{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE OverloadedStrings #-}

module Main where
import GHC.Generics

import Servant
import Data.Aeson.Types (ToJSON, FromJSON)
import Data.Text (Text)
import qualified Data.Text as T

type API = "position" :> Capture "x" Int :> Capture "y" Int :> Get '[JSON] Position
      :<|> "hello" :> QueryParam "name" Text :> Get '[JSON] HelloMessage
      :<|> "marketing" :> ReqBody '[JSON] ClientInfo :> Post '[JSON] Email

data Position = Position
  { xCoord :: Int
  , yCoord :: Int
  } deriving Generic

instance ToJSON Position

newtype HelloMessage = HelloMessage {
  msg :: Text
  } deriving Generic

instance ToJSON HelloMessage

data ClientInfo = ClientInfo
  { clientName :: Text
  , clientEmail :: Text
  , clientAge :: Int
  , clientInterestedIn :: [Text]
  } deriving Generic

instance FromJSON ClientInfo
instance ToJSON ClientInfo

data Email = Email
  { from :: Text
  , to :: Text
  , subject :: Text
  , body :: Text
  } deriving Generic

instance ToJSON Email

emailForClient :: ClientInfo -> Email
emailForClient client = Email from' to' sub' body'
  where
    from' = "great@company.com"
    to' = clientEmail client
    sub'= "Hey " <> clientName client <> " we miss you!"
    body' :: Text
    body'= "Hi " <> clientName client <> T.pack "\n\n"
        <> T.pack "since you've recently turned " <> T.pack (show $ clientAge client)
        <> T.pack ", Have you checked out our latest "
        <> T.intercalate (T.pack ", ") (clientInterestedIn client)
        <> T.pack " products? Give us a visit!"

main :: IO ()
main = do
  putStrLn "Hello, world!"