using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Threading.Tasks;
using Avalonia.Threading;
using DesertPaintCodex.Models;
using DesertPaintCodex.Services;
using ReactiveUI;

namespace DesertPaintCodex.ViewModels
{
    public class RecipeGeneratorViewModel : ViewModelBase
    {
        private const long   UpdateInterval  = 200;  // ms
        private const long   SaveInterval    = 30000; // ms
        private const string PaintStateFile  = "dp_generator_state";
        private const string RibbonStateFile = "dp_generator_ribbon_state";
        
        private int _selectedView = 0;
        public int SelectedView { get => _selectedView; private set => this.RaiseAndSetIfChanged(ref _selectedView, value); }
        
        private float _progress = 0;
        public float Progress { get => _progress; private set => this.RaiseAndSetIfChanged(ref _progress, value); }

        private string _permutationCount = "0";
        public string PermutationCount { get => _permutationCount; private set => this.RaiseAndSetIfChanged(ref _permutationCount, value); }
        

        private DateTime _mostRecentTime;
        public DateTime MostRecentTime { get => _mostRecentTime; private set => this.RaiseAndSetIfChanged(ref _mostRecentTime, value); }

        private GeneratorRecipe? _mostRecentRecipe;
        public GeneratorRecipe? MostRecentRecipe { get => _mostRecentRecipe; private set => this.RaiseAndSetIfChanged(ref _mostRecentRecipe, value); }


        private int _productIndex = 0;
        public int ProductIndex { get => _productIndex; private set => this.RaiseAndSetIfChanged(ref _productIndex, value); }

        private int _maxReagents;
        public int MaxReagents { get => _maxReagents; private set => this.RaiseAndSetIfChanged(ref _maxReagents, value); }
        
        private int _maxConcentration;
        public int MaxConcentration { get => _maxConcentration; private set => this.RaiseAndSetIfChanged(ref _maxConcentration, value); }
        
        private int _fullQuantity;
        public int FullQuantity { get => _fullQuantity; private set => this.RaiseAndSetIfChanged(ref _fullQuantity, value); }
        
        private int _fullQuantityDepth;
        public int FullQuantityDepth { get => _fullQuantityDepth; private set => this.RaiseAndSetIfChanged(ref _fullQuantityDepth, value); }

        private int _maxConcentrationMax;
        public int MaxConcentrationMax { get => _maxConcentrationMax; private set => this.RaiseAndSetIfChanged(ref _maxConcentrationMax, value); }
        
        private int _fullQuantitynMax;
        public int FullQuantityMax { get => _fullQuantitynMax; private set => this.RaiseAndSetIfChanged(ref _fullQuantitynMax, value); }
        
        
        #region Flags

        private bool _isPaused = false;
        public bool IsPaused  { get => _isPaused; private set => this.RaiseAndSetIfChanged(ref _isPaused, value); }

        private bool _isInProgress = false;
        public bool IsInProgress { get => _isInProgress; private set => this.RaiseAndSetIfChanged(ref _isInProgress, value); }

        private bool _isRunning = false;
        public bool IsRunning {  get => _isRunning; private set => this.RaiseAndSetIfChanged(ref _isRunning, value); }

        private bool _canStart = false;
        public bool CanStart {  get => _canStart; private set => this.RaiseAndSetIfChanged(ref _canStart, value); }
        
        private bool _canClear = false;
        public bool CanClear {  get => _canClear; private set => this.RaiseAndSetIfChanged(ref _canClear, value); }

        #endregion // Flags
        
        #region Collections
        
        public ObservableCollection<Reagent> Reagents { get; } = new();
        public ObservableCollection<GeneratorRecipe> AllRecipes { get; } = new();
        
        #endregion // Collections
        
        private readonly RecipeGenerator _generator;

        private DateTime _lastSave = DateTime.Now;
        private readonly PlayerProfile _profile;
        private uint _minConcentration;

        private readonly ConcurrentQueue<PaintRecipe> _pendingNewRecipes = new();
        private volatile int _newRecipeCount;
        private volatile bool _updatesAvailable;
        private readonly DispatcherTimer _updateTimer;
        
        private bool _ribbonMode;
        private bool _unsavedRecipes;
        private bool _saving;

        
        public RecipeGeneratorViewModel()
        {
            List<string> reagentNames = ReagentService.Names;
            foreach (string name in reagentNames)
            {
                Reagents.Add(ReagentService.GetReagent(name));
            }
            
            SettingsService.Get("Generator.RibbonMode", out bool ribbonMode, false);
            ProductIndex = ribbonMode ? 1 : 0;
            _ribbonMode = ribbonMode;

            PlayerProfile? profile = ProfileManager.CurrentProfile;
            Debug.Assert(profile != null);
            _profile = profile;
            
            _profile.LoadRecipes();

            _generator = new RecipeGenerator();

            _generator.Progress  += OnProgress;
            _generator.NewRecipe += OnNewRecipe;
            _generator.Finished  += OnGeneratorStopped;

            SettingsService.Get("Generator.Logging", out bool logGenerator, false);
            if (logGenerator)
            {
                string logDir = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
                _generator.Log = System.IO.Path.Combine(logDir, "dpl_generator.txt");
            }
            
            if (ribbonMode)
            {
                InitStateForRibbons();
            }
            else
            {
                InitStateForPaint();
            }

            _updateTimer = new DispatcherTimer {Interval = TimeSpan.FromMilliseconds(UpdateInterval)};
            _updateTimer.Tick += Update;

            this.WhenAnyValue(x => x.ProductIndex).Subscribe(_ => ChangeMode());
        }

        public void Start()
        {
            IsInProgress = true;
            IsRunning = true;
            ReagentService.SaveProfileReagents(_profile.ReagentFile);
            SaveSettings(_ribbonMode ? "Ribbon" : "Paint");
            _updateTimer.Start();
            SelectedView = 1;
            
            _generator.BeginRecipeGeneration(
                _minConcentration, 
                (uint)MaxConcentration, 
                1, 
                (uint)MaxReagents, 
                (uint)FullQuantityDepth, 
                (uint)FullQuantity);
        }

        
        public void End()
        {
            IsPaused     = false;
            IsRunning    = false;
            IsInProgress = false;
            _updateTimer.Stop();
            _profile.SaveRecipes();
            
            CanClear = true;
        }

        public void Pause()
        {
            IsPaused  = true;
            IsRunning = false;
            _updateTimer.Stop();
            _generator.Stop();
        }

        public void Resume()
        {
            IsPaused  = false;
            IsRunning = true;
            _updateTimer.Start();
            SelectedView = 1;
            
            _generator.ResumeRecipeGeneration();

        }

        public async Task Clear()
        {
            bool result = await ShowYesNoBox("Clear Recipes", "Are you sure you want to clear your recipes?");
            if (result)
            {
                CanClear = false;
                if (_ribbonMode)
                {
                    _profile.ClearRibbonRecipes();
                }
                else
                {
                    _profile.ClearPaintRecipes();
                }

                foreach (GeneratorRecipe recipe in AllRecipes)
                {
                    recipe.ClearRecipe();
                }
                
                _generator.Reset();
            }
        }

        private void InitStateForPaint()
        {
            MaxConcentrationMax = 20;
            FullQuantityMax = 20;
            InitState("Paint", PaintRecipe.PaintRecipeMinConcentration, _profile.Recipes, PaintStateFile);

        }

        private void InitStateForRibbons()
        {
            MaxConcentrationMax = 100;
            FullQuantityMax = 100;
            InitState("Ribbon", PaintRecipe.RibbonRecipeMinConcentration, _profile.RibbonRecipes, RibbonStateFile);
        }

        private void InitState(string mode, uint minConcentration, Dictionary<string, PaintRecipe> recipes, string stateFileName)
        {
            _minConcentration = minConcentration;
            _generator.InitRecipes(recipes);
            
            string stateFile = System.IO.Path.Combine(_profile.Directory, stateFileName);
            if (System.IO.File.Exists(stateFile))
            {
                _generator.LoadState(stateFile);

                // Always set these, or the values will be invalid
                MaxReagents = (int)_generator.MaxReagents;
                MaxConcentration = (int)_generator.MaxConcentration;
                FullQuantity = (int)_generator.FullQuantity;
                FullQuantityDepth = (int)_generator.FullQuantityDepth;

                if (_generator.CanResume)
                {
                    IsInProgress = true;
                    IsPaused = true;

                    SaveSettings(mode);
                }
                else
                {
                    IsInProgress = false;
                    IsPaused = false;
                    CanClear = true;
                }
            }
            else if (mode == "Paint")
            {
                LoadPaintSettings();
            }
            else
            {
                LoadRibbonSettings();
            }

            AllRecipes.Clear();

            foreach (PaintColor color in PaletteService.Colors)
            {
                GeneratorRecipe genRecipe = new(color);
                if (recipes.TryGetValue(color.Name, out PaintRecipe? recipe)) //  && recipe.IsValidForConcentration(minConcentration)) // This check is redundant, since they're checked when loading.
                {
                    genRecipe.DraftRecipe(recipe);
                }
                AllRecipes.Add(genRecipe);
            }
        }

        #region Event Handlers
        private void OnProgress(object? sender, EventArgs args)
        {
            _newRecipeCount = (int)_generator.RecipeCount;
            _updatesAvailable = true;
        }

        private void OnNewRecipe(object? sender, NewRecipeEventArgs args)
        {
            PaintRecipe recipe = new(args.Recipe);
            _pendingNewRecipes.Enqueue(recipe);
            _updatesAvailable = true;
        }
        
        
        private void OnGeneratorStopped(object? sender, EventArgs args)
        {
            SaveState();
            
            if (_saving)
            {
                _generator.ResumeRecipeGeneration();
                _lastSave = DateTime.Now;
                _saving = false;
                return;
            }

            if (IsPaused) return;

            End();
        }

        private void Update(object? sender, EventArgs e)
        {
            if (!_updatesAvailable) return;
            if (_saving) return;

            _updatesAvailable = false;

            DateTime now = DateTime.Now;

            // Update test count.
            PermutationCount = $"{_newRecipeCount:n0}";
            
            // Pull in new recipes.
            if (!_pendingNewRecipes.IsEmpty)
            {
                GeneratorRecipe? lastRecipe = null;
                while (_pendingNewRecipes.TryDequeue(out PaintRecipe? newRecipe))
                {
                    string recipeColor = PaletteService.FindNearest(newRecipe.ReactedColor);
                    foreach (GeneratorRecipe recipe in AllRecipes)
                    {
                        if (recipe.Color.Name != recipeColor) continue;
                        recipe.DraftRecipe(newRecipe);
                        lastRecipe = recipe;
                        if (_ribbonMode)
                        {
                            _profile.SetRibbonRecipe(recipeColor, newRecipe);
                        }
                        else
                        {
                            _profile.SetRecipe(recipeColor, newRecipe);
                        }
                        break;
                    }
                }

                // If at least one recipe was processed, let's check to see if it's time to save, and
                // highlight that recipe.
                if (lastRecipe != null)
                {
                    _unsavedRecipes = true;
                    MostRecentRecipe = lastRecipe;
                    MostRecentTime = now;
                }
            }
            
            // Save if it is time.
            if (!((now - _lastSave).TotalMilliseconds > SaveInterval)) return;
            
            if (_unsavedRecipes)
            {
                _profile.SaveRecipes();
                _unsavedRecipes = false;
            }

            _saving = true;
            _generator.Stop();
        }
        
        #endregion


        private void SavePaintSettings()
        {
            SaveSettings("Paint");
        }

        private void LoadPaintSettings()
        {
            LoadSettings("Paint", 5, 20, 20, 4);
        }

        private void SaveRibbonSettings()
        {
            SaveSettings("Ribbon");
        }

        private void LoadRibbonSettings()
        {
            LoadSettings("Ribbon", 5, 75, 75, 4);
        }


        private void SaveSettings(string mode)
        {
            SettingsService.Set($"Generator.{mode}.MaxReagents",       MaxReagents);
            SettingsService.Set($"Generator.{mode}.MaxConcentration",  MaxConcentration);
            SettingsService.Set($"Generator.{mode}.FullQuantity",      FullQuantity);
            SettingsService.Set($"Generator.{mode}.FulLQuantityDepth", FullQuantityDepth);
        }

        private void LoadSettings(string mode, int defaultMaxReagents, int defaultMaxConcentration,
            int defaultFullQuantity, int defaultFullQuantityDepth)
        {
            SettingsService.Get($"Generator.{mode}.MaxReagents",       out int  maxReagents,       defaultMaxReagents);
            SettingsService.Get($"Generator.{mode}.MaxConcentration",  out int  maxConcentration,  defaultMaxConcentration);
            SettingsService.Get($"Generator.{mode}.FullQuantity",      out int  fullQuantity,      defaultFullQuantity);
            SettingsService.Get($"Generator.{mode}.FullQuantityDepth", out int  fullQuantityDepth, defaultFullQuantityDepth);
            
            MaxReagents       = maxReagents;
            MaxConcentration  = maxConcentration;
            FullQuantity      = fullQuantity;
            FullQuantityDepth = fullQuantityDepth;
        }

        private void SaveState()
        {
            _generator.SaveState(System.IO.Path.Combine(_profile.Directory,
                _ribbonMode ? RibbonStateFile : PaintStateFile));
        }

        private void ChangeMode()
        {
            if (ProductIndex == 0)
            {
                if (!_ribbonMode) return;
                _ribbonMode = false;
                InitStateForPaint();
            }
            else
            {
                if (_ribbonMode) return;
                _ribbonMode = true;
                InitStateForRibbons();
            }
        }
    }
}