using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;


[UnityEngine.Scripting.Preserve]
public class AspectRatioPanel : VisualElement
{
    [UnityEngine.Scripting.Preserve]
    public new class UxmlFactory : UxmlFactory<AspectRatioPanel, UxmlTraits> { }

    [UnityEngine.Scripting.Preserve]
    public new class UxmlTraits : VisualElement.UxmlTraits
    {
        readonly UxmlIntAttributeDescription aspectRatioX = new() { name = "aspect-ratio-x", defaultValue = 16, restriction = new UxmlValueBounds { min = "1" } };
        readonly UxmlIntAttributeDescription aspectRatioY = new() { name = "aspect-ratio-y", defaultValue = 9, restriction = new UxmlValueBounds { min = "1" } };
        readonly UxmlIntAttributeDescription balanceX = new() { name = "balance-x", defaultValue = 50, restriction = new UxmlValueBounds { min = "0", max = "100" } };
        readonly UxmlIntAttributeDescription balanceY = new() { name = "balance-y", defaultValue = 50, restriction = new UxmlValueBounds { min = "0", max = "100" } };


        public override IEnumerable<UxmlChildElementDescription> uxmlChildElementsDescription
        {
            get { yield break; }
        }


        public override void Init(VisualElement visualElement, IUxmlAttributes attributes, CreationContext creationContext)
        {
            base.Init(visualElement, attributes, creationContext);
            var element = visualElement as AspectRatioPanel;
            if (element != null)
            {
                element.AspectRatioX = Mathf.Max(1, aspectRatioX.GetValueFromBag(attributes, creationContext));
                element.AspectRatioY = Mathf.Max(1, aspectRatioY.GetValueFromBag(attributes, creationContext));
                element.BalanceX = Mathf.Clamp(balanceX.GetValueFromBag(attributes, creationContext), 0, 100);
                element.BalanceY = Mathf.Clamp(balanceY.GetValueFromBag(attributes, creationContext), 0, 100);
                element.FitToParent();
            }
        }
    }


    public int AspectRatioX { get; private set; } = 16;
    public int AspectRatioY { get; private set; } = 9;
    public int BalanceX { get; private set; } = 50;
    public int BalanceY { get; private set; } = 50;


    public AspectRatioPanel()
    {
        style.position = Position.Absolute;
        style.left = 0;
        style.top = 0;
        style.right = StyleKeyword.Undefined;
        style.bottom = StyleKeyword.Undefined;
        RegisterCallback<AttachToPanelEvent>(OnAttachToPanelEvent);
    }


    void OnAttachToPanelEvent(AttachToPanelEvent e)
    {
        parent?.RegisterCallback<GeometryChangedEvent>(OnGeometryChangedEvent);
        FitToParent();
    }


    void OnGeometryChangedEvent(GeometryChangedEvent e)
    {
        FitToParent();
    }


    void FitToParent()
    {
        if (parent == null) return;
        var parentW = parent.resolvedStyle.width;
        var parentH = parent.resolvedStyle.height;
        if (float.IsNaN(parentW) || float.IsNaN(parentH)) return;

        style.position = Position.Absolute;
        style.left = 0;
        style.top = 0;
        style.right = StyleKeyword.Undefined;
        style.bottom = StyleKeyword.Undefined;

        if (AspectRatioX <= 0.0f || AspectRatioY <= 0.0f)
        {
            style.width = parentW;
            style.height = parentH;
            return;
        }

        var ratio = Mathf.Min(parentW / AspectRatioX, parentH / AspectRatioY);
        var targetW = Mathf.Floor(AspectRatioX * ratio);
        var targetH = Mathf.Floor(AspectRatioY * ratio);
        style.width = targetW;
        style.height = targetH;

        var marginX = parentW - targetW;
        var marginY = parentH - targetH;
        style.left = Mathf.Floor(marginX * BalanceX / 100.0f);
        style.top = Mathf.Floor(marginY * BalanceY / 100.0f);
    }
}