{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}

{- |
Module      : Unleash.Internal.JsonTypes
Copyright   : Copyright © FINN.no AS, Inc. All rights reserved.
License     : MIT
Stability   : experimental

Unleash domain transfer objects.
-}
module Unleash.Internal.JsonTypes (
    Features (..),
    Feature (..),
    Strategy (..),
    Constraint (..),
    Variant (..),
    Payload (..),
    Override (..),
    Context (..),
    emptyContext,
    Segment (..),
    VariantResponse (..),
    emptyVariantResponse,
    MetricsPayload (..),
    FullMetricsPayload (..),
    FullMetricsBucket (..),
    YesAndNoes (..),
    FullRegisterPayload (..),
    RegisterPayload (..),
) where

import Data.Aeson (FromJSON, Options (..), ToJSON (toJSON), defaultOptions, genericParseJSON, genericToJSON)
import Data.Aeson.Types (parseJSON)
import Data.Map.Strict (Map)
import Data.Text (Text)
import Data.Time (UTCTime)
import GHC.Generics (Generic)

-- | Feature toggle set.
data Features = Features
    { version :: Int,
      features :: [Feature],
      segments :: Maybe [Segment]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Feature toggle.
data Feature = Feature
    { name :: Text,
      description :: Maybe Text,
      enabled :: Bool,
      strategies :: [Strategy],
      variants :: Maybe [Variant]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Strategy. Encompasses all (supported) types of strategies.
data Strategy = Strategy
    { name :: Text,
      parameters :: Maybe (Map Text Text),
      constraints :: Maybe [Constraint],
      segments :: Maybe [Int]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Strategy constraint.
data Constraint = Constraint
    { contextName :: Text,
      operator :: Text,
      values :: Maybe [Text],
      caseInsensitive :: Maybe Bool,
      inverted :: Maybe Bool,
      value :: Maybe Text
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Variant.
data Variant = Variant
    { name :: Text,
      payload :: Maybe Payload,
      weight :: Int,
      stickiness :: Maybe Text,
      overrides :: Maybe [Override]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

typeWorkAroundOptions :: Options
typeWorkAroundOptions =
    defaultOptions {fieldLabelModifier = typeWorkaround}
    where
        typeWorkaround :: String -> String
        typeWorkaround s = case s of
            "type" -> "type_"
            "type_" -> "type"
            _ -> s

-- | Variant payload.
data Payload = Payload
    { -- | Payload type.
      type_ :: Text,
      -- | Payload.
      value :: Text
    }
    deriving stock (Eq, Show, Generic)

instance FromJSON Payload where
    parseJSON = genericParseJSON typeWorkAroundOptions

instance ToJSON Payload where
    toJSON = genericToJSON typeWorkAroundOptions

-- | Contextual override.
data Override = Override
    { contextName :: Text,
      values :: [Text]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Client context.
data Context = Context
    { -- | User ID.
      userId :: Maybe Text,
      -- | Session ID.
      sessionId :: Maybe Text,
      -- | Remote address.
      remoteAddress :: Maybe Text,
      -- | Current UTC time.
      currentTime :: Maybe Text,
      -- | Application environment (e.g. @Production@).
      environment :: Maybe Text,
      -- | Application name.
      appName :: Maybe Text,
      -- | Other custom properties.
      properties :: Maybe (Map Text (Maybe Text))
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | An initial client context.
emptyContext :: Context
emptyContext = Context Nothing Nothing Nothing Nothing Nothing Nothing Nothing

-- | Segment.
data Segment = Segment
    { id :: Int,
      constraints :: [Constraint]
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | Variant response.
data VariantResponse = VariantResponse
    { -- | Variant name.
      name :: Text,
      -- | Variant payload.
      payload :: Maybe Payload,
      -- | Variant state.
      enabled :: Bool
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (FromJSON, ToJSON)

-- | The default (disabled) variant response.
emptyVariantResponse :: VariantResponse
emptyVariantResponse =
    VariantResponse
        { name = "disabled",
          payload = Nothing,
          enabled = False
        }

-- | Metrics payload.
data MetricsPayload = MetricsPayload
    { -- | Application name.
      appName :: Text,
      -- | Instance identifier (typically hostname).
      instanceId :: Text,
      -- | Start timestamp for this interval.
      start :: UTCTime,
      -- | End timestamp for this interval.
      stop :: UTCTime,
      -- | Feature toggle usage metrics.
      toggles :: [(Text, Bool)]
    }
    deriving stock (Eq, Show, Generic)

-- | Full metrics payload.
data FullMetricsPayload = FullMetricsPayload
    { appName :: Text,
      instanceId :: Text,
      bucket :: FullMetricsBucket
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (ToJSON)

-- | Full metrics bucket.
data FullMetricsBucket = FullMetricsBucket
    { -- | Start timestamp for this interval.
      start :: UTCTime,
      -- | End timestamp for this interval.
      stop :: UTCTime,
      -- | Feature toggle usage metrics.
      toggles :: Map Text YesAndNoes
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (ToJSON)

-- | Helper data structure for metrics.
data YesAndNoes = YesAndNoes
    { -- | The number of times the feature toggle was fetched as enabled in an interval.
      yes :: Int,
      -- | The number of times the feature toggle was fetched as disabled in an interval.
      no :: Int
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (ToJSON)

-- | Full client registration payload.
data FullRegisterPayload = FullRegisterPayload
    { -- | Application name.
      appName :: Text,
      -- | Instance identifier (typically hostname).
      instanceId :: Text,
      -- | Unleash client SDK version.
      sdkVersion :: Text,
      -- | Supported strategies.
      strategies :: [Text],
      -- | When the application was started.
      started :: UTCTime,
      -- | Expected metrics sending interval.
      interval :: Int
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (ToJSON)

-- | Client registration payload.
data RegisterPayload = RegisterPayload
    { -- | Application name.
      appName :: Text,
      -- | Instance identifier (typically hostname).
      instanceId :: Text,
      -- | Client application startup timestamp.
      started :: UTCTime,
      -- | Intended metrics sending interval.
      intervalSeconds :: Int
    }
    deriving stock (Eq, Show, Generic)
    deriving anyclass (ToJSON)