svelte-i18n/src/runtime/includes/lookup.ts

import { getMessageFromDictionary } from '../stores/dictionary'
import { getFallbackOf } from '../stores/locale'

export const lookupCache: Record<string, Record<string, string>> = {}

const addToCache = (path: string, locale: string, message: string) => {
  if (!message) return message
  if (!(locale in lookupCache)) lookupCache[locale] = {}
  if (!(path in lookupCache[locale])) lookupCache[locale][path] = message
  return message
}

const searchForMessage = (path: string, locale: string): string => {
  if (locale == null) return null

  const message = getMessageFromDictionary(locale, path)
  if (message) return message

  return searchForMessage(path, getFallbackOf(locale))
}

export const lookup = (path: string, locale: string) => {
  if (locale in lookupCache && path in lookupCache[locale]) {
    return lookupCache[locale][path]
  }

  const message = searchForMessage(path, locale)
  if (message) {
    return addToCache(path, locale, message)
  }

  return null
}