import { metrics } from "@opentelemetry/api"
import { revalidateTag, unstable_cache } from "next/cache"

import { env } from "@/env/server"

import { generateServiceTokenTag } from "@/utils/generateTag"

import { ServiceTokenResponse } from "@/types/tokens"

// OpenTelemetry metrics: Service token
const meter = metrics.getMeter("trpc.context.serviceToken")
const fetchServiceTokenCounter = meter.createCounter(
  "trpc.context.serviceToken.fetch-new-token"
)
const fetchTempServiceTokenCounter = meter.createCounter(
  "trpc.context.serviceToken.fetch-temporary"
)
const fetchServiceTokenFailCounter = meter.createCounter(
  "trpc.context.serviceToken.fetch-fail"
)

async function fetchServiceToken(scopes: string[]) {
  fetchServiceTokenCounter.add(1)
  const response = await fetch(`${env.CURITY_ISSUER_USER}/oauth/v2/token`, {
    method: "POST",
    headers: {
      "Content-Type": "application/x-www-form-urlencoded",
      Accept: "application/json",
    },
    body: new URLSearchParams({
      grant_type: "client_credentials",
      client_id: env.CURITY_CLIENT_ID_SERVICE,
      client_secret: env.CURITY_CLIENT_SECRET_SERVICE,
      scope: scopes.join(" "),
    }),
  })

  if (!response.ok) {
    fetchServiceTokenFailCounter.add(1, {
      error_type: "http_error",
      error: JSON.stringify({
        status: response.status,
        statusText: response.statusText,
      }),
    })
    throw new Error("Failed to obtain service token")
  }

  return response.json()
}

export async function getServiceToken(): Promise<ServiceTokenResponse> {
  try {
    const scopes = ["profile", "hotel", "booking"]
    const tag = generateServiceTokenTag(scopes)
    const getCachedJwt = unstable_cache(
      async (scopes) => {
        const jwt = await fetchServiceToken(scopes)

        const expiresAt = Date.now() + jwt.expires_in * 1000
        return { expiresAt, jwt }
      },
      [tag],
      { tags: [tag] }
    )

    const cachedJwt = await getCachedJwt(scopes)
    if (cachedJwt.expiresAt < Date.now()) {
      console.log(
        "trpc.context.serviceToken: Service token expired, revalidating tag"
      )
      revalidateTag(tag)

      console.log(
        "trpc.context.serviceToken: Fetching new temporary service token."
      )
      fetchTempServiceTokenCounter.add(1)
      const newToken = await fetchServiceToken(scopes)
      return newToken
    }

    return cachedJwt.jwt
  } catch (error) {
    console.error("Error fetching service token:", error)
    throw error
  }
}