Revert "one way migrations"

This reverts commit 383e27799a.

squeal-postgresql/src/Squeal/PostgreSQL/Migration.hs

@@ -38,9 +38,10 @@ Now we can define some `Migration`s to make our tables.
 
 >>> :{
 let
-  makeUsers :: Migration (Iso Definition) (Public '[]) '["public" ::: '["users" ::: 'Table UsersTable]]
-  makeUsers = Migration "make users table" Iso
-    { up = createTable #users
+  makeUsers :: Migration Definition (Public '[]) '["public" ::: '["users" ::: 'Table UsersTable]]
+  makeUsers = Migration
+    { name = "make users table"
+    , up = createTable #users
         ( serial `as` #id :*
           notNullable text `as` #name )
         ( primaryKey #id `as` #pk_users )
@@ -50,10 +51,11 @@ let
 
 >>> :{
 let
-  makeEmails :: Migration (Iso Definition) '["public" ::: '["users" ::: 'Table UsersTable]]
+  makeEmails :: Migration Definition '["public" ::: '["users" ::: 'Table UsersTable]]
     '["public" ::: '["users" ::: 'Table UsersTable, "emails" ::: 'Table EmailsTable]]
-  makeEmails = Migration "make emails table" Iso
-    { up = createTable #emails
+  makeEmails = Migration
+    { name = "make emails table"
+    , up = createTable #emails
           ( serial `as` #id :*
             notNullable int `as` #user_id :*
             nullable text `as` #email )
@@ -83,9 +85,9 @@ withConnection "host=localhost port=5432 dbname=exampledb" $
 Migrate
 Rollback
 
-We can also create a simple executable using `mainMigrateIso`.
+We can also create a simple executable using `defaultMain`.
 
->>> let main = mainMigrateIso "host=localhost port=5432 dbname=exampledb" migrations
+>>> let main = defaultMain "host=localhost port=5432 dbname=exampledb" migrations
 
 >>> withArgs [] main
 Invalid command: "". Use:
@@ -140,12 +142,10 @@ module Squeal.PostgreSQL.Migration
     Migration (..)
   , Migratory (..)
   , Terminally (..)
-  , Iso (..)
   , terminally
   , pureMigration
-  , pureMigrationIso
   , MigrationsTable
-  , mainMigrateIso
+  , defaultMain
   ) where
 
 import Control.Category
@@ -187,7 +187,8 @@ import Squeal.PostgreSQL.Transaction
 data Migration p schemas0 schemas1 = Migration
   { name :: Text -- ^ The `name` of a `Migration`.
     -- Each `name` in a `Migration` should be unique.
-  , instruction :: p schemas0 schemas1 -- ^ The instruction of a `Migration`.
+  , up   :: p schemas0 schemas1 -- ^ The `up` instruction of a `Migration`.
+  , down :: p schemas1 schemas0 -- ^ The `down` instruction of a `Migration`.
   } deriving (GHC.Generic)
 
 {- |
@@ -197,10 +198,6 @@ SQL `Definition`s and the category of impure `Terminally` `PQ` `IO` actions.
 -}
 class Category p => Migratory p where
 
-  migrate
-    :: Path (Migration p) schemas0 schemas1
-    -> PQ schemas0 schemas1 IO ()
-
   {- |
   Run a `Path` of `Migration`s.
   Create the `MigrationsTable` as @public.schema_migrations@ if it does not already exist.
@@ -208,7 +205,7 @@ class Category p => Migratory p where
   if not, `up` the `Migration` and insert its `name` in the `MigrationsTable`.
   -}
   migrateUp
-    :: Path (Migration (Iso p)) schemas0 schemas1
+    :: Path (Migration p) schemas0 schemas1
     -> PQ schemas0 schemas1 IO ()
 
   {- |
@@ -218,13 +215,12 @@ class Category p => Migratory p where
   if so, `down` the `Migration` and delete its `name` in the `MigrationsTable`.
   -}
   migrateDown
-    :: Path (Migration (Iso p)) schemas0 schemas1
+    :: Path (Migration p) schemas0 schemas1
     -> PQ schemas1 schemas0 IO ()
 
 instance Migratory Definition where
-  migrate = migrate . cmap pureMigration
-  migrateUp = migrateUp . cmap pureMigrationIso
-  migrateDown = migrateDown . cmap pureMigrationIso
+  migrateUp = migrateUp . cmap pureMigration
+  migrateDown = migrateDown . cmap pureMigration
 
 {- | `Terminally` turns an indexed monad transformer and the monad it transforms
 into a category by restricting the return type to @()@ and permuting the type variables.
@@ -236,11 +232,6 @@ newtype Terminally trans monad x0 x1 = Terminally
   { runTerminally :: trans x0 x1 monad () }
   deriving GHC.Generic
 
-data Iso c x y = Iso
-  { up :: c x y
-  , down :: c y x
-  } deriving GHC.Generic
-
 instance
   ( IndexedMonadTransPQ trans
   , Monad monad
@@ -265,26 +256,13 @@ pureMigration
   -> Migration (Terminally PQ IO) schemas0 schemas1
 pureMigration migration = Migration
   { name = name migration
-  , instruction = terminally . define $ instruction migration
-  }
-
--- | A `pureMigrationIso` turns a reversible `Migration`
--- involving only pure SQL
--- `Definition`s into a `Migration` that may be combined with arbitrary `IO`.
-pureMigrationIso
-  :: Migration (Iso Definition) schemas0 schemas1
-  -> Migration (Iso (Terminally PQ IO)) schemas0 schemas1
-pureMigrationIso migration = Migration
-  { name = name migration
-  , instruction = Iso
-    { up = terminally . define . up $ instruction migration
-    , down = terminally . define . down $ instruction migration
-    }
+  , up = terminally . define $ up migration
+  , down = terminally . define $ down migration
   }
 
 instance Migratory (Terminally PQ IO) where
 
-  migrate migration = unsafePQ . transactionally_ $ do
+  migrateUp migration = unsafePQ . transactionally_ $ do
     define createMigrations
     upMigrations migration
 
@@ -303,7 +281,7 @@ instance Migratory (Terminally PQ IO) where
       upMigration step = do
         executed <- queryExecuted step
         unless (executed == 1) $ do
-          unsafePQ . runTerminally $ instruction step
+          unsafePQ . runTerminally $ up step
           manipulateParams_ insertMigration (Only (name step))
 
       queryExecuted
@@ -313,8 +291,6 @@ instance Migratory (Terminally PQ IO) where
         result <- runQueryParams selectMigration (Only (name step))
         ntuples result
 
-  migrateUp = migrate . cmap (\(Migration n iso) -> Migration n (up iso))
-
   migrateDown migrations = unsafePQ . transactionally_ $ do
     define createMigrations
     downMigrations migrations
@@ -322,23 +298,23 @@ instance Migratory (Terminally PQ IO) where
     where
 
       downMigrations
-        :: Path (Migration (Iso (Terminally PQ IO))) schemas0 schemas1
+        :: Path (Migration (Terminally PQ IO)) schemas0 schemas1
         -> PQ MigrationsSchemas MigrationsSchemas IO ()
       downMigrations = \case
         Done -> return ()
         step :>> steps -> downMigrations steps >> downMigration step
 
       downMigration
-        :: Migration (Iso (Terminally PQ IO)) schemas0 schemas1
+        :: Migration (Terminally PQ IO) schemas0 schemas1
         -> PQ MigrationsSchemas MigrationsSchemas IO ()
       downMigration step = do
         executed <- queryExecuted step
         unless (executed == 0) $ do
-          unsafePQ . runTerminally . down $ instruction step
+          unsafePQ . runTerminally $ down step
           manipulateParams_ deleteMigration (Only (name step))
 
       queryExecuted
-        :: Migration (Iso (Terminally PQ IO)) schemas0 schemas1
+        :: Migration (Terminally PQ IO) schemas0 schemas1
         -> PQ MigrationsSchemas MigrationsSchemas IO Row
       queryExecuted step = do
         result <- runQueryParams selectMigration (Only (name step))
@@ -403,16 +379,16 @@ data MigrateCommand
   | MigrateUp
   | MigrateDown deriving (GHC.Generic, Show)
 
-{- | `mainMigrateIso` creates a simple executable
+{- | `defaultMain` creates a simple executable
 from a connection string and a list of `Migration`s. -}
-mainMigrateIso
+defaultMain
   :: Migratory p
   => ByteString
   -- ^ connection string
-  -> Path (Migration (Iso p)) db0 db1
+  -> Path (Migration p) db0 db1
   -- ^ migrations
   -> IO ()
-mainMigrateIso connectTo migrations = do
+defaultMain connectTo migrations = do
   command <- readCommandFromArgs
   maybe (pure ()) performCommand command