using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text.RegularExpressions;

namespace HeuristicLab.Problems.DataAnalysis {
  public static class IntervalConstraintsParser {
    public static IEnumerable<IntervalConstraint> Parse(string input) {
      var options = RegexOptions.Multiline | RegexOptions.IgnoreCase;
      var matches = Regex.Matches(input, @"^(.*)\bin\b\s*([\[\]])(.*[^\s])(\s*\.\.\s*)([^\s].*)([\[\]])\n*\r*\s*$", options);

      for (var i = 0; i < matches.Count; ++i) {
        if (matches[i].Groups.Count == 7) {
          var intervalConstraint = new IntervalConstraint();
          //pattern 1 = defintion
          var definition = Regex.Replace(matches[i].Groups[1].Value, @"\s *", "");
          if (Regex.IsMatch(definition, @"\/")) {
            var splitted = Regex.Split(definition.Replace(" ", string.Empty), @"\/");
            var match = Regex.Match(splitted[0], @"([d∂])([0-9]|[²³])?(.*[^\s*])");
            if (match.Success) {
              intervalConstraint.NumberOfDerivation = match.Groups[2].Success ? ParseDerivationCount(match.Groups[2].Value) : 1;
              intervalConstraint.Definition = match.Groups[3].Value;
              intervalConstraint.IsDerivation = true;
              var formulation = Regex.Match(splitted[1], @"([d∂])(.*[^²³])([²³])?");
              if (formulation.Success) {
                intervalConstraint.Variable = formulation.Groups[2].Success ? formulation.Groups[2].Value : "";
              }
            } else {
              throw new ArgumentException($"An error occured in the derivation part: {splitted[0]}");
            }
          } else {
            intervalConstraint.Definition = Regex.Match(definition, @".*[^.\s]*").Value;
            intervalConstraint.IsDerivation = false;
          }
          intervalConstraint.Expression = matches[i].Groups[0].Value.Trim(' ', '\t', '\n', '\r');
          intervalConstraint.InclusiveLowerBound = (matches[i].Groups[2].Value == "[");
          intervalConstraint.InclusiveUpperBound = (matches[i].Groups[6].Value == "]");
          intervalConstraint.Interval = new Interval(ParseIntervalBounds(matches[i].Groups[3].Value.Replace(" ", string.Empty)),
            ParseIntervalBounds(matches[i].Groups[5].Value.Replace(" ", string.Empty)));

          yield return intervalConstraint;
        } else {
          throw new ArgumentException($"The given constraint: {matches[i].Value} is not valid.");
        }
      }
    }

    
    public static IEnumerable<IntervalConstraint> ParseInput(string input, string target = "", IEnumerable<string> variables = null) {
      var lines = input.Split(new[] { "\r\n", "\r", "\n" }, StringSplitOptions.None);
      foreach (var line in lines) {
        var trimmedLine = line.TrimStart();
        //Check for target-variable constraint
        if (trimmedLine.StartsWith("Target:")) {
          var start = "Target:".Length;
          var end = trimmedLine.Length;
          var targetConstraint = trimmedLine.Substring(start, end-start);
          var match = Regex.Match(targetConstraint,
            @"([^\s]*)\s*(\bin\b)\s*([\[\]])\s*(\S*)\s*(..)\s*(\S*)\s*([\[\]])");
          if (match.Success) {
            if (match.Groups.Count != 8) {
              throw new ArgumentException("The given target-constraint is not complete!");
            } else {
              if (target != "") {
                if (match.Groups[1].Value.Trim() != target) {
                  throw new ArgumentException("The given target variable is not in the given dataset!");
                }
              }
              var lowerBound = ParseIntervalBounds(match.Groups[4].Value);
              var upperBound = ParseIntervalBounds(match.Groups[6].Value);
              var constraint = new IntervalConstraint("Target:" + match.Groups[0].Value);
              constraint.Expression = "Target:" + match.Groups[0].Value;
              constraint.Definition = "Target " + match.Groups[1].Value.Trim();
              constraint.Variable = match.Groups[1].Value.Trim();
              constraint.InclusiveLowerBound = match.Groups[3].Value.Trim() == "[";
              constraint.InclusiveUpperBound = match.Groups[7].Value.Trim() == "]";
              constraint.IsDerivation = false;
              constraint.NumberOfDerivation = 0;
              constraint.Interval = new Interval(lowerBound, upperBound);

              yield return constraint;
            }
          } else {
            throw new ArgumentException("The inserted target constraint is not valid!");
          }
          //Check for derivation
        } else if (trimmedLine.StartsWith("d") || trimmedLine.StartsWith("\u2202")) {
          var match = Regex.Match(trimmedLine,
            @"([d∂])([²³])?\s*(\S*)\s*(\/)([d∂])\s*([^²³]*)([²³])?\s*\bin\b\s*([\[\]])\s*(\S*)\s*(..)\s*(\S*)\s*([\[\]])");

          if (match.Success) {
            if (match.Groups.Count != 13) {
              throw new ArgumentException("The given derivation-constraint is not complete");
            } else {
              if (target != "") {
                if (match.Groups[3].Value != target) 
                  throw new ArgumentException("The given target variable is not given in the dataset!");
              }

              if (variables != null && variables.Any()) {
                if (variables.All(v => v != match.Groups[6].Value.Trim())) {
                  throw new ArgumentException("The given variable does not exist in the dataset!");
                }
              }

              if (match.Groups[2].Value.Trim() != "" || match.Groups[7].Value.Trim() != "") {
                if (match.Groups[2].Value.Trim() == "" || match.Groups[7].Value.Trim() == "")
                  throw new ArgumentException("Number of derivation has to be written on both sides!");
                if (match.Groups[2].Value.Trim() != match.Groups[7].Value.Trim())
                  throw new ArgumentException("Derivation number is not equal on both sides!");
              }

              var lowerBound = ParseIntervalBounds(match.Groups[9].Value);
              var upperBound = ParseIntervalBounds(match.Groups[11].Value);
              var constraint = new IntervalConstraint(match.Groups[0].Value);
              constraint.Expression = match.Groups[0].Value;
              constraint.Definition = match.Groups[1].Value + match.Groups[2].Value + match.Groups[3].Value +
                                      match.Groups[4].Value + match.Groups[5].Value + match.Groups[6].Value + match.Groups[7].Value;
              constraint.IsDerivation = true;
              constraint.InclusiveLowerBound = match.Groups[8].Value.Trim() == "[";
              constraint.InclusiveUpperBound = match.Groups[12].Value.Trim() == "]";
              constraint.Variable = match.Groups[6].Value.Trim();
              constraint.NumberOfDerivation = ParseDerivationCount(match.Groups[2].Value.Trim());
              constraint.Interval = new Interval(lowerBound, upperBound);

              yield return constraint;
            }
          } else {
            throw new ArgumentException("The inserted derivation constraint is not valid!");
          }
          //Check for comment
        } else if (trimmedLine.StartsWith("#") || trimmedLine == "") {
          //If it is a comment just continue without saving anything
          continue;
        } else {
          throw new ArgumentException("Error at your constraints definition constraints have to start with Target: | d | \u2202 | #");
        }
      }
    }

    private static double ParseIntervalBounds(string input) {
      input = input.ToLower();
      switch (input) {
        case "+inf.":
        case "inf.":
          return double.PositiveInfinity;
        case "-inf.":
          return double.NegativeInfinity;
        default: {
            if (double.TryParse(input, NumberStyles.Any, CultureInfo.InvariantCulture, out var value)) {
              return value;
            } else {
              throw new ArgumentException("The given boundary is not a double value!");
            }
          }
      }
    }

    private static int ParseDerivationCount(string input) {
      switch (input) {
        case "":
          return 1;
        case "²":
          return 2;
        case "³":
          return 3;
        default:
          int.TryParse(input, out var value);
          return value;
      }
    }
  }
}