Metadata.hs

module Effectful.OpenTelemetry.Metrics.Metadata where

import Control.Applicative ((<|>))
import Data.Text (Text)
import Effectful.OpenTelemetry.Protocol.Attributes (Attributes)
import GHC.Generics (Generic)
import Prelude

-- | The optional descriptive parameters an instrument may carry.
--
-- See <https://opentelemetry.io/docs/specs/otel/metrics/api/#instrument the OpenTelemetry spec>.
data Metadata = Metadata
    { attributes :: Attributes
    , description :: Maybe Text
    , unit :: Maybe Text
    }
    deriving stock (Generic, Show, Eq)

-- | Merges 'attributes', right-biased for the 'Maybe' fields.
instance Semigroup Metadata where
    a <> b =
        Metadata
            { attributes = a.attributes <> b.attributes
            , description = b.description <|> a.description
            , unit = b.unit <|> a.unit
            }

instance Monoid Metadata where
    mempty =
        Metadata
            { attributes = mempty
            , description = Nothing
            , unit = Nothing
            }