using System;
using System.Linq;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Shapes;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Media;
using Avalonia.VisualTree;
using DelauneyTriangulation.ViewModels;

namespace DelauneyTriangulation.Views;

public partial class MainWindow : Window
{
    private bool _isPanning;
    private Point _panStart;
    private Vector _panOffset = new();
    
    private double _scale = 1.0;
    private const double MinScale = 0.2;
    private const double MaxScale = 8.0;

    private readonly TranslateTransform _panTransform = new();
    private readonly ScaleTransform _scaleTransform = new();
    private readonly TransformGroup _transformGroup = new();
    
    public MainWindow()
    {
        InitializeComponent();
        
        _transformGroup.Children.Add(_scaleTransform);
        _transformGroup.Children.Add(_panTransform);
        SceneContent.RenderTransform = _transformGroup;
        
        if (DataContext is MainWindowViewModel vm) vm.View = this;
    }
    
    private void OnTitleBarPointerPressed(object? sender, PointerPressedEventArgs e)
    {
        if (!e.GetCurrentPoint(this).Properties.IsLeftButtonPressed) return;
        BeginMoveDrag(e);
    }
    private void OnTitleBarDoubleTapped(object? sender, RoutedEventArgs e) => WindowState = WindowState == WindowState.Maximized ? WindowState.Normal : WindowState.Maximized;
    private void Scene_OnPointerPressed(object? sender, PointerPressedEventArgs e)
    {
        if (!e.GetCurrentPoint(Scene).Properties.IsLeftButtonPressed)
            return;

        _isPanning = true;
        _panStart = e.GetPosition(this);
        Scene.Cursor = new Cursor(StandardCursorType.SizeAll);
        e.Handled = true;
    }

    private void Scene_OnPointerMoved(object? sender, PointerEventArgs e)
    {
        if (!_isPanning) return;

        var pos = e.GetPosition(this);
        var delta = pos - _panStart;
        var current = _panOffset + delta;
        _panTransform.X = current.X;
        _panTransform.Y = current.Y;
        e.Handled = true;
    }

    private void Scene_OnPointerReleased(object? sender, PointerReleasedEventArgs e)
    {
        if (!_isPanning) return;

        var pos = e.GetPosition(this);
        var delta = pos - _panStart;
        _panOffset += delta;

        _isPanning = false;
        Scene.Cursor = new Cursor(StandardCursorType.Arrow);
        e.Handled = true;
    }

    private void Scene_OnWheel(object? sender, PointerWheelEventArgs e)
    {
        var mouse = e.GetPosition(Scene);

        var oldScale = _scale;
        var factor = Math.Pow(1.1, e.Delta.Y);
        var newScale = Math.Clamp(oldScale * factor, MinScale, MaxScale);
        var applied = newScale / oldScale;

        _scale = newScale;
        _scaleTransform.ScaleX = _scaleTransform.ScaleY = _scale;
        
        _panOffset = new Vector(
            mouse.X - applied * (mouse.X - _panOffset.X),
            mouse.Y - applied * (mouse.Y - _panOffset.Y)
        );

        _panTransform.X = _panOffset.X;
        _panTransform.Y = _panOffset.Y;

        e.Handled = true;
    }
}