using System.Collections.Generic;

namespace Engine.Core;

/// <summary>
/// Represents a controller for managing <see cref="IBehaviour"/>s. Connected to an <see cref="IUniverseObject"/>.
/// </summary>
public interface IBehaviourController : IEntity, IHasUniverseObject
{
    /// <summary>
    /// Event triggered when a <see cref="IBehaviour"/> is added to the <see cref="IBehaviourController"/>.
    /// </summary>
    Event<IBehaviourController, BehaviourAddedArguments> OnBehaviourAdded { get; }

    /// <summary>
    /// Event triggered when a <see cref="IBehaviour"/> is removed from the <see cref="IBehaviourController"/>.
    /// </summary>
    Event<IBehaviourController, BehaviourRemovedArguments> OnBehaviourRemoved { get; }

    /// <summary>
    /// Amount of <see cref="IBehaviour"/> collected.
    /// </summary>
    int Count { get; }

    /// <summary>
    /// Get a <see cref="IBehaviour"/> collected by it's index.
    /// </summary>
    IBehaviour this[System.Index index] { get; }

    /// <summary>
    /// Adds a <see cref="IBehaviour"/> to the <see cref="IBehaviourController"/>.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to add.</typeparam>
    /// <param name="behaviour">The <see cref="IBehaviour"/> to add.</param>
    /// <returns>The added <see cref="IBehaviour"/>.</returns>
    T AddBehaviour<T>(T behaviour) where T : class, IBehaviour;

    /// <summary>
    /// Adds a <see cref="IBehaviour"/> of the specified type to the <see cref="IBehaviourController"/>.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to add.</typeparam>
    /// <param name="args">Construction parameters for the <see cref="IBehaviour"/>.</param>
    /// <returns>The added <see cref="IBehaviour"/>.</returns>
    T AddBehaviour<T>(params object?[]? args) where T : class, IBehaviour;

    /// <summary>
    /// Gets a <see cref="IBehaviour"/> of the specified type.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
    /// <returns>The <see cref="IBehaviour"/> of the specified type if found; otherwise, <see cref="null"/>.</returns>
    T? GetBehaviour<T>();

    /// <summary>
    /// Gets all <see cref="IBehaviour"/>s of the specified type.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
    /// <returns>A list of <see cref="IBehaviour"/>s of the specified type.</returns>
    IReadOnlyList<T> GetBehaviours<T>();

    /// <summary>
    /// Gets all <see cref="IBehaviour"/>s of the specified type and stores them in the provided list.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
    /// <param name="results">The list to store the <see cref="IBehaviour"/>s.</param>
    /// <param name="collectionMethod">Whether to clear the <paramref name="results"/> before collection or append the results to the list.</param>
    void GetBehaviours<T>(IList<T> results, CollectionMethod collectionMethod = CollectionMethod.Clear);

    /// <summary>
    /// Removes <see cref="IBehaviour"/>s of the specified type from the <see cref="IBehaviourController"/>.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to remove.</typeparam>
    /// <param name="removeAll">A flag indicating whether to remove all <see cref="IBehaviour"/>s of the specified type.</param>
    void RemoveBehaviour<T>(bool removeAll = false) where T : class, IBehaviour;

    /// <summary>
    /// Removes the specified <see cref="IBehaviour"/> from the <see cref="IBehaviourController"/>.
    /// </summary>
    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to remove.</typeparam>
    /// <param name="behaviour">The <see cref="IBehaviour"/> to remove.</param>
    void RemoveBehaviour<T>(T behaviour) where T : class, IBehaviour;

    enum CollectionMethod { Clear, Append };

    readonly record struct BehaviourAddedArguments(IBehaviour BehaviourAdded);
    readonly record struct BehaviourRemovedArguments(IBehaviour BehaviourRemoved);
}