using Microsoft.CSharp;
using System;
using System.CodeDom.Compiler;
using System.Linq;
using System.Reflection;
using System.Text;

namespace FormulaEnginePoC.CSharpProvider
{
    public class CodeCompiler<TDelegate> where TDelegate : Delegate
    {
        private CompilerResults _compilerResults;

        public TDelegate CompiledDelegate { get; private set; }

        public CompilerError[] CompilerErrors => _compilerResults?.Errors.Cast<CompilerError>().ToArray()
                                                 ?? throw new InvalidOperationException("Not compile yet");

        public void Compile(string fullTypeName, string methodName, string code, params string[] referencedAssemblies)
        {
            var codeProvider = new CSharpCodeProvider();

            var parameters = new CompilerParameters
            {
                GenerateInMemory = true
                , GenerateExecutable = false
                , ReferencedAssemblies =
                {
                    "system.dll"
                }
            };

            foreach (var item in referencedAssemblies)
            {
                parameters.ReferencedAssemblies.Add(item);
            }

            _compilerResults = codeProvider.CompileAssemblyFromSource(parameters, code);

            if (_compilerResults.Errors.HasErrors)
            {
                var sb = new StringBuilder();
                foreach (CompilerError item in _compilerResults.Errors)
                {
                    sb.AppendLine($"{item.ErrorText}({item.ErrorNumber})");
                }

                throw new ArgumentException("Compile fail:" + sb);
            }

            var type = _compilerResults.CompiledAssembly.GetType(fullTypeName);

            var method = type.GetMethod(methodName, BindingFlags.Public | BindingFlags.Static)
                         ?? throw new MissingMethodException("Unable get static method from compiled assembly");

            CompiledDelegate = (TDelegate)Delegate.CreateDelegate(typeof(TDelegate), method);
        }
    }
}