using System.ComponentModel.DataAnnotations.Resources;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;

namespace System.ComponentModel.DataAnnotations.Schema {
    /// <summary>
    /// Denotes a property used as a foreign key in a relationship.
    /// The annotation may be placed on the foreign key property and specify the associated navigation property name, 
    /// or placed on a navigation property and specify the associated foreign key name.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
    [SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes", Justification = "We want users to be able to extend this class")]
    public class ForeignKeyAttribute : Attribute {
        private readonly string _name;

        /// <summary>
        /// Initializes a new instance of the <see cref="ForeignKeyAttribute"/> class.
        /// </summary>
        /// <param name="name">
        /// If placed on a foreign key property, the name of the associated navigation property.
        /// If placed on a navigation property, the name of the associated foreign key(s).
        /// If a navigation property has multiple foreign keys, a comma separated list should be supplied.
        /// </param>
        public ForeignKeyAttribute(string name) {
            if (string.IsNullOrWhiteSpace(name)) {
                throw new ArgumentException(String.Format(CultureInfo.CurrentCulture, DataAnnotationsResources.ArgumentIsNullOrWhitespace, "name"));
            }

            _name = name;
        }

        /// <summary>
        /// If placed on a foreign key property, the name of the associated navigation property.
        /// If placed on a navigation property, the name of the associated foreign key(s).
        /// </summary>
        public string Name {
            get { return _name; }
        }
    }
}