import dayjs from 'dayjs';

export interface NutritionGoals {
  calories: number;
  proteinGoal: number;
  fatGoal: number;
  carbsGoal: number;
  fiberGoal: number;
  sodiumGoal: number;
}

export interface UserProfileForNutrition {
  weight?: string;
  height?: string;
  birthDate?: Date;
  gender?: 'male' | 'female';
}

/**
 * 计算用户的营养目标
 * 基于Mifflin-St Jeor公式计算基础代谢率，然后计算各营养素目标
 */
export const calculateNutritionGoals = (userProfile?: UserProfileForNutrition): NutritionGoals => {
  const weight = parseFloat(userProfile?.weight || '70'); // 默认70kg
  const height = parseFloat(userProfile?.height || '170'); // 默认170cm
  const age = userProfile?.birthDate ?
    dayjs().diff(dayjs(userProfile.birthDate), 'year') : 25; // 默认25岁
  const isWoman = userProfile?.gender === 'female';

  // 基础代谢率计算（Mifflin-St Jeor Equation）
  let bmr;
  if (isWoman) {
    bmr = 10 * weight + 6.25 * height - 5 * age - 161;
  } else {
    bmr = 10 * weight + 6.25 * height - 5 * age + 5;
  }

  // 总热量需求（假设轻度活动）
  const totalCalories = bmr * 1.375;

  // 计算营养素目标
  const proteinGoal = weight * 1.6; // 1.6g/kg
  const fatGoal = totalCalories * 0.25 / 9; // 25%来自脂肪，9卡/克
  const carbsGoal = (totalCalories - proteinGoal * 4 - fatGoal * 9) / 4; // 剩余来自碳水

  // 纤维目标：成人推荐25-35g/天
  const fiberGoal = 25;

  // 钠目标：WHO推荐<2300mg/天
  const sodiumGoal = 2300;

  return {
    calories: Math.round(totalCalories),
    proteinGoal: Math.round(proteinGoal * 10) / 10,
    fatGoal: Math.round(fatGoal * 10) / 10,
    carbsGoal: Math.round(carbsGoal * 10) / 10,
    fiberGoal,
    sodiumGoal,
  };
};

/**
 * 计算剩余可摄入卡路里
 * 公式：还能吃 = 基础代谢 + 运动消耗 - 已摄入饮食
 */
export const calculateRemainingCalories = (params: {
  basalMetabolism: number;
  activeCalories: number;
  consumedCalories: number;
}): number => {
  const { basalMetabolism, activeCalories, consumedCalories } = params;

  // 总消耗 = 基础代谢 + 运动消耗
  const totalBurned = basalMetabolism + activeCalories;

  // 剩余可摄入 = 总消耗 - 已摄入
  return totalBurned - consumedCalories;
};