/**
 * Copyright 2019 Heroic Labs and contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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

namespace DemoGame.Scripts.Chat
{
    /// <summary>
    /// Manages user interface for group chat
    /// </summary>
    public class ChatChannelClanUI : ChatChannelUI
    {
        #region private serialized variables

        [Space()]
        [Header("Prefabs")]
        [Space()]
        [Header("ChatChannelClanUI")]

        /// <summary>
        /// Prefab for instantiating username in active users list
        /// </summary>    
        [SerializeField] private GameObject _activeUserTextPrefab = null;

        [Space()]
        [Header("UI elements")]

        /// <summary>
        /// Rect Transform of active users list, parent of active users usernames Texts
        /// </summary>
        [SerializeField] private RectTransform _activeUsersListPanel = null;

        #endregion

        #region private variables

        /// <summary>
        /// Actual list of spawned Texts with usernames on active users list
        /// </summary>
        private Dictionary<string, Text> _userTexts = new Dictionary<string, Text>();

        #endregion

        #region public methods

        /// <summary>
        /// <see cref="ChatChannelUI.SetChatChannel"/>  
        /// </summary>
        /// <param name="chatChannel"></param>
        public override void SetChatChannel(ChatChannel chatChannel)
        {
            //Checking if there was already connected ChatChannel to this UI
            if (_chatChannel != null)
            {
                //If connected ChatChannel is the same instance as the ChatChannel we want to connect - return
                if (_chatChannel == chatChannel)
                {
                    return;
                }
                //Unregister clan chat UI functions from old ChatChannel events
                _chatChannel.OnJoinedChannel -= AddUserToList;
                _chatChannel.OnLeftChannel -= DeleteUserFromList;
            }

            //Base connecting ChatChannel to UI
            base.SetChatChannel(chatChannel);

            //Clear active users list
            ClearAllActiveUsersTexts();

            //Fill in active users list with initial users
            PopulateActiveUsersList(chatChannel.ActiveUsersUsernames);

            //Register clan chat UI functions to new ChatChannel events
            _chatChannel.OnJoinedChannel += AddUserToList;
            _chatChannel.OnLeftChannel += DeleteUserFromList;
        }

        #endregion

        #region private methods

        /// <summary>
        /// Adds user to active users list
        /// </summary>
        /// <param name="user"></param>
        private void AddUserToList(ChatUser user)
        {
            _userTexts.Add(user.Username, InstantiateUsernameText(user.Username));
        }

        /// <summary>
        /// Removes user from active users list
        /// </summary>
        /// <param name="user"></param>
        private void DeleteUserFromList(ChatUser user)
        {
            Destroy(_userTexts[user.Username].gameObject);
            _userTexts.Remove(user.Username);
        }

        /// <summary>
        /// Fills in active users list with given usernames
        /// </summary>
        private void PopulateActiveUsersList(List<string> usernames)
        {
            //Add every username from given list to active users list
            foreach (string username in usernames)
            {
                _userTexts.Add(username, InstantiateUsernameText(username));
            }
        }

        /// <summary>
        /// Clears active users list
        /// </summary>
        private void ClearAllActiveUsersTexts()
        {
            //Destroying every previously added text
            List<Text> texts = new List<Text>(_userTexts.Values);

            foreach (Text text in texts)
            {
                Destroy(text.gameObject);
            }

            //Clearing _userTexts dictionary
            _userTexts.Clear();
        }

        /// <summary>
        /// Instantiate new user Text on active users list
        /// </summary>
        private Text InstantiateUsernameText(string username)
        {
            GameObject textGO = Instantiate(_activeUserTextPrefab, _activeUsersListPanel) as GameObject;
            Text text = textGO.GetComponent<Text>();
            if (text)
            {
                text.text = username;
                return text;
            }
            else
            {
                Debug.LogError("Invalid activeUserTextPrefab! Should contains Text component.");
                return null;
            }
        }

        #endregion
    }
}