const axios = require('axios')

const AUTHORIZE_TOKEN_URL = 'https://api.instagram.com/oauth/access_token'
const GRAPH_BASE_URL = 'https://graph.instagram.com'

/**
 * Exchange the short-lived OAuth `code` (from the Instagram Login redirect)
 * for a short-lived (1hr) user access token.
 */
async function exchangeCodeForToken (code) {
  const clientId = process.env.INSTAGRAM_CLIENT_ID
  const clientSecret = process.env.INSTAGRAM_APP_SECRET
  const redirectUri = process.env.INSTAGRAM_REDIRECT_URI

  if (!clientId || !clientSecret || !redirectUri) {
    throw new Error('Instagram OAuth is not configured (INSTAGRAM_CLIENT_ID/APP_SECRET/REDIRECT_URI)')
  }

  const params = new URLSearchParams({
    client_id: clientId,
    client_secret: clientSecret,
    grant_type: 'authorization_code',
    redirect_uri: redirectUri,
    code,
  })

  const { data } = await axios.post(AUTHORIZE_TOKEN_URL, params, {
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    timeout: 15000,
  })

  return {
    accessToken: data?.access_token,
    userId: data?.user_id,
  }
}

/**
 * Exchange a short-lived token for a long-lived one (~60 days).
 */
async function exchangeForLongLivedToken (shortLivedToken) {
  const clientSecret = process.env.INSTAGRAM_APP_SECRET
  if (!clientSecret) {
    throw new Error('INSTAGRAM_APP_SECRET is not configured')
  }

  const { data } = await axios.get(`${GRAPH_BASE_URL}/access_token`, {
    params: {
      grant_type: 'ig_exchange_token',
      client_secret: clientSecret,
      access_token: shortLivedToken,
    },
    timeout: 15000,
  })

  const expiresInSeconds = Number(data?.expires_in) || 60 * 24 * 60 * 60
  return {
    accessToken: data?.access_token,
    expiresAt: new Date(Date.now() + expiresInSeconds * 1000),
  }
}

/**
 * Refresh a long-lived token before it expires (must be at least 24h old, valid).
 */
async function refreshLongLivedToken (longLivedToken) {
  const { data } = await axios.get(`${GRAPH_BASE_URL}/refresh_access_token`, {
    params: {
      grant_type: 'ig_refresh_token',
      access_token: longLivedToken,
    },
    timeout: 15000,
  })

  const expiresInSeconds = Number(data?.expires_in) || 60 * 24 * 60 * 60
  return {
    accessToken: data?.access_token,
    expiresAt: new Date(Date.now() + expiresInSeconds * 1000),
  }
}

/**
 * Basic profile info for the connected Instagram Business/Creator account.
 */
async function getProfile (accessToken) {
  const { data } = await axios.get(`${GRAPH_BASE_URL}/me`, {
    params: {
      fields: 'id,username,account_type,name,biography,profile_picture_url',
      access_token: accessToken,
    },
    timeout: 15000,
  })

  return {
    id: data?.id,
    username: data?.username,
    accountType: data?.account_type || null,
    name: data?.name || null,
    biography: data?.biography || null,
    profilePictureUrl: data?.profile_picture_url || null,
  }
}

/**
 * Paginated media list (posts + reels). `after` is a Graph API paging cursor.
 */
async function getMedia (accessToken, { after } = {}) {
  const { data } = await axios.get(`${GRAPH_BASE_URL}/me/media`, {
    params: {
      fields: 'id,caption,media_type,media_product_type,media_url,permalink,timestamp',
      limit: 25,
      access_token: accessToken,
      ...(after ? { after } : {}),
    },
    timeout: 15000,
  })

  return {
    items: Array.isArray(data?.data) ? data.data : [],
    nextCursor: data?.paging?.cursors?.after || null,
    hasNext: Boolean(data?.paging?.next),
  }
}

module.exports = {
  exchangeCodeForToken,
  exchangeForLongLivedToken,
  refreshLongLivedToken,
  getProfile,
  getMedia,
}