{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE GADTs #-}

module Ringo.Generator.Populate.Dimension (dimensionTablePopulationSQL) where

import Prelude.Compat
import Control.Monad.Reader     (Reader, asks)
import Database.HsSqlPpp.Syntax (Statement, QueryExpr(..), Distinct(..), makeSelect, JoinType(..))
import Data.Maybe               (fromJust)
import Data.Text                (Text)

import Ringo.Extractor.Internal
import Ringo.Generator.Internal
import Ringo.Generator.Sql
import Ringo.Types.Internal

dimensionTablePopulationSQL :: TablePopulationMode -> Fact -> TableName -> Reader Env Text
dimensionTablePopulationSQL popMode fact dimTableName =
  ppStatement <$> dimensionTablePopulationStatement popMode fact dimTableName

dimensionTablePopulationStatement :: TablePopulationMode -> Fact -> TableName -> Reader Env Statement
dimensionTablePopulationStatement popMode fact dimTableName = do
  Settings {..}    <- asks envSettings
  tables           <- asks envTables
  defaults         <- asks envTypeDefaults
  let factTable    = fromJust $ findTable (factTableName fact) tables
      colMapping   = dimColumnMapping settingDimPrefix fact dimTableName
      selectCols   = [ flip sia (nmc cName) $ coalesceColumn defaults (factTableName fact) col
                       | (_, cName) <- colMapping
                       , let col    = fromJust . findColumn cName $ tableColumns factTable ]
      timeCol      = head ([ cName | FactColumn cName DimTime <- factColumns fact ] :: [ColumnName])
      isNotNullC   = parens . foldBinop "or" . map (postop "isnotnull" . ei . snd) $ colMapping
      selectWhereC = Just . foldBinop "and" $
                       [ isNotNullC, binop "<" (ei timeCol) placeholder ] ++
                         [ binop ">=" (ei timeCol) placeholder | popMode == IncrementalPopulation ]
      selectC      = makeSelect
                     { selDistinct   = Distinct
                     , selSelectList = sl selectCols
                     , selTref       = [tref $ factTableName fact]
                     , selWhere      = selectWhereC
                     }

      iTableName   = suffixTableName popMode settingTableNameSuffixTemplate dimTableName
      insertC      = insert iTableName (map fst colMapping) $ case popMode of
        FullPopulation        -> selectC
        IncrementalPopulation -> let alias = "x" in
          makeSelect
          { selSelectList = sl [si $ qstar alias]
          , selTref       =
              [ tjoin (subtrefa alias selectC) LeftOuter (tref dimTableName) . Just $
                  foldBinop "and" [ binop "=" (eqi dimTableName c1) (eqi alias c2) | (c1, c2) <- colMapping ] ]
          , selWhere      =
              Just . foldBinop "and" . map (postop "isnull" . eqi dimTableName . fst) $ colMapping
          }

  return insertC