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

/// <summary>
/// ChangeUserScreen scene manager
/// </summary>
public class ChangeUserScreen : MonoBehaviour
{
    /// <summary>
    /// Prefab of the user selection
    /// </summary>
    public GameObject userPrefab;

    /// <summary>
    /// Reference to the container to list all users
    /// </summary>
    public Transform usersContainer;

    /// <summary>
    /// UI Reference to the error GameObject to display an error message
    /// </summary>
    public GameObject error;

    /// <summary>
    /// Index of the current selected user in the UserList
    /// </summary>
    private int currentUserIndex;

    /// <summary>
    /// List of references to avatar background sprites (so we can color them nicely)
    /// </summary>
    private List<Image> userBackgrounds = new List<Image>();

    /// <summary>
    /// Start is called before the first frame update
    /// </summary>
    void Start()
    {
        PersistentDataController.GetInstance().Load();
        error.SetActive(false);
        DisplayUsers();
    }

    /// <summary>
    /// Add all users to the container to display them
    /// </summary>
    private void DisplayUsers()
    {
        foreach (Transform child in usersContainer)
            Destroy(child.gameObject);

        List<User> users = UserList.GetUsers();
        currentUserIndex = UserList.IndexOf(UserList.GetCurrentUser().GetUsername());
        for (int i = 0; i < users.Count; i++)
        {
            User user = users[i];

            // Create instance of prefab
            GameObject instance = GameObject.Instantiate(userPrefab, usersContainer);

            // Store value of i so we can use it the callback (else it would get the value of sprites.Count)
            int x = i;
            // Add user content
            UserCard card = instance.GetComponent<UserCard>();
            card.user = user;
            card.selectUser = () => UpdateSelection(x);
            card.updateUserCardContainer = DisplayUsers;
            card.displayError = () => error.SetActive(true);

            // Store reference to image for fancy coloring
            Image background = instance.GetComponent<Image>();
            userBackgrounds.Add(background);
            // Set background color
            background.color = i == currentUserIndex ? new Color(66 / 255f, 158 / 255f, 189 / 255f, 1f) : Color.gray;
        }
    }

    /// <summary>
    /// Update the current selected user
    /// </summary>
    /// <param name="index">Index to the user in the <c>this.userBackgrounds</c> list</param>
    private void UpdateSelection(int index)
    {
        userBackgrounds[currentUserIndex].color = Color.gray;
        currentUserIndex = index;
        userBackgrounds[currentUserIndex].color = new Color(66 / 255f, 158 / 255f, 189 / 255f, 1f);
    }

    /// <summary>
    /// Select the current selected user and return to the StartScreenScene
    /// </summary>
    public void IChooseYou()
    {
        UserList.ChangeCurrentUser(currentUserIndex);
        SystemController.GetInstance().BackToPreviousScene();
    }

    /// <summary>
    /// Callback to load the UserCreationScreen scene
    /// </summary>
    public void GotoUserCreation()
    {
        SystemController.GetInstance().LoadNextScene("Accounts/Scenes/UserCreationScreen");
    }
}