module CQRSExample.Query
       ( setupQueryDatabase
       , qFindUserPassword
       , qProjectList
       , qTaskList
       , qTimeSheet
       , qUserIdFromUserName
       , reactToUnseenEvents
       ) where

import           Control.Monad (liftM, void)
import           CQRSExample.Aggregates (UserId)
import           CQRSExample.Events (Event(..))
import           Data.Convertible (Convertible(..), convError)
import           Data.CQRS (enumerateEventStore, GUID, EventStore)
import qualified Data.CQRS.GUID as G
import           Data.CQRS.PersistedEvent (PersistedEvent(..))
import           Data.Enumerator (run_, (>>==))
import qualified Data.Enumerator.List as EL
import           Data.Foldable (forM_)
import           Data.Text (Text)
import           Data.Time.Calendar (Day)
import           Database.HDBC (IConnection, SqlValue(..), fromSql, quickQuery', run, runRaw, toSql, withTransaction)

-- Conversion between GUID and SQLValue.
instance Convertible GUID SqlValue where
  safeConvert g = Right $ toSql $ G.toByteString g

instance Convertible SqlValue GUID where
  safeConvert (SqlByteString s) = Right $ G.fromByteString s
  safeConvert a = convError "Invalid source value" a

-- Simple query with result field mapping.
smq :: IConnection c => c -> String -> [SqlValue] -> ([SqlValue] -> a) -> IO [a]
smq c sql params f = withTransaction c $ \_ ->
  fmap (map f) $ quickQuery' c sql params

-- Extract a single result (if any); fails if there is more than one result.
extract1 :: [a] -> Maybe a
extract1 [] = Nothing
extract1 [r] = Just r
extract1 _ = error "Too many results"

-- Initialize query database if necessary.
setupQueryDatabase :: IConnection c => c -> IO ()
setupQueryDatabase c = do
  runRaw c "CREATE TABLE IF NOT EXISTS gversion ( gversion INTEGER )"
  runRaw c "CREATE TABLE IF NOT EXISTS projects ( guid BLOB , name TEXT , short_desc TEXT )"
  runRaw c "CREATE TABLE IF NOT EXISTS tasks ( guid BLOB , project_guid BLOB , short_desc TEXT , long_desc TEXT )"
  runRaw c "CREATE TABLE IF NOT EXISTS users ( user_id BLOB , user_name TEXT , user_pass TEXT , first_name TEXT , last_name TEXT )"
  runRaw c "CREATE TABLE IF NOT EXISTS work_units ( task_guid BLOB , wu_guid BLOB , wu_date TEXT , wu_duration INTEGER , wu_comment TEXT , user_id BLOB )"
  runRaw c "CREATE TABLE IF NOT EXISTS tasks_starred_by ( task_id BLOB, user_id BLOB , user_name TEXT )"

-- Find user password from database.
qFindUserPassword :: IConnection c => c -> Text -> IO (Maybe Text)
qFindUserPassword c userName = fmap extract1 $ smq c "SELECT user_pass FROM users WHERE user_name = ?" [ toSql userName ] convert
  where
    convert :: [SqlValue] -> Text
    convert [p] = fromSql p
    convert _ = error "Invalid number of columns in SQL query result"

-- Query project list
qProjectList :: IConnection c => c -> IO [(GUID, Text, Text)]
qProjectList c = smq c "SELECT guid, name, short_desc FROM projects" [ ] convert
  where
    convert :: [SqlValue] -> (GUID, Text, Text)
    convert [spg, spn, spsd] = (fromSql spg, fromSql spn, fromSql spsd)
    convert _ = error "Invalid number of columns in SQL query result"

-- Query task list
qTaskList :: IConnection c => String -> Maybe GUID -> c -> IO [(GUID, Text, Bool)]
qTaskList userName mProjectId c =
  case mProjectId of
    Nothing ->
      smq c "SELECT T.guid, T.short_desc, TS.user_id IS NULL FROM tasks T LEFT OUTER JOIN tasks_starred_by TS ON T.guid = TS.task_id WHERE (TS.user_name = ? OR TS.user_name IS NULL)" [ toSql userName ] convert
    Just projectId ->
      smq c "SELECT T.guid, T.short_desc, TS.user_id IS NULL FROM tasks T LEFT OUTER JOIN tasks_starred_by TS ON T.guid = TS.task_id WHERE (TS.user_name = ? OR TS.user_name IS NULL) AND T.project_guid = ?" [ toSql userName, toSql projectId ] convert
  where
    convert :: [SqlValue] -> (GUID,Text,Bool)
    convert [ guid, short_desc, starred_by_user ] =
      (fromSql guid,
       fromSql short_desc,
       case (fromSql starred_by_user :: Int) of
         0 -> True
         1 -> False
         _ -> error "Invalid query result")
    convert _ = error "Invalid columns in SQL query result"

-- Query work units in a date interval. The result is a list of tasks
-- (IDs, short description), with daily totals (in minutes) for each task.
qTimeSheet :: IConnection c => Day -> Day -> String -> c -> IO [(GUID, Text, Maybe Day, Int)]
qTimeSheet startDate endDate userName c =
  (smq c "SELECT T.guid, W.wu_date, T.short_desc, COALESCE(SUM(W.wu_duration),0) FROM tasks T LEFT OUTER JOIN work_units W ON W.task_guid=T.guid LEFT OUTER JOIN tasks_starred_by ST ON ST.task_id=T.guid WHERE ((W.wu_duration IS NOT NULL) AND (W.wu_date>=? AND W.wu_date<?)) OR (ST.user_name = ?) GROUP BY T.guid, W.wu_date"
   [ toSql $ show startDate
   , toSql $ show endDate
   , toSql userName ] convert)
  where
    convert :: [SqlValue] -> (GUID, Text, Maybe Day, Int)
    convert [ taskId, day, taskShortDesc, total ] =
      (fromSql taskId, fromSql taskShortDesc, fromSql day, fromSql total)
    convert _ = error "Invalid columns in SQL query result"

-- Get user name for a given user ID.
qUserNameFromUserId :: IConnection c => c -> GUID -> IO (Maybe Text)
qUserNameFromUserId c userId = fmap extract1 $ smq c "SELECT U.user_name FROM users U WHERE U.user_id = ?" [ toSql userId ] convert
  where
    convert :: [SqlValue] -> Text
    convert [u] = fromSql u
    convert _ = error "Invalid columns in SQL query result"

-- Get user ID from user name.
qUserIdFromUserName :: IConnection c => c -> Text -> IO (Maybe GUID)
qUserIdFromUserName c userName = fmap extract1 $ smq c "SELECT U.user_id FROM users U WHERE U.user_name = ?" [ toSql $ userName ] convert
  where
    convert :: [SqlValue] -> GUID
    convert [u] = fromSql u
    convert _ = error "Invalid columns in SQL query result"

-- Event sourcing.
reactToUnseenEvents :: IConnection c => c -> EventStore Event -> IO ()
reactToUnseenEvents connection eventStore =
  withTransaction connection $ \_ -> do
    -- Find the version number to start at.
    startVersion <- getStartVersion
    -- Enumerate all the events form the event store since last run.
    evs <- run_ (EL.consume >>== enumerateEventStore eventStore startVersion)
    -- React to all the events.
    forM_ evs $ reactToEvent connection
    -- Update the global version number.
    updateStartVersion $ startVersion + length evs
    -- Done.
    return ()

  where
    getStartVersion :: IO Int
    getStartVersion = do
      liftM head $ smq connection "SELECT COALESCE(MAX(gversion), 1) FROM gversion" [ ]
        (\columns -> case columns of
            [i] -> fromSql i
            _ -> error "Invalid columns in SQL query result")

    updateStartVersion :: Int -> IO ()
    updateStartVersion newStartVersion = do
      _ <- run connection "DELETE FROM gversion;" []
      _ <- run connection "INSERT INTO gversion (gversion) VALUES (?);" [ toSql newStartVersion ]
      return ()

reactToEvent :: IConnection c => c -> PersistedEvent Event -> IO ()
reactToEvent connection ev = do
  let gv = peGlobalVer ev
  let e = peEvent ev
  putStrLn $ show $ "gv(" ++ show gv ++ "): guid: " ++ show g ++ " event: " ++ show e
  react e
  where
    g = peAggregateGUID ev

    react (ProjectCreated pn psd) = do
      go "INSERT INTO projects ( guid , name , short_desc ) VALUES ( ? , ? , ? );"
        [ toSql g
        , toSql pn
        , toSql psd
        ]

    react (ProjectRenamed pn) = do
      go "UPDATE projects SET name = ? WHERE guid = ?;"
        [ toSql pn
        , toSql g
        ]

    react (TaskAdded pid tsd) = do
      go "INSERT INTO tasks ( guid , project_guid , short_desc ) VALUES (?, ?, ?);"
        [ toSql g
        , toSql pid
        , toSql tsd ]

    react (RecordedWorkUnit wuId wuDay wuDuration wuComment wuUserId) = do
      go "INSERT INTO work_units ( task_guid , wu_guid , wu_date , wu_duration , wu_comment , user_id ) VALUES ( ? , ? , ? , ? , ? , ? );"
        [ toSql g
        , toSql wuId
        , toSql $ show wuDay
        , toSql $ wuDuration
        , toSql $ wuComment
        , toSql wuUserId
        ]

    react (UserCreated ucUserName ucPassword ucFirstName ucLastName) = do
      go "INSERT INTO users ( user_id , user_name , user_pass, first_name , last_name ) VALUES ( ? , ? , ? , ? , ? );"
        [ toSql g
        , toSql ucUserName
        , toSql ucPassword
        , toSql ucFirstName
        , toSql ucLastName
        ]

    react (TaskStarred userId) = do
      mUserName <- qUserNameFromUserId connection userId
      forM_ mUserName $ \userName -> do
        go "INSERT INTO tasks_starred_by ( task_id , user_id , user_name ) VALUES (?, ?, ?);"
          [ toSql g
          , toSql userId
          , toSql $ userName
          ]

    react (TaskUnstarred userId) = do
      go "DELETE FROM tasks_starred_by WHERE task_id = ? AND user_id = ?;"
        [ toSql g
        , toSql userId
        ]

    react (UserRegistered _) = do
      return () -- No need to record

    go :: String -> [SqlValue] -> IO ()
    go sql parameters = void $ run connection sql parameters