using System;
using System.Runtime.InteropServices;
using gaemstone.ECS.Utility;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public unsafe struct World
	: IEquatable<World>
	, IDisposable
{
	public ecs_world_t* Handle { get; }

	public bool IsDeferred      => ecs_is_deferred(this);
	public bool IsQuitRequested => ecs_should_quit(this);

	public World(ecs_world_t* handle)
		=> Handle = handle;

	/// <summary> Initializes a new Flecs world. </summary>
	/// <param name="minimal"> If true, doesn't automatically import built-in modules. </param>
	public World(bool minimal = false)
	{
		[UnmanagedCallersOnly]
		static void Abort() => throw new FlecsAbortException();

		ecs_os_set_api_defaults();
		var api = ecs_os_get_api();
		api.abort_ = new FnPtr_Void { Pointer = &Abort };
		ecs_os_set_api(&api);

		Handle = minimal ? ecs_mini() : ecs_init();
	}

	public bool Progress(TimeSpan delta)
		=> ecs_progress(this, (float)delta.TotalSeconds);

	public void Quit()
		=> ecs_quit(this);

	public void Dispose()
		=> ecs_fini(this);


	public Entity LookupAlive(Entity value)
		=> new(ecs_get_alive(this, value));

	public Entity LookupPath(EntityPath path, Entity parent = default,
	                         bool throwOnNotFound = false)
		=> new(EntityPath.Lookup(this, path, parent, throwOnNotFound));

	// TODO: Provide overload that uses a UTF-8 byte span?
	public Entity LookupSymbol(string symbol)
	{
		using var alloc = TempAllocator.Use();
		return new(ecs_lookup_symbol(this, alloc.AllocateCString(symbol), false));
	}


	public bool Equals(World other)
	{
		if (Handle == other.Handle) return true;
		return ecs_get_world((ecs_poly_t*)Handle)
			== ecs_get_world((ecs_poly_t*)other.Handle);
	}
	public override bool Equals(object? obj)
		=> (obj is World other) && Equals(other);
	public override int GetHashCode()
		=> ((nint)ecs_get_world((ecs_poly_t*)Handle)).GetHashCode();

	public static bool operator ==(World left, World right) =>  left.Equals(right);
	public static bool operator !=(World left, World right) => !left.Equals(right);

	public static implicit operator ecs_world_t*(World w) => w.Handle;
}