public static Expression BuildOrderExpression(
Expression queryExpression,
OrderingFields orderingFields)
{
queryExpression = GetOrderBy(queryExpression, orderingFields.Fields[0]);
foreach (OrderingField field in orderingFields.Fields.Skip(1))
{
queryExpression = GetThenBy(queryExpression, field);
}
return(queryExpression);
}
public IQueryable <OrderedItem> BuildAfterQuery(
IQueryable <TDbObject> query,
Expression <Func <TDbObject, TOrder> > orderBy,
Expression <Func <TOrder, TOrder, bool> > filter,
Expression <Func <TDbObject, TResult> > select,
Cursor after)
{
MemberInitExpression orderedItemInit = Expression.MemberInit(
Expression.New(typeof(OrderedItem)),
Expression.Bind(OrderMember, ParameterReplacer.RepalceParameter(new SortDirectionRemoverVisitor(orderBy.Body).Expression)),
Expression.Bind(ValueMember, ParameterReplacer.RepalceParameter(select.Body)));
Expression queryExpression = query.Expression;
OrderingFields orderingFields = OrderRequestBuilder.GetOrdering(orderBy);
if (_cursorFormatter.HasValue(after))
{
TOrder order = _cursorFormatter.ParseAs <TOrder>(after);
Expression filterBody =
filter != null
? FilterBuilder.RemapFilter(orderedItemInit, filter, order)
: FilterBuilder.BuildAutoFilter(orderedItemInit, orderingFields, order);
// add where filtration
queryExpression = Expression.Call(
typeof(Queryable),
nameof(Queryable.Where),
new System.Type[] { typeof(TDbObject) },
queryExpression,
Expression.Lambda <Func <TDbObject, bool> >(filterBody, DbItem));
}
// add passed order
queryExpression = OrderRequestBuilder.BuildOrderExpression(queryExpression, orderingFields);
// extend selection and add order fields
queryExpression = Expression.Call(
typeof(Queryable),
nameof(Queryable.Select),
new System.Type[] { typeof(TDbObject), typeof(OrderedItem) },
queryExpression,
Expression.Lambda <Func <TDbObject, OrderedItem> >(orderedItemInit, DbItem));
return(query.Provider.CreateQuery <OrderedItem>(queryExpression));
}
public static Expression BuildAutoFilter(
Expression mappingExpression,
OrderingFields orderingFields,
TOrder after)
{
var filters = new List <FilterValue>(capacity: orderingFields.Fields.Count);
foreach (OrderingField field in orderingFields.Fields)
{
var value = orderingFields.IsDirect ? after : GetValue(after, field);
filters.Add(new FilterValue
{
Expression = field.Expression,
Value = Expression.Constant(value),
IsLower = field.IsDescending,
});
}
Expression filter = null;
for (var current = 0; current < filters.Count; current++)
{
FilterValue currentValue = filters[current];
Expression currentFilter = null;
for (var prev = 0; prev < current; prev++)
{
FilterValue prevValue = filters[prev];
Expression equal = Expression.Equal(prevValue.Expression, prevValue.Value);
currentFilter = currentFilter != null?Expression.AndAlso(currentFilter, equal) : equal;
}
Expression compare = GreateCompareExpression(currentValue);
currentFilter = currentFilter != null?Expression.AndAlso(currentFilter, compare) : compare;
filter = filter != null?Expression.OrElse(filter, currentFilter) : currentFilter;
}
return(ParameterReplacer.RepalceParameter(filter));
}
public static OrderingFields GetOrdering(Expression <Func <TDbObject, TOrder> > orderBy)
{
var result = new OrderingFields
{
OrderParameter = orderBy.Parameters[0]
};
result.Fields =
(from item in new OrderingMappingVisitor(orderBy).GetMappingList()
where item.Member.DeclaringType == typeof(TOrder)
let property = (PropertyInfo)item.Member
let sortDirection = new SortDirectionVisitor(item.Expression)
select new OrderingField
{
Type = property.PropertyType,
Expression = sortDirection.Expression,
IsDescending = sortDirection.IsDescending,
Property = property,
}).ToArray();
// if order is simple direct field access like (item => item.id)
if (result.Fields.Count == 0)
{
var sortDirection = new SortDirectionVisitor(orderBy.Body);
result.Fields = new[]
{
new OrderingField
{
Type = typeof(TOrder),
Expression = sortDirection.Expression,
IsDescending = sortDirection.IsDescending,
}
};
result.IsDirect = true;
}
return(result);
}
