namespace System.Collections.Generic;

/// <summary>
/// Interface for queue implementations.
/// </summary>
/// <typeparam name="T">Provided type.</typeparam>
public interface IQueue<T> : IEnumerable<T>
{
    /// <summary>
    /// Returns the number of items in the queue.
    /// </summary>
    int Count { get; }
    /// <summary>
    /// Inserts item into the queue.
    /// </summary>
    /// <param name="item">Item to be inserted.</param>
    void Enqueue(T item);
    /// <summary>
    /// Remove the first item in the queue.
    /// </summary>
    /// <returns>First item in the queue.</returns>
    T Dequeue();
    /// <summary>
    /// Looks up the first item from the queue without removing it.
    /// </summary>
    /// <returns>First item from the queue.</returns>
    T Peek();
    /// <summary>
    /// Clears the contents of the queue.
    /// </summary>
    void Clear();
    /// <summary>
    /// Checks if queue contains an item.
    /// </summary>
    /// <param name="item">Item to be checked.</param>
    /// <returns>True if queue contains provided item. False otherwise.</returns>
    bool Contains(T item);
}