import { assert } from '../utils/assert'
import type { SizeFunction } from './types'

export function useItemSize<Props extends object>({
  containerSize,
  itemSize: itemSizeProp,
}: {
  containerSize: number;
  itemSize: number | string | SizeFunction<Props>;
}) {
  let itemSize: number | SizeFunction<Props>

  switch (typeof itemSizeProp) {
    case 'string': {
      assert(
        itemSizeProp.endsWith('%'),
        `Invalid item size: "${itemSizeProp}"; string values must be percentages (e.g. "100%")`,
      )
      assert(
        containerSize !== undefined,
        'Container size must be defined if a percentage item size is specified',
      )

      itemSize = (containerSize * parseInt(itemSizeProp)) / 100
      break
    }
    default: {
      itemSize = itemSizeProp
      break
    }
  }

  return itemSize
}