var Grant = require('../grant')


module.exports = function (args = {}) {
  var grant = Grant(args.config ? args : {config: args})
  app.config = grant.config

  var regex = new RegExp([
    '^',
    app.config.defaults.prefix,
    /(?:\/([^\/\?]+?))/.source, // /:provider
    /(?:\/([^\/\?]+?))?/.source, // /:override?
    /(?:\/$|\/?\?+.*)?$/.source, // querystring
  ].join(''), 'i')

  async function app (req, res, next) {
    var match = regex.exec(req.originalUrl)
    if (!match) {
      return next()
    }

    if (!req.session) {
      next(new Error('Grant: mount session middleware first'))
      return
    }
    if (req.method === 'POST' && !req.body) {
      next(new Error('Grant: mount body parser middleware first'))
      return
    }

    var {location, session, state} = await grant({
      method: req.method,
      params: {provider: match[1], override: match[2]},
      query: req.query,
      body: req.body,
      state: res.locals.grant,
      session: req.session.grant,
    })

    req.session.grant = session
    res.locals.grant = state
    location ? redirect(req, res, location) : next()
  }

  return app
}

var redirect = (req, res, location) =>
  typeof req.session.save === 'function' &&
    Object.getPrototypeOf(req.session).save.length
      ? req.session.save(() => res.redirect(location))
      : res.redirect(location)