package util;

import generator.Problem;
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.*;

public class FileUtils {
    private static final String FOLDER_PATH = "exams/";

    public static String getUserFolder(String username) {
        String folder = FOLDER_PATH + username;
        File dir = new File(folder);
        if (!dir.exists()) {
            dir.mkdirs();
        }
        return folder;
    }

    private static void processHistoryFile(File file, Set<String> history) {
        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
            String line;
            while ((line = br.readLine()) != null) {
                if (!line.trim().isEmpty() && line.matches("^\\d+\\..*")) {
                    // 仅提取题干 (表达式字符串) 用于查重
                    history.add(line.substring(line.indexOf('.') + 1).trim());
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static Set<String> loadHistory(String username) {
        Set<String> history = new HashSet<>();
        File dir = new File(getUserFolder(username));
        File[] files = dir.listFiles((d, name) -> name.endsWith(".txt"));

        if (files != null) {
            for (File file : files) {
                processHistoryFile(file, history);
            }
        }
        return history;
    }

    private static void writeProblem(BufferedWriter bw, int index, Problem problem) throws IOException {
        bw.write(index + "." + problem.getExpression());
        bw.newLine();

        char optionChar = 'A';
        StringBuilder optionsLine = new StringBuilder();
        for (String option : problem.getOptions()) {
            optionsLine.append(optionChar++).append(". ").append(option).append("  ");
        }

        bw.write(optionsLine.toString().trim());
        bw.newLine();
        bw.write("答案: " + problem.getCorrectAnswerOption());
        bw.newLine();
        bw.newLine();
    }

    public static void saveProblems(String username, List<Problem> problems) {
        String folder = getUserFolder(username);
        String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
        String filename = folder + "/" + timestamp + ".txt";

        try (BufferedWriter bw = new BufferedWriter(new FileWriter(filename))) {
            int index = 1;
            for (Problem problem : problems) {
                writeProblem(bw, index++, problem);
            }
            System.out.println("卷子已保存到: " + filename);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}