{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}

module Migration (testMigrations) where

import Control.Monad.Reader (runReaderT)
import qualified Data.Text as Text
import Database.Persist.Migration
import Database.Persist.Migration.Core (getMigration)
import Test.Tasty (TestName, TestTree, testGroup)

import Utils.Backends
    (MockDatabase(..), defaultDatabase, setDatabase, withTestBackend)
import Utils.Goldens (goldenVsText)

-- | Build a test suite for the given MigrateBackend.
testMigrations :: FilePath -> MigrateBackend -> TestTree
testMigrations dir backend = testGroup "goldens"
  [ goldenMigration' "Basic migration" defaultDatabase
      [ 0 ~> 1 :=
        [ CreateTable
            { name = "person"
            , schema =
                [ Column "id" SqlInt32 []
                , Column "name" SqlString [NotNull]
                , Column "age" SqlInt32 [NotNull]
                , Column "alive" SqlBool [NotNull]
                , Column "hometown" SqlInt64 [References ("cities", "id")]
                ]
            , constraints =
                [ PrimaryKey ["id"]
                , Unique "unique_name" ["name"]
                ]
            }
        ]
      , 1 ~> 2 :=
        [ AddColumn "person" (Column "gender" SqlString []) Nothing
        , DropColumn ("person", "alive")
        ]
      , 2 ~> 3 :=
        [ DropTable "person"
        ]
      ]
  , goldenMigration' "Partial migration" (withVersion 1)
      [ 0 ~> 1 := [createTablePerson []]
      , 1 ~> 2 := [DropTable "person"]
      ]
  , goldenMigration' "Complete migration" (withVersion 2)
      [ 0 ~> 1 := [createTablePerson []]
      , 1 ~> 2 := [DropTable "person"]
      ]
  , goldenMigration' "Migration with shorter path" defaultDatabase
      [ 0 ~> 1 := [createTablePerson []]
      , 1 ~> 2 := [AddColumn "person" (Column "gender" SqlString []) Nothing]
      , 0 ~> 2 := [createTablePerson [Column "gender" SqlString []]]
      ]
  , goldenMigration' "Partial migration avoids shorter path" (withVersion 1)
      [ 0 ~> 1 := [createTablePerson []]
      , 1 ~> 2 := [AddColumn "person" (Column "gender" SqlString []) Nothing]
      , 0 ~> 2 := [createTablePerson [Column "gender" SqlString []]]
      ]
  ]
  where
    goldenMigration' = goldenMigration dir backend

{- Helpers -}

-- | Run a goldens test for a migration.
goldenMigration
  :: FilePath -> MigrateBackend -> TestName -> MockDatabase -> Migration -> TestTree
goldenMigration dir backend testName testBackend migration = goldenVsText dir testName $ do
  setDatabase testBackend
  MigrateSql{..} <- concatSql Text.unlines <$> getMigration' migration
  return $ Text.unlines [sqlText, Text.pack $ show sqlVals]
  where
    getMigration' = withTestBackend . runReaderT . getMigration backend defaultSettings

-- | Set the version in the MockDatabase.
withVersion :: Version -> MockDatabase
withVersion v = defaultDatabase{version = Just v}

-- | Create a basic 'person' table.
createTablePerson :: [Column] -> Operation
createTablePerson cols = CreateTable
  { name = "person"
  , schema = Column "id" SqlInt64 [NotNull, AutoIncrement] : cols
  , constraints = [PrimaryKey ["id"]]
  }