using System;

namespace VersOne.Epub.Schema
{
    /// <summary>
    /// <para>Navigation header associated with a <see cref="Epub3NavLi" /> (represented by the &lt;span&gt; HTML tag in the navigation document).</para>
    /// <para>See <see href="https://www.w3.org/TR/epub-33/#sec-nav-def-model" /> for more information.</para>
    /// </summary>
    public class Epub3NavSpan
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="Epub3NavSpan" /> class.
        /// </summary>
        /// <param name="text">The textual content of the navigation header (represented by the inner content of the &lt;span&gt; HTML tag in the navigation document).</param>
        /// <param name="title">
        /// The alternative title of the navigation header (represented by the 'title' HTML attribute in the navigation document)
        /// or <c>null</c> if the alternative title is not specified.
        /// </param>
        /// <param name="alt">
        /// The alternative text of the navigation header (represented by the 'title' HTML attribute in the navigation document)
        /// or <c>null</c> if the alternative text is not specified.
        /// </param>
        /// <exception cref="ArgumentNullException">The <paramref name="text" /> parameter is <c>null</c>.</exception>
        public Epub3NavSpan(string text, string? title, string? alt = null)
        {
            Text = text ?? throw new ArgumentNullException(nameof(text));
            Title = title;
            Alt = alt;
        }

        /// <summary>
        /// <para>Gets the textual content of the navigation header (represented by the inner content of the &lt;span&gt; HTML tag in the navigation document).</para>
        /// <para>See <see href="https://www.w3.org/TR/epub-33/#sec-nav-def-model" /> for more information.</para>
        /// </summary>
        public string Text { get; }

        /// <summary>
        /// <para>
        /// Gets the alternative title of the navigation header (represented by the 'title' HTML attribute in the navigation document)
        /// or <c>null</c> if the alternative title is not specified.
        /// </para>
        /// <para>See <see href="https://www.w3.org/TR/epub-33/#sec-nav-def-model" /> for more information.</para>
        /// </summary>
        public string? Title { get; }

        /// <summary>
        /// <para>
        /// Gets the alternative text of the navigation header (represented by the 'title' HTML attribute in the navigation document)
        /// or <c>null</c> if the alternative text is not specified.
        /// </para>
        /// <para>See <see href="https://www.w3.org/TR/epub-33/#sec-nav-def-model" /> for more information.</para>
        /// </summary>
        public string? Alt { get; }
    }
}