using System.Collections.Generic;
using System.Linq;
using StardewModdingAPI.Framework.StateTracking.Comparers;
using StardewValley;

namespace StardewModdingAPI.Framework.StateTracking.Snapshots
{
    /// <summary>A frozen snapshot of the tracked game locations.</summary>
    internal class WorldLocationsSnapshot
    {
        /*********
        ** Fields
        *********/
        /// <summary>A map of tracked locations.</summary>
        private readonly Dictionary<GameLocation, LocationSnapshot> LocationsDict = new(new ObjectReferenceComparer<GameLocation>());


        /*********
        ** Accessors
        *********/
        /// <summary>Tracks changes to the location list.</summary>
        public SnapshotListDiff<GameLocation> LocationList { get; } = new();

        /// <summary>The tracked locations.</summary>
        public IEnumerable<LocationSnapshot> Locations => this.LocationsDict.Values;


        /*********
        ** Public methods
        *********/
        /// <summary>Update the tracked values.</summary>
        /// <param name="watcher">The watcher to snapshot.</param>
        public void Update(WorldLocationsTracker watcher)
        {
            // update location list
            this.LocationList.Update(watcher.IsLocationListChanged, watcher.Added, watcher.Removed);

            // remove missing locations
            foreach (var key in this.LocationsDict.Keys.Where(key => !watcher.HasLocationTracker(key)).ToArray())
                this.LocationsDict.Remove(key);

            // update locations
            foreach (LocationTracker locationWatcher in watcher.Locations)
            {
                if (!this.LocationsDict.TryGetValue(locationWatcher.Location, out LocationSnapshot? snapshot))
                    this.LocationsDict[locationWatcher.Location] = snapshot = new LocationSnapshot(locationWatcher.Location);

                snapshot.Update(locationWatcher);
            }
        }
    }
}