package com.service;


import com.model.*;
import com.util.FileUtils;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Type;
import java.text.SimpleDateFormat;
import java.util.*;

/**
 * 文件IO服务
 * 负责所有数据的读写操作
 */
public class FileIOService {

    private static final String DATA_DIR = "data";
    private static final String USERS_DIR = DATA_DIR + "/users";
    private static final String HISTORY_DIR = DATA_DIR + "/history";

    private static final String USERS_FILE = DATA_DIR + "/users.json";
    private static final String CURRENT_USER_FILE = DATA_DIR + "/current_user.json";

    private static final Gson gson = new GsonBuilder()
            .setPrettyPrinting()
            .setDateFormat("yyyy-MM-dd HH:mm:ss")
            .create();

    // ==================== 初始化 ====================

    public void initDataDirectory() throws IOException {
        FileUtils.createDirectoryIfNotExists(DATA_DIR);
        FileUtils.createDirectoryIfNotExists(USERS_DIR);
        FileUtils.createDirectoryIfNotExists(HISTORY_DIR);

        if (!FileUtils.exists(USERS_FILE)) {
            Map<String, List<User>> data = new HashMap<>();
            data.put("users", new ArrayList<>());
            FileUtils.saveAsJson(data, USERS_FILE);
        }

        System.out.println("✓ 数据目录初始化完成");
    }

    // ==================== 用户操作 ====================

    public void saveUser(User user) throws IOException {
        Type type = new TypeToken<Map<String, List<User>>>(){}.getType();
        Map<String, List<User>> data = FileUtils.readJsonToObject(USERS_FILE, type);

        List<User> users = data.get("users");

        boolean found = false;
        for (int i = 0; i < users.size(); i++) {
            if (users.get(i).getUsername().equals(user.getUsername())) {
                users.set(i, user);
                found = true;
                break;
            }
        }

        if (!found) {
            users.add(user);
        }

        FileUtils.saveAsJson(data, USERS_FILE);
    }

    public List<User> loadAllUsers() throws IOException {
        if (!FileUtils.exists(USERS_FILE)) {
            return new ArrayList<>();
        }

        Type type = new TypeToken<Map<String, List<User>>>(){}.getType();
        Map<String, List<User>> data = FileUtils.readJsonToObject(USERS_FILE, type);

        return data.get("users");
    }

    public User findUserByUsername(String username) throws IOException {
        List<User> users = loadAllUsers();

        for (User user : users) {
            if (user.getUsername().equals(username)) {
                return user;
            }
        }

        return null;
    }

    public boolean isUsernameExists(String username) throws IOException {
        return findUserByUsername(username) != null;
    }

    public void saveCurrentUser(User user) throws IOException {
        FileUtils.saveAsJson(user, CURRENT_USER_FILE);
    }

    public User loadCurrentUser() throws IOException {
        if (!FileUtils.exists(CURRENT_USER_FILE)) {
            return null;
        }
        return FileUtils.readJsonToObject(CURRENT_USER_FILE, User.class);
    }

    public void clearCurrentUser() {
        FileUtils.deleteFile(CURRENT_USER_FILE);
    }

    // ==================== 答题历史操作 ====================

    public void saveQuizHistory(QuizHistory history) throws IOException {
        String filename = HISTORY_DIR + "/" +
                sanitizeFilename(history.getUsername()) + "_" +
                System.currentTimeMillis() + ".txt";

        StringBuilder content = new StringBuilder();
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        content.append("========== 答题记录 ==========\n");
        content.append("用户：").append(history.getUsername()).append("\n");
        content.append("时间：").append(dateFormat.format(history.getTimestamp())).append("\n");
        content.append("总分：").append(history.getScore()).append(" 分\n");

        // 调用 QuizService 的业务方法计算正确数和错误数
        int correctCount = calculateCorrectCount(history);
        int wrongCount = history.getQuestions().size() - correctCount;

        content.append("正确：").append(correctCount).append(" 题  ");
        content.append("错误：").append(wrongCount).append(" 题\n");
        content.append("=============================\n\n");

        List<ChoiceQuestion> questions = history.getQuestions();
        List<Integer> userAnswers = history.getUserAnswers();

        for (int i = 0; i < questions.size(); i++) {
            ChoiceQuestion q = questions.get(i);
            Integer userAnswer = userAnswers.get(i);

            content.append("【题目 ").append(i + 1).append("】\n");
            content.append(q.getQuestionText()).append("\n");

            List<?> options = q.getOptions();
            for (int j = 0; j < options.size(); j++) {
                content.append((char)('A' + j)).append(". ")
                        .append(options.get(j)).append("    ");
            }
            content.append("\n");

            int correctIndex = getCorrectAnswerIndex(q);
            content.append("正确答案：").append((char)('A' + correctIndex)).append("\n");

            content.append("用户答案：");
            if (userAnswer != null) {
                content.append((char)('A' + userAnswer));
            } else {
                content.append("未作答");
            }
            content.append("\n");

            boolean isCorrect = (userAnswer != null && userAnswer == correctIndex);
            content.append("结果：").append(isCorrect ? "✓ 正确" : "✗ 错误").append("\n\n");
        }

        FileUtils.writeStringToFile(filename, content.toString());
    }

    public List<String> getHistoryQuestions() throws IOException {
        List<String> historyQuestions = new ArrayList<>();
        File[] files = FileUtils.listFiles(HISTORY_DIR);

        Arrays.sort(files, (f1, f2) -> Long.compare(f2.lastModified(), f1.lastModified()));

        int count = 0;
        for (File file : files) {
            if (count++ >= 20) break;

            try {
                String content = FileUtils.readFileToString(file.getAbsolutePath());
                String[] lines = content.split("\n");

                for (int i = 0; i < lines.length; i++) {
                    if (lines[i].startsWith("【题目")) {
                        if (i + 1 < lines.length) {
                            String questionText = lines[i + 1].trim();
                            if (!questionText.isEmpty()) {
                                historyQuestions.add(questionText);
                            }
                        }
                    }
                }
            } catch (IOException e) {
                System.err.println("读取历史文件失败: " + file.getName());
            }
        }

        return historyQuestions;
    }

    // ==================== 业务逻辑方法（从 Model 移过来）====================

    /**
     * 计算答题历史的正确数
     */
    private int calculateCorrectCount(QuizHistory history) {
        int count = 0;
        List<ChoiceQuestion> questions = history.getQuestions();
        List<Integer> userAnswers = history.getUserAnswers();

        for (int i = 0; i < questions.size(); i++) {
            ChoiceQuestion question = questions.get(i);
            Integer userAnswer = userAnswers.get(i);

            if (userAnswer != null && userAnswer == getCorrectAnswerIndex(question)) {
                count++;
            }
        }
        return count;
    }

    /**
     * 获取题目的正确答案索引
     */
    private int getCorrectAnswerIndex(ChoiceQuestion question) {
        return question.getOptions().indexOf(question.getCorrectAnswer());
    }

    // ==================== 工具方法 ====================

    private String sanitizeFilename(String filename) {
        if (filename == null) {
            return "unknown";
        }
        return filename.replaceAll("[\\\\/:*?\"<>|]", "_");
    }
}