using Umbraco.Core.Persistence.DatabaseModelDefinitions;

namespace Umbraco.Core.Services
{
    /// <summary>
    /// Represents ordering information.
    /// </summary>
    public class Ordering
    {
        private static readonly Ordering DefaultOrdering = new Ordering(null);

        /// <summary>
        /// Initializes a new instance of the <see cref="Ordering"/> class.
        /// </summary>
        /// <param name="orderBy">The name of the ordering field.</param>
        /// <param name="direction">The ordering direction.</param>
        /// <param name="culture">The (ISO) culture to consider when sorting multi-lingual fields.</param>
        /// <param name="isCustomField">A value indicating whether the ordering field is a custom user property.</param>
        /// <remarks>
        /// <para>The <paramref name="orderBy"/> can be null, meaning: not sorting. If it is the empty string, it becomes null.</para>
        /// <para>The <paramref name="culture"/> can be the empty string, meaning: invariant. If it is null, it becomes the empty string.</para>
        /// </remarks>
        public Ordering(string orderBy, Direction direction = Direction.Ascending, string culture = null, bool isCustomField = false)
        {
            OrderBy = orderBy.IfNullOrWhiteSpace(null); // empty is null and means, not sorting
            Direction = direction;
            Culture = culture.IfNullOrWhiteSpace(string.Empty); // empty is "" and means, invariant
            IsCustomField = isCustomField;
        }

        /// <summary>
        /// Creates a new instance of the <see cref="Ordering"/> class.
        /// </summary>
        /// <param name="orderBy">The name of the ordering field.</param>
        /// <param name="direction">The ordering direction.</param>
        /// <param name="culture">The (ISO) culture to consider when sorting multi-lingual fields.</param>
        /// <param name="isCustomField">A value indicating whether the ordering field is a custom user property.</param>
        /// <remarks>
        /// <para>The <paramref name="orderBy"/> can be null, meaning: not sorting. If it is the empty string, it becomes null.</para>
        /// <para>The <paramref name="culture"/> can be the empty string, meaning: invariant. If it is null, it becomes the empty string.</para>
        /// </remarks>
        public static Ordering By(string orderBy, Direction direction = Direction.Ascending, string culture = null, bool isCustomField = false)
            => new Ordering(orderBy, direction, culture, isCustomField);

        /// <summary>
        /// Gets the default <see cref="Ordering"/> instance.
        /// </summary>
        public static Ordering ByDefault()
            => DefaultOrdering;

        /// <summary>
        /// Gets the name of the ordering field.
        /// </summary>
        public string OrderBy { get; }

        /// <summary>
        /// Gets the ordering direction.
        /// </summary>
        public Direction Direction { get; }

        /// <summary>
        /// Gets (ISO) culture to consider when sorting multi-lingual fields.
        /// </summary>
        public string Culture { get; }

        /// <summary>
        /// Gets a value indicating whether the ordering field is a custom user property.
        /// </summary>
        public bool IsCustomField { get; }

        /// <summary>
        /// Gets a value indicating whether this ordering is the default ordering.
        /// </summary>
        public bool IsEmpty => this == DefaultOrdering || OrderBy == null;

        /// <summary>
        /// Gets a value indicating whether the culture of this ordering is invariant.
        /// </summary>
        public bool IsInvariant => this == DefaultOrdering || Culture == string.Empty;
    }
}