fix(sqlite): handle comparison operators and sorting

internal/engine/sqlite/convert.go

@@ -356,21 +356,103 @@ func (c *cc) convertComparison(n *parser.Expr_comparisonContext) ast.Node {
 		return &ast.In{
 			Expr:     lexpr,
 			List:     rexprs,
-			Not:      false,
+			Not:      n.NOT_() != nil,
 			Sel:      nil,
 			Location: n.GetStart().GetStart(),
 		}
 	}
 
+	operator := c.extractComparisonOperator(n)
+	rexprIdx := 1
+	rexpr := c.convert(n.Expr(rexprIdx))
+
+	// Special handling for IS NOT NULL where NOT NULL might be parsed as a unary expression
+	if operator == "IS" && len(n.AllExpr()) > 1 {
+		if rExpr, ok := n.Expr(1).(*parser.Expr_unaryContext); ok {
+			// Check if this is a NOT NULL expression by looking at the text content
+			text := rExpr.GetText()
+			if strings.ToUpper(text) == "NOTNULL" || strings.ToUpper(text) == "NOT NULL" {
+				operator = "IS NOT"
+				rexpr = &ast.A_Const{Val: &ast.Null{}}
+			}
+		}
+	}
+
 	return &ast.A_Expr{
 		Name: &ast.List{
 			Items: []ast.Node{
-				&ast.String{Str: "="}, // TODO: add actual comparison
+				&ast.String{Str: operator},
 			},
 		},
 		Lexpr: lexpr,
-		Rexpr: c.convert(n.Expr(1)),
+		Rexpr: rexpr,
+	}
+}
+
+func (c *cc) extractComparisonOperator(n *parser.Expr_comparisonContext) string {
+	switch {
+	case n.LT2() != nil:
+		return "<<"
+	case n.GT2() != nil:
+		return ">>"
+	case n.AMP() != nil:
+		return "&"
+	case n.PIPE() != nil:
+		return "|"
+	case n.LT_EQ() != nil:
+		return "<="
+	case n.GT_EQ() != nil:
+		return ">="
+	case n.LT() != nil:
+		return "<"
+	case n.GT() != nil:
+		return ">"
+	case n.NOT_EQ1() != nil:
+		return "!="
+	case n.NOT_EQ2() != nil:
+		return "<>"
+	case n.ASSIGN() != nil || n.EQ() != nil:
+		return "="
+	case n.IS_() != nil:
+		if n.NOT_() != nil {
+			return "IS NOT"
+		}
+		return "IS"
+	case n.LIKE_() != nil:
+		if n.NOT_() != nil {
+			return "NOT LIKE"
+		}
+		return "LIKE"
+	case n.GLOB_() != nil:
+		if n.NOT_() != nil {
+			return "NOT GLOB"
+		}
+		return "GLOB"
+	case n.MATCH_() != nil:
+		if n.NOT_() != nil {
+			return "NOT MATCH"
+		}
+		return "MATCH"
+	case n.REGEXP_() != nil:
+		if n.NOT_() != nil {
+			return "NOT REGEXP"
+		}
+		return "REGEXP"
+	}
+
+	var parts []string
+	for _, child := range n.GetChildren() {
+		if term, ok := child.(antlr.TerminalNode); ok {
+			text := strings.TrimSpace(term.GetText())
+			if text != "" {
+				parts = append(parts, text)
+			}
+		}
+	}
+	if len(parts) > 0 {
+		return strings.Join(parts, " ")
 	}
+	return "="
 }
 
 func (c *cc) convertMultiSelect_stmtContext(n *parser.Select_stmtContext) ast.Node {
@@ -514,6 +596,11 @@ func (c *cc) convertMultiSelect_stmtContext(n *parser.Select_stmtContext) ast.No
 	limitCount, limitOffset := c.convertLimit_stmtContext(n.Limit_stmt())
 	selectStmt.LimitCount = limitCount
 	selectStmt.LimitOffset = limitOffset
+	if orderBy := n.Order_by_stmt(); orderBy != nil {
+		if sortClause, ok := c.convertOrderby_stmtContext(orderBy).(*ast.List); ok {
+			selectStmt.SortClause = sortClause
+		}
+	}
 	selectStmt.WithClause = &ast.WithClause{Ctes: &ctes}
 	return selectStmt
 }
@@ -626,10 +713,34 @@ func (c *cc) convertOrderby_stmtContext(n parser.IOrder_by_stmtContext) ast.Node
 			if !ok {
 				continue
 			}
-			list.Items = append(list.Items, &ast.CaseExpr{
-				Xpr:      c.convert(term.Expr()),
-				Location: term.Expr().GetStart().GetStart(),
-			})
+
+			expr := c.convert(term.Expr())
+			sortBy := &ast.SortBy{
+				Node:        expr,
+				SortbyDir:   ast.SortByDirDefault,
+				SortbyNulls: ast.SortByNullsDefault,
+				UseOp:       &ast.List{},
+			}
+
+			if ascDescCtx := term.Asc_desc(); ascDescCtx != nil {
+				if ascDesc, ok := ascDescCtx.(*parser.Asc_descContext); ok {
+					if ascDesc.DESC_() != nil {
+						sortBy.SortbyDir = ast.SortByDirDesc
+					} else if ascDesc.ASC_() != nil {
+						sortBy.SortbyDir = ast.SortByDirAsc
+					}
+				}
+			}
+
+			if term.NULLS_() != nil {
+				if term.FIRST_() != nil {
+					sortBy.SortbyNulls = ast.SortByNullsFirst
+				} else if term.LAST_() != nil {
+					sortBy.SortbyNulls = ast.SortByNullsLast
+				}
+			}
+
+			list.Items = append(list.Items, sortBy)
 		}
 		return list
 	}
@@ -1135,6 +1246,63 @@ func (c *cc) convertCase(n *parser.Expr_caseContext) ast.Node {
 	return e
 }
 
+func (c *cc) convertUnaryExpr(n *parser.Expr_unaryContext) ast.Node {
+	// Handle unary expressions like NOT NULL
+	children := n.GetChildren()
+	if len(children) >= 2 {
+		for i, child := range children {
+			if term, ok := child.(antlr.TerminalNode); ok {
+				if term.GetSymbol().GetTokenType() == parser.SQLiteParserNOT_ {
+					if i+1 < len(children) {
+						if nextTerm, ok := children[i+1].(antlr.TerminalNode); ok {
+							if nextTerm.GetSymbol().GetTokenType() == parser.SQLiteParserNULL_ {
+								return &ast.A_Const{Val: &ast.Null{}}
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// For other unary expressions, try to convert the inner expression
+	if n.Expr() != nil {
+		return c.convert(n.Expr())
+	}
+
+	return todo("convertUnaryExpr", n)
+}
+
+func (c *cc) convertNullComparison(n *parser.Expr_null_compContext) ast.Node {
+	expr := c.convert(n.Expr())
+
+	var operator string
+	switch {
+	case n.ISNULL_() != nil:
+		operator = "IS NULL"
+	case n.NOTNULL_() != nil:
+		operator = "IS NOT NULL"
+	case n.NOT_() != nil && n.NULL_() != nil:
+		operator = "IS NOT NULL"
+	case n.NULL_() != nil:
+		operator = "IS NULL"
+	default:
+		operator = "IS NULL" // fallback
+	}
+
+	return &ast.A_Expr{
+		Name: &ast.List{
+			Items: []ast.Node{
+				&ast.String{Str: operator},
+			},
+		},
+		Lexpr: expr,
+		Rexpr: &ast.A_Const{
+			Val: &ast.Null{},
+		},
+	}
+}
+
 func (c *cc) convert(node node) ast.Node {
 	switch n := node.(type) {
 
@@ -1226,6 +1394,12 @@ func (c *cc) convert(node node) ast.Node {
 	case *parser.Expr_caseContext:
 		return c.convertCase(n)
 
+	case *parser.Expr_null_compContext:
+		return c.convertNullComparison(n)
+
+	case *parser.Expr_unaryContext:
+		return c.convertUnaryExpr(n)
+
 	default:
 		return todo("convert(case=default)", n)
 	}