using System;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Text.Json;
using System.Threading;
using Discord.Commands;
using NLua;

namespace ChaosBot.Services.ProgrammingLanguageInterpreter
{
    internal class LuaProgrammingLanguageInterpreter : IProgrammingLanguageInterpreter
    {
        private readonly StringBuilder _outputBuilder = new StringBuilder();
        private CancellationToken _ct;
        private Lua _state;

        public string Interpret(CancellationToken ct, LimitedSocketCommandContext context, string content, string command)
        {
            LoggingFacade.Debug($"Interpreting code for {command} using Lua");
            LoggingFacade.Trace($"Using CancellationToken: {ct}");
            _ct = ct;
            LoggingFacade.Trace("Starting Lua interpreter");
            _state = new Lua();
            LoggingFacade.Trace("Setting Lua debug hook");
            _state.SetDebugHook(KeraLua.LuaHookMask.Line, 0);
            _state.DebugHook += LuaDebugHook;

            MethodInfo printMethod = GetType().GetMethod("Print", BindingFlags.NonPublic | BindingFlags.Instance); 
            LoggingFacade.Trace($"Overwriting print function with {printMethod}");
            _state["print"] = _state.RegisterFunction("print", this, printMethod);
            LoggingFacade.Trace("Adding command context to environment");
            _state["context"] = context;
            
            LoggingFacade.Trace("Disabling Lua `import` function");
            _state.DoString ("\nimport = function () end\n");
            LoggingFacade.Trace("Disabling Lua `metatable` functionality");
            _state.DoString ("\ngetmetatable = function () end\n");
            _state.DoString ("\nsetmetatable = function () end\n");

            LoggingFacade.Trace("Running user Lua code");
            _state.DoString(content, command);

            LoggingFacade.Trace("Returning Lua output");
            return _outputBuilder.ToString().Trim();
        }

        private void LuaDebugHook(object sender, NLua.Event.DebugHookEventArgs e)
        {
            if (_ct.IsCancellationRequested)
            {
                Lua l = (Lua) sender;
                l.State.Error("Timeout kill");
            }
        }

        // This is being used in the `Interpret` function to register the print function
        // ReSharper disable once UnusedMember.Local
        private void Print(params object[] parameters)
        {
            string str = string.Join("\t", from param in parameters select param == null ? string.Empty : param.ToString());

            _outputBuilder.AppendLine(str);
        }
    }
}