import type { i18n } from 'i18next'
import { writable, type Readable, type Writable } from 'svelte/store'

export interface TranslationService {
  i18n: Readable<i18n>
}

export const isLoading = writable(true)

export class I18NextTranslationStore implements TranslationService {
  public i18n: Writable<i18n>
  public isLoading: Writable<boolean>

  constructor(i18n: i18n) {
    this.i18n = this.createInstance(i18n)
    this.isLoading = this.createLoadingInstance(i18n)
  }

  private createInstance(i18n: i18n): Writable<i18n> {
    const i18nWritable = writable(i18n)

    i18n.on('initialized', () => {
      i18nWritable.set(i18n)
    })
    i18n.on('loaded', () => {
      i18nWritable.set(i18n)
    })
    i18n.on('added', () => i18nWritable.set(i18n))
    i18n.on('languageChanged', () => {
      i18nWritable.set(i18n)
    })
    return i18nWritable
  }

  private createLoadingInstance(i18n: i18n): Writable<boolean> {
    // if loaded resources are empty || {}, set loading to true
    i18n.on('loaded', (resources) => {
      if (Object.keys(resources).length !== 0) {
        isLoading.set(false)
      }
    })

    // if resources failed loading, set loading to true
    i18n.on('failedLoading', () => {
      isLoading.set(true)
    })

    return isLoading
  }
}

export const createI18nStore = (i18n: i18n) => {
  const i18nStore = new I18NextTranslationStore(i18n)
  return i18nStore.i18n
}