using System.Collections;
using System.Globalization;
using System.IO;
using System.Reflection;
using System.Resources;
using System.Text.RegularExpressions;
using CursorLang.Models;

namespace CursorLang.Tests.Resources;

/// <summary>
/// Checks of the resources themselves: they carry every caption in the settings
/// window, and a missing key only shows on a live window.
/// </summary>
public sealed partial class StringsTests
{
    private static readonly ResourceManager Resources =
        new("CursorLang.Resources.Strings", typeof(App).Assembly);

    private static readonly CultureInfo English = CultureInfo.GetCultureInfo("en");
    private static readonly CultureInfo Russian = CultureInfo.GetCultureInfo("ru");

    [Theory]
    [MemberData(nameof(EnumKeys))]
    public void Every_list_value_has_an_English_caption(string key)
    {
        Assert.False(string.IsNullOrWhiteSpace(Resources.GetString(key, English)));
    }

    [Theory]
    [MemberData(nameof(EnumKeys))]
    public void Every_list_value_has_a_Russian_caption(string key)
    {
        Assert.False(string.IsNullOrWhiteSpace(Resources.GetString(key, Russian)));
    }

    [Fact]
    public void The_Russian_translation_covers_every_string()
    {
        List<string> missing = [];

        foreach (string key in NeutralKeys())
        {
            // An untranslated resource falls back to English, so the Russian set
            // is asked directly rather than through the string with a fallback
            if (RussianSet().GetString(key) is null)
            {
                missing.Add(key);
            }
        }

        Assert.Empty(missing);
    }

    [Fact]
    public void The_Russian_translation_has_no_extra_strings()
    {
        HashSet<string> neutral = [.. NeutralKeys()];
        List<string> extra = [];

        foreach (DictionaryEntry entry in RussianSet())
        {
            var key = (string)entry.Key;
            if (!neutral.Contains(key))
            {
                extra.Add(key);
            }
        }

        Assert.Empty(extra);
    }

    [Fact]
    public void There_are_no_empty_strings_in_the_resources()
    {
        foreach (string key in NeutralKeys())
        {
            Assert.False(string.IsNullOrWhiteSpace(Resources.GetString(key, English)), key);
            Assert.False(string.IsNullOrWhiteSpace(Resources.GetString(key, Russian)), key);
        }
    }

    /// <summary>
    /// Every key the settings window markup asks for has to exist in the
    /// resources: otherwise the user sees the key itself in its place.
    /// </summary>
    [Fact]
    public void Every_key_from_the_settings_window_markup_exists_in_the_resources()
    {
        HashSet<string> known = [.. NeutralKeys()];
        List<string> missing = [];

        foreach (Match match in LocalizationBinding().Matches(ReadSettingsWindowMarkup()))
        {
            string key = match.Groups["key"].Value;
            if (!known.Contains(key))
            {
                missing.Add(key);
            }
        }

        Assert.Empty(missing);
    }

    /// <summary>
    /// The version of an update is put into the string by the app, so the place
    /// for it has to be there in both languages.
    /// </summary>
    [Fact]
    public void The_string_about_an_available_update_has_room_for_the_version()
    {
        Assert.Contains("{0}", Resources.GetString("UpdateAvailable", English), StringComparison.Ordinal);
        Assert.Contains("{0}", Resources.GetString("UpdateAvailable", Russian), StringComparison.Ordinal);
    }

    /// <summary>The markup does ask for strings — otherwise the check above means nothing.</summary>
    [Fact]
    public void The_settings_window_markup_asks_for_resource_strings()
    {
        Assert.NotEmpty(LocalizationBinding().Matches(ReadSettingsWindowMarkup()));
    }

    public static TheoryData<string> EnumKeys()
    {
        var data = new TheoryData<string>();

        foreach (string key in EnumKeysOf<AppTheme>())
        {
            data.Add(key);
        }

        foreach (string key in EnumKeysOf<PopupPlacementMode>())
        {
            data.Add(key);
        }

        foreach (string key in EnumKeysOf<AnchorSide>())
        {
            data.Add(key);
        }

        foreach (string key in EnumKeysOf<ScreenPosition>())
        {
            data.Add(key);
        }

        return data;
    }

    // A caption key is built from the type name and the value: PopupPlacementMode_AtCursor
    private static IEnumerable<string> EnumKeysOf<TEnum>() where TEnum : struct, Enum =>
        Enum.GetValues<TEnum>().Select(value => $"{typeof(TEnum).Name}_{value}");

    private static IEnumerable<string> NeutralKeys()
    {
        ResourceSet set = Resources.GetResourceSet(CultureInfo.InvariantCulture, true, true)!;

        foreach (DictionaryEntry entry in set)
        {
            yield return (string)entry.Key;
        }
    }

    private static ResourceSet RussianSet() =>
        Resources.GetResourceSet(Russian, createIfNotExists: true, tryParents: false)!;

    private static string ReadSettingsWindowMarkup()
    {
        using Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("MainWindow.xaml")
            ?? throw new InvalidOperationException("The settings window markup is not embedded in the test assembly");

        using var reader = new StreamReader(stream);
        return reader.ReadToEnd();
    }

    [GeneratedRegex(@"Localization\[(?<key>\w+)\]")]
    private static partial Regex LocalizationBinding();
}