/// <summary>
/// Find some <see cref="Text"/> that is appropriate for the specified language tag.
/// </summary>
/// <param name="enumerable">
/// An enumerable list of <see cref="Text"/>.
/// </param>
/// <param name="language">
/// The <see cref="LanguageTag"/> of the <see cref="Text"/> that is needed. A <see cref="string"/>,
/// such as "zh-Hant" or "zh-TW", can also be used because it implicitly casts to a <see cref="LanguageTag"/>.
/// </param>
/// <returns>
/// Some appropriate text from the <paramref name="enumerable"/> for the specified <paramref name="language"/>.
/// If <paramref name="enumerable"/> is empty, then <see cref="Text.Empty"/> is returned.
/// </returns>,
/// <remarks>
/// TODO:
/// </remarks>
/// <example>
/// <code title="Multilingual Hello World" source="SepiaExamples\TextExample.cs" region="Hello World" language="C#" />
/// </example>
public static Text WrittenIn(this IEnumerable<Text> enumerable, LanguageTag language)
{
Guard.IsNotNull(language, "language");
var subtag = language.Name.Trim().ToLowerInvariant();
while (subtag != "")
{
foreach (var t in enumerable)
{
if (string.Equals(t.Language.Name, subtag, StringComparison.InvariantCultureIgnoreCase))
return t;
}
int dash = subtag.LastIndexOf('-');
if (dash < 0)
break;
subtag = subtag.Remove(dash);
}
// TODO: Find the script of language required and then return something close.
// Final fall-back, return the first element.
return enumerable.DefaultIfEmpty(Text.Empty).First();
}
/// <summary>
/// Determines if the <see cref="IEnumerable{Text}"/> contains a value
/// for a specific language code.
/// </summary>
/// <param name="enumerable">
/// An <see cref="IEnumerable{Text}"/> to search.
/// </param>
/// <param name="language">
/// The IETF language code to find.
/// </param>
/// <returns>
/// <b>true</b> if a <see cref="Text"/> exists with the exact <paramref name="language"/>.
/// </returns>
public static bool HasExactValue(this IEnumerable<Text> enumerable, LanguageTag language)
{
return enumerable.Any(t => t.Language == language);
}