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pagination.go
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pagination.go
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// Copyright (C) 2015 NTT Innovation Institute, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pagination
import (
"fmt"
"math"
"net/url"
"strconv"
"github.com/cloudwan/gohan/schema"
)
const (
//ASC ascending order
ASC = "asc"
//DESC descending order
DESC = "desc"
defaultSortKey = "id"
defaultSortOrder = ASC
)
//Paginator stores pagination data
type Paginator struct {
Key string
Order string
Limit uint64
Offset uint64
}
type OptionPaginator func(*Paginator) error
//NewPaginator create Paginator
func NewPaginator(options ...OptionPaginator) (*Paginator, error) {
pg := &Paginator{
Key: "",
Order: "",
Limit: math.MaxUint64,
Offset: 0,
}
for _, op := range options {
err := op(pg)
if err != nil {
return nil, err
}
}
return pg, nil
}
func OptionKey(s *schema.Schema, key string) OptionPaginator {
return func(pg *Paginator) error {
pg.Key = key
if s != nil && pg.Key != "" {
found := false
for _, p := range s.Properties {
if p.ID == pg.Key {
found = true
break
}
}
if !found {
return fmt.Errorf("Schema %s has no property %s which can used as sorting key", s.ID, pg.Key)
}
}
return nil
}
}
func OptionOrder(order string) OptionPaginator {
return func(pg *Paginator) error {
pg.Order = order
if pg.Order != "" && pg.Order != ASC && pg.Order != DESC {
return fmt.Errorf("Unknown sort order %s", pg.Order)
}
return nil
}
}
func OptionLimit(limit uint64) OptionPaginator {
return func(pg *Paginator) error {
pg.Limit = limit
return nil
}
}
func OptionOffset(offset uint64) OptionPaginator {
return func(pg *Paginator) error {
pg.Offset = offset
return nil
}
}
//FromURLQuery create Paginator from Query params
func FromURLQuery(s *schema.Schema, values url.Values) (pg *Paginator, err error) {
var sortKey string
var sortOrder string
var limit uint64
var offset uint64
if sortKey = values.Get("sort_key"); sortKey == "" {
sortKey = defaultSortKey
}
if sortOrder = values.Get("sort_order"); sortOrder == "" {
sortOrder = defaultSortOrder
}
if l := values.Get("limit"); l != "" {
limit, err = strconv.ParseUint(l, 10, 64)
if err != nil {
return
}
if limit < 0 {
return nil, fmt.Errorf("Request contains invalid limit value %d", limit)
}
} else {
limit = math.MaxUint64
}
if o := values.Get("offset"); o != "" {
offset, err = strconv.ParseUint(o, 10, 64)
if err != nil {
return
}
}
return NewPaginator(OptionKey(s, sortKey), OptionOrder(sortOrder), OptionLimit(limit), OptionOffset(offset))
}