package calc

import "caltrack/types"

// BMR calculates Basal Metabolic Rate using Mifflin-St Jeor equation.
func BMR(cfg types.Config) float64 {
	weight := cfg.CurrentWeightKg
	height := float64(cfg.HeightCm)
	age := float64(cfg.Age)

	if cfg.Sex == "female" {
		return 10*weight + 6.25*height - 5*age - 161
	}
	return 10*weight + 6.25*height - 5*age + 5
}

// ActivityMultiplier returns the multiplier for the given activity level.
func ActivityMultiplier(level string) float64 {
	switch level {
	case "sedentary":
		return 1.2
	case "light":
		return 1.375
	case "moderate":
		return 1.55
	case "active":
		return 1.725
	default:
		return 1.55
	}
}

// TDEE calculates Total Daily Energy Expenditure.
func TDEE(cfg types.Config) float64 {
	return BMR(cfg) * ActivityMultiplier(cfg.ActivityLevel)
}

// DailyTarget calculates the daily calorie target accounting for desired deficit.
func DailyTarget(cfg types.Config) int {
	tdee := TDEE(cfg)
	// 1 kg of fat ≈ 7700 kcal
	dailyDeficit := (cfg.WeeklyLossKg * 7700) / 7
	target := tdee - dailyDeficit
	if target < 1200 {
		target = 1200
	}
	return int(target)
}

// Deficit returns the daily calorie deficit.
func Deficit(cfg types.Config) int {
	return int(TDEE(cfg)) - DailyTarget(cfg)
}