using System.Collections.Generic;
using System.Text;
using UnityEngine;
using UnityEngine.UI;

namespace InteractiveVideo
{
    /// <summary>
    /// Debug drawing for validating coordinate alignment. Place it as a child of the video RawImage, stretched to
    /// the same rect. When VideoTrackingManager.ShowTrackingDebug is on it draws, for every object in the current
    /// resolved frame: bounding box, polygon outline, polygon vertices, and (via IMGUI) the track id, name, action,
    /// plus the current video frame / source tracked frame in the corner. Not a raycast target.
    /// </summary>
    [RequireComponent(typeof(CanvasRenderer))]
    [AddComponentMenu("Interactive Video/Tracking Debug Overlay")]
    public sealed class TrackingDebugOverlay : MaskableGraphic
    {
        [SerializeField] private InteractiveVideoPlayer player;
        [SerializeField] private VideoTrackingManager trackingManager;

        [Header("Style")]
        [SerializeField] private float lineWidth = 2f;
        [SerializeField] private float vertexSize = 6f;
        [SerializeField] private Color bboxColor = new Color(0f, 1f, 1f, 0.8f);
        [SerializeField] private Color polygonColor = new Color(0f, 1f, 0f, 0.9f);
        [SerializeField] private Color selectedColor = new Color(1f, 0.9f, 0.1f, 1f);
        [SerializeField] private Color hiddenColor = new Color(1f, 0.3f, 0.3f, 0.6f);
        [SerializeField] private bool drawLabels = true;

        private int _lastVersion = int.MinValue;
        private bool _lastEnabled;
        private readonly StringBuilder _sb = new StringBuilder(128);
        private GUIStyle _labelStyle;

        protected override void Awake()
        {
            base.Awake();
            raycastTarget = false;
            if (player == null) player = GetComponentInParent<InteractiveVideoPlayer>();
            if (player == null) player = FindAnyObjectByType<InteractiveVideoPlayer>();
            if (trackingManager == null && player != null) trackingManager = player.TrackingManager;
            if (trackingManager == null) trackingManager = FindAnyObjectByType<VideoTrackingManager>();
        }

        private bool Active => trackingManager != null && trackingManager.ShowTrackingDebug && player != null;

        private void Update()
        {
            bool active = Active;
            int version = trackingManager != null ? trackingManager.ResolvedVersion : 0;
            if (active != _lastEnabled || (active && version != _lastVersion))
            {
                _lastEnabled = active;
                _lastVersion = version;
                SetVerticesDirty();
            }
        }

        protected override void OnPopulateMesh(VertexHelper vh)
        {
            vh.Clear();
            if (!Active) return;
            var frame = trackingManager.CurrentTrackingFrame;
            if (frame == null) return;

            for (int i = 0; i < frame.Objects.Count; i++)
            {
                var o = frame.Objects[i];
                bool selected = trackingManager.IsSelected(o.TrackId);
                Color polyColor = !o.Visible ? hiddenColor : (selected ? selectedColor : polygonColor);

                // Bounding box (tracking rect: yMin is the top edge).
                Vector2 tl = ToLocal(new Vector2(o.Bounds.xMin, o.Bounds.yMin));
                Vector2 tr = ToLocal(new Vector2(o.Bounds.xMax, o.Bounds.yMin));
                Vector2 br = ToLocal(new Vector2(o.Bounds.xMax, o.Bounds.yMax));
                Vector2 bl = ToLocal(new Vector2(o.Bounds.xMin, o.Bounds.yMax));
                AddLine(vh, tl, tr, bboxColor); AddLine(vh, tr, br, bboxColor);
                AddLine(vh, br, bl, bboxColor); AddLine(vh, bl, tl, bboxColor);

                // Polygon edges and vertices.
                var poly = o.Polygon;
                for (int p = 0; p < poly.Count; p++)
                {
                    Vector2 a = ToLocal(poly[p]);
                    Vector2 b = ToLocal(poly[(p + 1) % poly.Count]);
                    if (poly.Count >= 2) AddLine(vh, a, b, polyColor);
                    AddQuad(vh, a, vertexSize, polyColor);
                }
            }
        }

        private Vector2 ToLocal(Vector2 tracking)
        {
            // Tracking -> RawImage local (player) -> world -> this overlay's local. Works even if the overlay
            // is not exactly the same rect as the RawImage.
            Vector2 rawLocal = player.TrackingToLocalPoint(tracking);
            Vector3 world = player.Display.rectTransform.TransformPoint(rawLocal);
            return rectTransform.InverseTransformPoint(world);
        }

        private void AddLine(VertexHelper vh, Vector2 a, Vector2 b, Color color)
        {
            Vector2 dir = b - a;
            if (dir.sqrMagnitude < 1e-6f) return;
            Vector2 n = new Vector2(-dir.y, dir.x).normalized * (lineWidth * 0.5f);
            int i = vh.currentVertCount;
            vh.AddVert(a - n, color, Vector4.zero);
            vh.AddVert(a + n, color, Vector4.zero);
            vh.AddVert(b + n, color, Vector4.zero);
            vh.AddVert(b - n, color, Vector4.zero);
            vh.AddTriangle(i, i + 1, i + 2);
            vh.AddTriangle(i, i + 2, i + 3);
        }

        private void AddQuad(VertexHelper vh, Vector2 center, float size, Color color)
        {
            float h = size * 0.5f;
            int i = vh.currentVertCount;
            vh.AddVert(center + new Vector2(-h, -h), color, Vector4.zero);
            vh.AddVert(center + new Vector2(-h, h), color, Vector4.zero);
            vh.AddVert(center + new Vector2(h, h), color, Vector4.zero);
            vh.AddVert(center + new Vector2(h, -h), color, Vector4.zero);
            vh.AddTriangle(i, i + 1, i + 2);
            vh.AddTriangle(i, i + 2, i + 3);
        }

        // ---- labels (IMGUI: debug only, works on every platform) ----

        private void OnGUI()
        {
            if (!drawLabels || !Active) return;
            if (_labelStyle == null)
            {
                _labelStyle = new GUIStyle(GUI.skin.label) { fontSize = 14, richText = false };
                _labelStyle.normal.textColor = Color.white;
            }

            Canvas canvas = GetComponentInParent<Canvas>();
            Camera cam = canvas != null && canvas.renderMode != RenderMode.ScreenSpaceOverlay ? canvas.worldCamera : null;

            _sb.Clear();
            _sb.Append("video frame ").Append(trackingManager.CurrentFrame);
            _sb.Append("   tracked frame ").Append(trackingManager.CurrentSourceFrame);
            if (trackingManager.CurrentIsInterpolated) _sb.Append(" (interpolated)");
            if (player != null && player.IsPrepared) _sb.Append("   ").Append(player.FrameRate.ToString("0.#")).Append(" fps");
            DrawLabel(new Vector2(10f, Screen.height - 10f), _sb.ToString(), true);

            var frame = trackingManager.CurrentTrackingFrame;
            if (frame == null) return;
            for (int i = 0; i < frame.Objects.Count; i++)
            {
                var o = frame.Objects[i];
                Vector3 world = player.Display.rectTransform.TransformPoint(player.TrackingToLocalPoint(new Vector2(o.Bounds.xMin, o.Bounds.yMin)));
                Vector2 screen = RectTransformUtility.WorldToScreenPoint(cam, world);
                _sb.Clear();
                _sb.Append(o.TrackId);
                if (o.Definition != null && o.Definition.Name != o.TrackId) _sb.Append(" · ").Append(o.Definition.Name);
                if (!string.IsNullOrEmpty(o.Action)) _sb.Append(" · ").Append(o.Action);
                if (!o.Visible) _sb.Append(" · hidden");
                DrawLabel(screen, _sb.ToString(), false);
            }
        }

        private void DrawLabel(Vector2 screenPos, string text, bool background)
        {
            // IMGUI has Y down; screen points have Y up.
            var content = new GUIContent(text);
            Vector2 size = _labelStyle.CalcSize(content);
            var rect = new Rect(screenPos.x, Screen.height - screenPos.y - size.y, size.x + 6f, size.y);
            GUI.color = new Color(0f, 0f, 0f, 0.6f);
            GUI.DrawTexture(rect, Texture2D.whiteTexture);
            GUI.color = Color.white;
            GUI.Label(new Rect(rect.x + 3f, rect.y, size.x, size.y), content, _labelStyle);
        }
    }
}