{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

-- |
-- Module      : Database.HDBC.Query.TH
-- Copyright   : 2013 Kei Hibino
-- License     : BSD3
--
-- Maintainer  : ex8k.hibino@gmail.com
-- Stability   : experimental
-- Portability : unknown
--
-- This module contains templates to generate Haskell record types
-- and HDBC instances correspond to RDB table schema.
module Database.HDBC.Query.TH (
  makeRecordPersistableDefault,

  defineTableDefault',
  defineTableDefault,

  defineTableFromDB',
  defineTableFromDB,

  inlineVerifiedQuery
  ) where

import Data.Maybe (listToMaybe, fromMaybe)
import qualified Data.Map as Map
import Control.Monad (when)

import Database.HDBC (IConnection, SqlValue, prepare)

import Language.Haskell.TH (Q, runIO, Name, TypeQ, Dec)
import Language.Haskell.TH.Name.CamelCase (ConName, varCamelcaseName)
import Language.Haskell.TH.Lib.Extra (reportWarning, reportMessage)

import Database.Record.TH (makeRecordPersistableWithSqlTypeDefault)
import qualified Database.Record.TH as Record
import Database.Relational.Query (Relation, Config, defaultConfig, relationalQuerySQL)
import Database.Relational.Query.SQL (QuerySuffix)
import qualified Database.Relational.Query.TH as Relational

import Database.HDBC.Session (withConnectionIO)
import Database.HDBC.Record.Persistable ()

import Database.HDBC.Schema.Driver (Driver, getFields, getPrimaryKey)


-- | Generate all persistable templates against defined record like type constructor.
makeRecordPersistableDefault :: Name    -- ^ Type constructor name
                             -> Q [Dec] -- ^ Resutl declaration
makeRecordPersistableDefault recTypeName = do
  rr <- Relational.makeRelationalRecordDefault recTypeName
  (pair, (_mayNs, cts)) <- Record.reifyRecordType recTypeName
  let width = length cts
  ps <- Record.makeRecordPersistableWithSqlType [t| SqlValue |]
        (Record.persistableFunctionNamesDefault recTypeName) pair width
  return $ rr ++ ps

-- | Generate all HDBC templates about table except for constraint keys using default naming rule.
defineTableDefault' :: Config            -- ^ Configuration to generate query with
                    -> String            -- ^ Schema name
                    -> String            -- ^ Table name
                    -> [(String, TypeQ)] -- ^ List of column name and type
                    -> [ConName]         -- ^ Derivings
                    -> Q [Dec]           -- ^ Result declaration
defineTableDefault' config schema table columns derives = do
  modelD <- Relational.defineTableTypesAndRecordDefault config schema table columns derives
  sqlvD  <- makeRecordPersistableWithSqlTypeDefault [t| SqlValue |] table $ length columns
  return $ modelD ++ sqlvD

-- | Generate all HDBC templates about table using default naming rule.
defineTableDefault :: Config            -- ^ Configuration to generate query with
                   -> String            -- ^ Schema name
                   -> String            -- ^ Table name
                   -> [(String, TypeQ)] -- ^ List of column name and type
                   -> [ConName]         -- ^ Derivings
                   -> [Int]             -- ^ Indexes to represent primary key
                   -> Maybe Int         -- ^ Index of not-null key
                   -> Q [Dec]           -- ^ Result declaration
defineTableDefault config schema table columns derives primary notNull = do
  modelD <- Relational.defineTableDefault config schema table columns derives primary notNull
  sqlvD  <- makeRecordPersistableWithSqlTypeDefault [t| SqlValue |] table $ length columns
  return $ modelD ++ sqlvD

-- | Generate all HDBC templates using system catalog informations with specified config.
defineTableFromDB' :: IConnection conn
                   => IO conn     -- ^ Connect action to system catalog database
                   -> Config      -- ^ Configuration to generate query with
                   -> Driver conn -- ^ Driver definition
                   -> String      -- ^ Schema name
                   -> String      -- ^ Table name
                   -> [ConName]   -- ^ Derivings
                   -> Q [Dec]     -- ^ Result declaration
defineTableFromDB' connect config drv scm tbl derives = do
  let getDBinfo =
        withConnectionIO connect
        (\conn ->  do
            (cols, notNullIdxs) <- getFields drv conn scm tbl
            primCols            <- getPrimaryKey drv conn scm tbl

            return (cols, notNullIdxs, primCols) )

  (cols, notNullIdxs, primaryCols) <- runIO getDBinfo
  when (null primaryCols) . reportWarning
    $ "getPrimaryKey: Primary key not found for table: " ++ scm ++ "." ++ tbl

  let colIxMap = Map.fromList $ zip [c | (c, _) <- cols] [(0 :: Int) .. ]
      ixLookups = [ (k, Map.lookup k colIxMap) | k <- primaryCols ]
      warnLk k = maybe
                 (reportWarning $ "defineTableFromDB: fail to find index of pkey - " ++ k ++ ". Something wrong!!")
                 (const $ return ())
      primaryIxs = fromMaybe [] . sequence $ map snd ixLookups
  mapM_ (uncurry warnLk) ixLookups

  defineTableDefault config scm tbl cols derives primaryIxs (listToMaybe notNullIdxs)

-- | Generate all HDBC templates using system catalog informations.
defineTableFromDB :: IConnection conn
                  => IO conn     -- ^ Connect action to system catalog database
                  -> Driver conn -- ^ Driver definition
                  -> String      -- ^ Schema name
                  -> String      -- ^ Table name
                  -> [ConName]   -- ^ Derivings
                  -> Q [Dec]     -- ^ Result declaration
defineTableFromDB connect = defineTableFromDB' connect defaultConfig

-- | Verify composed 'Query' and inline it in compile type.
inlineVerifiedQuery :: IConnection conn
                    => IO conn      -- ^ Connect action to system catalog database
                    -> Name         -- ^ Top-level variable name which has 'Relation' type
                    -> Relation p r -- ^ Object which has 'Relation' type
                    -> Config       -- ^ Configuration to generate SQL
                    -> QuerySuffix  -- ^ suffix SQL words
                    -> String       -- ^ Variable name to define as inlined query
                    -> Q [Dec]      -- ^ Result declarations
inlineVerifiedQuery connect relVar rel config sufs qns = do
  (p, r) <- Relational.reifyRelation relVar
  let sql = relationalQuerySQL config rel sufs
  _ <- runIO $ withConnectionIO connect
       (\conn -> do
           reportMessage $ "Verify with prepare: " ++ sql
           prepare conn sql)
  Relational.unsafeInlineQuery (return p) (return r) sql (varCamelcaseName qns)