import {createContext, useContext} from 'react'
import {QueryClient, useQuery} from '@tanstack/react-query'

import {APP_CONFIG_URL} from '#/env'

const qc = new QueryClient()
const appConfigQueryKey = ['app-config']

/**
 * Matches the types defined in our `app-config` worker
 */
type AppConfigResponse = {
  liveNow: {
    allow: string[]
    exceptions: {
      did: string
      allow: string[]
    }[]
  }
}

export const DEFAULT_APP_CONFIG_RESPONSE: AppConfigResponse = {
  liveNow: {
    allow: [],
    exceptions: [],
  },
}

let fetchAppConfigPromise: Promise<AppConfigResponse> | undefined

async function fetchAppConfig(): Promise<AppConfigResponse | null> {
  try {
    if (!fetchAppConfigPromise) {
      fetchAppConfigPromise = (async () => {
        const r = await fetch(`${APP_CONFIG_URL}/config`)
        if (!r.ok) throw new Error(await r.text())
        const data = await r.json()
        return data
      })()
    }
    return await fetchAppConfigPromise
  } catch (e) {
    fetchAppConfigPromise = undefined
    throw e
  }
}

const Context = createContext<AppConfigResponse>(DEFAULT_APP_CONFIG_RESPONSE)

export function Provider({children}: React.PropsWithChildren<{}>) {
  const {data} = useQuery<AppConfigResponse | null>(
    {
      staleTime: Infinity,
      queryKey: appConfigQueryKey,
      refetchInterval: query => {
        // refetch regularly if fetch failed, otherwise never refetch
        return query.state.status === 'error' ? 60e3 : Infinity
      },
      async queryFn() {
        return fetchAppConfig()
      },
    },
    qc,
  )
  return (
    <Context.Provider value={data ?? DEFAULT_APP_CONFIG_RESPONSE}>
      {children}
    </Context.Provider>
  )
}

export async function prefetchAppConfig() {
  try {
    const data = await fetchAppConfig()
    if (data) {
      qc.setQueryData(appConfigQueryKey, data)
    }
  } catch {}
}

export function useAppConfig() {
  const ctx = useContext(Context)
  if (!ctx) {
    throw new Error('useAppConfig must be used within a Provider')
  }
  return ctx
}