/**
 * HRV 与压力指数转换工具
 *
 * 提供统一的 HRV -> 压力指数映射及压力等级判定
 */

export type StressLevel = 'low' | 'moderate' | 'high';

export interface StressLevelInfo {
  level: StressLevel;
  label: string;
  description: string;
}

const MIN_HRV = 30;
const MAX_HRV = 130;

/**
 * 将 HRV（ms）转换为压力指数（0-100，数值越高表示压力越大）
 */
export function convertHrvToStressIndex(hrv: number | null | undefined): number | null {
  if (hrv == null || hrv <= 0) {
    return null;
  }

  const clamped = Math.max(MIN_HRV, Math.min(MAX_HRV, hrv));
  const normalized = 100 - ((clamped - MIN_HRV) / (MAX_HRV - MIN_HRV)) * 100;

  return Math.round(normalized);
}

/**
 * 根据压力指数获取压力等级信息
 */
export function getStressLevelInfo(stressIndex: number | null): StressLevelInfo {
  if (stressIndex == null) {
    return {
      level: 'moderate',
      label: '压力未知',
      description: '暂无有效的 HRV 数据',
    };
  }

  if (stressIndex >= 70) {
    return {
      level: 'high',
      label: '压力偏高',
      description: '建议立即放松，关注呼吸与休息',
    };
  }

  if (stressIndex >= 40) {
    return {
      level: 'moderate',
      label: '压力适中',
      description: '保持当前节奏，注意劳逸结合',
    };
  }

  return {
    level: 'low',
    label: '状态放松',
    description: '身心良好，继续保持',
  };
}