import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Scanner;
import java.util.Set;

/**
 * 中小学数学卷子自动生成程序
 * 支持小学、初中、高中三个学段的数学题目生成
 */
public class MathQuestionGenerator {
    
    // 常量定义
    private static final int MIN_OPERAND_COUNT = 1;
    private static final int MAX_OPERAND_COUNT = 5;
    private static final int MIN_OPERAND_VALUE = 1;
    private static final int MAX_OPERAND_VALUE = 100;
    private static final int MIN_QUESTION_COUNT = 10;
    private static final int MAX_QUESTION_COUNT = 30;
    private static final int MAX_GENERATION_ATTEMPTS = 100;
    
    // 预定义的用户账户
    private static final Map<String, User> USERS = new HashMap<>();
    
    // 题目生成器映射
    private static final Map<String, QuestionGenerator> GENERATORS = new HashMap<>();

    // 当前登录用户
    private static User currentUser = null;
    private static final Scanner scanner = new Scanner(System.in);

    static {
        initializeUsers();
        initializeGenerators();
    }
    
    /**
     * 初始化用户账户
     */
    private static void initializeUsers() {
        // 小学老师
        USERS.put("张三1", new User("张三1", "123", "小学"));
        USERS.put("张三2", new User("张三2", "123", "小学"));
        USERS.put("张三3", new User("张三3", "123", "小学"));

        // 初中老师
        USERS.put("李四1", new User("李四1", "123", "初中"));
        USERS.put("李四2", new User("李四2", "123", "初中"));
        USERS.put("李四3", new User("李四3", "123", "初中"));

        // 高中老师
        USERS.put("王五1", new User("王五1", "123", "高中"));
        USERS.put("王五2", new User("王五2", "123", "高中"));
        USERS.put("王五3", new User("王五3", "123", "高中"));
    }
    
    /**
     * 初始化题目生成器
     */
    private static void initializeGenerators() {
        GENERATORS.put("小学", new PrimaryQuestionGenerator());
        GENERATORS.put("初中", new JuniorQuestionGenerator());
        GENERATORS.put("高中", new SeniorQuestionGenerator());
    }

    /**
     * 主程序入口
     * @param args 命令行参数
     */
    public static void main(String[] args) {
        showWelcomeMessage();
        
        while (true) {
            if (!login()) {
                continue;
            }
            
            System.out.println("登录成功！欢迎 " + currentUser.getUsername() + " 老师");
            operateAfterLogin();
        }
    }
    
    /**
     * 显示欢迎信息
     */
    private static void showWelcomeMessage() {
        System.out.println("==========================================");
        System.out.println("        中小学数学卷子自动生成系统        ");
        System.out.println("==========================================");
        System.out.println();
        System.out.println("预设账户信息：");
        System.out.println("小学老师：张三1、张三2、张三3（密码：123）");
        System.out.println("初中老师：李四1、李四2、李四3（密码：123）");
        System.out.println("高中老师：王五1、王五2、王五3（密码：123）");
        System.out.println();
    }

    /**
     * 用户登录验证
     * @return 登录是否成功
     */
    private static boolean login() {
        System.out.println("=== 用户登录 ===");
        System.out.println("请输入用户名和密码（用空格隔开）：");
        System.out.print("> ");
        String input = scanner.nextLine().trim();

        String[] parts = input.split("\\s+");
        if (parts.length != 2) {
            System.out.println("请输入正确的用户名、密码");
            return false;
        }

        String username = parts[0];
        String password = parts[1];

        User user = USERS.get(username);
        if (user != null && user.getPassword().equals(password)) {
            currentUser = user;
            return true;
        } else {
            System.out.println("请输入正确的用户名、密码");
            return false;
        }
    }

    /**
     * 登录后的操作处理
     */
    private static void operateAfterLogin() {
        String currentGrade = currentUser.getGrade();
        showOperationMenu(currentGrade);

        while (true) {
            String input = getUserInput();
            
            if (handleExitCommand(input)) {
                break;
            }
            
            if (input.startsWith("切换为")) {
                if (handleSwitchCommand(input)) {
                    currentGrade = currentUser.getGrade();
                    showOperationMenu(currentGrade);
                }
                continue;
            }
            
            handleQuestionGeneration(input, currentGrade);
        }
    }
    
    /**
     * 获取用户输入
     * @return 用户输入
     */
    private static String getUserInput() {
        System.out.println();
        System.out.print("请输入操作：");
        return scanner.nextLine().trim();
    }
    
    /**
     * 处理退出命令
     * @param input 用户输入
     * @return 是否退出
     */
    private static boolean handleExitCommand(String input) {
        if (input.equals("-1")) {
            currentUser = null;
            System.out.println("退出当前用户，重新登录...");
            return true;
        }
        return false;
    }
    
    
    /**
     * 处理题目生成
     * @param input 用户输入
     * @param currentGrade 当前年级
     */
    private static void handleQuestionGeneration(String input, String currentGrade) {
        try {
            int count = Integer.parseInt(input);
            if (count < MIN_QUESTION_COUNT || count > MAX_QUESTION_COUNT) {
                System.out.println("题目数量应在" + MIN_QUESTION_COUNT + "-" + MAX_QUESTION_COUNT + "之间");
                return;
            }
            generateQuestions(count, currentGrade);
        } catch (NumberFormatException e) {
            System.out.println("请输入有效的数字（" + MIN_QUESTION_COUNT + "-" + MAX_QUESTION_COUNT + "）或切换命令");
        }
    }
    
    /**
     * 显示操作菜单
     * @param currentGrade 当前年级类型
     */
    private static void showOperationMenu(String currentGrade) {
        System.out.println();
        System.out.println("=== 操作菜单 ===");
        System.out.println("当前选择为" + currentGrade + "出题");
        System.out.println();
        System.out.println("可进行的操作：");
        System.out.println("1. 输入数字 " + MIN_QUESTION_COUNT + "-" + MAX_QUESTION_COUNT + "：生成指定数量的" + currentGrade + "数学题目");
        System.out.println("2. 输入 '切换为小学'：切换到小学出题模式");
        System.out.println("3. 输入 '切换为初中'：切换到初中出题模式");
        System.out.println("4. 输入 '切换为高中'：切换到高中出题模式");
        System.out.println("5. 输入 '-1'：退出当前用户，重新登录");
        System.out.println();
        System.out.flush();
    }

    /**
     * 处理切换命令
     * @param command 切换命令
     * @return 切换是否成功
     */
    private static boolean handleSwitchCommand(String command) {
        String targetGrade = command.substring(3).trim();

        if (targetGrade.equals("小学") || targetGrade.equals("初中") || targetGrade.equals("高中")) {
            currentUser = new User(currentUser.getUsername(), currentUser.getPassword(), targetGrade);
            System.out.println();
            System.out.println("✓ 切换成功！当前为" + targetGrade + "出题模式");
            System.out.flush();
            return true;
        } else {
            System.out.println();
            System.out.println("✗ 请输入小学、初中和高中三个选项中的一个");
            System.out.flush();
            return false;
        }
    }

    /**
     * 生成指定数量的题目
     * @param count 题目数量
     * @param grade 年级类型
     */
    private static void generateQuestions(int count, String grade) {
        File userDir = createUserDirectory();
        Set<String> historyQuestions = loadHistoryQuestions(userDir);
        List<String> newQuestions = generateNewQuestions(count, grade, historyQuestions);
        saveQuestionsToFile(newQuestions, userDir, count, grade);
    }
    
    /**
     * 创建用户文件夹
     * @return 用户文件夹
     */
    private static File createUserDirectory() {
        File userDir = new File(currentUser.getUsername());
        if (!userDir.exists()) {
            userDir.mkdir();
        }
        return userDir;
    }
    
    /**
     * 生成新题目
     * @param count 题目数量
     * @param grade 年级类型
     * @param historyQuestions 历史题目
     * @return 新题目列表
     */
    private static List<String> generateNewQuestions(int count, String grade, Set<String> historyQuestions) {
        List<String> newQuestions = new ArrayList<>();
        Random random = new Random();
        QuestionGenerator generator = GENERATORS.get(grade);

        for (int i = 1; i <= count; i++) {
            String question = generateSingleQuestion(generator, random, historyQuestions, newQuestions, i);
            newQuestions.add(question);
        }
        
        return newQuestions;
    }
    
    /**
     * 生成单个题目
     * @param generator 题目生成器
     * @param random 随机数生成器
     * @param historyQuestions 历史题目
     * @param newQuestions 新题目列表
     * @param questionNumber 题目编号
     * @return 生成的题目
     */
    private static String generateSingleQuestion(QuestionGenerator generator, Random random, 
                                               Set<String> historyQuestions, List<String> newQuestions, 
                                               int questionNumber) {
        String question;
        int attempts = 0;

        do {
            int operandCount = random.nextInt(MAX_OPERAND_COUNT - MIN_OPERAND_COUNT + 1) + MIN_OPERAND_COUNT;
            int[] operands = new int[operandCount];
            for (int i = 0; i < operandCount; i++) {
                operands[i] = random.nextInt(MAX_OPERAND_VALUE - MIN_OPERAND_VALUE + 1) + MIN_OPERAND_VALUE;
            }
            
            question = generator.generateQuestion(operands, random);
            attempts++;
            if (attempts > MAX_GENERATION_ATTEMPTS) {
                question = "备用题目：" + questionNumber;
                break;
            }
        } while (historyQuestions.contains(question) || newQuestions.contains(question));

        return question;
    }

    /**
     * 加载历史题目用于去重
     * @param userDir 用户文件夹
     * @return 历史题目集合
     */
    private static Set<String> loadHistoryQuestions(File userDir) {
        Set<String> historyQuestions = new HashSet<>();

        File[] files = userDir.listFiles((dir, name) -> name.endsWith(".txt"));
        if (files != null) {
            for (File file : files) {
                try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
                    String line;
                    while ((line = reader.readLine()) != null) {
                        if (line.matches("\\d+\\.\\s+.+")) {
                            String question = line.substring(line.indexOf(".") + 1).trim();
                            historyQuestions.add(question);
                        }
                    }
                } catch (IOException e) {
                    System.out.println("读取历史文件失败：" + file.getName());
                }
            }
        }

        return historyQuestions;
    }

    /**
     * 保存题目到文件
     * @param questions 题目列表
     * @param userDir 用户文件夹
     * @param count 题目数量
     * @param grade 年级类型
     */
    private static void saveQuestionsToFile(List<String> questions, File userDir, int count, String grade) {
        File outputFile = createOutputFile(userDir);
        writeQuestionsToFile(questions, outputFile);
        showGenerationResult(count, grade, outputFile);
    }
    
    /**
     * 创建输出文件
     * @param userDir 用户文件夹
     * @return 输出文件
     */
    private static File createOutputFile(File userDir) {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");
        String filename = dateFormat.format(new Date()) + ".txt";
        return new File(userDir, filename);
    }
    
    /**
     * 将题目写入文件
     * @param questions 题目列表
     * @param outputFile 输出文件
     */
    private static void writeQuestionsToFile(List<String> questions, File outputFile) {
        try (PrintWriter writer = new PrintWriter(new FileWriter(outputFile))) {
            for (int i = 0; i < questions.size(); i++) {
                writer.println((i + 1) + ". " + questions.get(i));
                if (i < questions.size() - 1) {
                    writer.println(); // 题目之间空一行
                }
            }
        } catch (IOException e) {
            System.out.println("保存文件失败：" + e.getMessage());
        }
    }
    
    /**
     * 显示生成结果
     * @param count 题目数量
     * @param grade 年级类型
     * @param outputFile 输出文件
     */
    private static void showGenerationResult(int count, String grade, File outputFile) {
        System.out.println();
        System.out.println("✓ 题目生成完成！");
        System.out.println("✓ 已生成 " + count + " 道" + grade + "数学题目");
        System.out.println("✓ 文件已保存到：" + outputFile.getName());
        System.out.println();
    }

    /**
     * 用户类，存储用户信息
     */
    static class User {
        private final String username;
        private final String password;
        private final String grade;

        /**
         * 构造函数
         * @param username 用户名
         * @param password 密码
         * @param grade 年级类型
         */
        public User(String username, String password, String grade) {
            this.username = username;
            this.password = password;
            this.grade = grade;
        }

        /**
         * 获取用户名
         * @return 用户名
         */
        public String getUsername() { 
            return username; 
        }
        
        /**
         * 获取密码
         * @return 密码
         */
        public String getPassword() { 
            return password; 
        }
        
        /**
         * 获取年级类型
         * @return 年级类型
         */
        public String getGrade() { 
            return grade; 
        }
    }
}