otel-effectful-1.0.0: src/Effectful/OpenTelemetry/Metrics/Instrument.hs

{-# LANGUAGE GADTs #-}

module Effectful.OpenTelemetry.Metrics.Instrument where

import Data.Text (Text)
import Effectful.OpenTelemetry.Metrics.Measurement (Measurement)
import Effectful.OpenTelemetry.Timestamp (Timestamp)
import Prelude

-- | Used to report 'Measurement's.
--
-- See <https://opentelemetry.io/docs/specs/otel/metrics/api/#instrument the OpenTelemetry spec>.
class Instrument i where
    -- | The name of the instrument.
    name :: i -> Text

    -- | Take a reading of the instrument, along with the time it was recorded.
    --
    -- An instrument may report several 'Measurement's: an asynchronous
    -- instrument backed by a multiple-instrument callback reports one per
    -- metric it covers. Reporting none means there is nothing to export yet.
    sample :: i -> IO [(Timestamp, Measurement)]

-- | A wrapper type for any 'Instrument' @i@ for all @i@.
data SomeInstrument = forall i. (Instrument i) => SomeInstrument i

instance Instrument SomeInstrument where
    name (SomeInstrument i) = name i
    sample (SomeInstrument i) = sample i