Refactor "WhereFilterClauseHook" to make it clearer (separating code …

…into auxiliar functions)

bql/semantic/hooks.go

@@ -672,6 +672,45 @@ func whereObjectClause() ElementHook {
 	return hook
 }
 
+// addOperationToWorkingFilter takes the filter operation in its string format and tries to add the
+// correspondent filter.Operation to workingFilter.
+func addOperationToWorkingFilter(op string, workingFilter *FilterClause) error {
+	if workingFilter == nil {
+		return fmt.Errorf("could not add filter function %q to nil filter clause (which is still nil probably because a call to st.ResetWorkingFilterClause was not made before start processing the first filter clause)", op)
+	}
+	if !workingFilter.Operation.IsEmpty() {
+		return fmt.Errorf("invalid filter function %q on filter clause since already set to %q", op, workingFilter.Operation)
+	}
+	lowercaseOp := strings.ToLower(op)
+	if _, ok := filter.SupportedOperations[lowercaseOp]; !ok {
+		return fmt.Errorf("filter function %q on filter clause is not supported", op)
+	}
+
+	workingFilter.Operation = filter.SupportedOperations[lowercaseOp]
+	return nil
+}
+
+// addBindingToWorkingFilter takes the given binding and tries to add it to workingFilter.
+func addBindingToWorkingFilter(bndg string, workingFilter *FilterClause) error {
+	if workingFilter == nil {
+		return fmt.Errorf("could not add binding %q to nil filter clause (which is still nil probably because a call to st.ResetWorkingFilterClause was not made before start processing the first filter clause)", bndg)
+	}
+	if workingFilter.Operation.IsEmpty() {
+		return fmt.Errorf("could not add binding %q to a filter clause that does not have a filter function previously set", bndg)
+	}
+	if workingFilter.Binding != "" {
+		return fmt.Errorf("invalid binding %q on filter clause since already set to %q", bndg, workingFilter.Binding)
+	}
+
+	workingFilter.Binding = bndg
+	return nil
+}
+
+// isValidFilterClause returns true if the given filter clause is valid and complete.
+func isValidFilterClause(f *FilterClause) bool {
+	return f != nil && !f.Operation.IsEmpty() && f.Binding != ""
+}
+
 // whereFilterClause returns an element hook that updates the working filter clause and,
 // if the filter clause is complete, populates the filters list of the statement.
 func whereFilterClause() ElementHook {
@@ -683,36 +722,22 @@ func whereFilterClause() ElementHook {
 		}
 
 		tkn := ce.Token()
-		currFilter := st.WorkingFilter()
 		switch tkn.Type {
 		case lexer.ItemFilterFunction:
-			if currFilter == nil {
-				return nil, fmt.Errorf("could not add filter function %q to nil filter clause", tkn.Text)
-			}
-			if !currFilter.Operation.IsEmpty() {
-				return nil, fmt.Errorf("invalid filter function %q on filter clause since already set to %q", tkn.Text, currFilter.Operation)
-			}
-			lowercaseFilter := strings.ToLower(tkn.Text)
-			if _, ok := filter.SupportedOperations[lowercaseFilter]; !ok {
-				return nil, fmt.Errorf("filter function %q on filter clause is not supported", tkn.Text)
+			err := addOperationToWorkingFilter(tkn.Text, st.WorkingFilter())
+			if err != nil {
+				return nil, err
 			}
-			currFilter.Operation = filter.SupportedOperations[lowercaseFilter]
 			return hook, nil
 		case lexer.ItemBinding:
-			if currFilter == nil {
-				return nil, fmt.Errorf("could not add binding %q to nil filter clause", tkn.Text)
-			}
-			if currFilter.Operation.IsEmpty() {
-				return nil, fmt.Errorf("could not add binding %q to a filter clause that does not have a filter function previously set", tkn.Text)
-			}
-			if currFilter.Binding != "" {
-				return nil, fmt.Errorf("invalid binding %q on filter clause since already set to %q", tkn.Text, currFilter.Binding)
+			err := addBindingToWorkingFilter(tkn.Text, st.WorkingFilter())
+			if err != nil {
+				return nil, err
 			}
-			currFilter.Binding = tkn.Text
 			return hook, nil
 		case lexer.ItemRPar:
-			if currFilter == nil || currFilter.Operation.IsEmpty() || currFilter.Binding == "" {
-				return nil, fmt.Errorf("could not add invalid working filter %q to the statement filters list", currFilter)
+			if !isValidFilterClause(st.WorkingFilter()) {
+				return nil, fmt.Errorf("could not add invalid working filter %q to the statement filters list", st.WorkingFilter())
 			}
 			st.AddWorkingFilterClause()
 		}