using System.Globalization;
using MeterVault.App;

namespace MeterVault.Integration.Tests.Localization;

/// <summary>
/// <see cref="Format"/> formats against the reader's culture rather than a fixed de-DE (SDD §12, M7).
/// </summary>
/// <remarks>
/// The importer's de-DE parsing is deliberately untouched by this: that dialect is a property of the
/// spreadsheet files, not of who is looking at the dashboard, and <c>GermanParsingTests</c> pins it.
/// </remarks>
public sealed class FormatCultureTests
{
    [Fact]
    public void Digit_grouping_follows_the_reader()
    {
        Assert.Equal("1.234,5", WithCulture("de", () => Format.Number(1234.5, 1)));
        Assert.Equal("1,234.5", WithCulture("en", () => Format.Number(1234.5, 1)));

        Assert.Equal("2.940", WithCulture("de", () => Format.Number(2940)));
        Assert.Equal("2,940", WithCulture("en", () => Format.Number(2940)));
    }

    [Fact]
    public void The_currency_symbol_stays_the_instances_own()
    {
        // Only the grouping is localized. The figures are in the instance's configured currency, so
        // an English reader must see the same money written their way — not relabelled as dollars.
        Assert.Equal("1.234,50 €", WithCulture("de", () => Format.Euro(1234.5)));
        Assert.Equal("1,234.50 €", WithCulture("en", () => Format.Euro(1234.5)));
    }

    [Fact]
    public void Percentages_keep_their_explicit_sign()
    {
        Assert.Equal("+12,4 %", WithCulture("de", () => Format.Percent(12.4)));
        Assert.Equal("+12.4 %", WithCulture("en", () => Format.Percent(12.4)));

        Assert.Equal("-7,2 %", WithCulture("de", () => Format.Percent(-7.2)));
        Assert.Equal("-7.2 %", WithCulture("en", () => Format.Percent(-7.2)));
    }

    [Fact]
    public void Month_labels_are_written_in_the_readers_language()
    {
        var march = new DateOnly(2025, 3, 1);

        var german = WithCulture("de", () => Format.MonthLabel(march));
        var english = WithCulture("en", () => Format.MonthLabel(march));

        // Asserting the exact German abbreviation would pin us to one ICU version ("Mrz" vs "Mär"),
        // so assert what actually matters: the label is culture-sensitive, not invariant.
        Assert.Equal("Mar 25", english);
        Assert.NotEqual(english, german);
        Assert.EndsWith("25", german, StringComparison.Ordinal);
    }

    [Fact]
    public void Direction_icons_are_language_neutral()
    {
        Assert.Equal("▲", Format.DirectionIcon(1));
        Assert.Equal("▼", Format.DirectionIcon(-1));
        Assert.Equal("—", Format.DirectionIcon(0));
    }

    private static T WithCulture<T>(string culture, Func<T> body)
    {
        var previous = CultureInfo.CurrentCulture;
        try
        {
            CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo(culture);
            return body();
        }
        finally
        {
            CultureInfo.CurrentCulture = previous;
        }
    }
}