using System;
using System.Collections.Generic;
using System.Linq;

namespace Encompass
{
    internal abstract class TypedComponentStore
    {
        public abstract int Count { get; }
        public abstract IEnumerable<(Entity, Type, IComponent)> AllInterfaceTyped();
        public abstract bool Has(Entity entity);
        public abstract void Remove(Entity entity);
        public abstract void Clear();
    }

    internal class TypedComponentStore<TComponent> : TypedComponentStore where TComponent : struct, IComponent
    {
        private readonly Dictionary<Entity, TComponent> store = new Dictionary<Entity, TComponent>(128);
        private readonly Dictionary<Entity, int> priorities = new Dictionary<Entity, int>(128);

        public override int Count { get => store.Count; }

        public TComponent Get(Entity entity)
        {
            return store[entity];
        }

        public void Set(Entity entity, TComponent component)
        {
            store[entity] = component;
        }

        public bool Set(Entity entity, TComponent component, int priority)
        {
            if (!priorities.ContainsKey(entity) || priority < priorities[entity]) {
                store[entity] = component;
                return true;
            }

            return false;
        }

        public override bool Has(Entity entity)
        {
            return store.ContainsKey(entity);
        }

        public override void Clear()
        {
            store.Clear();
        }

        public IEnumerable<(Entity, TComponent)> All()
        {
            return store.Select(kvp => (kvp.Key, kvp.Value));
        }

        public override IEnumerable<(Entity, Type, IComponent)> AllInterfaceTyped()
        {
            return store.Select(kvp => (kvp.Key, typeof(TComponent), (IComponent)kvp.Value));
        }

        // public override IEnumerable<T> All<T>()
        // {
        //     return store.Values.Cast<T>();
        // }

        public override void Remove(Entity entity)
        {
            store.Remove(entity);
            priorities.Remove(entity);
        }
    }
}