using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using HeuristicLab.Algorithms.DataAnalysis.KnowledgeIntegration.IntervalArithmetic;

namespace HeuristicLab.Algorithms.DataAnalysis.KnowledgeIntegration.Util {
  public class FormulationParser {

    private static readonly char LEFT_SQUARE_BRACKET = '[';
    private static readonly char RIGHT_SQUARE_BRACKET = ']';
    private static readonly char POSITIVE = '+';
    private static readonly char NEGATIVE = '-';
    private static readonly string INFINITY = "Inf";
    private static readonly string INTERVAL_SEPERATOR = "..";


    public Interval Parse(string intervalString) {
      var interval = new Interval();
      //Remove all whitespaces from interval string
      intervalString = intervalString.Replace(" ", String.Empty);

      if (intervalString[0] == LEFT_SQUARE_BRACKET) {
        //Closed interval start
      } else if (intervalString[0] == RIGHT_SQUARE_BRACKET) {
        //Opened interval start
      } else {
        throw new Exception("Interval has no valid starting symbol!");
      }
      if (intervalString[intervalString.Length-1] == LEFT_SQUARE_BRACKET) {
        //Closed interval start
      } else if (intervalString[intervalString.Length - 1] == RIGHT_SQUARE_BRACKET) {
        //Opened interval start
      } else {
        throw new Exception("Interval has no valid ending symbol!");
      }
      //Get lower bound of interval
      var splited = intervalString.Substring(1, intervalString.Length-2).Split(new string[] { INTERVAL_SEPERATOR }, StringSplitOptions.None);
      if (splited.Length != 2)
        throw new Exception("Interval has no lower/upper-bound seperator!");
      else {
        for (int i = 0; i < 2; ++i) { 
          if (int.TryParse(splited[i], out int lower)) {
            if (i == 0)
              interval.LowerBound = lower;
            else
              interval.UpperBound = lower;
          } else if (splited[i][0] == POSITIVE || splited[i][0] == NEGATIVE) {
            bool isPositive = true;
            if (splited[i][0] == POSITIVE) {
              isPositive = true;
            } else if (splited[i][0] == NEGATIVE) {
              isPositive = false;
            }
            if (splited[i].Substring(1, splited[i].Length-1) != INFINITY) {
              throw new Exception("Lower bound is not a valid interval bound!");
            } else {
              if (isPositive) { 
                if (i == 0)
                  interval.LowerBound = int.MaxValue;
              } else { 
                if (i == 0)
                  interval.LowerBound = int.MinValue;
                }
            }
          } else {
            throw new Exception("Lower bound is not a valid interval bound!");
          }
        }
      }


      return null;
    }
  }
}