{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
module OpenTelemetry.Resource.Host.Detector 
  ( detectHost
  , builtInHostDetectors
  , HostDetector
  ) where

import OpenTelemetry.Resource.Host

import qualified Data.Text as T
import Network.BSD
import Control.Monad
import System.Info (arch)

adaptedArch :: T.Text
adaptedArch = case arch of
  "aarch64" -> "arm64"
  "arm" -> "arm32"
  "x86_64" -> "amd64"
  "i386" -> "x86"
  "ia64" -> "ia64"
  "powerpc" -> "ppc32"
  "powerpc64" -> "ppc64"
  "powerpc64le" -> "ppc64"
  other -> T.pack other

-- | Detect as much host information as possible
detectHost :: IO Host
detectHost = do
  mhost <- foldM go Nothing builtInHostDetectors
  pure $ case mhost of
    Nothing -> Host Nothing Nothing Nothing Nothing Nothing Nothing Nothing
    Just host -> host
  where
    go Nothing hostDetector = hostDetector
    go mhost@(Just _host) _ = pure mhost

-- | A set of detectors for e.g. AWS, GCP, and other cloud providers.
--
-- Currently only emits hostName and hostArch. Additional detectors are
-- welcome via PR.
builtInHostDetectors :: [HostDetector]
builtInHostDetectors =
  [
  -- TODO
  -- AWS support
  -- GCP support
  -- any other user contributed
     fallbackHostDetector
  ]

type HostDetector = IO (Maybe Host)

fallbackHostDetector :: HostDetector
fallbackHostDetector = Just <$> do
  let hostId = Nothing
      hostType = Nothing
      hostArch = Just adaptedArch
      hostImageName = Nothing
      hostImageId = Nothing
      hostImageVersion = Nothing
  hostName <- Just . T.pack <$> getHostName
  pure Host{..}