using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using Xunit;

namespace ytLive.Tests;

/// <summary>A missing <c>{StaticResource}</c> key does not fail the build — WPF substitutes
/// <c>DependencyProperty.UnsetValue</c> and throws at the next layout pass. That is exactly how
/// the app crashed on 2026-10-30: the token conversion deleted <c>YtSliderKnobHoverBrush</c>
/// while two slider triggers still asked for it, so the first slider the creator touched
/// (the new socials opacity slider) killed the app inside <c>Ellipse.OnRender</c>.
///
/// <para>This guard scans every XAML file in the app and proves each referenced key exists —
/// either in the theme/App resources or in the same file — so the class cannot come back.</para></summary>
public class ThemeResourceTests
{
    [Fact]
    public void Every_StaticResource_reference_resolves_to_a_defined_key()
    {
        var root = System.IO.Path.GetDirectoryName(SourceAssert.RepoPath("App.xaml"))!;
        var globalKeys = new HashSet<string>(StringComparer.Ordinal);
        foreach (var file in new[] { System.IO.Path.Combine(root, "App.xaml") }
                     .Concat(Directory.GetFiles(System.IO.Path.Combine(root, "Themes"), "*.xaml")))
            globalKeys.UnionWith(KeysIn(File.ReadAllText(file)));

        var missing = new List<string>();

        foreach (var path in XamlFiles())
        {
            var text = File.ReadAllText(path);
            var localKeys = KeysIn(text);
            foreach (Match match in Regex.Matches(text, @"\{StaticResource ([^}]+)\}"))
            {
                var key = match.Groups[1].Value.Trim();
                if (key.StartsWith("{", StringComparison.Ordinal)) continue; // nested markup extension
                if (globalKeys.Contains(key) || localKeys.Contains(key)) continue;
                missing.Add($"{System.IO.Path.GetFileName(path)}: {key}");
            }
        }

        Assert.True(missing.Count == 0,
            "StaticResource keys with no definition (WPF throws UnsetValue at layout):\n  "
            + string.Join("\n  ", missing.Distinct()));
    }

    [Fact]
    public void A_dictionary_never_references_a_key_defined_later_in_itself()
    {
        // StaticResource resolves while the dictionary is being built, so a forward reference
        // fails at load with "Cannot find resource named …" — exactly how the app refused to
        // launch on 2026-10-30 (a BasedOn pointing at a style defined further down the file).
        var root = System.IO.Path.GetDirectoryName(SourceAssert.RepoPath("App.xaml"))!;
        var files = new[] { System.IO.Path.Combine(root, "App.xaml") }
            .Concat(Directory.GetFiles(System.IO.Path.Combine(root, "Themes"), "*.xaml"));

        var forward = new List<string>();
        foreach (var file in files)
        {
            var text = File.ReadAllText(file);
            var definitions = Regex.Matches(text, @"x:Key=""([^""]+)""")
                .ToDictionary(m => m.Groups[1].Value, m => m.Index, StringComparer.Ordinal);

            foreach (Match use in Regex.Matches(text, @"\{StaticResource ([^}]+)\}"))
            {
                var key = use.Groups[1].Value.Trim();
                if (!definitions.TryGetValue(key, out var defined)) continue;
                if (defined > use.Index)
                    forward.Add($"{System.IO.Path.GetFileName(file)}: {key} used before it is defined");
            }
        }

        Assert.True(forward.Count == 0,
            "Forward StaticResource references fail at load:\n  " + string.Join("\n  ", forward.Distinct()));
    }

    private static HashSet<string> KeysIn(string text)
        => Regex.Matches(text, @"x:Key=""([^""]+)""").Select(m => m.Groups[1].Value)
            .ToHashSet(StringComparer.Ordinal);

    private static IEnumerable<string> XamlFiles()
    {
        var root = System.IO.Path.GetDirectoryName(SourceAssert.RepoPath("App.xaml"))!;
        return Directory.EnumerateFiles(root, "*.xaml", SearchOption.AllDirectories)
            .Where(p => !p.Contains($"{System.IO.Path.DirectorySeparatorChar}obj{System.IO.Path.DirectorySeparatorChar}", StringComparison.Ordinal)
                     && !p.Contains($"{System.IO.Path.DirectorySeparatorChar}bin{System.IO.Path.DirectorySeparatorChar}", StringComparison.Ordinal)
                     && !p.Contains("ytLive.Tests", StringComparison.Ordinal));
    }
}