using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using Avalonia.Media;
using Nonemm.App.Configuration;
using Nonemm.App.Theming;
using Nonemm.App.Windows;

namespace Nonemm.App;

public partial class App : Application
{
    public override void Initialize() => AvaloniaXamlLoader.Load(this);

    public override void OnFrameworkInitializationCompleted()
    {
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            UserPaths paths = UserPaths.Default();
            if (paths.CreateFolders() is { } problem)
            {
                desktop.MainWindow = new StartupProblemWindow(problem, paths.Root);
                base.OnFrameworkInitializationCompleted();
                return;
            }
            Settings settings = Settings.Load(paths.SettingsFile);
            Themes.Use(settings.Theme);
            Themes.Changed += (_, _) => ApplyTheme();
            ApplyTheme();
            AppSession session = new(paths, settings);
            desktop.MainWindow = new EntryWindow(session);
            desktop.ShutdownRequested += (_, _) => session.Dispose();
        }
        base.OnFrameworkInitializationCompleted();
    }

    /// The window chrome follows the theme through these resources; everything
    /// that draws a station or a spot asks `Themes.Current` as it paints.
    private void ApplyTheme()
    {
        Theme theme = Themes.Current;
        RequestedThemeVariant = theme.Variant;
        Set("FormBackground", theme.FormBackground);
        Set("FormForeground", theme.FormForeground);
        Set("FieldBackground", theme.FieldBackground);
        Set("FieldForeground", theme.FieldForeground);
        // the keys the Fluent controls read, so a text box and a button take
        // the theme's colours in every state rather than only where a style of
        // ours reaches them
        foreach (string key in new[]
        {
            "TextControlBackground", "TextControlBackgroundPointerOver",
            "TextControlBackgroundFocused", "TextControlBackgroundDisabled",
            "ComboBoxBackground", "ComboBoxBackgroundPointerOver", "ComboBoxBackgroundPressed",
            "DataGridRowBackgroundBrush",
        })
        {
            Set(key, theme.FieldBackground);
        }
        foreach (string key in new[]
        {
            "TextControlForeground", "TextControlForegroundPointerOver",
            "TextControlForegroundFocused", "ComboBoxForeground", "ButtonForeground",
            "ButtonForegroundPointerOver", "ButtonForegroundPressed",
        })
        {
            Set(key, theme.FieldForeground);
        }
        Set("ButtonBackground", theme.ButtonBackground);
        Set("ButtonBackgroundPointerOver", Lighter(theme.ButtonBackground));
        Set("ButtonBackgroundPressed", Darker(theme.ButtonBackground));
    }

    private void Set(string key, Color colour) => Resources[key] = new SolidColorBrush(colour);

    private static Color Lighter(Color colour) => Shifted(colour, 12);

    private static Color Darker(Color colour) => Shifted(colour, -18);

    private static Color Shifted(Color colour, int by) => Color.FromRgb(
        (byte)Math.Clamp(colour.R + by, 0, 255),
        (byte)Math.Clamp(colour.G + by, 0, 255),
        (byte)Math.Clamp(colour.B + by, 0, 255));
}