using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using TMPro;
using DG.Tweening;
using Ashwild.Network;
using Ashwild.Player;

namespace Ashwild.UI
{
    /// <summary>
    /// The invitation card that slides in from the right when a friend invites the local player
    /// to their session. Shows the inviter's Steam avatar and name, with Join (connect to their
    /// room) and Cancel (dismiss) actions. Invites are queued and shown one at a time; each is
    /// animated entirely with DOTween. Drop this on a card in the menu canvas.
    /// </summary>
    [DisallowMultipleComponent]
    public class InviteNotificationUI : MonoBehaviour
    {
        #region Types

        /// <summary>
        /// One pending invitation: who sent it and the code needed to join their room.
        /// </summary>
        private readonly struct Invite
        {
            public readonly ulong SteamId;
            public readonly string Name;
            public readonly string Code;

            public Invite(ulong steamId, string name, string code)
            {
                SteamId = steamId;
                Name = name;
                Code = code;
            }
        }

        #endregion

        #region Serialized Fields

        [Header("References")]
        [Tooltip("The card RectTransform that slides in/out (anchored to the left edge).")]
        [SerializeField] private RectTransform card;
        [SerializeField] private Image avatarImage;
        [Tooltip("Receives the inviter's display name.")]
        [SerializeField] private TMP_Text nameText;
        [SerializeField] private Button joinButton;
        [SerializeField] private Button cancelButton;

        [Header("Slide Animation")]
        [Tooltip("Off-screen anchoredPosition.x (card hidden to the right).")]
        [SerializeField] private float hiddenX = 560f;
        [Tooltip("On-screen anchoredPosition.x (card resting position).")]
        [SerializeField] private float shownX = -24f;
        [SerializeField] private float slideInDuration = 0.4f;
        [SerializeField] private Ease slideInEase = Ease.OutBack;
        [SerializeField] private float slideOutDuration = 0.25f;
        [SerializeField] private Ease slideOutEase = Ease.InBack;

        #endregion

        #region State

        private readonly Queue<Invite> queue = new Queue<Invite>();
        private Invite current;
        private bool isShowing;
        private Tween slideTween;

        /// <summary>
        /// Texture backing the currently displayed Steam avatar — destroyed when replaced to
        /// avoid leaking a Texture2D per invitation.
        /// </summary>
        private Texture2D currentAvatarTexture;

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Wires the buttons and parks the card off-screen; runs once.
        /// </summary>
        private void Awake()
        {
            if (joinButton != null) joinButton.onClick.AddListener(HandleJoinClicked);
            if (cancelButton != null) cancelButton.onClick.AddListener(HandleCancelClicked);

            if (card != null)
            {
                card.anchoredPosition = new Vector2(hiddenX, card.anchoredPosition.y);
                card.gameObject.SetActive(false);
            }
        }

        /// <summary>
        /// Subscribes to incoming invitations.
        /// </summary>
        private void OnEnable()
        {
            PlayerEvents.InviteReceived += HandleInviteReceived;
        }

        /// <summary>
        /// Unsubscribes — mirrors OnEnable exactly.
        /// </summary>
        private void OnDisable()
        {
            PlayerEvents.InviteReceived -= HandleInviteReceived;
        }

        /// <summary>
        /// Kills the tween and frees the avatar texture on teardown.
        /// </summary>
        private void OnDestroy()
        {
            slideTween?.Kill();
            ReleaseAvatarTexture();
        }

        #endregion

        #region Event Handlers

        /// <summary>
        /// Queues a new invitation and shows it immediately if the card is idle.
        /// </summary>
        private void HandleInviteReceived(ulong steamId, string inviterName, string code)
        {
            queue.Enqueue(new Invite(steamId, inviterName, code));
            if (!isShowing) ShowNext();
        }

        /// <summary>
        /// Join the inviter's room, then slide the card away (the scene load takes over on success).
        /// </summary>
        private void HandleJoinClicked()
        {
            if (NetworkSessionManager.Instance != null && !string.IsNullOrEmpty(current.Code))
                NetworkSessionManager.Instance.JoinSession(current.Code);
            else
                Debug.LogError("[InviteNotification] Cannot join — NetworkSessionManager missing or code empty.", this);

            Dismiss();
        }

        /// <summary>
        /// Declines the current invitation and moves on to the next queued one.
        /// </summary>
        private void HandleCancelClicked() => Dismiss();

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Pops the next invitation off the queue and slides the card in; idles when empty.
        /// </summary>
        private void ShowNext()
        {
            if (queue.Count == 0)
            {
                isShowing = false;
                return;
            }

            current = queue.Dequeue();
            isShowing = true;

            if (nameText != null) nameText.text = current.Name;
            // Clear the previous invite's avatar; Steam fills it back in (almost always instantly,
            // since a friend's picture is normally already cached).
            SetAvatar(null, null);

            // Ask Steam for the real avatar; it may arrive now or a moment later.
            if (SteamInviteService.Instance != null)
            {
                ulong requestedId = current.SteamId;
                SteamInviteService.Instance.RequestAvatar(requestedId, sprite =>
                {
                    // Ignore a late avatar for an invitation we are no longer showing.
                    if (!isShowing || current.SteamId != requestedId || sprite == null) return;
                    SetAvatar(sprite, sprite.texture);
                });
            }

            slideTween?.Kill();
            card.gameObject.SetActive(true);
            card.anchoredPosition = new Vector2(hiddenX, card.anchoredPosition.y);
            slideTween = card.DOAnchorPosX(shownX, slideInDuration).SetEase(slideInEase);
        }

        /// <summary>
        /// Slides the card out and shows the next queued invitation when done.
        /// </summary>
        private void Dismiss()
        {
            slideTween?.Kill();
            slideTween = card.DOAnchorPosX(hiddenX, slideOutDuration)
                .SetEase(slideOutEase)
                .OnComplete(() =>
                {
                    card.gameObject.SetActive(false);
                    ShowNext();
                });
        }

        /// <summary>
        /// Swaps the avatar sprite, releasing any previous Steam-built texture first.
        /// </summary>
        private void SetAvatar(Sprite sprite, Texture2D ownedTexture)
        {
            ReleaseAvatarTexture();
            currentAvatarTexture = ownedTexture;
            if (avatarImage != null) avatarImage.sprite = sprite;
        }

        /// <summary>
        /// Destroys the previously shown Steam avatar texture, if we created one.
        /// </summary>
        private void ReleaseAvatarTexture()
        {
            if (currentAvatarTexture != null)
            {
                Destroy(currentAvatarTexture);
                currentAvatarTexture = null;
            }
        }

        #endregion
    }
}