using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using CompilerDesignIflr1;

namespace CompilerDesignIFlr1
{
    internal class StateMachine
    {
        internal LR1Table Table;
        internal LexicalAnalysis AnalysisResult;
        internal LR1Creator Creator;
        internal List<(LR1Unit, int)> stack = [(new LR1Unit("End","#"),0)];
        internal Stack<LR1Unit> Tokens;

        internal StateMachine(LR1Table table, LexicalAnalysis analysis, LR1Creator creator)
        {
            Table = table;
            AnalysisResult = analysis;
            Creator = creator;
            Tokens = AnalysisResult.GetStack();
            Compute();
        }

        internal void Compute()
        {
            while (true)
            {
                if (ComputeOnce(Tokens.Pop()))
                    break;
            }
        }

        internal bool ComputeOnce(LR1Unit unit)
        {
            var (action, destination) = Table.Rows[stack[^1].Item2].Next(unit.Name);
            switch (action)
            {
                case "GOTO":
                    stack.Add((unit, destination));
                    break;
                case "Reduce":
                    var reduceUnit = Creator.UnitIndex[destination];
                    if (reduceUnit.CanReduce(stack.Select(x => x.Item1).ToList()))
                    {
                        stack.RemoveRange(stack.Count - reduceUnit.Grammar.Count, reduceUnit.Grammar.Count); 
                    }
                    else
                        throw new Exception("Reduce not allow.");
                    Console.WriteLine(reduceUnit);
                    Tokens.Push(unit);
                    Tokens.Push(reduceUnit.Clone());
                    break;
                case "ACC":
                    Console.WriteLine(Creator.UnitIndex[destination]);
                    return true;
                default:
                    throw new Exception("Action is not recognized.");
            }
            return false;
        }
    }
}