using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Scripting;
using Microsoft.CodeAnalysis.Scripting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Tango.Scripting
{
    /// <summary>
    /// Represents a C# scripting engine capable of executing C# scripts using the Roslyn engine.
    /// </summary>
    public class ScriptEngine
    {
        private CancellationTokenSource _cancaller;
        private OnExecuteParameters _onExecuteParameters;
        public List<Type> ReferencedAssemblies { get; private set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="ScriptEngine"/> class.
        /// </summary>
        /// <param name="parameters">The parameters.</param>
        public ScriptEngine(OnExecuteParameters parameters)
        {
            _onExecuteParameters = parameters;
            ReferencedAssemblies = new List<Type>();
        }

        /// <summary>
        /// Runs the specified code.
        /// </summary>
        /// <param name="code">The code.</param>
        /// <returns></returns>
        public async Task Run(String code)
        {
            var options = CreateOptions();

            String methodParameters = CreateMethodParameters();

            _cancaller = new CancellationTokenSource();

            await CSharpScript.RunAsync(
               code +
               Environment.NewLine +
               Environment.NewLine +
               "await Task.Factory.StartNew(() => { OnExecute(" + methodParameters + "); });", options: options, globals: _onExecuteParameters, cancellationToken: _cancaller.Token);
        }

        public Task<List<CompilerError>> Compile(String code)
        {
            return Task.Factory.StartNew<List<CompilerError>>(() =>
            {
                var options = CreateOptions();

                String methodParameters = CreateMethodParameters();

                _cancaller = new CancellationTokenSource();

                var script = CSharpScript.Create(
                   code +
                   Environment.NewLine +
                   Environment.NewLine +
                   "await Task.Factory.StartNew(() => { OnExecute(" + methodParameters + "); });", options: options, globalsType: _onExecuteParameters.GetType());

                var results = script.Compile();

                return results.ToList().Select(x => new CompilerError() { Error = x.ToString() }).ToList();
            });
        }

        private String CreateMethodParameters()
        {
            return String.Join(", ", _onExecuteParameters.GetType().GetFields(BindingFlags.Public | BindingFlags.Instance).Select(x => x.Name));
        }

        private ScriptOptions CreateOptions()
        {
            //My References.
            var options = ScriptOptions.Default;

            //My Assemblies.
            options = options.AddReferences(typeof(Form).Assembly.Location);
            options = options.AddReferences(typeof(Enumerable).Assembly.Location);
            options = options.AddReferences(typeof(ScriptEngine).Assembly.Location);

            foreach (var asm in ReferencedAssemblies)
            {
                options = options.AddReferences(asm.Assembly.Location);
            }

            //Imports.
            options = options.AddImports(
            "System",
            "System.Collections.Generic",
            "System.Linq",
            "System.Text",
            "System.Diagnostics",
            "System.Windows.Forms"
            );

            return options;
        }

        /// <summary>
        /// Stops this instance.
        /// </summary>
        public void Stop()
        {
            _cancaller.Cancel();
        }
    }
}