package com.personalproject.auth;

import com.personalproject.model.DifficultyLevel;
import java.time.LocalDateTime;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

/**
 * 存放用户账号并提供认证和注册查询能力.
 */
public final class AccountRepository {

  private final Map<String, UserAccount> accounts = new HashMap<>();
  private final Map<String, String> registrationCodes = new HashMap<>();

  /**
   * 根据用户名与密码查找匹配的账号.
   *
   * @param username 用户名.
   * @param password 密码.
   * @return 匹配成功时返回账号信息，否则返回空结果.
   */
  public Optional<UserAccount> authenticate(String username, String password) {
    if (username == null || password == null) {
      return Optional.empty();
    }
    UserAccount account = accounts.get(username.trim());
    if (account == null || !account.isRegistered()) {
      return Optional.empty();
    }
    if (!account.password().equals(password.trim())) {
      return Optional.empty();
    }
    return Optional.of(account);
  }

  /**
   * Registers a new user account with email.
   *
   * @param username        The username
   * @param email           The email address
   * @param difficultyLevel The selected difficulty level
   * @return true if registration was successful, false if username already exists
   */
  public boolean registerUser(String username, String email, DifficultyLevel difficultyLevel) {
    String trimmedUsername = username.trim();
    String trimmedEmail = email.trim();

    if (accounts.containsKey(trimmedUsername)) {
      return false; // Username already exists
    }

    // Check if email is already used by another account
    for (UserAccount account : accounts.values()) {
      if (account.email().equals(trimmedEmail) && account.isRegistered()) {
        return false; // Email already registered
      }
    }

    UserAccount newAccount = new UserAccount(
        trimmedUsername,
        trimmedEmail,
        "", // Empty password initially
        difficultyLevel,
        LocalDateTime.now(),
        false); // Not registered until password is set
    accounts.put(trimmedUsername, newAccount);
    return true;
  }

  /**
   * Sets the password for a user after registration.
   *
   * @param username The username
   * @param password The password to set
   * @return true if successful, false if user doesn't exist
   */
  public boolean setPassword(String username, String password) {
    UserAccount account = accounts.get(username.trim());
    if (account == null) {
      return false;
    }

    UserAccount updatedAccount = new UserAccount(
        account.username(),
        account.email(),
        password,
        account.difficultyLevel(),
        account.registrationDate(),
        true); // Now registered
    accounts.put(username.trim(), updatedAccount);
    return true;
  }

  /**
   * Changes the password for an existing user.
   *
   * @param username    The username
   * @param oldPassword The current password
   * @param newPassword The new password
   * @return true if successful, false if old password is incorrect or user doesn't exist
   */
  public boolean changePassword(String username, String oldPassword, String newPassword) {
    UserAccount account = accounts.get(username.trim());
    if (account == null || !account.password().equals(oldPassword) || !account.isRegistered()) {
      return false;
    }

    UserAccount updatedAccount = new UserAccount(
        account.username(),
        account.email(),
        newPassword,
        account.difficultyLevel(),
        account.registrationDate(),
        true);
    accounts.put(username.trim(), updatedAccount);
    return true;
  }

  /**
   * Checks if a user exists in the system.
   *
   * @param username The username to check
   * @return true if user exists, false otherwise
   */
  public boolean userExists(String username) {
    return accounts.containsKey(username.trim());
  }

  /**
   * Gets a user account by username.
   *
   * @param username The username
   * @return Optional containing the user account if found
   */
  public Optional<UserAccount> getUser(String username) {
    return Optional.ofNullable(accounts.get(username.trim()));
  }
}