack.PushOperand(_3);
                    } else
                    {
                        op.Left = _2;
                        op.Right = _1;
                        _stack.PushOperand(op);
                    }
                } else
                {
                    throw new InvalidOperationException("Insufficient operands for CONCAT operator.");
                }
            } else if (op.EqualityTypeConvert == RegexElementLabel.COUNT)
            {
                if (_stack.TryPopOperand(out RegexAstNode? _1))
                {
                    op.Left = _1;
                    _stack.PushOperand(op);
                } else
                {
                    throw new InvalidOperationException("Insufficient operands for CONCAT operator.");
                }
            } else if (op.EqualityTypeConvert == RegexElementLabel.ALT)
            {
                if (_stack.TryPopOperand(out RegexAstNode? _1) &&
                    _stack.TryPopOperand(out RegexAstNode? _2))
                {
                    op.Left = _1;
                    op.Right = _2;
                    _stack.PushOperand(op);
                } else
                {
                    throw new InvalidOperationException("Insufficient operands for CONCAT operator.");
                }
            }
        }

    }
}