using System;
using System.Collections;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.Video;
using OctoCore.Transitions;
using Unheimlich.Core;

namespace Unheimlich.Transitions
{
    /// <summary>
    /// Persistent singleton engine for "eyelid blink" transitions (eyelids + optional video overlay).
    /// Lives outside the OctoCore package (this project already references LeanTween here), and
    /// implements IOctoSceneTransition so OctoNavigation can drive it without the package ever
    /// depending on LeanTween or this concrete type. Registers itself with OctoTransitionProvider
    /// once ready so the package can find it at runtime.
    /// </summary>
    public class OctoEyelidBlink : Singleton<OctoEyelidBlink>, IOctoSceneTransition
    {
        [Header("Eyelids")]
        [SerializeField] private Image _topEyelid;
        [SerializeField] private Image _bottomEyelid;

        [Header("Video")]
        [Tooltip("RawImage displaying the shared RenderTexture. Its material is swapped per call.")]
        [SerializeField] private RawImage _videoDisplay;
        [SerializeField] private VideoPlayer _videoPlayer;
        [SerializeField] private bool _skipOnDrop = true;
        [SerializeField] private bool _logVideoDebug = false;

        [Header("Positions")]
        [SerializeField] private float _openOffset = 600f;
        [SerializeField] private float _closedOffset = 0f;

        /// <summary>True while a blink sequence is currently animating.</summary>
        public bool IsBusy { get; private set; }

        private int _topTweenId = -1;
        private int _bottomTweenId = -1;
        private int _delayTweenId = -1;
        private int _videoTweenId = -1;

        private bool _isWarmedUp;
        private bool _videoShown;
        private VideoClip _pendingClip;
        private Material _defaultMaterial;

        private bool HasVideo => _videoPlayer != null && _videoDisplay != null && _videoPlayer.clip != null;

        protected override void OnAwake()
        {
            OctoTransitionProvider.Current = this;

            // Only call DontDestroyOnLoad on a root object. If this component already lives
            // under the persistent Octo prefab, the parent handles persistence and this is a no-op.
            if (transform.parent == null)
                DontDestroyOnLoad(gameObject);

            if (_videoDisplay != null)
                _defaultMaterial = _videoDisplay.material;

            SetEyelidsOpen();
            SetVideoVisible(false);
            ConfigureVideoPlayer();
        }

        // Re-registers with the transition provider whenever Instance is restored
        // (e.g. after a SubsystemRegistration reset with Domain Reload disabled).
        protected override void OnEnabled()
        {
            OctoTransitionProvider.Current = this;
        }

        protected override void OnDestroyInstance()
        {
            if (OctoTransitionProvider.Current == (IOctoSceneTransition)this)
                OctoTransitionProvider.Current = null;
        }

        // ---------- IOctoSceneTransition ----------

        /// <summary>
        /// Assigns the video clip and optional material to use during the next CloseEyes() call
        /// and starts warming the clip up. Pass a null clip to perform a plain blink with no video.
        /// A null material falls back to the RawImage's default material.
        /// </summary>
        public void SetClip(VideoClip clip, Material material)
        {
            if (_videoDisplay != null)
                _videoDisplay.material = material != null ? material : _defaultMaterial;

            if (_videoPlayer == null)
                return;

            _isWarmedUp = false;
            _pendingClip = clip;
            _videoPlayer.clip = clip;

            if (clip != null)
                StartCoroutine(WarmUpVideo());
        }

        /// <summary>Closes the eyelids over the given duration and invokes the callback on completion.</summary>
        public void CloseEyes(float duration, Action onComplete)
        {
            IsBusy = true;
            CancelCurrent();
            ResetVideoToStart();
            _videoShown = false;

            RectTransform top = _topEyelid.rectTransform;
            RectTransform bottom = _bottomEyelid.rectTransform;

            _topTweenId = LeanTween.moveY(top, _closedOffset, duration)
                .setEase(LeanTweenType.easeOutQuad)
                .setOnComplete(() =>
                {
                    _topTweenId = -1;
                    onComplete?.Invoke();
                })
                .id;

            _bottomTweenId = LeanTween.moveY(bottom, -_closedOffset, duration)
                .setEase(LeanTweenType.easeOutQuad)
                .setOnComplete(() => _bottomTweenId = -1)
                .id;
        }

        /// <summary>Opens the eyelids over the given duration and invokes the callback on completion.</summary>
        public void OpenEyes(float duration, Action onComplete)
        {
            RectTransform top = _topEyelid.rectTransform;
            RectTransform bottom = _bottomEyelid.rectTransform;

            _topTweenId = LeanTween.moveY(top, _openOffset, duration)
                .setEase(LeanTweenType.easeInQuad)
                .setOnComplete(() =>
                {
                    _topTweenId = -1;
                    onComplete?.Invoke();
                })
                .id;

            _bottomTweenId = LeanTween.moveY(bottom, -_openOffset, duration)
                .setEase(LeanTweenType.easeInQuad)
                .setOnComplete(() =>
                {
                    _bottomTweenId = -1;
                    IsBusy = false;
                })
                .id;
        }

        /// <summary>Stops playback, resets the video to its first frame, and hides the overlay.</summary>
        public void HideVideo()
        {
            if (!HasVideo)
                return;

            _videoPlayer.Pause();
            _videoPlayer.time = 0.0;
            SetVideoVisible(false);
            _videoShown = false;
        }

        /// <summary>Reveals and plays the video overlay after the given delay, once warm-up has completed.</summary>
        public void ShowVideoAfterDelay(float delay)
        {
            if (!HasVideo)
                return;

            _videoTweenId = LeanTween.delayedCall(gameObject, delay, () =>
            {
                _videoTweenId = -1;
                ShowVideo();
            }).id;
        }

        // ---------- Extra API (not part of the interface, used by HallucinationFlash directly) ----------

        /// <summary>Waits for the given duration before invoking the callback.</summary>
        public void Hold(float duration, Action onComplete)
        {
            _delayTweenId = LeanTween.delayedCall(gameObject, duration, () =>
            {
                _delayTweenId = -1;
                onComplete?.Invoke();
            }).id;
        }

        // ---------- Video internals ----------

        private void ConfigureVideoPlayer()
        {
            if (_videoPlayer == null)
                return;

            _videoPlayer.playOnAwake = false;
            _videoPlayer.isLooping = false;
            _videoPlayer.waitForFirstFrame = true;
            _videoPlayer.skipOnDrop = _skipOnDrop;
        }

        /// <summary>
        /// Prepares and briefly plays the assigned clip while hidden, forcing Unity to
        /// decode the first frames ahead of time. Prevents a blank/garbage frame from
        /// being visible the first time the video is actually shown.
        /// </summary>
        private IEnumerator WarmUpVideo()
        {
            if (!HasVideo)
                yield break;

            SetVideoVisible(false);
            ConfigureVideoPlayer();
            _videoPlayer.Prepare();

            while (!_videoPlayer.isPrepared)
                yield return null;

            _videoPlayer.Play();
            while (!_videoPlayer.isPlaying)
                yield return null;

            // Wait a few frames so the RenderTexture actually receives video data.
            yield return null;
            yield return null;
            yield return null;

            _videoPlayer.Pause();
            _videoPlayer.time = 0.0;

            // Wait one additional frame after seeking back to the start.
            yield return null;

            _isWarmedUp = true;

            if (_logVideoDebug)
                Debug.Log($"[OctoEyelidBlink] Warm-up complete for clip: {_pendingClip?.name}");
        }

        private void ShowVideo()
        {
            if (!HasVideo || _videoShown)
                return;

            // Safety check: if warm-up hasn't completed yet (e.g. clip assigned too late),
            // skip showing the video rather than risk a corrupted first frame. The eyelid
            // blink itself remains unaffected.
            if (!_isWarmedUp)
            {
                if (_logVideoDebug)
                    Debug.LogWarning("[OctoEyelidBlink] Video not warmed up in time, skipping display.");

                return;
            }

            _videoShown = true;
            SetVideoVisible(true);
            _videoPlayer.Play();
        }

        private void ResetVideoToStart()
        {
            if (!HasVideo)
                return;

            _videoPlayer.Pause();
            _videoPlayer.time = 0.0;
        }

        private void SetVideoVisible(bool visible)
        {
            if (_videoDisplay != null)
                _videoDisplay.enabled = visible;
        }

        // ---------- Eyelid internals ----------

        private void SetEyelidsOpen()
        {
            _topEyelid.rectTransform.anchoredPosition =
                new Vector2(_topEyelid.rectTransform.anchoredPosition.x, _openOffset);
            _bottomEyelid.rectTransform.anchoredPosition =
                new Vector2(_bottomEyelid.rectTransform.anchoredPosition.x, -_openOffset);
        }

        private void CancelCurrent()
        {
            if (_topTweenId != -1) { LeanTween.cancel(_topTweenId); _topTweenId = -1; }
            if (_bottomTweenId != -1) { LeanTween.cancel(_bottomTweenId); _bottomTweenId = -1; }
            if (_delayTweenId != -1) { LeanTween.cancel(_delayTweenId); _delayTweenId = -1; }
            if (_videoTweenId != -1) { LeanTween.cancel(_videoTweenId); _videoTweenId = -1; }
        }
    }
}