using System;
using System.Collections.Generic;
using System.Globalization;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;
using System.Windows.Controls;
using Mages.Core;
using Flow.Launcher.Plugin.Calculator.Views;
using Flow.Launcher.Plugin.Calculator.ViewModels;

namespace Flow.Launcher.Plugin.Calculator
{
    public class Main : IPlugin, IPluginI18n, ISettingProvider
    {
        private static readonly Regex RegValidExpressChar = MainRegexHelper.GetRegValidExpressChar();
        private static readonly Regex RegBrackets = MainRegexHelper.GetRegBrackets();
        private static Engine MagesEngine;
        private const string Comma = ",";
        private const string Dot = ".";

        internal static PluginInitContext Context { get; set; } = null!;

        private Settings _settings;
        private SettingsViewModel _viewModel;

        public void Init(PluginInitContext context)
        {
            Context = context;
            _settings = context.API.LoadSettingJsonStorage<Settings>();
            _viewModel = new SettingsViewModel(_settings);

            MagesEngine = new Engine(new Configuration
            {
                Scope = new Dictionary<string, object>
                {
                    { "e", Math.E }, // e is not contained in the default mages engine
                }
            });
        }

        public List<Result> Query(Query query)
        {
            if (!CanCalculate(query))
            {
                return new List<Result>();
            }

            try
            {
                string expression;

                switch (_settings.DecimalSeparator)
                {
                    case DecimalSeparator.Comma:
                    case DecimalSeparator.UseSystemLocale when CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator == ",":
                        expression = query.Search.Replace(",", ".");
                        break;
                    default:
                        expression = query.Search;
                        break;
                }

                var result = MagesEngine.Interpret(expression);

                if (result?.ToString() == "NaN")
                    result = Localize.flowlauncher_plugin_calculator_not_a_number();

                if (result is Function)
                    result = Localize.flowlauncher_plugin_calculator_expression_not_complete();

                if (!string.IsNullOrEmpty(result?.ToString()))
                {
                    decimal roundedResult = Math.Round(Convert.ToDecimal(result), _settings.MaxDecimalPlaces, MidpointRounding.AwayFromZero);
                    string newResult = ChangeDecimalSeparator(roundedResult, GetDecimalSeparator());

                    return new List<Result>
                    {
                        new Result
                        {
                            Title = newResult,
                            IcoPath = "Images/calculator.png",
                            Score = 300,
                            SubTitle = Localize.flowlauncher_plugin_calculator_copy_number_to_clipboard(),
                            CopyText = newResult,
                            Action = c =>
                            {
                                try
                                {
                                    Context.API.CopyToClipboard(newResult);
                                    return true;
                                }
                                catch (ExternalException)
                                {
                                    Context.API.ShowMsgBox(Localize.flowlauncher_plugin_calculator_failed_to_copy());
                                    return false;
                                }
                            }
                        }
                    };
                }
            }
            catch (Exception)
            {
                // ignored
            }

            return new List<Result>();
        }

        private bool CanCalculate(Query query)
        {
            // Don't execute when user only input "e" or "i" keyword
            if (query.Search.Length < 2)
            {
                return false;
            }

            if (!RegValidExpressChar.IsMatch(query.Search))
            {
                return false;
            }

            if (!IsBracketComplete(query.Search))
            {
                return false;
            }

            if ((query.Search.Contains(Dot) && GetDecimalSeparator() != Dot) ||
                (query.Search.Contains(Comma) && GetDecimalSeparator() != Comma))
                return false;

            return true;
        }

        private static string ChangeDecimalSeparator(decimal value, string newDecimalSeparator)
        {
            if (string.IsNullOrEmpty(newDecimalSeparator))
            {
                return value.ToString();
            }

            var numberFormatInfo = new NumberFormatInfo
            {
                NumberDecimalSeparator = newDecimalSeparator
            };
            return value.ToString(numberFormatInfo);
        }

        private  string GetDecimalSeparator()
        {
            string systemDecimalSeparator = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
            return _settings.DecimalSeparator switch
            {
                DecimalSeparator.UseSystemLocale => systemDecimalSeparator,
                DecimalSeparator.Dot => Dot,
                DecimalSeparator.Comma => Comma,
                _ => systemDecimalSeparator,
            };
        }

        private static bool IsBracketComplete(string query)
        {
            var matchs = RegBrackets.Matches(query);
            var leftBracketCount = 0;
            foreach (Match match in matchs)
            {
                if (match.Value == "(" || match.Value == "[")
                {
                    leftBracketCount++;
                }
                else
                {
                    leftBracketCount--;
                }
            }

            return leftBracketCount == 0;
        }

        public string GetTranslatedPluginTitle()
        {
            return Localize.flowlauncher_plugin_caculator_plugin_name();
        }

        public string GetTranslatedPluginDescription()
        {
            return Localize.flowlauncher_plugin_caculator_plugin_description();
        }

        public Control CreateSettingPanel()
        {
            return new CalculatorSettings(_settings);
        }

        public void OnCultureInfoChanged(CultureInfo newCulture)
        {
            DecimalSeparatorLocalized.UpdateLabels(_viewModel.AllDecimalSeparator);
        }
    }
}