public class JuniorQuestionGenerator extends AbstractQuestionGenerator {
	private static final String[] OPERATORS = {"+", "-", "×", "÷"};   
    private static boolean h = false;
    private static StringBuilder q;
    
    @Override
    public String generateQuestion() {
        int attempts = 0;
        while (attempts < 100) {
            attempts++;
            
            int operandCount = random.nextInt(5) + 1; // 1~5个操作数
            StringBuilder question = new StringBuilder();
            boolean hasSpecialOperator = false;
            
            AddSpecialOperator(operandCount, hasSpecialOperator, question);
            hasSpecialOperator = h;
            question = q;
            
            
            String result = addReasonableParentheses(question.toString(), operandCount);
            result = ensureBalancedParentheses(result);
            
            // 检查平方后是否有运算符
            if (!hasProperOperatorSpacing(result)) {
                continue;
            }
            
            if (isQuestionUnique(result) && isValidParentheses(result) && 
                (hasOperator(result) || hasSpecialOperator)) {
                addToGeneratedQuestions(result);
                String regex = "(?<!\\s)\\)(?=[^)]*$)";
                result = result.replaceAll(regex, " )");
                return result;
            }
        }
        return "√4 + 3²"; // 备用题目
    }  
    
    private void AddSpecialOperator(int operandCount, boolean hasSpecialOperator, StringBuilder question) {
    	for (int i = 0; i < operandCount; i++) {
            if (!hasSpecialOperator && random.nextDouble() < 0.4) {// 决定是否添加特殊运算符（平方或开方）
                if (random.nextBoolean()) {
                    question.append(generateNumber()).append("²");
                } else {
                    question.append("√").append(generateNumber());
                }
                hasSpecialOperator = true;
            } else {
                question.append(generateNumber());
            }
            if (i < operandCount - 1) {
                String operator = generateOperator(OPERATORS);
                question.append(" ").append(operator).append(" ");
            }
        }
        if (!hasSpecialOperator) {// 如果还没有特殊运算符，强制添加一个
            String[] parts = question.toString().split(" ");
            int pos = random.nextInt(parts.length / 2 + 1) * 2;
            if (pos >= parts.length) pos = parts.length - 1;
            if (random.nextBoolean()) {
                parts[pos] = parts[pos] + "²";
            } else {
                parts[pos] = "√" + parts[pos];
            }
            question = new StringBuilder(String.join(" ", parts));
        	hasSpecialOperator = true;
        }
        h = hasSpecialOperator;
        q = question;
    }
    
    private boolean hasProperOperatorSpacing(String expression) {
        String[] parts = expression.split(" ");
        for (int i = 0; i < parts.length - 1; i++) {
            // 如果当前部分是平方或开方，下一部分必须是运算符
            if ((parts[i].endsWith("²") || parts[i].startsWith("√")) && 
                i + 1 < parts.length && !isOperator(parts[i + 1])) {
                return false;
            }
            // 如果当前部分是数字，下一部分不是运算符，也不合理
            if (parts[i].matches("\\d+") && i + 1 < parts.length && !isOperator(parts[i + 1])) {
                return false;
            }
        }
        return true;
    }
    
    private boolean isOperator(String str) {
        return str.equals("+") || str.equals("-") || str.equals("×") || str.equals("÷");
    }
    
    public String addReasonableParentheses(String expression, int operandCount) { 
    	if (operandCount <= 2 || random.nextDouble() < 0.4) {
            return expression;
        }
        
        String[] parts = expression.split(" ");
        if (parts.length < 5) return expression;
        
        StringBuilder newExpr = new StringBuilder();
        int start = random.nextInt(Math.max(1, parts.length / 2 - 1));
        int end = start + 1 + random.nextInt(Math.max(1, parts.length / 2 - start - 1));
        
        for (int i = 0; i < parts.length; i++) {
            if (i == start * 2 && start * 2 < parts.length - 3) {
                newExpr.append("( ");
            }
            newExpr.append(parts[i]);
            if (i == end * 2 && i < parts.length - 2 && end * 2 > start * 2 + 2) {
                newExpr.append(" )");
            }
            if (i < parts.length - 1) {
                newExpr.append(" ");
            }
        }
        
        return newExpr.toString().trim();
    	
    }
    
}