Financial Calculations

Financial Calculations

LivestockAI uses decimal.js for precise financial calculations. All monetary values are stored as DECIMAL(19,2) in the database.

Currency Utilities

Located in app/​features/​settings/​currency.ts:

import {
  toDecimal,
  toNumber,
  toDbString,
  formatCurrency,
  multiply,
  divide,
  sumAmounts,
} from '~/​features/​settings/​currency'

Core Functions

Converting Values

// From any input to Decimal
const amount = toDecimal('1234.56')
const amount2 = toDecimal(1234.56)

// To number for display
const num = toNumber('1234.56') // 1234.56

// To string for database
const dbVal = toDbString(1234.56) // "1234.56"

Arithmetic Operations

// Multiplication (quantity × price)
const total = multiply(100, 5.5) // Decimal(550)

// Division (with null safety)
const perUnit = divide(total, 100) // Decimal(5.50) or null

// Subtraction
const profit = subtract(revenue, costs)

// Sum multiple amounts
const totalCost = sumAmounts(feedCost, laborCost, overheadCost)

Formatting

// Format for display (uses user settings)
formatCurrency(1234.56) // "₦1,234.56" or "$1,234.56"

// Compact format
formatCurrencyCompact(1500000) // "₦1.5M"

// Percentage
calculatePercentage(50, 200) // 25

React Hook

In components, use the useFormatCurrency hook:

import { useFormatCurrency } from '~/​features/​settings'

function PriceDisplay({ amount }: { amount: number }) {
  const { format, symbol } = useFormatCurrency()

  return <span>{format(amount)}</​span> // "₦1,234.56"
}

Database Storage

All monetary values are stored as DECIMAL(19,2):

// Inserting
await db.insertInto('sales').values({
  totalAmount: toDbString(1234.56), // "1234.56"
})

// Reading
const sale = await db.selectFrom('sales').executeTakeFirst()
const amount = toNumber(sale.totalAmount) // 1234.56

Business Logic Examples

Batch Total Cost

export function calculateBatchTotalCost(
  initialQuantity: number,
  costPerUnit: number,
): string {
  if (initialQuantity <= 0 || costPerUnit < 0) {
    return toDbString(0)
  }
  return toDbString(multiply(initialQuantity, costPerUnit))
}

Profit Calculation

export function calculateProfit(
  revenue: MoneyInput,
  costs: MoneyInput,
): Decimal {
  return subtract(revenue, costs)
}

Related Skills

• multi-currency - Currency settings and formatting
• three-layer-architecture - Service layer calculations