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

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

    [UnityEngine.Scripting.Preserve]
    public new class UxmlTraits : Label.UxmlTraits
    {
        readonly UxmlIntAttributeDescription minFontSize = new UxmlIntAttributeDescription
        {
            name = "min-font-size",
            defaultValue = 10,
            restriction = new UxmlValueBounds { min = "1" }
        };

        readonly UxmlIntAttributeDescription maxFontSize = new UxmlIntAttributeDescription
        {
            name = "max-font-size",
            defaultValue = 200,
            restriction = new UxmlValueBounds { min = "1" }
        };

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

        public override void Init(VisualElement ve, IUxmlAttributes bag, CreationContext cc)
        {
            base.Init(ve, bag, cc);

            LabelAutoFit instance = ve as LabelAutoFit;
            instance.minFontSize = Mathf.Max(minFontSize.GetValueFromBag(bag, cc), 1);
            instance.maxFontSize = Mathf.Max(maxFontSize.GetValueFromBag(bag, cc), 1);
            instance.RegisterCallback<GeometryChangedEvent>(instance.OnGeometryChanged);
            instance.style.fontSize = 1; // Triggers OnGeometryChanged callback
        }
    }

    // Setting a limit of max text font refreshes from a single OnGeometryChanged to avoid repeating cycles in some extreme cases
    private const int MAX_FONT_REFRESHES = 2;

    private int m_textRefreshes = 0;

    public int minFontSize { get; set; }
    public int maxFontSize { get; set; }

    // Call this if the font size does not update by just setting the text
    // Should probably wait till the end of frame to get the real font size, instead of using this method
    // Works well in OnRenderObject() too
    public void SetText(string text)
    {
        this.text = text;
        UpdateFontSize();
    }

    private void OnGeometryChanged(GeometryChangedEvent evt)
    {
        UpdateFontSize();
    }

    private void UpdateFontSize()
    {
        if (m_textRefreshes < MAX_FONT_REFRESHES)
        {
            Vector2 textSize = MeasureTextSize(text, float.MaxValue, MeasureMode.AtMost, float.MaxValue, MeasureMode.AtMost);
            float fontSize = Mathf.Max(style.fontSize.value.value, 1); // Unity can return a font size of 0 which would break the auto fit // Should probably wait till the end of frame to get the real font size
            float heightDictatedFontSize = Mathf.Abs(contentRect.height);
            float widthDictatedFontSize = Mathf.Abs(contentRect.width / textSize.x) * fontSize;
            float newFontSize = Mathf.FloorToInt(Mathf.Min(heightDictatedFontSize, widthDictatedFontSize));
            newFontSize = Mathf.Clamp(newFontSize, minFontSize, maxFontSize);
            if (Mathf.Abs(newFontSize - fontSize) > 1)
            {
                m_textRefreshes++;
                style.fontSize = new StyleLength(new Length(newFontSize));
            }
        }
        else
        {
            m_textRefreshes = 0;
        }
    }
}