{-# LANGUAGE ConstraintKinds            #-}
{-# LANGUAGE DataKinds                  #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TypeFamilies               #-}
{-# LANGUAGE TypeOperators              #-}
{-# LANGUAGE UndecidableInstances       #-}
-----------------------------------------------------------------------------
--
-- Provides 'SwaggerUI' and corresponding 'swaggerUIServer' to embed
-- <http://swagger.io/swagger-ui/ swagger ui> into the application.
--
-- All of UI files are embedded into the binary.
--
-- /An example:/
--
-- @
-- -- | Actual API.
-- type BasicAPI = Get '[PlainText, JSON] Text
--     :\<|> "cat" :> Capture ":name" CatName :> Get '[JSON] Cat
--
-- -- | API type with bells and whistles, i.e. schema file and swagger-ui.
-- type API = 'SwaggerSchemaUI' "swagger-ui" "swagger.json"
--     :\<|> BasicAPI
--
-- -- | Servant server for an API
-- server :: Server API
-- server = 'swaggerSchemaUIServer' swaggerDoc
--     :\<|> (pure "Hello World" :\<|> catEndpoint)
--   where
--     catEndpoint name = pure $ Cat name False
-- @

module Servant.Swagger.UI.Core (
    -- * Swagger UI API
    SwaggerSchemaUI,
    SwaggerSchemaUI',

    -- * Implementation details
    SwaggerUiHtml(..),
    swaggerSchemaUIServerImpl,
    swaggerSchemaUIServerImpl',
    Handler,
    ) where

import Data.Aeson                     (ToJSON (..), Value)
import Data.ByteString                (ByteString)
import GHC.TypeLits                   (KnownSymbol, Symbol, symbolVal)
import Network.Wai.Application.Static (embeddedSettings, staticApp)
import Servant
import Servant.HTML.Blaze             (HTML)
import Text.Blaze                     (ToMarkup (..))

import qualified Data.Text as T

-- | Swagger schema + ui api.
--
-- @SwaggerSchemaUI "swagger-ui" "swagger.json"@ will result into following hierarchy:
--
-- @
-- \/swagger.json
-- \/swagger-ui
-- \/swagger-ui\/index.html
-- \/swagger-ui\/...
-- @
--
-- This type does not actually force served type to be @Swagger@ from @swagger2@ package,
-- it could be arbitrary @aeson@ 'Value'.
type SwaggerSchemaUI (dir :: Symbol) (schema :: Symbol) =
    SwaggerSchemaUI' dir (schema :> Get '[JSON] Value)

-- | Use 'SwaggerSchemaUI'' when you need even more control over
-- where @swagger.json@ is served (e.g. subdirectory).
type SwaggerSchemaUI' (dir :: Symbol) (api :: *) =
    api
    :<|> dir :>
        ( Get '[HTML] (SwaggerUiHtml dir api)
        :<|> "index.html" :> Get '[HTML] (SwaggerUiHtml dir api)
        :<|> Raw
        )

-- | Index file for swagger ui.
--
-- It's configured by the location of swagger schema and directory it lives under.
--
-- Implementation detail: the @index.html@ is prepopulated with parameters
-- to find schema file automatically.
data SwaggerUiHtml (dir :: Symbol) (api :: *) = SwaggerUiHtml T.Text

instance (KnownSymbol dir, HasLink api, Link ~ MkLink api Link, IsElem api api)
    => ToMarkup (SwaggerUiHtml dir api)
  where
    toMarkup (SwaggerUiHtml template) = preEscapedToMarkup
        $ T.replace "SERVANT_SWAGGER_UI_SCHEMA" schema
        $ T.replace "SERVANT_SWAGGER_UI_DIR" dir
        $ template
      where
        schema = T.pack $ uriPath . linkURI $ safeLink proxyApi proxyApi
        dir    = T.pack $ symbolVal (Proxy :: Proxy dir)
        proxyApi = Proxy :: Proxy api

swaggerSchemaUIServerImpl
    :: (Monad m, ServerT api m ~ m Value, ToJSON a)
    => T.Text -> [(FilePath, ByteString)]
    -> a -> ServerT (SwaggerSchemaUI' dir api) m
swaggerSchemaUIServerImpl indexTemplate files swagger
  = swaggerSchemaUIServerImpl' indexTemplate files $ return $ toJSON swagger

-- | Use a custom server to serve the Swagger spec source.
swaggerSchemaUIServerImpl'
    :: Monad m
    => T.Text
    -> [(FilePath, ByteString)]
    -> ServerT api m
    -> ServerT (SwaggerSchemaUI' dir api) m
swaggerSchemaUIServerImpl' indexTemplate files server
       = server
    :<|> return (SwaggerUiHtml indexTemplate)
    :<|> return (SwaggerUiHtml indexTemplate)
    :<|> rest
  where
    rest = Tagged $ staticApp $ embeddedSettings files