import type { TolgeeStaticData } from '@tolgee/svelte'
import { env } from '$env/dynamic/private'
import { loadAsync } from 'jszip'

class TranslationCacheItem {
  constructor(
    public translastions: TolgeeStaticData,
    public timestamp: number,
  ) {}

  get isExpired(): boolean {
    const now = Date.now()

    const TTL = Number(env.TRANSLATION_CACHE_TTL)

    if (Number.isNaN(TTL)) return false

    return now - this.timestamp > TTL * 1000
  }
}

class LanguageService {
  protected cache: Record<string, TranslationCacheItem> = {}

  async getTranslations(
    languageCodes: string[],
  ): Promise<Record<string, TolgeeStaticData>> {
    const languageCodesToFetch = new Set<string>()

    const result: Record<string, TolgeeStaticData> = {}

    for (const lang of languageCodes) {
      const cacheItem = this.cache[lang]

      if (!cacheItem || cacheItem.isExpired) {
        languageCodesToFetch.add(lang)
        continue
      }

      Object.assign(result, { [lang]: cacheItem.translastions })
    }

    if (languageCodesToFetch.size === 0) {
      return result
    }

    const freshTranslations = await this.fetchTranslations(
      Array.from(languageCodesToFetch),
    )

    for (const langKey of Object.keys(freshTranslations)) {
      if (langKey in this.cache) {
        delete this.cache[langKey]
      }
      this.cache[langKey] = new TranslationCacheItem(
        freshTranslations[langKey],
        Date.now(),
      )
      result[langKey] = Object.assign(freshTranslations[langKey])
    }

    return result
  }

  protected async fetchTranslations(languageCodes: string | string[]) {
    const url = new URL(`${env.TOLGEE_API_URL}/v2/projects/2/export`)

    url.searchParams.append('format', 'JSON')
    url.searchParams.append('zip', 'true')
    url.searchParams.append('supportArrays', 'true')

    for (const lang of languageCodes) {
      url.searchParams.append('languages', lang)
    }

    if (!env.TOLGEE_API_KEY) {
      throw new Error('TOLGEE_API_KEY not set')
    }

    const response = await fetch(url, {
      method: 'GET',
      headers: {
        'X-API-Key': env.TOLGEE_API_KEY,
        Accept: 'application/*',
      },
    })

    const zippedBuffer = await response.arrayBuffer()

    const zip = await loadAsync(zippedBuffer)

    const translations: Record<string, TolgeeStaticData> = {}

    for (const [filename, file] of Object.entries(zip.files)) {
      if (!file.dir && filename.endsWith('.json')) {
        const content = await file.async('string')
        const locale = filename.replace('.json', '')
        translations[locale] = JSON.parse(content)
      }
    }

    return translations
  }
}

export const languageService = new LanguageService()