package mathlearning.service;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import mathlearning.model.User;
import at.favre.lib.crypto.bcrypt.BCrypt;

import java.io.File;
import java.io.IOException;
import java.time.LocalDateTime;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

public class UserService {
    private static final String USERS_FILE = "data/users.json";
    private static final long VERIFICATION_CODE_EXPIRY_MINUTES = 10;

    private Map<String, User> users;
    private Map<String, LocalDateTime> verificationCodeTimestamps;
    private ObjectMapper objectMapper;

    public UserService() {
        this.users = new ConcurrentHashMap<>();
        this.verificationCodeTimestamps = new ConcurrentHashMap<>();
        this.objectMapper = new ObjectMapper();
        objectMapper.registerModule(new JavaTimeModule());
        loadUsers();
    }

    private void loadUsers() {
        try {
            File file = new File(USERS_FILE);
            if (file.exists() && file.length() > 0) {
                User[] userArray = objectMapper.readValue(file, User[].class);
                for (User user : userArray) {
                    users.put(user.getEmail(), user);
                }
                System.out.println("成功加载 " + userArray.length + " 个用户");
            } else {
                saveUsers();
                System.out.println("创建新的用户数据文件");
            }
        } catch (IOException e) {
            System.err.println("加载用户数据失败: " + e.getMessage());
            backupAndRecreateFile();
        }
    }

    private void backupAndRecreateFile() {
        try {
            File file = new File(USERS_FILE);
            if (file.exists()) {
                File backup = new File(USERS_FILE + ".bak." + System.currentTimeMillis());
                file.renameTo(backup);
                System.err.println("损坏的文件已备份为: " + backup.getName());
            }
            saveUsers();
            System.out.println("已重新创建用户数据文件");
        } catch (Exception e) {
            System.err.println("备份文件失败: " + e.getMessage());
        }
    }

    private void saveUsers() {
        try {
            File file = new File(USERS_FILE);
            file.getParentFile().mkdirs();
            objectMapper.writerWithDefaultPrettyPrinter().writeValue(file, users.values().toArray(new User[0]));
        } catch (IOException e) {
            System.err.println("保存用户数据失败: " + e.getMessage());
            e.printStackTrace();
        }
    }

    public boolean registerUser(String email, String verificationCode) {
        if (users.containsKey(email)) {
            return false; // 用户已存在
        }

        // 生成密码占位符，实际密码在验证后设置
        String tempPasswordHash = BCrypt.withDefaults().hashToString(12, "temp".toCharArray());
        User user = new User(email, tempPasswordHash, verificationCode);
        users.put(email, user);
        verificationCodeTimestamps.put(email, LocalDateTime.now());
        saveUsers();
        return true;
    }

    public boolean verifyUser(String username, String email, String verificationCode, String password) {
        User user = users.get(email);
        if (user == null || !user.getVerificationCode().equals(verificationCode)) {
            return false;
        }

        // 检查验证码是否过期
        LocalDateTime codeTime = verificationCodeTimestamps.get(email);
        if (codeTime == null || codeTime.plusMinutes(VERIFICATION_CODE_EXPIRY_MINUTES).isBefore(LocalDateTime.now())) {
            return false;
        }

        // 验证密码格式
        if (!validatePassword(password)) {
            return false;
        }

        // 设置实际密码
        String passwordHash = BCrypt.withDefaults().hashToString(12, password.toCharArray());
        user.setPasswordHash(passwordHash);
        user.setUsername(username);
        user.setVerified(true);
        verificationCodeTimestamps.remove(email);
        saveUsers();
        return true;
    }

    public boolean login(String email, String password) {
        User user = users.get(email);
        if (user == null || !user.isVerified()) {
            return false;
        }

        BCrypt.Result result = BCrypt.verifyer().verify(password.toCharArray(), user.getPasswordHash());
        return result.verified;
    }

    public boolean changePassword(String email, String oldPassword, String newPassword) {
        User user = users.get(email);
        if (user == null) {
            return false;
        }

        // 验证旧密码
        BCrypt.Result result = BCrypt.verifyer().verify(oldPassword.toCharArray(), user.getPasswordHash());
        if (!result.verified) {
            return false;
        }

        // 验证新密码格式
        if (!validatePassword(newPassword)) {
            return false;
        }

        // 更新密码
        String newPasswordHash = BCrypt.withDefaults().hashToString(12, newPassword.toCharArray());
        user.setPasswordHash(newPasswordHash);
        saveUsers();
        return true;
    }

    public boolean setPasswordResetCode(String email, String verificationCode) {
        User user = users.get(email);
        if (user == null) {
            return false; // 用户不存在
        }

        user.setVerificationCode(verificationCode);
        verificationCodeTimestamps.put(email, LocalDateTime.now());
        saveUsers();
        return true;
    }

    public boolean resetPasswordWithCode(String email, String verificationCode, String newPassword) {
        User user = users.get(email);
        if (user == null) {
            return false;
        }

        // 验证验证码
        if (!user.getVerificationCode().equals(verificationCode)) {
            return false;
        }

        // 检查验证码是否过期
        LocalDateTime codeTime = verificationCodeTimestamps.get(email);
        if (codeTime == null || codeTime.plusMinutes(VERIFICATION_CODE_EXPIRY_MINUTES).isBefore(LocalDateTime.now())) {
            return false;
        }

        // 验证新密码格式
        if (!validatePassword(newPassword)) {
            return false;
        }

        // 更新密码
        String newPasswordHash = BCrypt.withDefaults().hashToString(12, newPassword.toCharArray());
        user.setPasswordHash(newPasswordHash);
        verificationCodeTimestamps.remove(email); // 清除验证码
        saveUsers();
        return true;
    }

    public boolean validatePassword(String password) {
        if (password.length() < 6 || password.length() > 10) {
            return false;
        }

        boolean hasUpper = false;
        boolean hasLower = false;
        boolean hasDigit = false;

        for (char c : password.toCharArray()) {
            if (Character.isUpperCase(c)) hasUpper = true;
            if (Character.isLowerCase(c)) hasLower = true;
            if (Character.isDigit(c)) hasDigit = true;
        }

        return hasUpper && hasLower && hasDigit;
    }

    public boolean userExists(String email) {
        return users.containsKey(email);
    }

    public boolean isUserExistsAndVerified(String email) {
        User user = users.get(email);
        return user != null && user.isVerified();
    }

    public boolean isValidEmail(String email) {
        return email.matches("^[A-Za-z0-9+_.-]+@(.+)$");
    }

    public User getUser(String email ) {
        User user = users.get(email);
        return user;
    }
}