using ClawdDotNet.Core.Scheduling;
using Shouldly;

namespace ClawdDotNet.Core.Tests.Scheduling;

/// <summary>
/// Time zones are named differently on Windows and Linux. Task files travel between
/// the two — so each side must be able to interpret the other's spelling.
///
/// The tests deliberately run on both platforms with the same expectations: exactly
/// that is the property we need.
/// </summary>
public sealed class TimeZonesTests
{
    [Theory]
    [InlineData("Europe/Berlin")]
    [InlineData("W. Europe Standard Time")]
    [InlineData("America/New_York")]
    [InlineData("Eastern Standard Time")]
    [InlineData("UTC")]
    public void Both_spellings_can_be_resolved(string id)
    {
        TimeZones.TryResolve(id).ShouldNotBeNull();
        TimeZones.IsKnown(id).ShouldBeTrue();
    }

    [Fact]
    public void Both_spellings_mean_the_same_zone()
    {
        var iana = TimeZones.TryResolve("Europe/Berlin");
        var windows = TimeZones.TryResolve("W. Europe Standard Time");

        var summer = new DateTime(2026, 7, 31, 12, 0, 0, DateTimeKind.Utc);

        iana!.GetUtcOffset(summer).ShouldBe(windows!.GetUtcOffset(summer));
        iana.GetUtcOffset(summer).ShouldBe(TimeSpan.FromHours(2)); // CEST
    }

    [Theory]
    [InlineData("Phantasie/Ort")]
    [InlineData("Nicht Existierende Standard Time")]
    [InlineData("völliger Unsinn")]
    public void Unknown_identifiers_are_reported_instead_of_guessed(string id)
    {
        TimeZones.TryResolve(id).ShouldBeNull();
        TimeZones.IsKnown(id).ShouldBeFalse();
    }

    [Fact]
    public void Empty_counts_as_valid_because_it_means_no_value()
    {
        TimeZones.IsKnown("").ShouldBeTrue();
        TimeZones.IsKnown(null).ShouldBeTrue();
        TimeZones.IsKnown("   ").ShouldBeTrue();
    }

    [Theory]
    [InlineData("W. Europe Standard Time", "Europe/Berlin")]
    [InlineData("Europe/Berlin", "Europe/Berlin")]
    [InlineData("", "")]
    public void Normalising_gives_the_IANA_form(string input, string expected)
    {
        TimeZones.ToIana(input).ShouldBe(expected);
    }

    [Fact]
    public void An_unconvertible_identifier_stays_unchanged()
    {
        // Falsifying would be worse than passing through — that way, in case of doubt,
        // what originally stood there stays visible.
        TimeZones.ToIana("Phantasie Standard Time").ShouldBe("Phantasie Standard Time");
    }

    [Fact]
    public void The_local_zone_is_returned_in_IANA_form()
    {
        var local = TimeZones.LocalIanaId;

        local.ShouldNotBeNullOrWhiteSpace();
        TimeZones.IsKnown(local).ShouldBeTrue();

        // The actual point: what comes out here is written into task files
        // and must be readable on the other platform. IANA identifiers contain a
        // slash, Windows identifiers never — UTC is the exception with neither.
        if (local != "UTC")
            local.ShouldContain("/");
    }
}