using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using StardewModdingAPI.Framework.StateTracking.FieldWatchers;
using StardewValley;
using StardewValley.Buildings;
using StardewValley.Locations;
using StardewValley.Objects;
using StardewValley.TerrainFeatures;
using SObject = StardewValley.Object;

namespace StardewModdingAPI.Framework.StateTracking
{
    /// <summary>Tracks changes to a location's data.</summary>
    internal class LocationTracker : IWatcher
    {
        /*********
        ** Fields
        *********/
        /// <summary>The underlying watchers.</summary>
        private readonly List<IWatcher> Watchers = new();


        /*********
        ** Accessors
        *********/
        /// <summary>Whether the value changed since the last reset.</summary>
        public bool IsChanged => this.Watchers.Any(p => p.IsChanged);

        /// <summary>The tracked location.</summary>
        public GameLocation Location { get; }

        /// <summary>Tracks added or removed buildings.</summary>
        public ICollectionWatcher<Building> BuildingsWatcher { get; }

        /// <summary>Tracks added or removed debris.</summary>
        public ICollectionWatcher<Debris> DebrisWatcher { get; }

        /// <summary>Tracks added or removed large terrain features.</summary>
        public ICollectionWatcher<LargeTerrainFeature> LargeTerrainFeaturesWatcher { get; }

        /// <summary>Tracks added or removed NPCs.</summary>
        public ICollectionWatcher<NPC> NpcsWatcher { get; }

        /// <summary>Tracks added or removed objects.</summary>
        public IDictionaryWatcher<Vector2, SObject> ObjectsWatcher { get; }

        /// <summary>Tracks added or removed terrain features.</summary>
        public IDictionaryWatcher<Vector2, TerrainFeature> TerrainFeaturesWatcher { get; }

        /// <summary>Tracks added or removed furniture.</summary>
        public ICollectionWatcher<Furniture> FurnitureWatcher { get; }

        /// <summary>Tracks items added or removed to chests.</summary>
        public IDictionary<Vector2, ChestTracker> ChestWatchers { get; } = new Dictionary<Vector2, ChestTracker>();


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="location">The location to track.</param>
        public LocationTracker(GameLocation location)
        {
            this.Location = location;

            // init watchers
            this.BuildingsWatcher = location is BuildableGameLocation buildableLocation ? WatcherFactory.ForNetCollection(buildableLocation.buildings) : WatcherFactory.ForImmutableCollection<Building>();
            this.DebrisWatcher = WatcherFactory.ForNetCollection(location.debris);
            this.LargeTerrainFeaturesWatcher = WatcherFactory.ForNetCollection(location.largeTerrainFeatures);
            this.NpcsWatcher = WatcherFactory.ForNetCollection(location.characters);
            this.ObjectsWatcher = WatcherFactory.ForNetDictionary(location.netObjects);
            this.TerrainFeaturesWatcher = WatcherFactory.ForNetDictionary(location.terrainFeatures);
            this.FurnitureWatcher = WatcherFactory.ForNetCollection(location.furniture);

            this.Watchers.AddRange(new IWatcher[]
            {
                this.BuildingsWatcher,
                this.DebrisWatcher,
                this.LargeTerrainFeaturesWatcher,
                this.NpcsWatcher,
                this.ObjectsWatcher,
                this.TerrainFeaturesWatcher,
                this.FurnitureWatcher
            });

            this.UpdateChestWatcherList(added: location.Objects.Pairs, removed: Array.Empty<KeyValuePair<Vector2, SObject>>());
        }

        /// <summary>Update the current value if needed.</summary>
        public void Update()
        {
            foreach (IWatcher watcher in this.Watchers)
                watcher.Update();

            this.UpdateChestWatcherList(added: this.ObjectsWatcher.Added, removed: this.ObjectsWatcher.Removed);

            foreach (var watcher in this.ChestWatchers)
                watcher.Value.Update();
        }

        /// <summary>Set the current value as the baseline.</summary>
        public void Reset()
        {
            foreach (IWatcher watcher in this.Watchers)
                watcher.Reset();

            foreach (var watcher in this.ChestWatchers)
                watcher.Value.Reset();
        }

        /// <summary>Stop watching the player fields and release all references.</summary>
        public void Dispose()
        {
            foreach (IWatcher watcher in this.Watchers)
                watcher.Dispose();

            foreach (var watcher in this.ChestWatchers.Values)
                watcher.Dispose();
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Update the watcher list for added or removed chests.</summary>
        /// <param name="added">The objects added to the location.</param>
        /// <param name="removed">The objects removed from the location.</param>
        private void UpdateChestWatcherList(IEnumerable<KeyValuePair<Vector2, SObject>> added, IEnumerable<KeyValuePair<Vector2, SObject>> removed)
        {
            // remove unused watchers
            foreach ((Vector2 tile, SObject? obj) in removed)
            {
                if (obj is Chest && this.ChestWatchers.TryGetValue(tile, out ChestTracker? watcher))
                {
                    watcher.Dispose();
                    this.ChestWatchers.Remove(tile);
                }
            }

            // add new watchers
            foreach ((Vector2 tile, SObject? obj) in added)
            {
                if (obj is Chest chest && !this.ChestWatchers.ContainsKey(tile))
                    this.ChestWatchers.Add(tile, new ChestTracker(chest));
            }
        }
    }
}