using System.Collections.Generic;
using System.Text.RegularExpressions;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

/// <summary>
/// UserCreationScreen scene manager
/// </summary>
public class UserCreationScreen : MonoBehaviour
{
    /// <summary>
    /// Maximum lenght of a username
    /// </summary>
    private const int MAX_USERNAME_LENGTH = 12;

    /// <summary>
    /// Reference to the error message to display when a certain usernmae is invalid or already exists
    /// </summary>
    public GameObject errorMessage;

    /// <summary>
    /// Reference to the input text field for username
    /// </summary>
    public TMP_InputField inputName;

    /// <summary>
    /// Reference to the avatar-list container
    /// </summary>
    public Transform avatarsContainer;

    /// <summary>
    /// Avatar prefab
    /// </summary>
    public GameObject avatarPrefab;

    /// <summary>
    /// Current selected avatar
    /// </summary>
    private int selectedAvatar = 0;

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

    /// <summary>
    /// Reference to the back button, so we can deactivate it when the user cannot go back (when no user is found at startup)
    /// </summary>
    public GameObject backButton;

    /// <summary>
    /// Boolean used to check whether the user can go back to the previous scene
    /// </summary>
    public static bool canGoBack = true;

    /// <summary>
    /// Start is called before the first frame update
    /// </summary>
    void Start()
    {
        errorMessage.SetActive(false);
        backButton.SetActive(canGoBack);

        // Reset to default value
        UserCreationScreen.canGoBack = true;

        for (int i = 0; i < UserList.AVATARS.Count; i++)
        {
            // Create instance of prefab
            GameObject instance = GameObject.Instantiate(avatarPrefab, avatarsContainer);

            // Store value of i so we can use it the callback (else it would get the value of sprites.Count)
            int x = i;
            // Add onClick callback
            instance.GetComponent<Button>().onClick.AddListener(() => UpdateAvatar(x));

            // Store reference to image for fancy coloring
            Image background = instance.GetComponent<Image>();
            avatars.Add(background);
            // Set background color
            background.color = selectedAvatar == i ? new Color(66 / 255f, 158 / 255f, 189 / 255f, 1f) : Color.gray;
            // Find correct component for setting the sprite
            instance.transform.Find("Image").GetComponent<Image>().sprite = UserList.AVATARS[i];
        }
    }

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

    /// <summary>
    /// Check if a given string is a correct username (using Regex)
    /// </summary>
    /// <param name="username">The username to be checked</param>
    /// <returns><c>true</c> if the username was valid, <c>false</c> otherwise</returns>
    static public bool IsValidUsername(string username)
    {
        return new Regex($@"^[abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789]{{1,{MAX_USERNAME_LENGTH}}}$").IsMatch(username);
    }

    /// <summary>
    /// Create a new user
    /// (this method will be called by a button callback)
    /// </summary>
    public void CreateUser()
    {
        string username = inputName.text;
        if (IsValidUsername(username))
        {
            if (UserList.GetUserByUsername(username) == null)
            {
                // Create a new entry in the UserList ScriptableObject
                UserList.AddUser(username, UserList.AVATARS[selectedAvatar]);
                SystemController.GetInstance().BackToPreviousScene();
            }
            // Warn user that username already exists
            else
            {
                errorMessage.SetActive(true);
                errorMessage.GetComponent<TMP_Text>().text = "Deze gebruikersnaam bestaat al! Kies een andere.";
            }
        }
        // Warn user that username is invalid
        else
        {
            errorMessage.SetActive(true);
            errorMessage.GetComponent<TMP_Text>().text = "Je gebruikersnaam moet bestaan uit minimum 1 en maximum 12 letters (a-z en A-Z) of cijfers (0-9).";
        }
    }
}