func QueryForPage(
query *db.Query,
criteria Criteria,
target interface{},
transformer func(in interface{}) interface{},
) (Page, error) {
max := criteria.PageSize
first := (criteria.Page - 1) * max
// for the first page the offset is zero
query.Skip(first)
if max > 0 {
query.Limit(max + 1)
}
var entities coll.Collection
var err error
var results []interface{}
if reflect.TypeOf(target).Kind() == reflect.Func {
results, err = query.ListInto(target)
} else if _, ok := target.(tk.Hasher); ok {
entities, err = query.ListFlatTreeOf(target)
} else {
entities, err = query.ListOf(target)
}
if err != nil {
return Page{}, err
}
if results == nil {
results = entities.Elements()
}
page := Page{}
size := int64(len(results))
if max > 0 && size > max {
page.Last = false
page.Results = results[:max]
} else {
page.Last = true
page.Results = results
}
// transform results
if transformer != nil {
for k, v := range page.Results {
page.Results[k] = transformer(v)
}
}
// count records
if criteria.CountRecords {
DB := query.GetDb()
cnt := DB.Query(query.GetTable())
cnt.Copy(query)
cnt.ColumnsReset()
cnt.CountAll()
cnt.OrdersReset()
var recs int64
_, err = cnt.SelectInto(&recs)
if err != nil {
return Page{}, err
}
page.Count = Int64(recs)
}
return page, nil
}