using UnityEngine;
using UnityEngine.UIElements;

namespace BITKit.UX
{

    // An element that displays progress inside a partially filled circle
    public class RadialProgress : VisualElement
    {
        public new class UxmlTraits : VisualElement.UxmlTraits
        {
            // The progress property is exposed to UXML.
            private readonly UxmlFloatAttributeDescription m_ProgressAttribute = new UxmlFloatAttributeDescription()
            {
                name = "progress"
            };

            // Use the Init method to assign the value of the progress UXML attribute to the C# progress property.
            public override void Init(VisualElement ve, IUxmlAttributes bag, CreationContext cc)
            {
                base.Init(ve, bag, cc);

                ((RadialProgress)ve).progress = m_ProgressAttribute.GetValueFromBag(bag, cc);
            }
        }

        // Define a factory class to expose this control to UXML.
        public new class UxmlFactory : UxmlFactory<RadialProgress, UxmlTraits> { }

        // These are USS class names for the control overall and the label.
        public static readonly string ussClassName = "radial-progress";
        public static readonly string ussLabelClassName = "radial-progress__label";

        // These objects allow C# code to access custom USS properties.
        static CustomStyleProperty<Color> s_TrackColor = new CustomStyleProperty<Color>("--track-color");
        static CustomStyleProperty<Color> s_ProgressColor = new CustomStyleProperty<Color>("--progress-color");

        Color m_TrackColor = Color.gray;
        Color m_ProgressColor = Color.red;

        // This is the label that displays the percentage.
        Label m_Label;

        // This is the number that the Label displays as a percentage.
        float m_Progress;

        // A value between 0 and 100
        public float progress
        {
            // The progress property is exposed in C#.
            get => m_Progress;
            set
            {
                // Whenever the progress property changes, MarkDirtyRepaint() is named. This causes a call to the
                // generateVisualContents callback.
                m_Progress = value;
                m_Label.text = Mathf.Clamp(Mathf.Round(value), 0, 100) + "%";
                MarkDirtyRepaint();
            }
        }

        // This default constructor is RadialProgress's only constructor.
        public RadialProgress()
        {
            // Create a Label, add a USS class name, and add it to this visual tree.
            m_Label = new Label();
            m_Label.AddToClassList(ussLabelClassName);
            Add(m_Label);

            // Add the USS class name for the overall control.
            AddToClassList(ussClassName);

            // Register a callback after custom style resolution.
            RegisterCallback<CustomStyleResolvedEvent>(evt => CustomStylesResolved(evt));

            // Register a callback to generate the visual content of the control.
            generateVisualContent += GenerateVisualContent;

            progress = 0.0f;
        }

        static void CustomStylesResolved(CustomStyleResolvedEvent evt)
        {
            RadialProgress element = (RadialProgress)evt.currentTarget;
            element.UpdateCustomStyles();
        }

        // After the custom colors are resolved, this method uses them to color the meshes and (if necessary) repaint
        // the control.
        void UpdateCustomStyles()
        {
            bool repaint = false;
            if (customStyle.TryGetValue(s_ProgressColor, out m_ProgressColor))
                repaint = true;

            if (customStyle.TryGetValue(s_TrackColor, out m_TrackColor))
                repaint = true;

            if (repaint)
                MarkDirtyRepaint();
        }

        void GenerateVisualContent(MeshGenerationContext context)
        {
            float width = contentRect.width;
            float height = contentRect.height;

            var painter = context.painter2D;
            painter.lineWidth = 10.0f;
            painter.lineCap = LineCap.Butt;

            // Draw the track
            painter.strokeColor = m_TrackColor;
            painter.BeginPath();
            painter.Arc(new Vector2(width * 0.5f, height * 0.5f), width * 0.5f, 0.0f, 360.0f);
            painter.Stroke();

            // Draw the progress
            painter.strokeColor = m_ProgressColor;
            painter.BeginPath();
            painter.Arc(new Vector2(width * 0.5f, height * 0.5f), width * 0.5f, -90.0f, 360.0f * (progress / 100.0f) - 90.0f);
            painter.Stroke();
        }
    }
}