using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using Microsoft.Xna.Framework.Graphics;
using StardewModdingAPI.Events;
using StardewModdingAPI.Framework.Content;
using StardewModdingAPI.Framework.Deprecations;
using StardewModdingAPI.Framework.Reflection;
using StardewModdingAPI.Framework.Utilities;
using StardewModdingAPI.Internal;
using StardewValley;
using xTile;
using xTile.Tiles;

namespace StardewModdingAPI.Framework.ContentManagers
{
    /// <summary>A content manager which handles reading files from the game content folder with support for interception.</summary>
    internal class GameContentManager : BaseContentManager
    {
        /*********
        ** Fields
        *********/
        /// <summary>The assets currently being intercepted by <see cref="IAssetLoader"/> instances. This is used to prevent infinite loops when a loader loads a new asset.</summary>
        private readonly ContextHash<string> AssetsBeingLoaded = new();

        /// <summary>Whether the next load is the first for any game content manager.</summary>
        private static bool IsFirstLoad = true;

        /// <summary>A callback to invoke the first time *any* game content manager loads an asset.</summary>
        private readonly Action OnLoadingFirstAsset;

        /// <summary>A callback to invoke when an asset is fully loaded.</summary>
        private readonly Action<BaseContentManager, IAssetName> OnAssetLoaded;


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="name">A name for the mod manager. Not guaranteed to be unique.</param>
        /// <param name="serviceProvider">The service provider to use to locate services.</param>
        /// <param name="rootDirectory">The root directory to search for content.</param>
        /// <param name="currentCulture">The current culture for which to localize content.</param>
        /// <param name="coordinator">The central coordinator which manages content managers.</param>
        /// <param name="monitor">Encapsulates monitoring and logging.</param>
        /// <param name="reflection">Simplifies access to private code.</param>
        /// <param name="onDisposing">A callback to invoke when the content manager is being disposed.</param>
        /// <param name="onLoadingFirstAsset">A callback to invoke the first time *any* game content manager loads an asset.</param>
        /// <param name="onAssetLoaded">A callback to invoke when an asset is fully loaded.</param>
        /// <param name="aggressiveMemoryOptimizations">Whether to enable more aggressive memory optimizations.</param>
        public GameContentManager(string name, IServiceProvider serviceProvider, string rootDirectory, CultureInfo currentCulture, ContentCoordinator coordinator, IMonitor monitor, Reflector reflection, Action<BaseContentManager> onDisposing, Action onLoadingFirstAsset, Action<BaseContentManager, IAssetName> onAssetLoaded, bool aggressiveMemoryOptimizations)
            : base(name, serviceProvider, rootDirectory, currentCulture, coordinator, monitor, reflection, onDisposing, isNamespaced: false, aggressiveMemoryOptimizations: aggressiveMemoryOptimizations)
        {
            this.OnLoadingFirstAsset = onLoadingFirstAsset;
            this.OnAssetLoaded = onAssetLoaded;
        }

        /// <inheritdoc />
        public override bool DoesAssetExist<T>(IAssetName assetName)
        {
            if (base.DoesAssetExist<T>(assetName))
                return true;

            // vanilla asset
            if (File.Exists(Path.Combine(this.RootDirectory, $"{assetName.Name}.xnb")))
                return true;

            // managed asset
            if (this.Coordinator.TryParseManagedAssetKey(assetName.Name, out string? contentManagerID, out IAssetName? relativePath))
                return this.Coordinator.DoesManagedAssetExist<T>(contentManagerID, relativePath);

            // custom asset from a loader
            string locale = this.GetLocale();
            IAssetInfo info = new AssetInfo(locale, assetName, typeof(T), this.AssertAndNormalizeAssetName);
            AssetLoadOperation[] loaders = this.GetLoaders<object>(info).ToArray();

            if (!this.AssertMaxOneRequiredLoader(info, loaders, out string? error))
            {
                this.Monitor.Log(error, LogLevel.Warn);
                return false;
            }

            return loaders.Any();
        }

        /// <inheritdoc />
        public override T LoadExact<T>(IAssetName assetName, bool useCache)
        {
            // raise first-load callback
            if (GameContentManager.IsFirstLoad)
            {
                GameContentManager.IsFirstLoad = false;
                this.OnLoadingFirstAsset();
            }

            // get from cache
            if (useCache && this.IsLoaded(assetName))
                return this.RawLoad<T>(assetName, useCache: true);

            // get managed asset
            if (this.Coordinator.TryParseManagedAssetKey(assetName.Name, out string? contentManagerID, out IAssetName? relativePath))
            {
                T managedAsset = this.Coordinator.LoadManagedAsset<T>(contentManagerID, relativePath);
                this.TrackAsset(assetName, managedAsset, useCache);
                return managedAsset;
            }

            // load asset
            T data;
            if (this.AssetsBeingLoaded.Contains(assetName.Name))
            {
                this.Monitor.Log($"Broke loop while loading asset '{assetName}'.", LogLevel.Warn);
                this.Monitor.Log($"Bypassing mod loaders for this asset. Stack trace:\n{Environment.StackTrace}");
                data = this.RawLoad<T>(assetName, useCache);
            }
            else
            {
                data = this.AssetsBeingLoaded.Track(assetName.Name, () =>
                {
                    IAssetInfo info = new AssetInfo(assetName.LocaleCode, assetName, typeof(T), this.AssertAndNormalizeAssetName);
                    IAssetData asset =
                        this.ApplyLoader<T>(info)
                        ?? new AssetDataForObject(info, this.RawLoad<T>(assetName, useCache), this.AssertAndNormalizeAssetName, this.Reflection);
                    asset = this.ApplyEditors<T>(info, asset);
                    return (T)asset.Data;
                });
            }

            // update cache
            this.TrackAsset(assetName, data, useCache);

            // raise event & return data
            this.OnAssetLoaded(this, assetName);
            return data;
        }

        /// <inheritdoc />
        public override LocalizedContentManager CreateTemporary()
        {
            return this.Coordinator.CreateGameContentManager("(temporary)");
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Load the initial asset from the registered loaders.</summary>
        /// <param name="info">The basic asset metadata.</param>
        /// <returns>Returns the loaded asset metadata, or <c>null</c> if no loader matched.</returns>
        private IAssetData? ApplyLoader<T>(IAssetInfo info)
            where T : notnull
        {
            // find matching loader
            AssetLoadOperation? loader;
            {
                AssetLoadOperation[] loaders = this.GetLoaders<T>(info).OrderByDescending(p => p.Priority).ToArray();

                if (!this.AssertMaxOneRequiredLoader(info, loaders, out string? error))
                {
                    this.Monitor.Log(error, LogLevel.Warn);
                    return null;
                }

                loader = loaders.FirstOrDefault();
            }

            // no loader found
            if (loader == null)
                return null;

            // fetch asset from loader
            IModMetadata mod = loader.Mod;
            T data;
            try
            {
                data = (T)loader.GetData(info);
                this.Monitor.Log($"{mod.DisplayName} loaded asset '{info.Name}'{this.GetOnBehalfOfLabel(loader.OnBehalfOf)}.");
            }
            catch (Exception ex)
            {
                mod.LogAsMod($"Mod crashed when loading asset '{info.Name}'{this.GetOnBehalfOfLabel(loader.OnBehalfOf)}. SMAPI will use the default asset instead. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
                return null;
            }

            // return matched asset
            return this.TryFixAndValidateLoadedAsset(info, data, loader)
                ? new AssetDataForObject(info, data, this.AssertAndNormalizeAssetName, this.Reflection)
                : null;
        }

        /// <summary>Apply any editors to a loaded asset.</summary>
        /// <typeparam name="T">The asset type.</typeparam>
        /// <param name="info">The basic asset metadata.</param>
        /// <param name="asset">The loaded asset.</param>
        private IAssetData ApplyEditors<T>(IAssetInfo info, IAssetData asset)
            where T : notnull
        {
            IAssetData GetNewData(object data) => new AssetDataForObject(info, data, this.AssertAndNormalizeAssetName, this.Reflection);

            // special case: if the asset was loaded with a more general type like 'object', call editors with the actual type instead.
            {
                Type actualType = asset.Data.GetType();
                Type? actualOpenType = actualType.IsGenericType ? actualType.GetGenericTypeDefinition() : null;

                if (typeof(T) != actualType && (actualOpenType == typeof(Dictionary<,>) || actualOpenType == typeof(List<>) || actualType == typeof(Texture2D) || actualType == typeof(Map)))
                {
                    return (IAssetData)this.GetType()
                        .GetMethod(nameof(this.ApplyEditors), BindingFlags.NonPublic | BindingFlags.Instance)!
                        .MakeGenericMethod(actualType)
                        .Invoke(this, new object[] { info, asset })!;
                }
            }

            // edit asset
            AssetEditOperation[] editors = this.GetEditors<T>(info).OrderBy(p => p.Priority).ToArray();
            foreach (AssetEditOperation editor in editors)
            {
                IModMetadata mod = editor.Mod;

                // try edit
                object prevAsset = asset.Data;
                try
                {
                    editor.ApplyEdit(asset);
                    this.Monitor.Log($"{mod.DisplayName} edited {info.Name}{this.GetOnBehalfOfLabel(editor.OnBehalfOf)}.");
                }
                catch (Exception ex)
                {
                    mod.LogAsMod($"Mod crashed when editing asset '{info.Name}'{this.GetOnBehalfOfLabel(editor.OnBehalfOf)}, which may cause errors in-game. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
                }

                // validate edit
                // ReSharper disable once ConditionIsAlwaysTrueOrFalse -- it's only guaranteed non-null after this method
                if (asset.Data == null)
                {
                    mod.LogAsMod($"Mod incorrectly set asset '{info.Name}'{this.GetOnBehalfOfLabel(editor.OnBehalfOf)} to a null value; ignoring override.", LogLevel.Warn);
                    asset = GetNewData(prevAsset);
                }
                else if (asset.Data is not T)
                {
                    mod.LogAsMod($"Mod incorrectly set asset '{asset.Name}'{this.GetOnBehalfOfLabel(editor.OnBehalfOf)} to incompatible type '{asset.Data.GetType()}', expected '{typeof(T)}'; ignoring override.", LogLevel.Warn);
                    asset = GetNewData(prevAsset);
                }
            }

            // return result
            return asset;
        }

        /// <summary>Get the asset loaders which handle an asset.</summary>
        /// <typeparam name="T">The asset type.</typeparam>
        /// <param name="info">The basic asset metadata.</param>
        private IEnumerable<AssetLoadOperation> GetLoaders<T>(IAssetInfo info)
            where T : notnull
        {
            return this.Coordinator
                .GetAssetOperations<T>(info)
                .SelectMany(p => p.LoadOperations);
        }

        /// <summary>Get the asset editors to apply to an asset.</summary>
        /// <typeparam name="T">The asset type.</typeparam>
        /// <param name="info">The basic asset metadata.</param>
        private IEnumerable<AssetEditOperation> GetEditors<T>(IAssetInfo info)
            where T : notnull
        {
            return this.Coordinator
                .GetAssetOperations<T>(info)
                .SelectMany(p => p.EditOperations);
        }

        /// <summary>Assert that at most one loader will be applied to an asset.</summary>
        /// <param name="info">The basic asset metadata.</param>
        /// <param name="loaders">The asset loaders to apply.</param>
        /// <param name="error">The error message to show to the user, if the method returns false.</param>
        /// <returns>Returns true if only one loader will apply, else false.</returns>
        private bool AssertMaxOneRequiredLoader(IAssetInfo info, AssetLoadOperation[] loaders, [NotNullWhen(false)] out string? error)
        {
            AssetLoadOperation[] required = loaders.Where(p => p.Priority == AssetLoadPriority.Exclusive).ToArray();
            if (required.Length <= 1)
            {
                error = null;
                return true;
            }

            string[] loaderNames = required
                .Select(p => p.Mod.DisplayName + this.GetOnBehalfOfLabel(p.OnBehalfOf))
                .OrderBy(p => p)
                .Distinct()
                .ToArray();
            string errorPhrase = loaderNames.Length > 1
                ? $"Multiple mods want to provide the '{info.Name}' asset: {string.Join(", ", loaderNames)}"
                : $"The '{loaderNames[0]}' mod wants to provide the '{info.Name}' asset multiple times";

            error = $"{errorPhrase}. An asset can't be loaded multiple times, so SMAPI will use the default asset instead. Uninstall one of the mods to fix this. (Message for modders: you should usually use {typeof(IAssetEditor)} instead to avoid conflicts.)";
            return false;
        }

        /// <summary>Get a parenthetical label for log messages for the content pack on whose behalf the action is being performed, if any.</summary>
        /// <param name="onBehalfOf">The content pack on whose behalf the action is being performed.</param>
        /// <param name="parenthetical">whether to format the label as a parenthetical shown after the mod name like <c> (for the 'X' content pack)</c>, instead of a standalone label like <c>the 'X' content pack</c>.</param>
        /// <returns>Returns the on-behalf-of label if applicable, else <c>null</c>.</returns>
        [return: NotNullIfNotNull("onBehalfOf")]
        private string? GetOnBehalfOfLabel(IModMetadata? onBehalfOf, bool parenthetical = true)
        {
            if (onBehalfOf == null)
                return null;

            return parenthetical
                ? $" (for the '{onBehalfOf.Manifest.Name}' content pack)"
                : $"the '{onBehalfOf.Manifest.Name}' content pack";
        }

        /// <summary>Validate that an asset loaded by a mod is valid and won't cause issues, and fix issues if possible.</summary>
        /// <typeparam name="T">The asset type.</typeparam>
        /// <param name="info">The basic asset metadata.</param>
        /// <param name="data">The loaded asset data.</param>
        /// <param name="loader">The loader which loaded the asset.</param>
        /// <returns>Returns whether the asset passed validation checks (after any fixes were applied).</returns>
        private bool TryFixAndValidateLoadedAsset<T>(IAssetInfo info, [NotNullWhen(true)] T? data, AssetLoadOperation loader)
            where T : notnull
        {
            IModMetadata mod = loader.Mod;

            // can't load a null asset
            if (data == null)
            {
                mod.LogAsMod($"SMAPI blocked asset replacement for '{info.Name}': {this.GetOnBehalfOfLabel(loader.OnBehalfOf, parenthetical: false) ?? "mod"} incorrectly set asset to a null value.", LogLevel.Error);
                return false;
            }

            // when replacing a map, the vanilla tilesheets must have the same order and IDs
            if (data is Map loadedMap)
            {
                TilesheetReference[] vanillaTilesheetRefs = this.Coordinator.GetVanillaTilesheetIds(info.Name.Name);
                foreach (TilesheetReference vanillaSheet in vanillaTilesheetRefs)
                {
                    // add missing tilesheet
                    if (loadedMap.GetTileSheet(vanillaSheet.Id) == null)
                    {
                        mod.Monitor!.LogOnce("SMAPI fixed maps loaded by this mod to prevent errors. See the log file for details.", LogLevel.Warn);
                        this.Monitor.Log($"Fixed broken map replacement: {mod.DisplayName} loaded '{info.Name}' without a required tilesheet (id: {vanillaSheet.Id}, source: {vanillaSheet.ImageSource}).");

                        loadedMap.AddTileSheet(new TileSheet(vanillaSheet.Id, loadedMap, vanillaSheet.ImageSource, vanillaSheet.SheetSize, vanillaSheet.TileSize));
                    }

                    // handle mismatch
                    if (loadedMap.TileSheets.Count <= vanillaSheet.Index || loadedMap.TileSheets[vanillaSheet.Index].Id != vanillaSheet.Id)
                    {
                        // only show warning if not farm map
                        // This is temporary: mods shouldn't do this for any vanilla map, but these are the ones we know will crash. Showing a warning for others instead gives modders time to update their mods, while still simplifying troubleshooting.
                        bool isFarmMap = info.Name.IsEquivalentTo("Maps/Farm") || info.Name.IsEquivalentTo("Maps/Farm_Combat") || info.Name.IsEquivalentTo("Maps/Farm_Fishing") || info.Name.IsEquivalentTo("Maps/Farm_Foraging") || info.Name.IsEquivalentTo("Maps/Farm_FourCorners") || info.Name.IsEquivalentTo("Maps/Farm_Island") || info.Name.IsEquivalentTo("Maps/Farm_Mining");

                        string reason = $"{this.GetOnBehalfOfLabel(loader.OnBehalfOf, parenthetical: false) ?? "mod"} reordered the original tilesheets, which {(isFarmMap ? "would cause a crash" : "often causes crashes")}.\nTechnical details for mod author: Expected order: {string.Join(", ", vanillaTilesheetRefs.Select(p => p.Id))}. See https://stardewvalleywiki.com/Modding:Maps#Tilesheet_order for help.";

                        SCore.DeprecationManager.PlaceholderWarn("3.8.2", DeprecationLevel.PendingRemoval);
                        if (isFarmMap)
                        {
                            mod.LogAsMod($"SMAPI blocked a '{info.Name}' map load: {reason}", LogLevel.Error);
                            return false;
                        }
                        mod.LogAsMod($"SMAPI found an issue with a '{info.Name}' map load: {reason}", LogLevel.Warn);
                    }
                }
            }

            return true;
        }
    }
}