import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class HistoryCommand {
    // 使用List<String>存储所有输入的命令
    private List<String> commandHistory;
    
    public HistoryCommand() {
        this.commandHistory = new ArrayList<>();
    }
    
    // 添加命令到历史记录
    public void addCommand(String command) {
        if (command != null && !command.trim().isEmpty()) {
            commandHistory.add(command.trim());
        }
    }
    
    // 获取所有命令历史
    public List<String> getCommandHistory() {
        return new ArrayList<>(commandHistory); // 返回副本，防止外部修改
    }
    
    // 获取命令数量
    public int getCommandCount() {
        return commandHistory.size();
    }
    
    // 查看指定索引的命令
    public String getCommand(int index) {
        if (index >= 0 && index < commandHistory.size()) {
            return commandHistory.get(index);
        }
        return null;
    }
    
    // 清空命令历史
    public void clearHistory() {
        commandHistory.clear();
    }
    
    // 显示最近的n条命令
    public void showRecentCommands(int n) {
        int start = Math.max(0, commandHistory.size() - n);
        System.out.println("最近 " + (commandHistory.size() - start) + " 条命令：");
        for (int i = start; i < commandHistory.size(); i++) {
            System.out.println((i + 1) + ". " + commandHistory.get(i));
        }
    }
    
    // 显示所有命令历史
    public void showAllCommands() {
        System.out.println("所有命令历史（共 " + commandHistory.size() + " 条）：");
        for (int i = 0; i < commandHistory.size(); i++) {
            System.out.println((i + 1) + ". " + commandHistory.get(i));
        }
    }
    
    // 命令行交互测试
    public static void main(String[] args) {
        HistoryCommand history = new HistoryCommand();
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("命令历史记录器 - 输入 'exit' 退出，输入 'history' 查看历史记录");
        
        while (true) {
            System.out.print("> ");
            String input = scanner.nextLine();
            
            // 添加到历史记录
            history.addCommand(input);
            
            if ("exit".equalsIgnoreCase(input)) {
                System.out.println("退出程序...");
                break;
            } else if ("history".equalsIgnoreCase(input)) {
                history.showAllCommands();
            } else if (input.startsWith("history ")) {
                try {
                    int n = Integer.parseInt(input.substring(8).trim());
                    history.showRecentCommands(n);
                } catch (NumberFormatException e) {
                    System.out.println("无效的数字格式");
                }
            } else if ("clear".equalsIgnoreCase(input)) {
                history.clearHistory();
                System.out.println("历史记录已清空");
            } else {
                System.out.println("执行命令: " + input);
            }
        }
        
        scanner.close();
    }
}