import { writeFileSync } from 'node:fs'
import path from 'node:path'

const SCOPE = 'https://www.googleapis.com/auth/youtube'
const FORM = { 'Content-Type': 'application/x-www-form-urlencoded' }

// Googles device-flöde för YT Music (ytmusicapi-kompatibel oauth.json).
// Klienten (settings-sidan) visar kod + länk och pollar tills godkänt.
export function ytmusicFlow({ config, store, fetchImpl = fetch }) {
  const dataDir = config.youtubarr?.dataDir ?? '/youtubarr-data'

  function creds() {
    const s = store.load()
    return { clientId: s.ytmusic?.clientId ?? '', clientSecret: s.ytmusic?.clientSecret ?? '' }
  }

  return {
    oauthPath: path.join(dataDir, 'oauth.json'),

    async start() {
      const { clientId } = creds()
      if (!clientId) return { error: 'spara Client ID först' }
      const res = await fetchImpl('https://oauth2.googleapis.com/device/code', {
        method: 'POST',
        headers: FORM,
        body: new URLSearchParams({ client_id: clientId, scope: SCOPE }).toString(),
      })
      const js = await res.json()
      if (!res.ok) return { error: js.error_description ?? js.error ?? 'okänt fel från Google' }
      return {
        deviceCode: js.device_code,
        userCode: js.user_code,
        url: js.verification_url ?? 'https://www.google.com/device',
        interval: js.interval ?? 5,
        expiresIn: js.expires_in,
      }
    },

    async poll(deviceCode) {
      const { clientId, clientSecret } = creds()
      if (!clientId || !clientSecret) return { status: 'error', message: 'client id/secret saknas' }
      const res = await fetchImpl('https://oauth2.googleapis.com/token', {
        method: 'POST',
        headers: FORM,
        body: new URLSearchParams({
          client_id: clientId,
          client_secret: clientSecret,
          device_code: deviceCode,
          grant_type: 'urn:ietf:params:oauth:grant-type:device_code',
        }).toString(),
      })
      const js = await res.json()
      if (js.error === 'authorization_pending' || js.error === 'slow_down') return { status: 'pending' }
      if (js.error) return { status: 'error', message: js.error_description ?? js.error }
      const token = {
        scope: js.scope ?? SCOPE,
        token_type: js.token_type ?? 'Bearer',
        access_token: js.access_token,
        refresh_token: js.refresh_token,
        expires_in: js.expires_in,
        expires_at: Math.floor(Date.now() / 1000) + (js.expires_in ?? 0),
      }
      writeFileSync(this.oauthPath, JSON.stringify(token, null, 2))
      return { status: 'klar' }
    },
  }
}