using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

using CSStatus = FFXIVClientStructs.FFXIV.Client.Game.Status;

namespace Dalamud.Game.ClientState.Statuses;

/// <summary>
/// This collection represents the status effects an actor is afflicted by.
/// </summary>
public sealed unsafe partial class StatusList
{
    /// <summary>
    /// Initializes a new instance of the <see cref="StatusList"/> class.
    /// </summary>
    /// <param name="address">Address of the status list.</param>
    internal StatusList(nint address)
    {
        this.Address = address;
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="StatusList"/> class.
    /// </summary>
    /// <param name="pointer">Pointer to the status list.</param>
    internal unsafe StatusList(void* pointer)
        : this((nint)pointer)
    {
    }

    /// <summary>
    /// Gets the address of the status list in memory.
    /// </summary>
    public nint Address { get; }

    /// <summary>
    /// Gets the amount of status effect slots the actor has.
    /// </summary>
    public int Length => Struct->NumValidStatuses;

    private static int StatusSize { get; } = Marshal.SizeOf<FFXIVClientStructs.FFXIV.Client.Game.Status>();

    private FFXIVClientStructs.FFXIV.Client.Game.StatusManager* Struct => (FFXIVClientStructs.FFXIV.Client.Game.StatusManager*)this.Address;

    /// <summary>
    /// Get a status effect at the specified index.
    /// </summary>
    /// <param name="index">Status Index.</param>
    /// <returns>The status at the specified index.</returns>
    public IStatus? this[int index]
    {
        get
        {
            if (index < 0 || index > this.Length)
                return null;

            var addr = this.GetStatusAddress(index);
            return CreateStatusReference(addr);
        }
    }

    /// <summary>
    /// Create a reference to an FFXIV actor status list.
    /// </summary>
    /// <param name="address">The address of the status list in memory.</param>
    /// <returns>The status object containing the requested data.</returns>
    public static StatusList? CreateStatusListReference(nint address)
    {
        if (address == IntPtr.Zero)
            return null;

        // The use case for CreateStatusListReference and CreateStatusReference to be static is so
        // fake status lists can be generated. Since they aren't exposed as services, it's either
        // here or somewhere else.
        var clientState = Service<ClientState>.Get();

        if (clientState.LocalContentId == 0)
            return null;

        if (address == 0)
            return null;

        return new StatusList(address);
    }

    /// <summary>
    /// Create a reference to an FFXIV actor status.
    /// </summary>
    /// <param name="address">The address of the status effect in memory.</param>
    /// <returns>The status object containing the requested data.</returns>
    public static IStatus? CreateStatusReference(nint address)
    {
        if (address == IntPtr.Zero)
            return null;

        if (address == 0)
            return null;

        return new Status((CSStatus*)address);
    }

    /// <summary>
    /// Gets the address of the status at the specific index in the status list.
    /// </summary>
    /// <param name="index">The index of the status.</param>
    /// <returns>The memory address of the status.</returns>
    public nint GetStatusAddress(int index)
    {
        if (index < 0 || index >= this.Length)
            return 0;

        return (nint)Unsafe.AsPointer(ref this.Struct->Status[index]);
    }
}

/// <summary>
/// This collection represents the status effects an actor is afflicted by.
/// </summary>
public sealed partial class StatusList : IReadOnlyCollection<IStatus>, ICollection
{
    /// <inheritdoc/>
    int IReadOnlyCollection<IStatus>.Count => this.Length;

    /// <inheritdoc/>
    int ICollection.Count => this.Length;

    /// <inheritdoc/>
    bool ICollection.IsSynchronized => false;

    /// <inheritdoc/>
    object ICollection.SyncRoot => this;

    /// <inheritdoc/>
    public IEnumerator<IStatus> GetEnumerator()
    {
        return new Enumerator(this);
    }

    /// <inheritdoc/>
    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();

    /// <inheritdoc/>
    void ICollection.CopyTo(Array array, int index)
    {
        for (var i = 0; i < this.Length; i++)
        {
            array.SetValue(this[i], index);
            index++;
        }
    }

    private struct Enumerator(StatusList statusList) : IEnumerator<IStatus>
    {
        private int index = -1;

        public IStatus Current { get; private set; }

        object IEnumerator.Current => this.Current;

        public bool MoveNext()
        {
            while (++this.index < statusList.Length)
            {
                var status = statusList[this.index];
                if (status != null && status.StatusId != 0)
                {
                    this.Current = status;
                    return true;
                }
            }

            this.Current = default;
            return false;
        }

        public void Reset()
        {
            this.index = -1;
        }

        public void Dispose()
        {
        }
    }
}