name: Financial Calculations description: Decimal precision and financial math patterns in LivestockAI

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