Bootstrapped my haskell client

haskell/src/SpaceTraders/Database.hs

@@ -0,0 +1,56 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module SpaceTraders.Database
+  ( close
+  , open
+  ) where
+
+import Control.Exception
+import qualified Database.SQLite.Simple as S
+import Text.RawString.QQ
+
+migrations :: [S.Query]
+migrations = [
+  [r|CREATE TABLE schema_version (
+       version INTEGER NOT NULL
+     );
+  |],
+  [r|CREATE TABLE tokens (
+       id INTEGER PRIMARY KEY,
+       data TEXT NOT NULL
+     );
+  |],
+  [r|CREATE TABLE agents (
+       id INTEGER PRIMARY KEY,
+       data TEXT NOT NULL
+     );
+  |],
+  [r|CREATE TABLE contracts (
+       id INTEGER PRIMARY KEY,
+       data TEXT NOT NULL
+     );
+  |]]
+
+close :: S.Connection -> IO ()
+close conn = S.close conn
+
+open :: IO S.Connection
+open = do
+  conn <- S.open "spacetraders.db"
+  S.execute_ conn "PRAGMA foreign_keys = ON;"
+  S.execute_ conn "PRAGMA journal_mode = WAL;"
+  S.withTransaction conn $ do
+    version <- getSchemaVersion conn `catch` defaultVersion
+    mapM_ (S.execute_ conn) $ drop version migrations
+    S.execute_ conn "DELETE FROM schema_version;"
+    S.execute conn "INSERT INTO schema_version (version) VALUES (?);" (S.Only $ length migrations)
+  return conn
+
+getSchemaVersion :: S.Connection -> IO Int
+getSchemaVersion conn = do
+  [[v]] <- S.query_ conn "SELECT version FROM schema_version;"
+  return v
+
+defaultVersion :: SomeException -> IO Int
+defaultVersion _ = return 0