{-# LANGUAGE StandaloneKindSignatures #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE AllowAmbiguousTypes #-} -- why?
{-# LANGUAGE GADTs #-}
{-# LANGUAGE InstanceSigs #-}

module Lib where
import Data.Kind (Type)

type GetRequest :: Type -> Type
-- I know we can use associated types but I found this easier to follow
type family GetRequest route

type GetContext :: Type -> Type
type family GetContext route

type GetResponse :: Type -> Type
type family GetResponse route

class Route route where
    -- how we know which route to use
    requestKey :: route -> String

    -- parse the route into object, should be an either 
    -- to signifiy this failed to deserialize for some reason
    requestParse :: route -> String -> GetRequest route

    -- transform request into response (will later return a new context as well)
    handle :: route -> GetRequest route -> GetResponse route
    -- handle :: GetContext route -> GetRequest route -> (GetContext route, GetResponse route)

    -- turn response object into string (will be json irl)
    responseSerialize :: route -> GetResponse route -> String

data InitRoute = InitRoute
data InitRequest = InitRequest
type instance GetRequest InitRoute = InitRequest
data InitResponse = InitResponse
type instance GetResponse InitRoute = InitResponse
instance Route InitRoute where
  requestKey _ = "init"
  requestParse _ _ = InitRequest
  handle _ InitRequest = InitResponse
  responseSerialize _ InitResponse = "init_ok"

data ReadRoute = ReadRoute
data ReadRequest = ReadRequest
type instance GetRequest ReadRoute = ReadRequest
data ReadResponse = ReadResponse
type instance GetResponse ReadRoute = ReadResponse
instance Route ReadRoute where
  requestKey _ = "read"
  requestParse _ _ = ReadRequest
  handle _ ReadRequest = ReadResponse
  responseSerialize _ ReadResponse = "read_ok"

-- go through all the routes, see which ones match
-- once we find a matching one return that type
routeHandler :: [RouteHolder] -> (String, String) -> IO String
routeHandler routes (reqType, reqPayload) = do
    -- irl add error handling
    let routeMatch = head $ filter (\route -> requestKey route == reqType) routes
    let parsedRequest = requestParse routeMatch reqPayload
    let response = handle routeMatch parsedRequest
    let serializedResponse = responseSerialize routeMatch response
    pure serializedResponse


-- how to solve this??
{-
    Lists in haskell have to homogenous so we can't make this
    we can create a sum type to contain all the routes but do I want that?
    I tried creating a routeholder but that didn't work
-}

data RouteHolder = forall a. Route a => RouteHolder a
instance Route RouteHolder where
  requestKey = requestKey
  requestParse = requestParse
  handle :: RouteHolder -> GetRequest RouteHolder -> GetResponse RouteHolder
  handle = handle
  responseSerialize = responseSerialize

myRoutes :: [RouteHolder]
myRoutes = [RouteHolder ReadRoute, RouteHolder InitRoute]

fakeLines :: [String]
fakeLines = ["init", "read", "something"]

-- fake reading
server :: Int -> IO ()
server lineNum = do
    let req = fakeLines !! lineNum
    resp <- routeHandler myRoutes (req, "") -- would be json not empty string irl
    print resp
    server (lineNum + 1)

someFunc :: IO ()
someFunc = putStrLn "someFunc"