/**
 * 卡路里计算工具
 * 基于标准 MET (Metabolic Equivalent of Task) 公式
 */

export interface FoodItem {
    name: string
    emoji: string
    calories: number
    unit: string
}

export interface FoodComparison {
    food: FoodItem
    ratio: number
    message: string
}

export interface CalorieCalculationConfig {
    totalReps: number
    bpm: number
    userWeight?: number // 默认 60kg
}

// 食物卡路里数据库
export const FOOD_CALORIES: Record<string, FoodItem> = {
    apple: { name: '苹果', emoji: '🍎', calories: 52, unit: '个（100g）' },
    egg: { name: '鸡蛋', emoji: '🥚', calories: 70, unit: '个' },
    chocolate: { name: '巧克力', emoji: '🍫', calories: 54, unit: '块（10g）' },
    banana: { name: '香蕉', emoji: '🍌', calories: 89, unit: '根' },
    rice: { name: '米饭', emoji: '🍚', calories: 116, unit: '碗（100g）' },
}

/**
 * 计算卡路里消耗
 * 公式：卡路里 = MET × 体重(kg) × 时长(小时)
 *
 * @param config 计算配置
 * @returns 卡路里消耗（kcal，保留一位小数）
 */
export function calculateCalories(config: CalorieCalculationConfig): number {
    const MET = 3.5 // 握力环训练的标准 MET 值
    const weight = config.userWeight || 60 // 默认 60kg

    // 边界情况：无效输入
    if (config.totalReps <= 0 || config.bpm <= 0) {
        return 0
    }

    const secondsPerRep = 60 / config.bpm
    const activeTimeHours = (config.totalReps * secondsPerRep) / 3600

    const calories = MET * weight * activeTimeHours
    return Math.round(calories * 10) / 10 // 保留一位小数
}

/**
 * 自动匹配最接近的食物对比
 *
 * @param burnedCalories 消耗的卡路里
 * @returns 食物对比信息
 */
export function getFoodComparison(burnedCalories: number): FoodComparison {
    const foods = Object.values(FOOD_CALORIES)

    // 边界情况：食物数据库为空
    if (foods.length === 0) {
        throw new Error('食物数据库为空')
    }

    // 边界情况：卡路里为 0 或负数
    if (burnedCalories <= 0) {
        return {
            food: foods[0],
            ratio: 0,
            message: `暂无消耗`,
        }
    }

    // 找到卡路里最接近的食物
    const closest = foods.reduce((prev, curr) => {
        const prevDiff = Math.abs(prev.calories - burnedCalories)
        const currDiff = Math.abs(curr.calories - burnedCalories)
        return currDiff < prevDiff ? curr : prev
    })

    const ratio = burnedCalories / closest.calories
    const ratioRounded = Math.round(ratio * 100) / 100 // 保留两位小数

    // 格式化显示：ratio < 1 时显示分数形式更直观
    let displayText: string
    if (ratioRounded < 1) {
        displayText = `相当于 ${ratioRounded.toFixed(2)} 个${closest.name} ${closest.emoji}`
    } else {
        displayText = `相当于 ${ratioRounded.toFixed(2)} ${closest.unit}${closest.name} ${closest.emoji}`
    }

    return {
        food: closest,
        ratio: ratioRounded,
        message: displayText,
    }
}

/**
 * 格式化时长（秒 → 分:秒）
 *
 * @param seconds 秒数
 * @returns 格式化字符串（如 "3:45"）
 */
export function formatDuration(seconds: number): string {
    const mins = Math.floor(seconds / 60)
    const secs = seconds % 60
    return `${mins}:${secs.toString().padStart(2, '0')}`
}