import type {
	DayMealsByType,
	Ingredient,
	Meal,
	MealItem,
	NutritionTotals,
} from '@/types/domain'

const round2 = (value: number): number => Math.round(value * 100) / 100

export const emptyTotals = (): NutritionTotals => ({
	protein_g: 0,
	carbs_g: 0,
	sugar_g: 0,
	fat_g: 0,
	fiber_g: 0,
	kcal: 0,
})

export const computeItemNutrition = (ingredient: Ingredient, grams: number): NutritionTotals => {
	const factor = grams / 100
	const protein = round2(ingredient.protein_g_100 * factor)
	const carbs = round2(ingredient.carbs_g_100 * factor)
	const sugar = round2(ingredient.sugar_g_100 * factor)
	const fat = round2(ingredient.fat_g_100 * factor)
	const fiber = round2(ingredient.fiber_g_100 * factor)
	const kcal = round2(protein * 4 + carbs * 4 + fat * 9)

	return {
		protein_g: protein,
		carbs_g: carbs,
		sugar_g: sugar,
		fat_g: fat,
		fiber_g: fiber,
		kcal,
	}
}

export const addTotals = (base: NutritionTotals, add: NutritionTotals): NutritionTotals => {
	return {
		protein_g: round2(base.protein_g + add.protein_g),
		carbs_g: round2(base.carbs_g + add.carbs_g),
		sugar_g: round2(base.sugar_g + add.sugar_g),
		fat_g: round2(base.fat_g + add.fat_g),
		fiber_g: round2(base.fiber_g + add.fiber_g),
		kcal: round2(base.kcal + add.kcal),
	}
}

export const computeMealTotals = (items: MealItem[]): NutritionTotals => {
	let totals = emptyTotals()

	for (const item of items) {
		if (!item.ingredient || item.grams <= 0) {
			continue
		}
		const itemTotals = computeItemNutrition(item.ingredient, item.grams)
		totals = addTotals(totals, itemTotals)
	}

	return totals
}

export const computeDayTotals = (mealsByType: Partial<DayMealsByType>): NutritionTotals => {
	let totals = emptyTotals()

	for (const meal of Object.values(mealsByType)) {
		if (!meal) {
			continue
		}
		const mealTotals = computeMealTotals(meal.items ?? [])
		totals = addTotals(totals, mealTotals)
	}

	return totals
}

export const withComputedMealTotals = (meal: Meal): Meal => {
	return {
		...meal,
		totals: computeMealTotals(meal.items ?? []),
	}
}