// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

import { useCallback, useEffect, useState } from "react"
import { apiFetch } from "src/api"
import { VersionInfo } from "src/types"

// see ipnstate.UpdateProgress
export type UpdateProgress = {
  status: "UpdateFinished" | "UpdateInProgress" | "UpdateFailed"
  message: string
  version: string
}

export enum UpdateState {
  UpToDate,
  Available,
  InProgress,
  Complete,
  Failed,
}

// useInstallUpdate initiates and tracks a Tailscale self-update via the LocalAPI,
// and returns state messages showing the progress of the update.
export function useInstallUpdate(currentVersion: string, cv?: VersionInfo) {
  const [updateState, setUpdateState] = useState<UpdateState>(
    cv?.RunningLatest ? UpdateState.UpToDate : UpdateState.Available
  )

  const [updateLog, setUpdateLog] = useState<string>("")

  const appendUpdateLog = useCallback(
    (msg: string) => {
      setUpdateLog(updateLog + msg + "\n")
    },
    [updateLog, setUpdateLog]
  )

  useEffect(() => {
    if (updateState !== UpdateState.Available) {
      // useEffect cleanup function
      return () => {}
    }

    setUpdateState(UpdateState.InProgress)

    apiFetch("/local/v0/update/install", "POST").catch((err) => {
      console.error(err)
      setUpdateState(UpdateState.Failed)
    })

    let tsAwayForPolls = 0
    let updateMessagesRead = 0

    let timer: NodeJS.Timeout | undefined

    function poll() {
      apiFetch<UpdateProgress[]>("/local/v0/update/progress", "GET")
        .then((res) => {
          // res contains a list of UpdateProgresses that is strictly increasing
          // in size, so updateMessagesRead keeps track (across calls of poll())
          // of how many of those we have already read. This is why it is not
          // initialized to zero here and we don't just use res.forEach()
          for (; updateMessagesRead < res.length; ++updateMessagesRead) {
            const up = res[updateMessagesRead]
            if (up.status === "UpdateFailed") {
              setUpdateState(UpdateState.Failed)
              if (up.message) appendUpdateLog("ERROR: " + up.message)
              return
            }

            if (up.status === "UpdateFinished") {
              // if update finished and tailscaled did not go away (ie. did not restart),
              // then the version being the same might not be an error, it might just require
              // the user to restart Tailscale manually (this is required in some cases in the
              // clientupdate package).
              if (up.version === currentVersion && tsAwayForPolls > 0) {
                setUpdateState(UpdateState.Failed)
                appendUpdateLog(
                  "ERROR: Update failed, still running Tailscale " + up.version
                )
                if (up.message) appendUpdateLog("ERROR: " + up.message)
              } else {
                setUpdateState(UpdateState.Complete)
                if (up.message) appendUpdateLog("INFO: " + up.message)
              }
              return
            }

            setUpdateState(UpdateState.InProgress)
            if (up.message) appendUpdateLog("INFO: " + up.message)
          }

          // If we have gone through the entire loop without returning out of the function,
          // the update is still in progress. So we want to poll again for further status
          // updates.
          timer = setTimeout(poll, 1000)
        })
        .catch((err) => {
          ++tsAwayForPolls
          if (tsAwayForPolls >= 5 * 60) {
            setUpdateState(UpdateState.Failed)
            appendUpdateLog(
              "ERROR: tailscaled went away but did not come back!"
            )
            appendUpdateLog("ERROR: last error received:")
            appendUpdateLog(err.toString())
          } else {
            timer = setTimeout(poll, 1000)
          }
        })
    }

    poll()

    // useEffect cleanup function
    return () => {
      if (timer) clearTimeout(timer)
      timer = undefined
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [])

  return !cv
    ? { updateState: UpdateState.UpToDate, updateLog: "" }
    : { updateState, updateLog }
}