using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Xml.Linq;
using Xunit;

namespace ytLive.Tests;

/// <summary>DESIGN.md became the visual standard on 2026-10-30. This is its guard: the document
/// is the contract, `Themes/Tokens.xaml` is the implementation, and a token documented in one but
/// missing (or different) in the other fails here — so the palette cannot drift into two truths
/// the way the 2026-10-26 and 2026-10-29 Stitch exports did.
///
/// <para>Deliberately parses the markdown rather than duplicating a list: adding a colour to the
/// standard requires implementing it, and changing a value in the theme without the document is a
/// lie the gate catches.</para></summary>
public class DesignTokensTests
{
    private static readonly XNamespace Xaml = "http://schemas.microsoft.com/winfx/2006/xaml";

    [Fact]
    public void Every_colour_in_the_standard_exists_as_a_token_brush_with_the_documented_value()
    {
        var documented = DocumentedColours();
        Assert.True(documented.Count >= 20,
            $"parsed only {documented.Count} colour tokens out of DESIGN.md — the table format changed");

        var brushes = Brushes();

        foreach (var (token, hex) in documented)
        {
            var key = "Brush." + Pascal(token);
            Assert.True(brushes.ContainsKey(key),
                $"DESIGN.md documents `{token}` ({hex}) but Themes/Tokens.xaml has no `{key}` brush");
            Assert.Equal(hex, brushes[key], ignoreCase: true);
        }
    }

    [Fact]
    public void The_meter_bands_are_the_standard_three()
    {
        var brushes = Brushes();

        // DESIGN.md -> "Meter thresholds": nominal to -12 dB, caution to -3 dB, red above.
        Assert.Equal("#38bdf8", brushes["Brush.Meter.Nominal"], ignoreCase: true);
        Assert.Equal("#ffb95f", brushes["Brush.Meter.Caution"], ignoreCase: true);
        Assert.Equal("#ff5451", brushes["Brush.Meter.Peak"], ignoreCase: true);
    }

    [Fact]
    public void Tokens_merge_before_the_theme_so_styles_can_resolve_them()
    {
        var app = XDocument.Load(SourceAssert.RepoPath("App.xaml"));
        var sources = app.Descendants()
            .Where(e => e.Name.LocalName == "ResourceDictionary")
            .Select(e => (string?)e.Attribute("Source"))
            .Where(s => s != null)
            .ToList();

        var tokens = sources.FindIndex(s => s!.EndsWith("Themes/Tokens.xaml", StringComparison.Ordinal));
        var controls = sources.FindIndex(s => s!.EndsWith("Themes/Controls.xaml", StringComparison.Ordinal));

        Assert.True(tokens >= 0, "App.xaml does not merge Themes/Tokens.xaml");
        Assert.True(controls >= 0, "App.xaml no longer merges Themes/Controls.xaml");
        Assert.True(tokens < controls,
            "Themes/Tokens.xaml must merge BEFORE Themes/Controls.xaml, or styles cannot resolve a token");
    }

    [Fact]
    public void The_retired_brand_red_is_not_a_token()
    {
        // #e94560 was the general accent in 15 files. It is retired (DESIGN.md, 2026-10-30):
        // blue is interactive, red means live/record. Re-introducing it as a token would undo
        // the rule, so it must not appear anywhere in the token sheet.
        Assert.DoesNotContain("#e94560", File.ReadAllText(SourceAssert.RepoPath("Themes", "Tokens.xaml")),
            StringComparison.OrdinalIgnoreCase);
    }

    /// <summary>The `| Token | Hex |` tables under "## Colour", stopping at "## Typography".
    /// The "Rejected from the export" table lives further down and must not count.</summary>
    private static Dictionary<string, string> DocumentedColours()
    {
        var result = new Dictionary<string, string>(StringComparer.Ordinal);
        var inColour = false;

        foreach (var raw in File.ReadAllLines(SourceAssert.RepoPath("DESIGN.md")))
        {
            var line = raw.Trim();
            if (line.StartsWith("## ", StringComparison.Ordinal))
            {
                inColour = line.StartsWith("## Colour", StringComparison.Ordinal);
                continue;
            }
            if (!inColour || !line.StartsWith("| `", StringComparison.Ordinal)) continue;

            var cells = line.Split('|').Select(c => c.Trim()).Where(c => c.Length > 0).ToArray();
            if (cells.Length < 2) continue;

            // The token cell may carry a note after the backticked name("`tertiary` (electric blue)").
            var token = Backticked(cells[0]);
            var hex = Backticked(cells[1]);
            if (!hex.StartsWith("#", StringComparison.Ordinal) || hex.Length != 7) continue;
            result[token] = hex;
        }

        return result;
    }

    private static Dictionary<string, string> Brushes()
    {
        var dict = XDocument.Load(SourceAssert.RepoPath("Themes", "Tokens.xaml"));
        return dict.Descendants()
            .Where(e => e.Name.LocalName == "SolidColorBrush")
            .Select(e => ((string?)e.Attribute(Xaml + "Key"), (string?)e.Attribute("Color")))
            .Where(p => p.Item1 != null && p.Item2 != null)
            .ToDictionary(p => p.Item1!, p => p.Item2!, StringComparer.Ordinal);
    }

    /// <summary>The first `backticked` run in a markdown cell, or the trimmed cell itself.</summary>
    private static string Backticked(string cell)
    {
        var start = cell.IndexOf('`');
        if (start < 0) return cell.Trim();
        var end = cell.IndexOf('`', start + 1);
        return end < 0 ? cell.Trim() : cell[(start + 1)..end].Trim();
    }

    /// <summary>`surface-container-lowest` → `SurfaceContainerLowest`.</summary>
    private static string Pascal(string token) =>
        string.Concat(token.Split('-', StringSplitOptions.RemoveEmptyEntries)
            .Select(part => char.ToUpperInvariant(part[0]) + part[1..]));
}