github.com/mmatczuk/gohan@v0.0.0-20170206152520-30e45d9bdb69/db/pagination/pagination.go (about)

     1  // Copyright (C) 2015 NTT Innovation Institute, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
    12  // implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  
    16  package pagination
    17  
    18  import (
    19  	"fmt"
    20  	"net/url"
    21  	"strconv"
    22  
    23  	"github.com/cloudwan/gohan/schema"
    24  )
    25  
    26  const (
    27  	//ASC ascending order
    28  	ASC = "asc"
    29  	//DESC descending order
    30  	DESC = "desc"
    31  
    32  	defaultSortKey   = "id"
    33  	defaultSortOrder = ASC
    34  )
    35  
    36  //Paginator stores pagination data
    37  type Paginator struct {
    38  	Key    string
    39  	Order  string
    40  	Limit  uint64
    41  	Offset uint64
    42  }
    43  
    44  //NewPaginator create Paginator
    45  func NewPaginator(s *schema.Schema, key, order string, limit, offset uint64) (*Paginator, error) {
    46  	if key == "" {
    47  		key = defaultSortKey
    48  	}
    49  	if order == "" {
    50  		order = defaultSortOrder
    51  	}
    52  	if order != ASC && order != DESC {
    53  		return nil, fmt.Errorf("Unknown sort order %s", order)
    54  	}
    55  	if s != nil {
    56  		found := false
    57  		for _, p := range s.Properties {
    58  			if p.ID == key {
    59  				found = true
    60  				break
    61  			}
    62  		}
    63  		if !found {
    64  			return nil, fmt.Errorf("Schema %s has no property %s which can used as sorting key", s.ID, key)
    65  		}
    66  	}
    67  	return &Paginator{
    68  		Key:    key,
    69  		Order:  order,
    70  		Limit:  limit,
    71  		Offset: offset,
    72  	}, nil
    73  }
    74  
    75  //FromURLQuery create Paginator from Query params
    76  func FromURLQuery(s *schema.Schema, values url.Values) (pg *Paginator, err error) {
    77  	sortKey := values.Get("sort_key")
    78  	sortOrder := values.Get("sort_order")
    79  	var limit uint64
    80  	var offset uint64
    81  
    82  	if l := values.Get("limit"); l != "" {
    83  		limit, err = strconv.ParseUint(l, 10, 64)
    84  	}
    85  	if err != nil {
    86  		return
    87  	}
    88  
    89  	if o := values.Get("offset"); o != "" {
    90  		offset, err = strconv.ParseUint(o, 10, 64)
    91  	}
    92  	if err != nil {
    93  		return
    94  	}
    95  	return NewPaginator(s, sortKey, sortOrder, limit, offset)
    96  }