import type { Product } from '@/types'

export type QuantityMode = 'meter' | 'roll'

export function rollMetersForProduct(product: Product): number {
  if (product.rollMeters && product.rollMeters > 0) return product.rollMeters
  if (product.minMeterage > 0) return product.minMeterage
  return 50
}

export function orderMultiplierForProduct(product: Product): number {
  const step = product.orderMultiplier ?? product.orderStep
  return step && step > 0 ? step : 10
}

export function meterageFromQuantity(product: Product, mode: QuantityMode, value: number): number {
  if (mode === 'roll') return value * rollMetersForProduct(product)
  return value
}

export function rollsFromMeterage(product: Product, meterage: number): number {
  const rollMeters = rollMetersForProduct(product)
  return rollMeters > 0 ? meterage / rollMeters : 0
}

/** همان قواعد سرور هنگام ثبت سفارش */
export function validateOrderMeterage(
  product: Product,
  meterage: number,
  minRollsSetting = 1,
): string | null {
  if (!meterage || meterage <= 0) {
    return 'مقدار باید بزرگ‌تر از صفر باشد.'
  }
  if (meterage < product.minMeterage) {
    return `حداقل متراژ برای ${product.name} برابر ${product.minMeterage} است`
  }
  const multiplier = orderMultiplierForProduct(product)
  const rem = Math.round((meterage / multiplier) * 1000) / 1000
  if (Math.abs(rem - Math.round(rem)) > 1e-6) {
    return `متراژ ${product.name} باید مضرب ${multiplier} باشد`
  }
  const rollMeters = rollMetersForProduct(product)
  const minRolls = minRollsSetting > 0 ? minRollsSetting : 1
  if (meterage / rollMeters + 1e-9 < minRolls) {
    return `حداقل سفارش برای ${product.name} برابر ${minRolls} طاقه است`
  }
  return null
}