import java.util.List;
import java.util.Random;

/**
 * 生成高中题目
 */
public class SeniorProblem implements ProblemsGenerator {
  private static final Random RANDOM = new Random();
  private final BracketManager bracketManager = new BracketManager();
  private final PowerManager powerManager = new PowerManager();
  private final TrigManager trigManager = new TrigManager();
  private final ExpressionBuilder expressionBuilder = new ExpressionBuilder();
  
  @Override
  public String generate() {
    String expression;
    boolean hasTrig;
    do {
      int numCount = RANDOM.nextInt(5) + 1;
      expression = expressionBuilder.generateBasicExpression(numCount);
      List<Integer> numPositions = expressionBuilder.getNumberPositions(expression);
      
      if (RANDOM.nextDouble() < 0.8) {
        int pairs = bracketManager.decideParenthesesPairs(numCount);
        if (pairs > 0) {
          expression = bracketManager.addParentheses(expression, pairs, numPositions);
        }
      }
      
      // 添加三角函数并检查是否存在
      expression = trigManager.addTrigOperations(expression, numPositions);
      List<Integer> trigPositions = expressionBuilder.getNumberPositions(expression);
      hasTrig = expression.contains("sin") || expression.contains("cos") || expression.contains("tan");
      
      // 40% 概率加幂运算，避免与 trig 重叠
      if (RANDOM.nextDouble() < 0.4) {
        expression = powerManager.addPowerOperationsAvoid(expression, numPositions, trigPositions);
      }
    } while (expressionBuilder.hasDivideByZero(expression) || !hasTrig);
    
    return expression;
  }
}