import { NextRequest, NextResponse } from "next/server"
import { AuthError } from "next-auth"

import { Lang } from "@/constants/languages"
import { env } from "@/env/server"
import { badRequest, internalServerError } from "@/server/errors/next"

import { signIn } from "@/auth"

export async function GET(
  request: NextRequest,
  context: { params: { lang: Lang } }
) {
  const returnUrl = request.headers.get("x-returnurl")

  // If all else fails, always redirect to startpage
  const finalDestination =
    returnUrl ||
    request.headers.get("x-redirect-to") ||
    request.nextUrl.searchParams.get("redirectTo") ||
    request.headers.get("Referer") ||
    "/"

  let redirectTo = finalDestination
  if (!returnUrl) {
    // This is a regular login request, not a seamless login request
    // We should initiate the seamless login flow
    try {
      let redirectUrlValue
      switch (context.params.lang) {
        case Lang.da:
          redirectUrlValue = env.SEAMLESS_LOGIN_DA
          break
        case Lang.de:
          redirectUrlValue = env.SEAMLESS_LOGIN_DE
          break
        case Lang.en:
          redirectUrlValue = env.SEAMLESS_LOGIN_EN
          break
        case Lang.fi:
          redirectUrlValue = env.SEAMLESS_LOGIN_FI
          break
        case Lang.no:
          redirectUrlValue = env.SEAMLESS_LOGIN_NO
          break
        case Lang.sv:
          redirectUrlValue = env.SEAMLESS_LOGIN_SV
          break
      }
      const redirectUrl = new URL(redirectUrlValue)
      redirectUrl.searchParams.set("returnurl", finalDestination)
      redirectTo = redirectUrl.toString()
    } catch (e) {
      console.error("Unable to create URL for seamless login")
      console.error(e)
      return internalServerError()
    }
  }

  try {
    /**
     * Passing `redirect: false` to `signIn` will return the URL instead of
     * automatically redirecting to it inside of `signIn`.
     * https://github.com/nextauthjs/next-auth/blob/3c035ec/packages/next-auth/src/lib/actions.ts#L76
     */
    const url = await signIn(
      "curity",
      {
        redirectTo,
        redirect: false,
      },
      {
        ui_locales: context.params.lang,
      }
    )

    if (url) {
      return NextResponse.redirect(url)
    }
  } catch (error) {
    if (error instanceof AuthError) {
      console.log({ signInAuthError: error })
    } else {
      console.log({ signInError: error })
    }
  }

  return badRequest()
}