#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2018 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
  [Item("C# Symbolic Expression Tree Formatter", "A string formatter that converts symbolic expression trees to C# code.")]
  [StorableClass]
  public sealed class CSharpSymbolicExpressionTreeStringFormatter : NamedItem, ISymbolicExpressionTreeStringFormatter {
    [StorableConstructor]
    private CSharpSymbolicExpressionTreeStringFormatter(bool deserializing) : base(deserializing) { }
    private CSharpSymbolicExpressionTreeStringFormatter(CSharpSymbolicExpressionTreeStringFormatter original, Cloner cloner) : base(original, cloner) { }
    public CSharpSymbolicExpressionTreeStringFormatter()
      : base() {
      Name = ItemName;
      Description = ItemDescription;
    }
    public override IDeepCloneable Clone(Cloner cloner) {
      return new CSharpSymbolicExpressionTreeStringFormatter(this, cloner);
    }

    public string Format(ISymbolicExpressionTree symbolicExpressionTree) {
      // skip root and start symbols
      StringBuilder strBuilder = new StringBuilder();
      GenerateHeader(strBuilder, symbolicExpressionTree);
      FormatRecursively(symbolicExpressionTree.Root.GetSubtree(0).GetSubtree(0), strBuilder);
      GenerateFooter(strBuilder);
      return strBuilder.ToString();
    }

    private string VariableName2Identifier(string name) {     
      /*
       * identifier-start-character:
       *    letter-character
       *    _ (the underscore character U+005F)
       *  identifier-part-characters:
       *    identifier-part-character
       *    identifier-part-characters   identifier-part-character
       *  identifier-part-character:
       *    letter-character
       *    decimal-digit-character
       *    connecting-character
       *    combining-character
       *    formatting-character
       *  letter-character:
       *    A Unicode character of classes Lu, Ll, Lt, Lm, Lo, or Nl 
       *    A unicode-escape-sequence representing a character of classes Lu, Ll, Lt, Lm, Lo, or Nl
       *  combining-character:
       *    A Unicode character of classes Mn or Mc 
       *    A unicode-escape-sequence representing a character of classes Mn or Mc
       *  decimal-digit-character:
       *    A Unicode character of the class Nd 
       *    A unicode-escape-sequence representing a character of the class Nd
       *  connecting-character:
       *    A Unicode character of the class Pc 
       *    A unicode-escape-sequence representing a character of the class Pc
       *  formatting-character:
       *    A Unicode character of the class Cf 
       *    A unicode-escape-sequence representing a character of the class Cf
       */

      var invalidIdentifierStarts = new Regex(@"[^_\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}\p{Nl}]");
      var invalidIdentifierParts = new Regex(@"[^\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}\p{Nl}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\p{Cf}]");
      return "@" +
        (invalidIdentifierStarts.IsMatch(name.Substring(0, 1)) ? "_" : "") + // prepend '_' if necessary
        invalidIdentifierParts.Replace(name, "_");
    }

    private void FormatRecursively(ISymbolicExpressionTreeNode node, StringBuilder strBuilder) {
      // TODO: adapt to interpreter semantics. The HL interpreter also allows Boolean operations on reals
      if (node.Subtrees.Any()) {
        if (node.Symbol is Addition) {
          FormatOperator(node, "+", strBuilder);
        } else if (node.Symbol is And) {
          FormatOperator(node, "&&", strBuilder);
        } else if (node.Symbol is Average) {
          FormatFunction(node, "Average", strBuilder);
        } else if (node.Symbol is Cosine) {
          FormatFunction(node, "Math.Cos", strBuilder);
        } else if (node.Symbol is Division) {
          FormatDivision(node, strBuilder);
        } else if (node.Symbol is Exponential) {
          FormatFunction(node, "Math.Exp", strBuilder);
        } else if (node.Symbol is GreaterThan) {
          FormatOperator(node, ">", strBuilder);
        } else if (node.Symbol is IfThenElse) {
          FormatFunction(node, "EvaluateIf", strBuilder);
        } else if (node.Symbol is LessThan) {
          FormatOperator(node, "<", strBuilder);
        } else if (node.Symbol is Logarithm) {
          FormatFunction(node, "Math.Log", strBuilder);
        } else if (node.Symbol is Multiplication) {
          FormatOperator(node, "*", strBuilder);
        } else if (node.Symbol is Not) {
          FormatOperator(node, "!", strBuilder);
        } else if (node.Symbol is Or) {
          FormatOperator(node, "||", strBuilder);
        } else if (node.Symbol is Xor) {
          FormatOperator(node, "^", strBuilder);
        } else if (node.Symbol is Sine) {
          FormatFunction(node, "Math.Sin", strBuilder);
        } else if (node.Symbol is Subtraction) {
          FormatSubtraction(node, strBuilder);
        } else if (node.Symbol is Tangent) {
          FormatFunction(node, "Math.Tan", strBuilder);
        } else if (node.Symbol is Square) {
          FormatSquare(node, strBuilder);
        } else if (node.Symbol is SquareRoot) {
          FormatFunction(node, "Math.Sqrt", strBuilder);
        } else if (node.Symbol is Power) {
          FormatFunction(node, "Math.Pow", strBuilder);
        } else if (node.Symbol is Root) {
          FormatRoot(node, strBuilder);
        } else {
          throw new NotSupportedException("Formatting of symbol: " + node.Symbol + " not supported for C# symbolic expression tree formatter.");
        }
      } else {
        if (node is VariableTreeNode) {
          var varNode = node as VariableTreeNode;
          strBuilder.AppendFormat("{0} * {1}", VariableName2Identifier(varNode.VariableName), varNode.Weight.ToString("g17", CultureInfo.InvariantCulture));
        } else if (node is ConstantTreeNode) {
          var constNode = node as ConstantTreeNode;
          strBuilder.Append(constNode.Value.ToString("g17", CultureInfo.InvariantCulture));
        } else if (node.Symbol is FactorVariable) {
          var factorNode = node as FactorVariableTreeNode;
          FormatFactor(factorNode, strBuilder);
        } else if (node.Symbol is BinaryFactorVariable) {
          var binFactorNode = node as BinaryFactorVariableTreeNode;
          FormatBinaryFactor(binFactorNode, strBuilder);
        } else {
          throw new NotSupportedException("Formatting of symbol: " + node.Symbol + " not supported for C# symbolic expression tree formatter.");
        }
      }
    }

    private void FormatFactor(FactorVariableTreeNode node, StringBuilder strBuilder) {
      strBuilder.AppendFormat("EvaluateFactor({0}, new [] {{ {1} }}, new [] {{ {2} }})", VariableName2Identifier(node.VariableName),
        string.Join(",", node.Symbol.GetVariableValues(node.VariableName).Select(name => "\"" + name + "\"")), string.Join(",", node.Weights.Select(v => v.ToString(CultureInfo.InvariantCulture))));
    }

    private void FormatBinaryFactor(BinaryFactorVariableTreeNode node, StringBuilder strBuilder) {
      strBuilder.AppendFormat(CultureInfo.InvariantCulture, "EvaluateBinaryFactor({0}, \"{1}\", {2})", VariableName2Identifier(node.VariableName), node.VariableValue, node.Weight);
    }

    private void FormatSquare(ISymbolicExpressionTreeNode node, StringBuilder strBuilder) {
      strBuilder.Append("Math.Pow(");
      FormatRecursively(node.GetSubtree(0), strBuilder);
      strBuilder.Append(", 2)");
    }

    private void FormatRoot(ISymbolicExpressionTreeNode node, StringBuilder strBuilder) {
      strBuilder.Append("Math.Pow(");
      FormatRecursively(node.GetSubtree(0), strBuilder);
      strBuilder.Append(", 1.0 / (");
      FormatRecursively(node.GetSubtree(1), strBuilder);
      strBuilder.Append("))");
    }

    private void FormatDivision(ISymbolicExpressionTreeNode node, StringBuilder strBuilder) {
      if (node.SubtreeCount == 1) {
        strBuilder.Append("1.0 / ");
        FormatRecursively(node.GetSubtree(0), strBuilder);
      } else {
        FormatRecursively(node.GetSubtree(0), strBuilder);
        strBuilder.Append("/ (");
        for (int i = 1; i < node.SubtreeCount; i++) {
          if (i > 1) strBuilder.Append(" * ");
          FormatRecursively(node.GetSubtree(i), strBuilder);
        }
        strBuilder.Append(")");
      }
    }

    private void FormatSubtraction(ISymbolicExpressionTreeNode node, StringBuilder strBuilder) {
      if (node.SubtreeCount == 1) {
        strBuilder.Append("-");
        FormatRecursively(node.GetSubtree(0), strBuilder);
        return;
      }
      //Default case: more than 1 child
      FormatOperator(node, "-", strBuilder);
    }

    private void FormatOperator(ISymbolicExpressionTreeNode node, string symbol, StringBuilder strBuilder) {
      strBuilder.Append("(");
      foreach (var child in node.Subtrees) {
        FormatRecursively(child, strBuilder);
        if (child != node.Subtrees.Last())
          strBuilder.Append(" " + symbol + " ");
      }
      strBuilder.Append(")");
    }

    private void FormatFunction(ISymbolicExpressionTreeNode node, string function, StringBuilder strBuilder) {
      strBuilder.Append(function + "(");
      foreach (var child in node.Subtrees) {
        FormatRecursively(child, strBuilder);
        if (child != node.Subtrees.Last())
          strBuilder.Append(", ");
      }
      strBuilder.Append(")");
    }

    private void GenerateHeader(StringBuilder strBuilder, ISymbolicExpressionTree symbolicExpressionTree) {
      strBuilder.AppendLine("using System;");
      strBuilder.AppendLine("using System.Linq;" + Environment.NewLine);
      strBuilder.AppendLine("namespace HeuristicLab.Models {");
      strBuilder.AppendLine("public static class Model {");
      GenerateAverageSource(strBuilder);
      GenerateIfThenElseSource(strBuilder);
      GenerateFactorSource(strBuilder);
      GenerateBinaryFactorSource(strBuilder);
      strBuilder.Append(Environment.NewLine + "public static double Evaluate (");

      // here we don't have access to problemData to determine the type for each variable (double/string) therefore we must distinguish based on the symbol type
      HashSet<string> doubleVarNames = new HashSet<string>();
      foreach (var node in symbolicExpressionTree.IterateNodesPostfix().Where(x => x is VariableTreeNode || x is VariableConditionTreeNode)) {
        doubleVarNames.Add(((IVariableTreeNode)node).VariableName);
      }

      HashSet<string> stringVarNames = new HashSet<string>();
      foreach (var node in symbolicExpressionTree.IterateNodesPostfix().Where(x => x is BinaryFactorVariableTreeNode || x is FactorVariableTreeNode)) {
        stringVarNames.Add(((IVariableTreeNode)node).VariableName);
      }

      var orderedNames = stringVarNames.OrderBy(n => n, new NaturalStringComparer()).Select(n => "string " + VariableName2Identifier(n) + " /* " + n + " */");
      strBuilder.Append(string.Join(", ", orderedNames));

      if (stringVarNames.Any() && doubleVarNames.Any())
        strBuilder.AppendLine(",");
      orderedNames = doubleVarNames.OrderBy(n => n, new NaturalStringComparer()).Select(n => "double " + VariableName2Identifier(n) + " /* " + n + " */");
      strBuilder.Append(string.Join(", ", orderedNames));


      strBuilder.AppendLine(") {");
      strBuilder.Append("double result = ");
    }

    private void GenerateFooter(StringBuilder strBuilder) {
      strBuilder.AppendLine(";");

      strBuilder.AppendLine("return result;");
      strBuilder.AppendLine("}");
      strBuilder.AppendLine("}");
      strBuilder.AppendLine("}");
    }

    private void GenerateAverageSource(StringBuilder strBuilder) {
      strBuilder.AppendLine("private static double Average(params double[] values) {");
      strBuilder.AppendLine("  return values.Average();");
      strBuilder.AppendLine("}");
    }

    private void GenerateIfThenElseSource(StringBuilder strBuilder) {
      strBuilder.AppendLine("private static double EvaluateIf(bool condition, double then, double @else) {");
      strBuilder.AppendLine("   return condition ? then : @else;");
      strBuilder.AppendLine("}");
    }

    private void GenerateFactorSource(StringBuilder strBuilder) {
      strBuilder.AppendLine("private static double EvaluateFactor(string factorValue, string[] factorValues, double[] constants) {");
      strBuilder.AppendLine("   for(int i=0;i<factorValues.Length;i++) " +
                            "      if(factorValues[i] == factorValue) return constants[i];" +
                            "   throw new ArgumentException();");
      strBuilder.AppendLine("}");
    }

    private void GenerateBinaryFactorSource(StringBuilder strBuilder) {
      strBuilder.AppendLine("private static double EvaluateBinaryFactor(string factorValue, string targetValue, double weight) {");
      strBuilder.AppendLine("  return factorValue == targetValue ? weight : 0.0;");
      strBuilder.AppendLine("}");
    }

  }
}