//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="AbstractSyntaxTree"
// 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.Collections;

using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Xml.Schema;

namespace StgSharp.RegularAnalysis.Abstraction
{
    public sealed class AbstractSyntaxTree<TNode, TType> where TNode : ISyntaxNode<TNode, TType>
        where TType : unmanaged
    {

        private HashSet<TNode> _allToken = new();

        public HashSet<TNode> AllNodes
        {
            get { return _allToken; }
        }

        public int Count
        {
            get { return _allToken.Count; }
        }

        public TNode Root
        {
            get;
            internal set
            {
                if (_allToken.Contains(value)) {
                    field = value;
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool AddNode(
                    TNode node
        )
        {
            return _allToken.Add(node);
        }

        public bool Contains(
                    TNode node
        )
        {
            return _allToken.Contains(node);
        }

        public IEnumerator<TNode> GetEnumerator()
        {
            return new Enumerator(this);
        }

        private class Enumerator : IEnumerator<TNode>
        {

            private int _state,_target; // 0: not started, 1: on right, 2: ended
            private Stack<Record> _recycle;
            private Stack<Record> _stack;
            private TNode _lRoot;
            private TNode _root;

            public Enumerator(
                   AbstractSyntaxTree<TNode, TType> tree
            )
            {
                _root = tree.Root;
                _stack = [];
                _recycle = [];
            }

            public TNode Current
            {
                get
                {
                    if (_stack.TryPeek(out Record? r)) {
                        return r.Node;
                    }
                    return TNode.Empty;
                }
            }

            public void Dispose()
            {
                return;
            }

            public bool MoveNext()
            {
                while (_stack.TryPeek(out Record? cur))
                {
                    switch (cur.State)
                    {
                        case 0:
                            cur.State++;
                            if (TNode.IsNullOrEmpty(cur.Node.Left))
                            {
                                goto case 1;
                            } else
                            {
                                _stack.Push(GetNewRecord(cur.Node.Left));
                                return true;
                            }
                        case 1:
                            cur.State++;
                            if (TNode.IsNullOrEmpty(cur.Node.Right))
                            {
                                goto case 2;
                            } else
                            {
                                _stack.Push(GetNewRecord(cur.Node.Right));
                                return true;
                            }
                        case 2:
                            if (TNode.IsNullOrEmpty(cur.Node.Next))
                            {
                                _recycle.Push(_stack.Pop());
                                if (_stack.Count == 0) {
                                    return false;
                                }
                            } else
                            {
                                _stack.Push(GetNewRecord(cur.Node.Next));
                                return true;
                            }
                            break;
                        default:
                            break;
                    }
                }
                _stack.Push(GetNewRecord(_root));
                return true;
            }

            public void Reset()
            {
                _stack.Clear();
                _state = 0;
            }

            private Record GetNewRecord(
                           TNode node
            )
            {
                if (_recycle.TryPop(out Record? r))
                {
                    r.State = 0;
                    r.Node = node;
                    return r;
                }
                return new Record(node, 0);
            }

            object IEnumerator.Current => Current;

            private class Record(
                          TNode node,
                          int state
            )
            {

                public int State { get; set; } = state;

                public TNode Node { get; set; } = node;

            }

        }

    }
}