/*
 * TSqlAgg.prg — GROUP BY aggregation and HAVING filter
 *
 * FiveSql — SQL Engine for Harbour DBF/NTX
 *
 * Copyright (c) 2025 Charles KWON (Charles KWON OhJun)
 * Email: charleskwonohjun@gmail.com
 *
 * All rights reserved.
 */

#include "hbclass.ch"
#include "FiveSqlDef.ch"

CLASS TSqlAgg

   METHOD New() CONSTRUCTOR
   METHOD GroupBy( aRows, aFN, aCols, aGroupBy, xHaving, aTables, aParams )
   METHOD FindGroupIdx( xGroupExpr, aCols, aFN )
   METHOD ExpandGroupingSets( aGroupBy )
   METHOD ExprInSet( xSelExpr, aSet )
   METHOD ComputeAgg( xE, aGR, aFN )
   METHOD FindColIdx( xExpr, aFN )
   METHOD FindColIdx2( cN, aFN )
   METHOD EvalHaving( xHaving, aNewRow, aCols, aGroupRows, aFN, aParams )
   METHOD HasAgg( aCols )
   METHOD EvalHavingExpr( xE, aNewRow, aCols, aGR, aFN, aParams )

ENDCLASS


METHOD New() CLASS TSqlAgg
RETURN SELF


METHOD HasAgg( aCols ) CLASS TSqlAgg

   LOCAL i

   FOR i := 1 TO Len( aCols )
      IF SqlExprHasAgg( aCols[ i ][ 1 ] )
         RETURN .T.
      ENDIF
   NEXT

RETURN .F.


METHOD GroupBy( aRows, aFN, aCols, aGroupBy, xHaving, aTables, aParams ) CLASS TSqlAgg

   LOCAL hGroups := { => }
   LOCAL i, j, cKey, aGroupRows, aResult := {}
   LOCAL aNewRow
   LOCAL nGCol, cN, nCI, lPass
   LOCAL aGroupIdx := {}
   LOCAL aSets, aCurSet, nSet, hOmitIdx, aSubResult

   /* Aggregate on empty set */
   IF Len( aRows ) == 0 .AND. ::HasAgg( aCols )
      aNewRow := {}
      FOR j := 1 TO Len( aCols )
         IF SqlExprHasAgg( aCols[ j ][ 1 ] )
            AAdd( aNewRow, 0 )
         ELSE
            AAdd( aNewRow, NIL )
         ENDIF
      NEXT
      RETURN { aNewRow }
   ENDIF

   /* SQL:2003 ROLLUP / CUBE / GROUPING SETS — expand into a list of
    * flat grouping key sets and run aggregation once per set. Columns
    * absent from the current set emit NIL (the standard "subtotal"
    * placeholder). */
   aSets := ::ExpandGroupingSets( aGroupBy )
   IF Len( aSets ) > 1
      FOR nSet := 1 TO Len( aSets )
         aCurSet := aSets[ nSet ]
         /* Recurse with the plain expanded set; no ROLLUP/CUBE nodes */
         aSubResult := ::GroupBy( aRows, aFN, aCols, aCurSet, xHaving, aTables, aParams )
         /* For each result row, NIL-out any SELECT column whose source
          * GROUP BY expression is not in the current set. */
         hOmitIdx := { => }
         FOR i := 1 TO Len( aCols )
            IF ! SqlExprHasAgg( aCols[ i ][ 1 ] )
               IF ! ::ExprInSet( aCols[ i ][ 1 ], aCurSet )
                  hOmitIdx[ i ] := .T.
               ENDIF
            ENDIF
         NEXT
         FOR i := 1 TO Len( aSubResult )
            FOR j := 1 TO Len( aSubResult[ i ] )
               IF hb_HHasKey( hOmitIdx, j )
                  aSubResult[ i ][ j ] := NIL
               ENDIF
            NEXT
            AAdd( aResult, aSubResult[ i ] )
         NEXT
      NEXT
      RETURN aResult
   ENDIF

   /* Build group buckets.
    * Pre-resolve the GROUP BY columns to their position in the SELECT
    * list by matching against the SOURCE expressions in aCols, not the
    * alias list in aFN. */
   FOR j := 1 TO Len( aGroupBy )
      nGCol := ::FindGroupIdx( aGroupBy[ j ], aCols, aFN )
      AAdd( aGroupIdx, nGCol )
   NEXT

   IF Len( aGroupBy ) == 0 .AND. ::HasAgg( aCols )
      hGroups[ "__ALL__" ] := aRows
   ELSE
      FOR i := 1 TO Len( aRows )
         cKey := ""
         FOR j := 1 TO Len( aGroupBy )
            nGCol := aGroupIdx[ j ]
            IF nGCol > 0 .AND. nGCol <= Len( aRows[ i ] )
               cKey += SqlValToStr( aRows[ i ][ nGCol ] ) + "|"
            ENDIF
         NEXT
         IF ! hb_HHasKey( hGroups, cKey )
            hGroups[ cKey ] := {}
         ENDIF
         AAdd( hGroups[ cKey ], aRows[ i ] )
      NEXT
   ENDIF

   /* Compute aggregates for each group */
   FOR EACH aGroupRows IN hb_HValues( hGroups )
      aNewRow := {}
      FOR j := 1 TO Len( aCols )
         IF SqlExprHasAgg( aCols[ j ][ 1 ] )
            AAdd( aNewRow, ::ComputeAgg( aCols[ j ][ 1 ], aGroupRows, aFN ) )
         ELSE
            cN := SqlExprName( aCols[ j ][ 1 ] )
            nCI := ::FindColIdx2( cN, aFN )
            IF nCI > 0 .AND. Len( aGroupRows ) > 0 .AND. nCI <= Len( aGroupRows[ 1 ] )
               AAdd( aNewRow, aGroupRows[ 1 ][ nCI ] )
            ELSE
               AAdd( aNewRow, NIL )
            ENDIF
         ENDIF
      NEXT

      /* HAVING filter */
      IF xHaving != NIL
         lPass := ::EvalHaving( xHaving, aNewRow, aCols, aGroupRows, aFN, aParams )
         IF ! lPass
            LOOP
         ENDIF
      ENDIF

      AAdd( aResult, aNewRow )
   NEXT

RETURN aResult


/* Expand SQL:2003 ROLLUP / CUBE / GROUPING SETS into a list of flat
 * grouping sets. Each returned set is an array of expressions that
 * would be the plain GROUP BY for one pass of aggregation.
 *
 *   GROUP BY a, ROLLUP(b, c)         → {(a,b,c), (a,b), (a)}
 *   GROUP BY CUBE(a, b)              → {(a,b), (a), (b), ()}
 *   GROUP BY GROUPING SETS ((a,b), (a), ())  → as-is
 *
 * If aGroupBy is a plain column list with no aggregate-set modifiers,
 * returns a single-element list with aGroupBy itself — letting the
 * caller short-circuit to the fast path unchanged.
 */
METHOD ExpandGroupingSets( aGroupBy ) CLASS TSqlAgg

   LOCAL aSets, aCurrent, i, j, xTerm, aExpand, aNewSets, aBase
   LOCAL nBits, nMask, bit, aCubeSet

   /* Fast path: no ROLLUP/CUBE/GROUPING SETS node → single set */
   aExpand := .F.
   FOR i := 1 TO Len( aGroupBy )
      IF aGroupBy[ i ] != NIL .AND. ValType( aGroupBy[ i ] ) == "A" .AND. ;
         aGroupBy[ i ][ 1 ] == ND_FN .AND. ;
         ( Upper( aGroupBy[ i ][ 2 ] ) == "ROLLUP" .OR. ;
           Upper( aGroupBy[ i ][ 2 ] ) == "CUBE" .OR. ;
           Upper( aGroupBy[ i ][ 2 ] ) == "GROUPING SETS" )
         aExpand := .T.
         EXIT
      ENDIF
   NEXT
   IF ! aExpand
      RETURN { aGroupBy }
   ENDIF

   /* Seed with a single empty set — we'll cross-expand each term */
   aSets := { {} }

   FOR i := 1 TO Len( aGroupBy )
      xTerm := aGroupBy[ i ]
      aNewSets := {}

      IF xTerm != NIL .AND. ValType( xTerm ) == "A" .AND. xTerm[ 1 ] == ND_FN
         DO CASE
         CASE Upper( xTerm[ 2 ] ) == "ROLLUP"
            /* ROLLUP(c1..cN) → N+1 sets:
             *   (c1..cN), (c1..cN-1), ..., (c1), ()
             * Cross-product: existing × each prefix including empty */
            aBase := xTerm[ 3 ]
            FOR j := 1 TO Len( aSets )
               FOR nBits := Len( aBase ) TO 0 STEP -1
                  aCurrent := AClone( aSets[ j ] )
                  FOR nMask := 1 TO nBits
                     AAdd( aCurrent, aBase[ nMask ] )
                  NEXT
                  AAdd( aNewSets, aCurrent )
               NEXT
            NEXT

         CASE Upper( xTerm[ 2 ] ) == "CUBE"
            /* CUBE(c1..cN) → 2^N sets (every subset).
             * For each bitmask, include cols where bit is set. */
            aBase := xTerm[ 3 ]
            FOR j := 1 TO Len( aSets )
               FOR nMask := 0 TO ( 2 ^ Len( aBase ) ) - 1
                  aCurrent := AClone( aSets[ j ] )
                  FOR bit := 1 TO Len( aBase )
                     IF hb_BitAnd( nMask, hb_BitShift( 1, bit - 1 ) ) != 0
                        AAdd( aCurrent, aBase[ bit ] )
                     ENDIF
                  NEXT
                  AAdd( aNewSets, aCurrent )
               NEXT
            NEXT

         CASE Upper( xTerm[ 2 ] ) == "GROUPING SETS"
            /* Explicit list — each element is a flat list of cols (or ()) */
            aBase := xTerm[ 3 ]
            FOR j := 1 TO Len( aSets )
               FOR nBits := 1 TO Len( aBase )
                  aCurrent := AClone( aSets[ j ] )
                  IF ValType( aBase[ nBits ] ) == "A"
                     FOR nMask := 1 TO Len( aBase[ nBits ] )
                        AAdd( aCurrent, aBase[ nBits ][ nMask ] )
                     NEXT
                  ENDIF
                  AAdd( aNewSets, aCurrent )
               NEXT
            NEXT

         OTHERWISE
            /* Unknown ND_FN in GROUP BY — treat as opaque term */
            FOR j := 1 TO Len( aSets )
               aCurrent := AClone( aSets[ j ] )
               AAdd( aCurrent, xTerm )
               AAdd( aNewSets, aCurrent )
            NEXT
         ENDCASE
      ELSE
         /* Plain column — append to every existing set */
         FOR j := 1 TO Len( aSets )
            aCurrent := AClone( aSets[ j ] )
            AAdd( aCurrent, xTerm )
            AAdd( aNewSets, aCurrent )
         NEXT
      ENDIF

      aSets := aNewSets
   NEXT

RETURN aSets


/* Does a SELECT expression reference a column that appears in the
 * given grouping set? Used to decide which SELECT cols to NIL out
 * when reporting a partial grouping (subtotal) row. */
METHOD ExprInSet( xSelExpr, aSet ) CLASS TSqlAgg

   LOCAL i, xG, cSelName, cGName, nDot

   IF xSelExpr == NIL .OR. xSelExpr[ 1 ] != ND_COL
      RETURN .F.
   ENDIF

   cSelName := Upper( xSelExpr[ 2 ] )
   nDot := At( ".", cSelName )
   IF nDot > 0
      cSelName := SubStr( cSelName, nDot + 1 )
   ENDIF

   FOR i := 1 TO Len( aSet )
      xG := aSet[ i ]
      IF xG != NIL .AND. ValType( xG ) == "A" .AND. xG[ 1 ] == ND_COL
         cGName := Upper( xG[ 2 ] )
         IF "." $ cGName
            cGName := SubStr( cGName, At( ".", cGName ) + 1 )
         ENDIF
         IF cGName == cSelName
            RETURN .T.
         ENDIF
      ENDIF
   NEXT

RETURN .F.


/* Resolve a GROUP BY expression to its column position in the output row.
 * Walks the SELECT list's source expressions (aCols[i][1]) rather than
 * the alias list (aFN[i]). For `SELECT d.name AS foo GROUP BY d.name`,
 * aFN is {"FOO"} but aCols[1][1] is ND_COL "d.name" — we need to match
 * the latter, otherwise the group key collapses every row into one
 * bucket. Falls back to FindColIdx (alias/name lookup) for cases where
 * the GROUP BY uses a simple identifier that isn't in the SELECT list.
 */
METHOD FindGroupIdx( xGroupExpr, aCols, aFN ) CLASS TSqlAgg

   LOCAL i, xSel, cGName, cSName, nDot

   IF xGroupExpr == NIL .OR. xGroupExpr[ 1 ] != ND_COL
      RETURN ::FindColIdx( xGroupExpr, aFN )
   ENDIF

   cGName := Upper( xGroupExpr[ 2 ] )
   nDot := At( ".", cGName )
   IF nDot > 0
      cGName := SubStr( cGName, nDot + 1 )
   ENDIF

   FOR i := 1 TO Len( aCols )
      xSel := aCols[ i ][ 1 ]
      IF xSel != NIL .AND. xSel[ 1 ] == ND_COL
         cSName := Upper( xSel[ 2 ] )
         IF "." $ cSName
            cSName := SubStr( cSName, At( ".", cSName ) + 1 )
         ENDIF
         IF cSName == cGName
            RETURN i
         ENDIF
      ENDIF
   NEXT

   /* Last resort: alias-based lookup (handles GROUP BY of unrelated cols) */
RETURN ::FindColIdx( xGroupExpr, aFN )


METHOD FindColIdx( xExpr, aFN ) CLASS TSqlAgg

   LOCAL cN, i

   IF xExpr != NIL .AND. xExpr[ 1 ] == ND_COL
      cN := Upper( xExpr[ 2 ] )
      IF "." $ cN
         cN := SubStr( cN, At( ".", cN ) + 1 )
      ENDIF
      FOR i := 1 TO Len( aFN )
         IF Upper( aFN[ i ] ) == cN
            RETURN i
         ENDIF
      NEXT
   ENDIF

RETURN 0


METHOD FindColIdx2( cN, aFN ) CLASS TSqlAgg

   LOCAL i

   cN := Upper( cN )
   FOR i := 1 TO Len( aFN )
      IF Upper( aFN[ i ] ) == cN
         RETURN i
      ENDIF
   NEXT

RETURN 0


METHOD ComputeAgg( xE, aGR, aFN ) CLASS TSqlAgg

   LOCAL cFunc, cArgName, nCol, i, xVal
   LOCAL nCount := 0, nSum := 0, xMin := NIL, xMax := NIL
   LOCAL cResult, cSep
   LOCAL xArg

   IF xE == NIL .OR. xE[ 1 ] != ND_FN
      RETURN 0
   ENDIF

   cFunc := Upper( xE[ 2 ] )

   IF Len( xE[ 3 ] ) > 0
      xArg := xE[ 3 ][ 1 ]
      IF xArg[ 1 ] == ND_COL .AND. xArg[ 2 ] == "*"
         IF cFunc == "COUNT"
            RETURN Len( aGR )
         ENDIF
         RETURN 0
      ENDIF
      cArgName := SqlExprName( xArg )
   ELSE
      IF cFunc == "COUNT"
         RETURN Len( aGR )
      ENDIF
      RETURN 0
   ENDIF

   nCol := ::FindColIdx2( cArgName, aFN )
   IF nCol == 0 .AND. xArg[ 1 ] == ND_COL
      IF cFunc == "COUNT"
         RETURN Len( aGR )
      ENDIF
      RETURN 0
   ENDIF

   FOR i := 1 TO Len( aGR )
      IF nCol > 0 .AND. nCol <= Len( aGR[ i ] )
         xVal := aGR[ i ][ nCol ]
      ELSEIF nCol == 0
         /* Complex expression (CASE, BIN, etc.) inside aggregate:
          * evaluate the expression tree against the current row data. */
         xVal := SqlEvalRowExpr( xArg, aFN, aGR[ i ] )
      ELSE
         xVal := NIL
      ENDIF
      IF xVal != NIL
         nCount++
         nSum += SqlCoerceNum( xVal )
         /* Use SqlCmpLt for type-safe comparison (handles strings, dates) */
         IF xMin == NIL .OR. SqlCmpLt( xVal, xMin )
            xMin := xVal
         ENDIF
         IF xMax == NIL .OR. SqlCmpLt( xMax, xVal )
            xMax := xVal
         ENDIF
      ENDIF
   NEXT

   DO CASE
   CASE cFunc == "COUNT"
      RETURN nCount
   CASE cFunc == "SUM"
      /* SQL standard: SUM of all NULLs = NULL, not 0 */
      RETURN iif( nCount > 0, nSum, NIL )
   CASE cFunc == "AVG"
      RETURN iif( nCount > 0, nSum / nCount, NIL )
   CASE cFunc == "MIN"
      RETURN xMin
   CASE cFunc == "MAX"
      RETURN xMax
   CASE cFunc == "GROUP_CONCAT" .OR. cFunc == "STRING_AGG"
      cResult := ""
      cSep := ", "
      FOR i := 1 TO Len( aGR )
         IF nCol > 0 .AND. nCol <= Len( aGR[ i ] )
            xVal := aGR[ i ][ nCol ]
         ELSEIF nCol == 0
            xVal := SqlEvalRowExpr( xArg, aFN, aGR[ i ] )
         ELSE
            xVal := NIL
         ENDIF
         IF xVal != NIL
            IF ! Empty( cResult )
               cResult += cSep
            ENDIF
            cResult += SqlCoerceStr( xVal )
         ENDIF
      NEXT
      RETURN cResult
   ENDCASE

RETURN 0


METHOD EvalHaving( xHaving, aNewRow, aCols, aGroupRows, aFN, aParams ) CLASS TSqlAgg

   LOCAL xResult

   xResult := ::EvalHavingExpr( xHaving, aNewRow, aCols, aGroupRows, aFN, aParams )

RETURN SqlIsTrue( xResult )


METHOD EvalHavingExpr( xE, aNewRow, aCols, aGR, aFN, aParams ) CLASS TSqlAgg

   LOCAL xL, xR, cOp, i, nCI, cN

   IF xE == NIL
      RETURN NIL
   ENDIF

   DO CASE
   CASE xE[ 1 ] == ND_LIT
      RETURN xE[ 2 ]

   CASE xE[ 1 ] == ND_NIL
      RETURN NIL

   CASE xE[ 1 ] == ND_COL
      cN := xE[ 2 ]
      IF "." $ cN
         cN := SubStr( cN, At( ".", cN ) + 1 )
      ENDIF
      FOR i := 1 TO Len( aCols )
         IF Upper( aCols[ i ][ 2 ] ) == Upper( cN ) .AND. i <= Len( aNewRow )
            RETURN aNewRow[ i ]
         ENDIF
      NEXT
      nCI := ::FindColIdx2( cN, aFN )
      IF nCI > 0 .AND. Len( aGR ) > 0 .AND. nCI <= Len( aGR[ 1 ] )
         RETURN aGR[ 1 ][ nCI ]
      ENDIF
      RETURN NIL

   CASE xE[ 1 ] == ND_FN
      IF SqlIsAggName( xE[ 2 ] )
         RETURN ::ComputeAgg( xE, aGR, aFN )
      ENDIF
      RETURN NIL

   CASE xE[ 1 ] == ND_BIN
      cOp := xE[ 2 ]
      IF cOp == "AND"
         xL := ::EvalHavingExpr( xE[ 3 ], aNewRow, aCols, aGR, aFN, aParams )
         xR := ::EvalHavingExpr( xE[ 4 ], aNewRow, aCols, aGR, aFN, aParams )
         RETURN SqlIsTrue( xL ) .AND. SqlIsTrue( xR )
      ENDIF
      IF cOp == "OR"
         xL := ::EvalHavingExpr( xE[ 3 ], aNewRow, aCols, aGR, aFN, aParams )
         xR := ::EvalHavingExpr( xE[ 4 ], aNewRow, aCols, aGR, aFN, aParams )
         RETURN SqlIsTrue( xL ) .OR. SqlIsTrue( xR )
      ENDIF
      xL := ::EvalHavingExpr( xE[ 3 ], aNewRow, aCols, aGR, aFN, aParams )
      xR := ::EvalHavingExpr( xE[ 4 ], aNewRow, aCols, aGR, aFN, aParams )
      xL := SqlCoerceForCmp( xL )
      xR := SqlCoerceForCmp( xR )
      IF cOp == "=" .OR. cOp == "=="
         RETURN SqlCmpEq( xL, xR )
      ENDIF
      IF cOp == "<>" .OR. cOp == "!="
         RETURN ! SqlCmpEq( xL, xR )
      ENDIF
      IF cOp == ">"
         RETURN SqlCmpLt( xR, xL )
      ENDIF
      IF cOp == "<"
         RETURN SqlCmpLt( xL, xR )
      ENDIF
      IF cOp == ">="
         RETURN SqlCmpEq( xL, xR ) .OR. SqlCmpLt( xR, xL )
      ENDIF
      IF cOp == "<="
         RETURN SqlCmpEq( xL, xR ) .OR. SqlCmpLt( xL, xR )
      ENDIF
      RETURN NIL

   CASE xE[ 1 ] == ND_UNI
      IF xE[ 2 ] == "NOT"
         xL := ::EvalHavingExpr( xE[ 3 ], aNewRow, aCols, aGR, aFN, aParams )
         RETURN ! SqlIsTrue( xL )
      ENDIF
      RETURN NIL

   ENDCASE

RETURN NIL