using System;
using System.Collections.Generic;

namespace StardewModdingAPI.Framework.Utilities
{
    /// <summary>An in-memory dictionary cache that stores data for the duration of a game update tick.</summary>
    /// <typeparam name="TKey">The dictionary key type.</typeparam>
    /// <typeparam name="TValue">The dictionary value type.</typeparam>
    internal class TickCacheDictionary<TKey, TValue>
        where TKey : notnull
    {
        /*********
        ** Fields
        *********/
        /// <summary>The last game tick for which data was cached.</summary>
        private uint? LastGameTick;

        /// <summary>The underlying cached data.</summary>
        private readonly Dictionary<TKey, TValue> Cache = new();


        /*********
        ** Public methods
        *********/
        /// <summary>Get a value from the cache, fetching it first if it's not cached yet.</summary>
        /// <param name="cacheKey">The unique key for the cached value.</param>
        /// <param name="get">Get the latest data if it's not in the cache yet.</param>
        public TValue GetOrSet(TKey cacheKey, Func<TValue> get)
        {
            // clear cache on new tick
            if (SCore.ProcessTicksElapsed != this.LastGameTick)
            {
                this.Cache.Clear();
                this.LastGameTick = SCore.ProcessTicksElapsed;
            }

            // fetch value
            if (!this.Cache.TryGetValue(cacheKey, out TValue? cached))
                this.Cache[cacheKey] = cached = get();
            return cached;
        }

        /// <summary>Remove an entry from the cache.</summary>
        /// <param name="cacheKey">The unique key for the cached value.</param>
        /// <returns>Returns whether the key was present in the dictionary.</returns>
        public bool Remove(TKey cacheKey)
        {
            return this.Cache.Remove(cacheKey);
        }
    }
}