using System;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace InteractiveVideo
{
    /// <summary>
    /// Sits on the video RawImage. Turns pointer events (mouse, touch, XR ray via the EventSystem) into a hit test
    /// against the tracking manager and updates the selection.
    ///
    /// Needs the usual UI plumbing: an EventSystem in the scene, a GraphicRaycaster on the Canvas (or a
    /// TrackedDeviceGraphicRaycaster for XR), and raycastTarget on the RawImage (forced on in Awake).
    /// </summary>
    [DisallowMultipleComponent]
    [RequireComponent(typeof(RectTransform))]
    [AddComponentMenu("Interactive Video/Video Click Handler")]
    public sealed class VideoClickHandler : MonoBehaviour, IPointerClickHandler, IPointerDownHandler
    {
        public enum SelectTrigger { Click, PointerDown }
        public enum EmptyClickBehavior { KeepSelection, ClearSelection }

        [SerializeField] private InteractiveVideoPlayer player;
        [SerializeField] private VideoTrackingManager trackingManager;

        [Header("Behaviour")]
        [Tooltip("Click = press and release on the image (ignores drags). PointerDown = react immediately on press.")]
        [SerializeField] private SelectTrigger trigger = SelectTrigger.Click;
        [Tooltip("What a click on the background (or on a letterbox bar) does to the current selection.")]
        [SerializeField] private EmptyClickBehavior emptyClick = EmptyClickBehavior.ClearSelection;
        [Tooltip("Clicking the already selected object deselects it.")]
        [SerializeField] private bool toggleOnReselect;
        [Tooltip("Only react to the primary pointer (left mouse button / first finger).")]
        [SerializeField] private bool primaryButtonOnly = true;

        /// <summary>Raised on every handled click. hit is null for background/letterbox clicks; point is in TRACKING coordinates.</summary>
        public event Action<Vector2, TrackedObjectInstance> VideoClicked;

        public EmptyClickBehavior EmptyClick { get => emptyClick; set => emptyClick = value; }
        public SelectTrigger Trigger { get => trigger; set => trigger = value; }

        private RectTransform _rectTransform;

        private void Reset()
        {
            player = GetComponentInParent<InteractiveVideoPlayer>();
            if (player == null) player = FindAnyObjectByType<InteractiveVideoPlayer>();
            if (player != null) trackingManager = player.TrackingManager;
        }

        private void Awake()
        {
            _rectTransform = (RectTransform)transform;
            var graphic = GetComponent<Graphic>();
            if (graphic == null)
                Debug.LogWarning("[InteractiveVideo] VideoClickHandler needs a Graphic (RawImage) on the same object to receive pointer events.", this);
            else
                graphic.raycastTarget = true;

            if (player == null) Debug.LogWarning("[InteractiveVideo] VideoClickHandler has no InteractiveVideoPlayer assigned.", this);
            if (trackingManager == null && player != null) trackingManager = player.TrackingManager;
        }

        public void OnPointerClick(PointerEventData eventData)
        {
            if (trigger == SelectTrigger.Click) Handle(eventData);
        }

        public void OnPointerDown(PointerEventData eventData)
        {
            if (trigger == SelectTrigger.PointerDown) Handle(eventData);
        }

        private void Handle(PointerEventData eventData)
        {
            if (primaryButtonOnly && eventData.button != PointerEventData.InputButton.Left) return;
            if (player == null || trackingManager == null) return;

            bool onVideo = TryEventToTracking(eventData, out Vector2 trackingPoint);
            TrackedObjectInstance hit = onVideo ? trackingManager.GetObjectAtPoint(trackingPoint) : null;

            if (hit != null)
            {
                if (toggleOnReselect && trackingManager.IsSelected(hit.TrackId)) trackingManager.Deselect(hit.TrackId);
                else trackingManager.Select(hit.TrackId);
            }
            else if (emptyClick == EmptyClickBehavior.ClearSelection)
            {
                trackingManager.ClearSelection();
            }

            VideoClicked?.Invoke(trackingPoint, hit);
        }

        /// <summary>
        /// Pointer event to tracking coordinates. Screen-space events go through the screen point; XR ray events
        /// (raycaster is not a GraphicRaycaster) use the world hit position so world-space canvases work too.
        /// </summary>
        public bool TryEventToTracking(PointerEventData eventData, out Vector2 trackingPoint)
        {
            trackingPoint = default;
            if (player == null) return false;

            var raycast = eventData.pointerCurrentRaycast;
            bool worldHit = raycast.isValid && !(raycast.module is GraphicRaycaster) && raycast.worldPosition != Vector3.zero;
            if (worldHit)
            {
                Vector2 local = _rectTransform.InverseTransformPoint(raycast.worldPosition);
                return player.TryLocalPointToTracking(local, out trackingPoint);
            }

            Camera cam = eventData.pressEventCamera != null ? eventData.pressEventCamera : eventData.enterEventCamera;
            return player.TryScreenPointToTracking(eventData.position, cam, out trackingPoint);
        }
    }
}