added files

CHANGELOG.md

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+# Revision history for databases
+
+## 0.1.0.0 -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.

app/Main.hs

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+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Main where
+
+import System.Environment
+import System.IO
+import Text.Read hiding (lift)
+import Control.Monad
+import Control.Monad.Trans.Maybe
+import Control.Monad.Trans.Class
+import Data.String.Interpolate
+
+import Network.Wai
+import Network.HTTP.Types (status200)
+import Network.Wai.Handler.Warp (run)
+import Data.Binary.Builder
+import Data.ByteString (ByteString)
+import Queries
+
+type Args = Int -- for now
+
+printError :: String -> IO ()
+printError = hPutStrLn stderr
+
+response200 :: ByteString -> Response
+response200 = responseBuilder status200 [("Content-Type", "text/plain")] . fromByteString 
+
+argsParse' :: MaybeT IO Args
+argsParse' = do
+  args <- lift getArgs
+  guard $ length args == 1
+  port <- hoistMaybe $ readMaybe $ head args
+  guard $ port > 0
+  guard $ port < 65535
+  hoistMaybe $ Just port
+
+app :: Application
+app req respond = do -- the points req and respond will probably be used later
+  results <- runTestQuery
+  respond $ response200 [i|The output is: #{results}|]
+
+main :: IO ()
+main = do
+  arguments <- runMaybeT argsParse'
+  case arguments of
+    Just port -> do
+      putStrLn [i|Running on port #{port}.|]
+      run port app
+    Nothing -> printError "Invalid input for port number."
+

app/Queries.hs

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+{-# LANGUAGE OverloadedStrings #-}
+
+module Queries (runTestQuery) where
+
+import Database.MySQL.Simple
+import Data.ByteString
+import Data.ByteString.Char8 as B
+import System.Environment
+
+connectDB :: IO Connection
+connectDB = do
+  host <- getEnv "DB_HOST"
+  user <- getEnv "DB_USER"
+  passwd <- getEnv "DB_PASSWORD"
+  database <- getEnv "DB_DATABASE"
+  connect defaultConnectInfo {
+                                connectHost = host,
+                                connectUser = user,
+                                connectPassword = passwd,
+                                connectDatabase = database
+                             }
+
+runTestQuery :: IO ByteString
+runTestQuery = do
+  c <- connectDB
+  execute_ c "DROP TABLE IF EXISTS diagnostic" -- we don't really care what these queries output
+  execute_ c "CREATE TABLE diagnostic(id INT PRIMARY KEY, text VARCHAR(255) NOT NULL)"
+  execute_ c "INSERT INTO diagnostic (id, text) VALUES (1, 'MySQL is working')"
+  rows <- query_ c "SELECT * FROM diagnostic" :: IO [(Int, String)]
+  return $ B.pack $ show rows 
+
+
+

databases.cabal

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+cabal-version:      3.0
+-- The cabal-version field refers to the version of the .cabal specification,
+-- and can be different from the cabal-install (the tool) version and the
+-- Cabal (the library) version you are using. As such, the Cabal (the library)
+-- version used must be equal or greater than the version stated in this field.
+-- Starting from the specification version 2.2, the cabal-version field must be
+-- the first thing in the cabal file.
+
+-- Initial package description 'databases' generated by
+-- 'cabal init'. For further documentation, see:
+--   http://haskell.org/cabal/users-guide/
+--
+-- The name of the package.
+name:               databases
+
+-- The package version.
+-- See the Haskell package versioning policy (PVP) for standards
+-- guiding when and how versions should be incremented.
+-- https://pvp.haskell.org
+-- PVP summary:     +-+------- breaking API changes
+--                  | | +----- non-breaking API additions
+--                  | | | +--- code changes with no API change
+version:            0.1.0.0
+
+-- A short (one-line) description of the package.
+-- synopsis:
+
+-- A longer description of the package.
+-- description:
+
+-- The license under which the package is released.
+license:            NONE
+
+-- The package author(s).
+author:             Robert
+
+-- An email address to which users can send suggestions, bug reports, and patches.
+maintainer:         [email protected]
+
+-- A copyright notice.
+-- copyright:
+build-type:         Simple
+
+-- Extra doc files to be distributed with the package, such as a CHANGELOG or a README.
+extra-doc-files:    CHANGELOG.md
+
+-- Extra source files to be distributed with the package, such as examples, or a tutorial module.
+-- extra-source-files:
+
+common warnings
+    ghc-options: -Wall
+
+executable databases
+    -- Import common warning flags.
+    import:           warnings
+
+    -- .hs or .lhs file containing the Main module.
+    main-is:          Main.hs
+
+    -- Modules included in this executable, other than Main.
+    other-modules: Queries
+
+    -- LANGUAGE extensions used by modules in this package.
+    -- other-extensions:
+
+    -- Other library packages from which modules are imported.
+    build-depends:    base ^>=4.18.0.0, string-interpolate, warp, transformers, wai, http-types, binary, bytestring, mysql-simple, aeson
+
+    -- Directories containing source files.
+    hs-source-dirs:   app
+
+    -- Base language which the package is written in.
+    default-language: Haskell2010