using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Drawing.Design;
using System.Linq;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
using HeuristicLab.Problems.DataAnalysis;
using HeuristicLab.Problems.DataAnalysis.Symbolic;

namespace HeuristicLab.Problems.GeneticProgramming.GlucosePrediction {
  public static class Interpreter {
    private class Data {
      public double[] realGluc;
      public double[] realIns;
      public double[] realCh;
      public double[] predGluc;
    }

    public static IEnumerable<double> Apply(ISymbolicExpressionTreeNode model, IDataset dataset, IEnumerable<int> rows) {
      double[] targetGluc = dataset.GetDoubleValues("Glucose_target", rows).ToArray(); // only for skipping rows for which we should not produce an output

      var data = new Data {
        realGluc = dataset.GetDoubleValues("Glucose_Interpol", rows).ToArray(),
        realIns = dataset.GetDoubleValues("Insuline", rows).ToArray(),
        realCh = dataset.GetDoubleValues("CH", rows).ToArray(),
      };
      data.predGluc = new double[data.realGluc.Length];
      Array.Copy(data.realGluc, data.predGluc, data.predGluc.Length);
      for (int k = 0; k < data.predGluc.Length; k++) {
        if (double.IsNaN(targetGluc[k])) {
          data.predGluc[k] = double.NaN;
        } else {
          var rawPred = InterpretRec(model, data, k);
          data.predGluc[k] = Math.Max(0, Math.Min(400, rawPred)); // limit output values of the model to 0 ... 400
        }
      }
      return data.predGluc;
    }

    private static double InterpretRec(ISymbolicExpressionTreeNode node, Data data, int k) {
      if (node.Symbol is SimpleSymbol) {
        switch (node.Symbol.Name) {
          case "+":
          case "+Ins":
          case "+Ch": {
              return InterpretRec(node.GetSubtree(0), data, k) + InterpretRec(node.GetSubtree(1), data, k);
            }
          case "-":
          case "-Ins":
          case "-Ch": {
              return InterpretRec(node.GetSubtree(0), data, k) - InterpretRec(node.GetSubtree(1), data, k);
            }
          case "*":
          case "*Ins":
          case "*Ch": {
              return InterpretRec(node.GetSubtree(0), data, k) * InterpretRec(node.GetSubtree(1), data, k);
            }
          case "/Ch":
          case "/Ins":
          case "/": {
              return InterpretRec(node.GetSubtree(0), data, k) / InterpretRec(node.GetSubtree(1), data, k);
            }
          case "Exp":
          case "ExpIns":
          case "ExpCh": {
              return Math.Exp(InterpretRec(node.GetSubtree(0), data, k));
            }
          case "Sin":
          case "SinIns":
          case "SinCh": {
              return Math.Sin(InterpretRec(node.GetSubtree(0), data, k));
            }
          case "CosCh":
          case "CosIns":
          case "Cos": {
              return Math.Cos(InterpretRec(node.GetSubtree(0), data, k));
            }
          case "LogCh":
          case "LogIns":
          case "Log": {
              return Math.Log(InterpretRec(node.GetSubtree(0), data, k));
            }
          case "Func": {
              // <exprgluc> + <exprch> - <exprins>
              return InterpretRec(node.GetSubtree(0), data, k)
                     + InterpretRec(node.GetSubtree(1), data, k)
                     - InterpretRec(node.GetSubtree(2), data, k);
            }
          case "ExprGluc": {
              return InterpretRec(node.GetSubtree(0), data, k);
            }
          case "ExprCh": {
              return InterpretRec(node.GetSubtree(0), data, k);
            }
          case "ExprIns": {
              return InterpretRec(node.GetSubtree(0), data, k);
            }
          default: {
              throw new InvalidProgramException("Found an unknown symbol " + node.Symbol);
            }
        }
      } else if (node.Symbol is PredictedGlucoseVariableSymbol) {
        var n = (PredictedGlucoseVariableTreeNode)node;
        return n.Weight * data.predGluc[k + n.RowOffset];
      } else if (node.Symbol is RealGlucoseVariableSymbol) {
        var n = (RealGlucoseVariableTreeNode)node;
        return n.Weight * data.realGluc[k + n.RowOffset];
      } else if (node.Symbol is CurvedChVariableSymbol) {
        var n = (CurvedChVariableTreeNode)node;
        double prevVal;
        int prevValDistance;
        GetPrevDataAndDistance(data.realCh, k, out prevVal, out prevValDistance, maxDistance: 48);
        return n.Weight * prevVal * Beta(prevValDistance / 48.0, n.Alpha, n.Beta);
      } else if (node.Symbol is RealInsulineVariableSymbol) {
        var n = (RealInsulineVariableTreeNode)node;
        return n.Weight * data.realIns[k + n.RowOffset];
      } else if (node.Symbol is CurvedInsVariableSymbol) {
        var n = (CurvedInsVariableTreeNode)node;
        double maxVal;
        int maxValDistance;
        var sum = GetSumOfValues(48, k, data.realIns);

        GetMaxValueAndDistance(data.realIns, k, out maxVal, out maxValDistance, maxDistance: 48);
        return n.Weight * (sum - maxVal) * maxVal * Beta(maxValDistance / 48.0, n.Alpha, n.Beta);
      } else if (node.Symbol is Constant) {
        var n = (ConstantTreeNode)node;
        return n.Value;
      } else {
        throw new InvalidProgramException("found unknown symbol " + node.Symbol);
      }
    }

    private static double Beta(double x, double alpha, double beta) {
      return 1.0 / alglib.beta(alpha, beta) * Math.Pow(x, alpha - 1) * Math.Pow(1 - x, beta - 1);
    }

    private static void GetPrevDataAndDistance(double[] vals, int k, out double val, out int dist, int maxDistance = 48, double threshold = 0.0) {
      // look backward from the current idx k and find the first value above the threshold
      for (int i = k; i >= 0 && i >= (k - maxDistance); i--) {
        if (vals[i] > threshold) {
          val = vals[i];
          dist = k - i;
          return;
        }
      }
      val = 0;
      dist = maxDistance;
    }

    private static double GetSumOfValues(int windowSize, int k, double[] vals) {
      var sum = 0.0;
      for (int i = k; i >= 0 && i >= k - windowSize; i--)
        sum += vals[i];
      return sum;
    }

    private static void GetMaxValueAndDistance(double[] vals, int k, out double maxVal, out int dist, int maxDistance = 48) {
      // look backward from the current idx k and find the max value and it's distance
      maxVal = vals[k];
      dist = 0;
      for (int i = k; i >= 0 && i >= (k - maxDistance); i--) {
        if (vals[i] > maxVal) {
          maxVal = vals[i];
          dist = k - i;
        }
      }
    }
  }
}