{-# LANGUAGE OverloadedStrings #-}

module Main where

import Control.Applicative

import Database.HDBC.PostgreSQL (connectPostgreSQL)

import Network.Wai
import Network.Wai.Handler.Warp hiding (Connection)
import Network.HTTP.Types.Status
import Network.HTTP.Types.Header
import Network.HTTP.Types.Method

import Options.Applicative hiding (columns)

import PgStructure (printTables, printColumns, selectAll)

data AppConfig = AppConfig {
    configDbUri :: String
  , configPort  :: Int }

argParser :: Parser AppConfig
argParser = AppConfig
  <$> strOption (long "db" <> short 'd' <> metavar "URI"
    <> help "database uri to expose, e.g. postgres://user:pass@host:port/database")
  <*> option (long "port" <> short 'p' <> metavar "NUMBER" <> value 3000
    <> help "port number on which to run HTTP server")

main :: IO ()
main = do
  conf <- execParser (info (helper <*> argParser) describe)

  Prelude.putStrLn $ "Listening on port " ++ (show $ configPort conf :: String)
  run (configPort conf) $ app conf

  where
    describe = progDesc "create a REST API to an existing Postgres database"

app ::  AppConfig -> Application
app config req respond =
  case path of
    []      -> respond =<< responseLBS status200 [json] <$> (printTables =<< conn)
    [table] -> respond =<< if verb == methodOptions
                              then responseLBS status200 [json] <$> (printColumns table =<< conn)
                              else responseLBS status200 [json] <$> (selectAll table =<< conn)
    _       -> respond $ responseLBS status404 [] ""
  where
    path = pathInfo req
    verb = requestMethod req
    json = (hContentType, "application/json")
    conn = connectPostgreSQL $ configDbUri config