export type BillingTier = 'PRO' | 'BUSINESS'
export type BillingInterval = 'month' | 'year'

export interface DynamicPrice {
  display: string
  amount: number
  currency: string
}

export const DEFAULT_PRICES: Record<BillingTier, Record<BillingInterval, DynamicPrice>> = {
  PRO: {
    month: { display: '9,90 €', amount: 9.9, currency: 'EUR' },
    year: { display: '99,00 €', amount: 99, currency: 'EUR' },
  },
  BUSINESS: {
    month: { display: '29,90 €', amount: 29.9, currency: 'EUR' },
    year: { display: '299,00 €', amount: 299, currency: 'EUR' },
  },
}

export function formatBillingAmount(amount: number, currency = 'EUR'): string {
  const c = currency.toUpperCase()
  if (c === 'EUR') {
    return `${amount.toLocaleString('fr-FR', { minimumFractionDigits: 2, maximumFractionDigits: 2 })} €`
  }
  if (c === 'USD') {
    return `$${amount.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 })}`
  }
  if (c === 'GBP') {
    return `£${amount.toLocaleString('en-GB', { minimumFractionDigits: 2, maximumFractionDigits: 2 })}`
  }
  return `${amount.toLocaleString('fr-FR', { minimumFractionDigits: 2, maximumFractionDigits: 2 })} ${c}`
}

/** Prix annuel ramené au mois (99 € / an → 8,25 € / mois). */
export function yearToMonthlyEquivalent(yearAmount: number): number {
  return Math.round((yearAmount / 12) * 100) / 100
}

/** Remise réelle : 9,90 € × 12 vs 99 € / an → 17 %. */
export function annualDiscountPercent(monthlyAmount: number, yearlyAmount: number): number {
  const paidMonthlyForYear = monthlyAmount * 12
  if (paidMonthlyForYear <= 0) return 0
  const raw = (1 - yearlyAmount / paidMonthlyForYear) * 100
  if (!Number.isFinite(raw) || raw <= 0) return 0
  return Math.round(raw)
}