using System.Collections.Generic;

namespace Syntriax.Engine.Core.Abstract;

/// <summary>
/// Represents an <see cref="IEntity"/> that can enter and exit a hierarchy within the <see cref="IGameManager"/> system.
/// This interface allows for tracking the object's presence in the hierarchy and provides events 
/// for notifying when the see enters or exits the hierarchy.
/// </summary>
public interface IHierarchyObject : IEntity, IActive, INameable, IHasBehaviourController, IEnumerable<IHierarchyObject>
{
    /// <summary>
    /// Event triggered when the <see cref="IHierarchyObject"/> enters the hierarchy.
    /// </summary>
    event EnteredHierarchyEventHandler? OnEnteredHierarchy;

    /// <summary>
    /// Event triggered when the <see cref="IHierarchyObject"/> exits the hierarchy.
    /// </summary>
    event ExitedHierarchyEventHandler? OnExitedHierarchy;

    /// <summary>
    /// Event triggered when the <see cref="Parent"/> of the <see cref="IHierarchyObject"/> changes. The second parameter is the old <see cref="IHierarchyObject"/>.
    /// </summary>
    event ParentChangedEventHandler? OnParentChanged;

    /// <summary>
    /// Event triggered when a new <see cref="IHierarchyObject"/> is added to the <see cref="Children"/>.
    /// </summary>
    event ChildrenAddedEventHandler? OnChildrenAdded;

    /// <summary>
    /// Event triggered when an <see cref="IHierarchyObject"/> is removed from the <see cref="Children"/>.
    /// </summary>
    event ChildrenRemovedEventHandler? OnChildrenRemoved;

    /// <summary>
    /// Gets the <see cref="IGameManager"/> this <see cref="IHierarchyObject"/> is connected to, if any.
    /// </summary>
    IGameManager GameManager { get; }

    /// <summary>
    /// Indicates whether the <see cref="IHierarchyObject"/> is currently in the hierarchy.
    /// </summary>
    bool IsInHierarchy { get; }

    /// <summary>
    /// The parent <see cref="IHierarchyObject"/> of the <see cref="IHierarchyObject"/>.
    /// </summary>
    IHierarchyObject? Parent { get; }

    /// <summary>
    /// The <see cref="IHierarchyObject"/>s that have this <see cref="IHierarchyObject"/> as their <see cref="Parent"/>.
    /// </summary>
    IReadOnlyList<IHierarchyObject> Children { get; }

    /// <summary>
    /// Internal method to handle entering the hierarchy.
    /// This should be called by the system to properly manage hierarchy states.
    /// </summary>
    /// <param name="gameManager">The <see cref="IGameManager"/> that is managing this hierarchy.</param>
    /// <returns>
    /// <see cref="true"/> if the <see cref="IHierarchyObject"/> successfully entered the hierarchy; 
    /// <see cref="false"/> if it failed to do so.
    /// </returns>
    internal bool EnterHierarchy(IGameManager gameManager);

    /// <summary>
    /// Internal method to handle exiting the hierarchy.
    /// This should be called by the system to properly manage hierarchy states.
    /// </summary>
    /// <returns>
    /// <see cref="true"/> if the <see cref="IHierarchyObject"/> successfully exited the hierarchy; 
    /// <see cref="false"/> if it failed to do so.
    /// </returns>
    internal bool ExitHierarchy();

    /// <summary>
    /// Sets the parent <see cref="IHierarchyObject"/> of this <see cref="IHierarchyObject"/>.
    /// </summary>
    /// <param name="hierarchyObject">The parent <see cref="IHierarchyObject"/> to set.</param>
    void SetParent(IHierarchyObject? hierarchyObject);

    /// <summary>
    /// Adds a child <see cref="IHierarchyObject"/> to this <see cref="IHierarchyObject"/>.
    /// </summary>
    /// <param name="hierarchyObject">The child <see cref="IHierarchyObject"/> to add.</param>
    void AddChild(IHierarchyObject hierarchyObject);

    /// <summary>
    /// Removes a child <see cref="IHierarchyObject"/> from this <see cref="IHierarchyObject"/>.
    /// </summary>
    /// <param name="hierarchyObject">The child <see cref="IHierarchyObject"/> to remove.</param>
    void RemoveChild(IHierarchyObject hierarchyObject);

    /// <summary>
    /// EventHandler delegate for the event triggered when the <see cref="IHierarchyObject"/> enters the hierarchy of a <see cref="IGameManager">.
    /// </summary>
    /// <param name="sender">The <see cref="IHierarchyObject"/> that entered the hierarchy.</param>
    /// <param name="gameManager">The <see cref="IGameManager"/> that the <see cref="IHierarchyObject"/> has entered it's hierarchy.</param>
    delegate void EnteredHierarchyEventHandler(IHierarchyObject sender, IGameManager gameManager);

    /// <summary>
    /// EventHandler delegate for the event triggered when the <see cref="IHierarchyObject"/> exits the hierarchy of a <see cref="IGameManager">.
    /// </summary>
    /// <param name="sender">The <see cref="IHierarchyObject"/> that exited the hierarchy.</param>
    /// <param name="gameManager">The <see cref="IGameManager"/> that the <see cref="IHierarchyObject"/> has exited it's hierarchy.</param>
    delegate void ExitedHierarchyEventHandler(IHierarchyObject sender, IGameManager gameManager);

    /// <summary>
    /// Delegate for the event triggered when the <see cref="IHierarchyObject"/>'s parent changes.
    /// </summary>
    /// <param name="sender">The <see cref="IHierarchyObject"/> that the parent has changed.</param>
    /// <param name="previousParent">The previous <see cref="IHierarchyObject"/> the sender was a child of.</param>
    /// <param name="newParent">The new and current <see cref="IHierarchyObject"/> the sender is a child of.</param>
    delegate void ParentChangedEventHandler(IHierarchyObject sender, IHierarchyObject? previousParent, IHierarchyObject? newParent);

    /// <summary>
    /// Delegate for the event triggered when a new <see cref="IHierarchyObject"/> added as a child.
    /// </summary>
    /// <param name="sender">The parent <see cref="IHierarchyObject"/> this event is being called from.</param>
    /// <param name="childrenAdded">The <see cref="IHierarchyObject"/> that got removed as a children of the sender <see cref="IHierarchyObject"/>.</param>
    delegate void ChildrenAddedEventHandler(IHierarchyObject sender, IHierarchyObject childrenAdded);

    /// <summary>
    /// Delegate for the event triggered when a new <see cref="IHierarchyObject"/> removed from being a child.
    /// </summary>
    /// <param name="sender">The parent <see cref="IHierarchyObject"/> this event is being called from.</param>
    /// <param name="childrenAdded">The <see cref="IHierarchyObject"/> that got removed as a children of the sender <see cref="IHierarchyObject"/>.</param>
    delegate void ChildrenRemovedEventHandler(IHierarchyObject sender, IHierarchyObject childrenRemoved);
}