using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;

namespace HeuristicLab.Problems.GrammaticalOptimization {
  public class PermutationProblem : ISymbolicExpressionTreeProblem {
    private const string grammarString = @"
G(S):
S -> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | a | b | c | d | e | f | 0S | 1S | 2S | 3S | 4S | 5S | 6S | 7S | 8S | 9S | aS | bS | cS | dS | eS | fS
";

    private const string hlGrammarString = @"
G(S):
S -> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | a | b | c | d | e | f | SS
";

    private readonly IGrammar grammar;
    public string Name { get { return "Permutation"; } }
    public PermutationProblem() {
      this.grammar = new Grammar(grammarString);
      this.TreeBasedGPGrammar = new Grammar(hlGrammarString);
    }

    public double BestKnownQuality(int maxLen) {
      return Math.Min(16.0, maxLen);
    }

    public IGrammar Grammar {
      get { return grammar; }
    }

    public double Evaluate(string sentence) {
      // sentence must contain only terminal symbols, we are not checking if the sentence is syntactically valid here because it would be too slow!
      Debug.Assert(sentence.Any(c => grammar.IsTerminal(c)));
      return sentence.Distinct().Count();
    }

    public string CanonicalRepresentation(string phrase) {
      return phrase;
    }

    public IEnumerable<Feature> GetFeatures(string phrase) {
      throw new NotImplementedException();
    }
    public IGrammar TreeBasedGPGrammar { get; private set; }
    public string ConvertTreeToSentence(ISymbolicExpressionTree tree) {
      var sb = new StringBuilder();
      foreach (var s in tree.Root.GetSubtree(0).GetSubtree(0).IterateNodesPrefix()) {
        if (s.Symbol.Name == "S") continue;
        sb.Append(s.Symbol.Name);
      }
      return sb.ToString();
    }
  }
}