using System.Diagnostics;
using System.Runtime.InteropServices;

namespace Djup.Native;

[StructLayout(LayoutKind.Sequential)]
public struct EntityId
{
    public int Id { get; }

    public static readonly EntityId Invalid = new(-1);

    public EntityId(int id)
    {
        Id = id;
    }

    public bool IsInvalid => Id < 0;

    public override string ToString() => $"#{Id}";

    public override bool Equals(object? other)
    {
        if (other is EntityId id)
        {
            return this == id;
        }
        return false;
    }

    public override int GetHashCode() => Id.GetHashCode();

    public static bool operator ==(EntityId a, EntityId b)
    {
        if (a < 0)
            return b < 0;
        if (b < 0)
            return false;
        return a.Id == b.Id;
    }
    public static bool operator !=(EntityId a, EntityId b) => !(a == b);
    public static implicit operator int(EntityId entityId) => entityId.Id;
    public static implicit operator EntityId(int id) => new(id);
}

public enum Component : int
{
    Exists,
    Ball,
    PlayerInput
}

[Flags]
public enum Components : int
{
    Exists = 1 << Component.Exists,
    Ball = 1 << Component.Ball,
    PlayerInput = 1 << Component.PlayerInput
}

[StructLayout(LayoutKind.Sequential)]
public unsafe struct OdinSlice<T>
{
    public void* Data { get; }
    public nint Len { get; }

    public Span<T> AsSpan() => new Span<T>(Data, Len.ToInt32());
    public ReadOnlySpan<T> AsReadOnlySpan() => new ReadOnlySpan<T>(Data, Len.ToInt32());
}

[StructLayout(LayoutKind.Sequential)]
public unsafe struct OdinString
{
    public sbyte* Data { get; }
    public nint Len { get; }

    public override string ToString() => new string(Data, 0, Len.ToInt32());
}

[StructLayout(LayoutKind.Sequential)]
public struct Vec2
{
    public float X { get; set; }
    public float Y { get; set; }

    public Vec2(float x, float y)
    {
        Debug.Assert(float.IsFinite(x));
        Debug.Assert(float.IsFinite(y));

        X = x;
        Y = y;
    }

    public override string ToString() => $"({X}, {Y})";
}

[StructLayout(LayoutKind.Sequential)]
public struct Ball
{
    public Vec2 Position { get; set; }
    public Vec2 Velocity { get; set; }
}

[StructLayout(LayoutKind.Sequential)]
public struct PlayerInput
{
    public Vec2 Direction { get; set; }
}

[StructLayout(LayoutKind.Sequential)]
public struct Snapshot
{
    private readonly byte active;
    public uint Tick { get; }
    public OdinSlice<Components> Metadata { get; }
    public OdinSlice<Ball> Balls { get; }
    public OdinSlice<PlayerInput> PlayerInputs { get; }
    private IntPtr ctx;
}

public enum LogLevel
{
    Debug,
    Info,
    Warn,
    Error,
    Fatal
}

public delegate void LoggerDelegate(LogLevel level, OdinString message, OdinString procedure, OdinString file, int line);
public delegate void AssertDelegate(OdinString prefix, OdinString message, OdinString procedure, OdinString file, int line);