/*****************************************************************************

This class has been written by Łukasz Światkowski
Cleaned up spaghetti code and improved by Elmü (elmue@gmx.de)

*****************************************************************************/

using Microsoft.CSharp;
using System;
using System.CodeDom.Compiler;
using System.Reflection;
using System.Text;
using delRendererFunction = Plot3D.Editor3D.delRendererFunction;

namespace Plot3D
{
	public delegate double delCompiledFunction(params double[] x);

	public static class FunctionCompiler
	{
		private const String EVAL_CLASS =
			  "using {1};\n"
			+ "public class Eval\n"
			+ "{{\n"
			+ "	public static double e  {{ get {{ return System.Math.E;  }}  }}\n"
			+ "	public static double pi {{ get {{ return System.Math.PI; }}  }}\n"
			// -------------------------------------------------------
			+ "	public static double abs  (double x)           {{ return System.Math.Abs(x);      }}\n"
			+ "	public static double acos (double x)           {{ return System.Math.Acos(x);     }}\n"
			+ "	public static double asin (double x)           {{ return System.Math.Asin(x);     }}\n"
			+ "	public static double atan (double x)           {{ return System.Math.Atan(x);     }}\n"
			+ "	public static double atan2(double x, double y) {{ return System.Math.Atan2(x, y); }}\n"
			+ "	public static double ceil (double x)           {{ return System.Math.Ceiling(x);  }}\n"
			+ "	public static double cos  (double x)           {{ return System.Math.Cos(x);      }}\n"
			+ "	public static double cosh (double x)           {{ return System.Math.Cosh(x);     }}\n"
			+ "	public static double exp  (double x)           {{ return System.Math.Exp(x);      }}\n"
			+ "	public static double floor(double x)           {{ return System.Math.Floor(x);    }}\n"
			+ "	public static double log  (double x)           {{ return System.Math.Log(x);      }}\n"
			+ "	public static double log2 (double x)           {{ return System.Math.Log(x, 2.0); }}\n"
			+ "	public static double log10(double x)           {{ return System.Math.Log10(x);    }}\n"
			+ "	public static double max  (double x, double y) {{ return System.Math.Max(x, y);   }}\n"
			+ "	public static double min  (double x, double y) {{ return System.Math.Min(x, y);   }}\n"
			+ "	public static double pow  (double x, double y) {{ return System.Math.Pow(x, y);   }}\n"
			+ "	public static double round(double x)           {{ return System.Math.Round(x);    }}\n"
			+ "	public static double sign (double x)           {{ return System.Math.Sign(x);     }}\n"
			+ "	public static double sin  (double x)           {{ return System.Math.Sin(x);      }}\n"
			+ "	public static double sinh (double x)           {{ return System.Math.Sinh(x);     }}\n"
			+ "	public static double sqrt (double x)           {{ return System.Math.Sqrt(x);     }}\n"
			+ "	public static double tan  (double x)           {{ return System.Math.Tan(x);      }}\n"
			+ "	public static double tanh (double x)           {{ return System.Math.Tanh(x);     }}\n"
			// -------------------------------------------------------
			+ "	public static double __eval(params double[] __X)\n"
			+ "	{{\n"
			+ "		double x = __X[0];\n"
			+ "		double y = __X[1];\n"
			+ "		return {0};\n"
			+ "	}}\n"
			+ "	public static {2} __get()\n"
			+ "	{{\n"
			+ "		return __eval;\n"
			+ "	}}\n"
			+ "}}";

		public static delRendererFunction Compile(string functionBody)
		{
			functionBody = functionBody.Trim().ToLower();
			if (functionBody.Contains(";"))
				throw new Exception("Function string cannot contain semicolon");

			string s_Class = string.Format(EVAL_CLASS, functionBody, typeof(delCompiledFunction).Namespace, typeof(delCompiledFunction).Name);

			CSharpCodeProvider i_Provider = new CSharpCodeProvider();
			CompilerParameters i_Params = new CompilerParameters();
			i_Params.CompilerOptions = "/t:library";
			i_Params.GenerateInMemory = true;
			i_Params.ReferencedAssemblies.Add("mscorlib.dll");
			i_Params.ReferencedAssemblies.Add("System.dll");
			i_Params.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location);

			CompilerResults i_Result = i_Provider.CompileAssemblyFromSource(i_Params, s_Class);
			if (i_Result.Errors.HasErrors)
			{
				StringBuilder s_Error = new StringBuilder();
				if (i_Result.Errors.Count == 1)
					s_Error.Append("Compilation error:\n");
				else
					s_Error.AppendFormat("{0} Compilation errors:\n", i_Result.Errors.Count);

				foreach (CompilerError i_Error in i_Result.Errors)
				{
					s_Error.Append(i_Error.ErrorText);
					s_Error.Append("\n");
				}

				s_Error.Append("\nSupported math functions are:\n"
							 + "e, pi, abs(), acos(), asin(), atan(), atan2(), ceil(), cos(), cosh(), "
							 + "exp(), floor(), log(), log2(), log10(), max(), min(), pow(), "
							 + "round(), sign(), sin(), sinh(), sqrt(), tan(), tanh()\n");

				throw new Exception(s_Error.ToString());
			}

			MethodInfo i_Method = i_Result.CompiledAssembly.GetType("Eval").GetMethod("__get");
			delCompiledFunction f_Compiled = (delCompiledFunction)i_Method.Invoke(null, null);
			delRendererFunction f_Render = delegate (double X, double Y)
			{
				return f_Compiled(X, Y);
			};
			return f_Render;
		}
	}
}