using System;
using System.Collections.Generic;
using System.Linq;
using HeuristicLab.Core;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
using HeuristicLab.EvolutionTracking;

namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
  public class SymbolicDataAnalysisExpressionAfterCrossoverOperator : AfterCrossoverOperator<ISymbolicExpressionTree> {
    public override IOperation Apply() {
      var child = ChildParameter.ActualValue;
      var childVertex = (IGenealogyGraphNode)GenealogyGraph[child];
      var arcs = childVertex.InArcs.ToList();
      var nodes0 = (List<ISymbolicExpressionTreeNode>)arcs[0].Data;
      var nodes1 = (List<ISymbolicExpressionTreeNode>)arcs[1].Data;
      var childNodes = child.IterateNodesPrefix().ToList();
      IFragment<ISymbolicExpressionTreeNode> fragment = null;
      for (int i = 0; i < Math.Min(nodes0.Count, childNodes.Count); ++i) {
        if (nodes0[i] == childNodes[i]) continue;
        fragment = new Fragment<ISymbolicExpressionTreeNode> {
          Root = childNodes[i],
          Index1 = i,
        };
        fragment.Index2 = nodes1.IndexOf(fragment.Root);
        break;
      }
      // if the fragment is null then it means crossover did not do anything
      //      if (fragment == null) throw new Exception("Could not determine fragment!");

      arcs[0].Data = null;
      arcs[1].Data = fragment;

      return base.Apply();
    }
  }
}