using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Diagnostics;

using System.IO;

using System.Linq;

using System.Text.RegularExpressions;

using System.Threading;

using DesertPaintCodex.Models;

namespace DesertPaintCodex.Services

{

    public class NewRecipeEventArgs : EventArgs

    {

        public NewRecipeEventArgs(string color, PaintRecipe recipe)

        {

            Color  = color;

            Recipe = recipe;

        }

        public string Color { get; }

        public PaintRecipe Recipe { get; }

    }

    public class RecipeGenerator

    {

        public enum SearchType {

            DepthFirst,

            BreadthFirst

        };

        public SearchType Mode { get; set; }

        public uint MinConcentration { get; private set; } // minimum paint concentration

        public uint MaxConcentration { get; private set; } // maximum paint concentration

        public uint MaxReagents { get; private set; } // maximum number of reagents to use in the recipe

        public uint MinReagents { get; private set; } // minimum number of reagents to use in the recipe

        public uint FullQuantityDepth { get; private set; } // at or equal this number of reagents, ignore ingredient settings for max quantity

        public uint FullQuantity { get; private set; }  // The max number of a reagent to use at full quantity

        public uint MaxThreads { get; set; } = 15;

        private bool _running = false;

        private int _runningThreads = 0;

        private readonly Dictionary<string, uint> _recipeCosts = new ();

        private readonly Dictionary<string, PaintRecipe> _recipes = new();

        private uint _totalReagents;

        private readonly List<Reagent> _costSortedReagents = new();

        private readonly ConcurrentQueue<RecipeSearchNode> _searchQueue = new();

        private ulong _recipeCount = 0;

        private readonly List<Thread> _generatorThreads = new();

        private readonly object _workerLock = new();

        private bool _requestCancel = false;

        private StreamWriter? _log;

        // events

        public event EventHandler? Finished;

        public event EventHandler? Progress;

        public event EventHandler<NewRecipeEventArgs>? NewRecipe;

        public RecipeGenerator()

        {

            Mode = SearchType.BreadthFirst;

            foreach (PaintColor color in PaletteService.Colors)

            {

                _recipes.Add(color.Name, new PaintRecipe());

                _recipeCosts.Add(color.Name, uint.MaxValue);

            }

            MinReagents = 1;

            MaxReagents = 5;

            MinConcentration = 10;

            MaxConcentration = 20;

        }

        public Dictionary<string, PaintRecipe> Recipes => _recipes;

        public ulong RecipeCount => _recipeCount;

        public bool CanResume => (!_running && (_searchQueue.Count > 0));

        public string? Log

        {

            set => _log = value != null ? new StreamWriter(value) : null;

        }

        public void FlushLog()

        {

            _log?.Flush();

        }

        public void CloseLog()

        {

            _log?.Close();

            _log = null;

        }

        private void WriteLog(string msg)

        {

            if (_log == null) return;

            lock (_workerLock)

            {

                _log.WriteLine(msg);

            }

        }

        private void WriteLog(string msg, params object[] args)

        {

            if (_log == null) return;

            lock(_workerLock)

            {

                _log.WriteLine(msg, args);

            }

        }

        private class ReagentCostSort : IComparer<Reagent>

        {

            public int Compare(Reagent? reagent1, Reagent? reagent2)

            {

                if (reagent1 == null)

                {

                    if (reagent2 == null) return 0;

                    return -1;

                }

                if (reagent2 == null) return 1;

                return (int)reagent1.Cost - (int)reagent2.Cost;

            }

        }

        public void InitRecipes(Dictionary<string, PaintRecipe> initialRecipes)

        {

            if (_running)

            {

                return;

            }

            _recipeCosts.Clear();

            _recipes.Clear();

            foreach (PaintRecipe recipe in initialRecipes.Values)

            {

                //PaintRecipe recipeCopy = new PaintRecipe(recipe);

                AddCheapestRecipe(recipe);

            }

        }

        private void InitSortedReagents()

        {

            _costSortedReagents.Clear();

            foreach (string name in ReagentService.Names)

            {

                Reagent reagent = ReagentService.GetReagent(name);

                _costSortedReagents.Add(reagent);

            }

            _costSortedReagents.Sort(new ReagentCostSort());

        }

        // Generate paint recipes.

        // minConcentration - the minimum permitted concentration in a recipe (10 for paint, 50 for ribbons)

        // maxConcentration - the maximum concentration for a recipe

        // minReagents - the minimum number of ingredients in a recipe

        // maxReagents - the maximum number of ingredients allowed in a recipe

        // fullQuantityDepth - at this depth of ingredient or below, allow up to fullQuantity of any reagent

        // fullQuantity - the maximum amount of any reagent to permit up to the full quantity depth. After that, reagents are limited by the

        //                per-reagent value

        public void BeginRecipeGeneration(uint minConcentration, uint maxConcentration, uint minReagents, uint maxReagents, uint fullQuantityDepth, uint fullQuantity)

        {

            if (_running)

            {

                // Already running - don't start again

                return;

            }

            MinConcentration = minConcentration;

            MaxConcentration = maxConcentration;

            MinReagents = minReagents;

            MaxReagents = maxReagents;

            FullQuantity = fullQuantity;

            FullQuantityDepth = fullQuantityDepth;

            // first, sort reagents by cost.

            InitSortedReagents();

            _totalReagents = (uint)_costSortedReagents.Count;

            // Pre-populate recipes list with:

            // 1) 1-ingredient recipes @ min concentration for all enabled ingredients with a count >= min concentration

            // 2) any previously-generated recipes

            WriteLog($"===================== BEGIN RECIPE GENERATION ========================== {DateTime.Now}");

            WriteLog("Pre-populating basic recipes.");

            int enabledReagentCount = 0;

            PaintRecipe recipe = new();

            foreach (var reagent in _costSortedReagents.Where(reagent => reagent.Enabled))

            {

                if (!reagent.IsCatalyst && ((reagent.RecipeMax >= minConcentration) || ((FullQuantityDepth > 0) && (FullQuantity >= minConcentration))))

                {

                    recipe.Clear();

                    recipe.AddReagent(reagent.Name, minConcentration);

                    AddCheapestRecipe(recipe);

                }

                ++enabledReagentCount;

            }

            MaxReagents = (uint)Math.Min(enabledReagentCount, MaxReagents);

            MinReagents = Math.Min(MinReagents, MaxReagents);

            _searchQueue.Clear();

            for (uint reagentIdx = 0; reagentIdx < _costSortedReagents.Count; ++reagentIdx)

            {

                if (!_costSortedReagents[(int) reagentIdx].Enabled) continue;

                // queue up all combinations of MinReagents

                RecipeSearchNode initialNode = new(_costSortedReagents, reagentIdx)

                {

                    FullQuantity      = FullQuantity,

                    FullQuantityDepth = FullQuantityDepth,

                    MinConcentration  = minConcentration,

                    MaxConcentration  = maxConcentration,

                    MinReagents       = minReagents,

                    MaxReagents       = maxReagents

                };

                initialNode.WriteLog = WriteLog;

                if (MinReagents > 1)

                {

                    while (NextReagentSetBreadthFirst(initialNode, 1, minReagents))

                    {

                        if (initialNode.ReagentCount != minReagents) continue;

                        //Console.WriteLine("Initial node at size {0}/{1} with recipe: {2}", initialNode.ReagentCount, minReagents, initialNode.TestRecipe.ToString());

                        RecipeSearchNode searchNode = new RecipeSearchNode(initialNode);

                        searchNode.WriteLog = WriteLog;

                        _searchQueue.Enqueue(searchNode);

                    }

                }

                else

                {

                    _searchQueue.Enqueue(initialNode);

                }

            }

            _recipeCount = 0;

            WriteLog("Begin recipe generation: MaxConcentration={0} MinReagents={1} MaxReagents={2} FullQuantity={3} FullQuantityDepth={4}", MaxConcentration, MinReagents, MaxReagents, FullQuantity, FullQuantityDepth);

            // start worker threads to do the actual work

            ResumeRecipeGeneration();

        }

        public void ResumeRecipeGeneration()

        {

            if (_running)

            {

                // Already running - don't start again

                return;

            }

            _running = true;

            _requestCancel = false;

            WriteLog("Resuming recipe generation: pre-threads={0} reagent count={1} search queue={2}", _runningThreads, _costSortedReagents.Count, _searchQueue.Count);

            _runningThreads = 0; // presumably!

            int threadCount = Math.Min(Math.Min(_costSortedReagents.Count, _searchQueue.Count), (int)MaxThreads);

            if (threadCount == 0)

            {

                Finished?.Invoke(this, EventArgs.Empty);

            }

            _generatorThreads.Clear();

            Console.WriteLine("Starting {0} generator threads.", threadCount);

            WriteLog($"===== Starting {threadCount} threads.");

            for (int i = 0; i < threadCount; ++i)

            {

                Thread thr = new(Generate) {Priority = ThreadPriority.BelowNormal};

                _generatorThreads.Add(thr);

            }

            foreach (Thread thr in _generatorThreads)

            {

                thr.Start();

            }

        }

        public bool SaveState(string file)

        {

            if (_running)

            {

                // can't save state while running

                return false;

            }

            lock(_workerLock)

            {

                using StreamWriter writer = new(file, false);

                writer.WriteLine("MinReagents: {0}", MinReagents);

                writer.WriteLine("MaxReagents: {0}", MaxReagents);

                writer.WriteLine("FullQuantityDepth: {0}", FullQuantityDepth);

                writer.WriteLine("FullQuantity: {0}", FullQuantity);

                writer.WriteLine("TotalReagents: {0}", _totalReagents);

                writer.WriteLine("RecipeCount: {0}", _recipeCount);

                writer.WriteLine("SearchType: {0}", Mode.ToString());

                foreach (KeyValuePair<string, PaintRecipe> pair in _recipes)

                {

                    PaintRecipe recipe    = pair.Value;

                    string      colorName = PaletteService.FindNearest(recipe.ReactedColor);

                    writer.WriteLine("BeginRecipe: {0}", colorName);

                    foreach (PaintRecipe.ReagentQuantity reagent in recipe.Reagents)

                    {

                        writer.WriteLine("Ingredient: {0}={1}", reagent.Name, reagent.Quantity);

                    }

                    writer.WriteLine("EndRecipe: {0}", colorName);

                }

                writer.WriteLine("SearchNodes: {0}", _searchQueue.Count);

                foreach (RecipeSearchNode node in _searchQueue)

                {

                    node.SaveState(writer);

                }

            }

            return true;

        }

        private static readonly Regex _keyValueRegex = new Regex(@"(?<key>\w+)\:\s*(?<value>.+)\s*");

        private static readonly Regex _reagentRegex = new Regex(@"(?<ingredient>(\w+\s)*\w+)\s*=\s*(?<quantity>\d)\s*");

        public bool LoadState(string file)

        {

            // cannot be running, and reactions must be set

            if (_running)

            {

                return false;

            }

            InitSortedReagents();

            bool success = true;

            PaintRecipe? currentRecipe = null;

            using StreamReader reader = new(file, false);

            string? line;

            while (success && ((line = reader.ReadLine()) != null))

            {

                Match match = _keyValueRegex.Match(line);

                if (match.Success)

                {

                    string value = match.Groups["value"].Value;

                    switch(match.Groups["key"].Value)

                    {

                        case "MinReagents":

                            MinReagents = uint.Parse(value);

                            MaxReagents = Math.Max(MinReagents, MaxReagents);

                            break;

                        case "MaxReagents":

                            MaxReagents = uint.Parse(value);

                            MinReagents = Math.Min(MinReagents, MaxReagents);

                            break;

                        case "FullQuantityDepth":

                            FullQuantityDepth = uint.Parse(value);

                            break;

                        case "FullQuantity":

                            FullQuantity = uint.Parse(value);

                            break;

                        case "TotalReagents":

                            _totalReagents = uint.Parse(value);

                            break;

                        case "RecipeCount":

                            if (!ulong.TryParse(value, out _recipeCount))

                            {

                                // must have rolled to negative - try as an int and convert

                                long recipeCountInt = int.Parse(value);

                                _recipeCount = (ulong)(recipeCountInt & 0x00000000ffffffffL);

                            }

                            break;

                        case "BeginRecipe":

                            currentRecipe = new PaintRecipe();

                            break;

                        case "EndRecipe":

                            if (currentRecipe != null)

                            {

                                PaintColor color = currentRecipe.ReactedColor;

                                uint       cost  = currentRecipe.Cost;

                                _recipes[color.Name]     = currentRecipe; // replace

                                _recipeCosts[color.Name] = cost;

                                currentRecipe            = null;

                            }

                            break;

                        case "Ingredient":

                            if (currentRecipe != null)

                            {

                                Match ingredientMatch = _reagentRegex.Match(match.Groups["value"].Value);

                                if (ingredientMatch.Success)

                                {

                                    uint quantity = uint.Parse(ingredientMatch.Groups["quantity"].Value);

                                    currentRecipe.AddReagent(ingredientMatch.Groups["ingredient"].Value, quantity);

                                }

                                else

                                {

                                    success = false;

                                }

                            }

                            break;

                        case "SearchNodes":

                            int nodeCount = int.Parse(match.Groups["value"].Value);

                            for (int i = 0; i < nodeCount; ++i)

                            {

                                RecipeSearchNode node = new(_costSortedReagents)

                                {

                                    FullQuantity      = FullQuantity,

                                    FullQuantityDepth = FullQuantityDepth,

                                    MinReagents       = MinReagents,

                                    MaxReagents       = MaxReagents,

                                    MaxConcentration  = MaxConcentration

                                };

                                node.WriteLog = WriteLog;

                                success                = success && node.LoadState(reader);

                                if (success)

                                {

                                    _searchQueue.Enqueue(node);

                                }

                            }

                            break;

                        case "SearchType":

                            Mode = (SearchType)Enum.Parse(typeof(SearchType), match.Groups["value"].Value);

                            break;

                        default:

                            success = false;

                            break;

                    }

                }

                else

                {

                    success = false;

                    break;

                }

            }

            return success;

        }

        private void Generate()

        {

            lock(_workerLock)

            {

                ++_runningThreads;

            }

            bool ok;

            do

            {

                RecipeSearchNode? node;

                lock (_workerLock)

                {

                    ok = _searchQueue.TryDequeue(out node);

                }

                if (!ok) break;

                Debug.Assert(node != null);

                node.WriteLog = WriteLog;

                if (Mode == SearchType.DepthFirst)

                {

                    uint targetQuantity = (node.ReagentCount <= FullQuantityDepth)

                        ? ((uint)node.ReagentCount * FullQuantity) 

                        : node.MaxConcentration + 1;

                    do {

                        --targetQuantity;

                        if (node.ShouldLog)

                        {

                            WriteLog($" == Initializing {node} for quantity {targetQuantity}");

                        }

                        node.InitForQuantity(targetQuantity);

                    } while (targetQuantity > MinConcentration && (node.CurrentTargetQuantity != node.UsedQuantity));

                    while ((ok = IterateDepthFirst(node)) && !_requestCancel)

                    {

                        Progress?.Invoke(this, EventArgs.Empty);

                    }

                }

                else

                {

                    // breadth-first search

                    uint targetQuantity = MinConcentration - 1;

                    uint quantityLimit = (node.ReagentCount <= FullQuantityDepth) 

                        ? (FullQuantity * (uint)node.ReagentCount) 

                        : node.MaxConcentration;

                    do {

                        ++targetQuantity;

                        if (node.ShouldLog)

                        {

                            WriteLog($" == Initializing {node} for quantity {targetQuantity}");

                        }

                        node.InitForQuantity(targetQuantity);

                    } while ((targetQuantity < quantityLimit) && (node.CurrentTargetQuantity != node.UsedQuantity));

                    while ((ok = IterateBreadthFirst(node)) && !_requestCancel)

                    {

                        Progress?.Invoke(this, EventArgs.Empty);

                    }

                }

                if (ok)

                {

                    // stopped because cancel was requested - requeue the node in its current state for resume

                    _searchQueue.Enqueue(node);

                }

            } while (!_requestCancel);

            bool done;

            lock(_workerLock)

            {

                --_runningThreads;

                //generatorThreads.Remove(Thread.CurrentThread);

                done = (_runningThreads == 0);

            }

            if (!done) return;

            _running       = false;

            _requestCancel = false;

            Finished?.Invoke(this, EventArgs.Empty);

        }

        // Add the cheapest recipe to the recipe list

        // returns the discarded recipe from the pair (or null if no original recipe to replace)

        private void AddCheapestRecipe(PaintRecipe recipe)

        {

            if (!recipe.IsValidForConcentration(MinConcentration)) return;

            string colorName = PaletteService.FindNearest(recipe.ReactedColor);

            lock (_workerLock)

            {

                uint newCost = recipe.Cost;

                if (_recipeCosts.TryGetValue(colorName, out var cost))

                {

                    if (cost < newCost)

                    {

                        // WriteLog($"Skipping recipe (cost {newCost} > {cost}): {recipe}");

                        return;

                    }

                    PaintRecipe origRecipe = _recipes[colorName];

                    if (cost == newCost && recipe.Concentration >= origRecipe.Concentration)

                    {

                        // Same cost, greater concentration - use the lower concentration recipe

                        WriteLog($"Skipping recipe (cost {newCost}, {recipe.Concentration} >= {origRecipe.Concentration}): {recipe}");

                        return;

                    }

                    _recipes[colorName].CopyFrom(recipe); // Copy recipe because the one passed in should be const and will get overwritten

                    _recipeCosts[colorName] = newCost;

                    WriteLog($"Replacing recipe (cost {newCost} < {cost}): {recipe}");

                    if (NewRecipe == null) return;

                    NewRecipeEventArgs args = new(colorName, _recipes[colorName]);

                    NewRecipe(this, args);

                }

                else

                {

                    // This would be an error!

                    _recipeCosts.Add(colorName, newCost);

                    PaintRecipe newRecipe = new PaintRecipe(recipe); // Copy recipe because the one passed in should be const and will get overwritten

                    _recipes.Add(colorName, newRecipe);

                    WriteLog($"New recipe (cost {newCost}): {recipe}");

                    if (NewRecipe == null) return;

                    NewRecipeEventArgs args = new(colorName, newRecipe);

                    NewRecipe(this, args);

                }

            }

        }

        private bool IterateDepthFirst(RecipeSearchNode node)

        {

            TestCurrentRecipe(node);

            // pick recipe quantities at current recipe ingredients/size

            if (NextRecipe(node))

            {

                lock(_workerLock)

                {

                    ++_recipeCount;

                }

                //System.Console.WriteLine("Found next recipe at size {0} qty {1}", node.Reagents.Count, node.CurrentTargetQuantity);

                return true;

            }

            if (NextRecipeSize(node))

            {

                //System.Console.WriteLine("Found next recipe size {0}", node.CurrentTargetQuantity);

                return true;

            }

            // Search for next ingredient combo - all quantity combos for previous were searched

            //System.Console.WriteLine("Finding next ingredient combo");

            do

            {

                if (node.AddNextReagent()) continue;

                while ((node.ReagentCount > node.MinReagents) && (node.LastReagent == (_totalReagents-1)))

                {

                    node.RemoveLastReagent();

                }

                if (node.ReagentCount == node.MinReagents)

                {

                    // done

                    return false;

                }

                uint nextReagent = node.NextFreeReagent(node.LastReagent);

                while ((node.ReagentCount > node.MinReagents) && (nextReagent >= _totalReagents))

                {

                    // No more reagents to try at this level

                    node.RemoveLastReagent();

                    if (node.ReagentCount > node.MinReagents)

                    {

                        nextReagent = node.NextFreeReagent(node.LastReagent);

                    }

                }

                if (node.ReagentCount == node.MinReagents)

                {

                    // done

                    return false;

                }

                node.ReplaceLastReagent(nextReagent);

            } while (node.MaxConcentration < (node.MinConcentration + node.CatalystCount));

            node.InitForQuantity(node.MaxConcentration);

            //string outStr = "{0} : {1} : ";

            //for (int i = 0; i < currentReagents.Count; ++i)

            //{

            //    Reagent reagent = costSortedReagents[(int)currentReagents[i]];

            //    if (i > 0)

            //    {

            //        outStr += ", ";

            //    }

            //    outStr += reagent.Name + " (" + reagent.Cost + ")";

            //}

            //Console.WriteLine(outStr, currentReagents.Count, recipeCount);

            return true;

        }

        private bool IterateBreadthFirst(RecipeSearchNode node)

        {

            // pick recipe quantities at current recipe ingredients/size

            TestCurrentRecipe(node);

            lock(_workerLock)

            {

                ++_recipeCount;

            }

            // search all quantities of current recipe

            if (NextRecipe(node))

            {

                //System.Console.WriteLine("Found next recipe at size {0} qty {1}", node.ReagentCount, node.CurrentTargetQuantity);

                return true;

            }

            string origNodeVal = node.ToString();

            // Try next quantity

            uint newQuantity;

            uint quantityLimit = ((uint)node.ReagentCount <= FullQuantityDepth) ? ((uint)node.ReagentCount * FullQuantity) : node.MaxConcentration;

            do {

                newQuantity = node.CurrentTargetQuantity + 1;

                //Console.WriteLine("Try quantity {0}", newQuantity);

                if (newQuantity > quantityLimit) continue;

                if (node.ShouldLog)

                {

                    WriteLog($" == Initializing {node} for quantity {newQuantity}");

                }

                node.InitForQuantity(newQuantity);

                if (node.CurrentTargetQuantity <= node.UsedQuantity)

                {

                    //if (log != null) { lock(log) { log.WriteLine("Update quantity to {0}", node.CurrentTargetQuantity); } }

                    if (node.ShouldLog)

                    {

                        WriteLog($"  == {node} quantity {newQuantity}");

                    }

                    return true;

                }

            } while (newQuantity < quantityLimit);

            bool ok = NextReagentSetBreadthFirst(node, node.MinReagents, node.MaxReagents);

            if (node.ShouldLog)

            {

                if (ok)

                {

                    WriteLog($"==== {origNodeVal} next reagent set: {node} @ {node.CurrentTargetQuantity}");

                }

                else

                {

                    WriteLog($"==== done with reagent set: {origNodeVal}");

                }

            }

            return ok;

        }

        private bool NextReagentSetBreadthFirst(RecipeSearchNode node, uint minReagents, uint maxReagents)

        {

            // search all variants at this depth of recipe

            // increase recipe depth

            // next reagent in last position

            // if at end, pop reagent

            //Console.WriteLine("Finding new recipe after quantity {0}/{1} used {2}", newQuantity, node.MaxConcentration, node.UsedQuantity);

            if (node.ShouldLog)

            {

                WriteLog($" == Initializing {node} for quantity {node.MinConcentration + node.CatalystCount}");