using System;
using System.Globalization;
using System.Reflection;
using System.Threading;
using Xunit.Sdk;

/// <summary>
///     Apply this attribute to your test method to replace the <see cref="Thread.CurrentThread" />
///     <see cref="CultureInfo.CurrentCulture" /> and <see cref="CultureInfo.CurrentUICulture" /> with another culture.
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class UseCultureAttribute : BeforeAfterTestAttribute
{
    readonly Lazy<CultureInfo> culture;
    readonly Lazy<CultureInfo> uiCulture;

    CultureInfo originalCulture;
    CultureInfo originalUICulture;

    /// <summary>Replaces the culture and UI culture of the current thread with <paramref name="culture" /></summary>
    /// <param name="culture">The name of the culture.</param>
    /// <remarks>
    ///     <para>
    ///         This constructor overload uses <paramref name="culture" /> for both <see cref="Culture" /> and
    ///         <see cref="UICulture" />.
    ///     </para>
    /// </remarks>
    public UseCultureAttribute(string culture) : this(culture, culture) {}

    /// <summary>
    ///     Replaces the culture and UI culture of the current thread with <paramref name="culture" /> and
    ///     <paramref name="uiCulture" />
    /// </summary>
    /// <param name="culture">The name of the culture.</param>
    /// <param name="uiCulture">The name of the UI culture.</param>
    public UseCultureAttribute(string culture, string uiCulture)
    {
        this.culture   = new Lazy<CultureInfo>(() => new CultureInfo(culture));
        this.uiCulture = new Lazy<CultureInfo>(() => new CultureInfo(uiCulture));
    }

    /// <summary>Gets the culture.</summary>
    public CultureInfo Culture => culture.Value;

    /// <summary>Gets the UI culture.</summary>
    public CultureInfo UICulture => uiCulture.Value;

    /// <summary>
    ///     Stores the current <see cref="Thread.CurrentPrincipal" /> <see cref="CultureInfo.CurrentCulture" /> and
    ///     <see cref="CultureInfo.CurrentUICulture" /> and replaces them with the new cultures defined in the constructor.
    /// </summary>
    /// <param name="methodUnderTest">The method under test</param>
    public override void Before(MethodInfo methodUnderTest)
    {
#if NETCORE
        originalCulture = CultureInfo.CurrentCulture;
        originalUICulture = CultureInfo.CurrentUICulture;

        CultureInfo.CurrentCulture = Culture;
        CultureInfo.CurrentUICulture = Culture;
#else
        originalCulture   = Thread.CurrentThread.CurrentCulture;
        originalUICulture = Thread.CurrentThread.CurrentUICulture;

        Thread.CurrentThread.CurrentCulture   = Culture;
        Thread.CurrentThread.CurrentUICulture = UICulture;
#endif
    }

    /// <summary>
    ///     Restores the original <see cref="CultureInfo.CurrentCulture" /> and
    ///     <see cref="CultureInfo.CurrentUICulture" /> to <see cref="Thread.CurrentPrincipal" />
    /// </summary>
    /// <param name="methodUnderTest">The method under test</param>
    public override void After(MethodInfo methodUnderTest)
    {
#if NETCORE
        CultureInfo.CurrentCulture = originalCulture;
        CultureInfo.CurrentUICulture = originalUICulture;
#else
        Thread.CurrentThread.CurrentCulture   = originalCulture;
        Thread.CurrentThread.CurrentUICulture = originalUICulture;
#endif
    }
}