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// Copyright 2021 Northern.tech AS
//
// 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 rest
import (
"fmt"
"net/http"
"net/url"
"strconv"
"github.com/pkg/errors"
)
const (
PerPageDefault = 20
PerPageMax = 500
pageQueryParam = "page"
perPageQueryParam = "per_page"
)
var (
ErrPerPageLimit = errors.Errorf(
`parameter "per_page" above limit (max: %d)`, PerPageMax,
)
)
// ParsePagingParameters parses the paging parameters from the URL query
// string and returns the parsed page, per_page or a parsing error respectively.
func ParsePagingParameters(r *http.Request) (int64, int64, error) {
q := r.URL.Query()
var (
err error
page int64
perPage int64
)
qPage := q.Get(pageQueryParam)
if qPage == "" {
page = 1
} else {
page, err = strconv.ParseInt(qPage, 10, 64)
if err != nil {
return -1, -1, errors.Errorf(
"invalid page query: \"%s\"",
qPage,
)
} else if page < 1 {
return -1, -1, errors.New("invalid page query: " +
"value must be a non-zero positive integer",
)
}
}
qPerPage := q.Get(perPageQueryParam)
if qPerPage == "" {
perPage = PerPageDefault
} else {
perPage, err = strconv.ParseInt(qPerPage, 10, 64)
if err != nil {
return -1, -1, errors.Errorf(
"invalid per_page query: \"%s\"",
qPerPage,
)
} else if perPage < 1 {
return -1, -1, errors.New("invalid per_page query: " +
"value must be a non-zero positive integer",
)
} else if perPage > PerPageMax {
return page, perPage, ErrPerPageLimit
}
}
return page, perPage, nil
}
type PagingHints struct {
// TotalCount provides the total count of elements available,
// if provided adds another link to the last page available.
TotalCount *int64
// HasNext instructs adding the "next" link header. This option
// has no effect if TotalCount is given.
HasNext *bool
// Pagination parameters
Page, PerPage *int64
}
func NewPagingHints() *PagingHints {
return new(PagingHints)
}
func (h *PagingHints) SetTotalCount(totalCount int64) *PagingHints {
h.TotalCount = &totalCount
return h
}
func (h *PagingHints) SetHasNext(hasNext bool) *PagingHints {
h.HasNext = &hasNext
return h
}
func (h *PagingHints) SetPage(page int64) *PagingHints {
h.Page = &page
return h
}
func (h *PagingHints) SetPerPage(perPage int64) *PagingHints {
h.PerPage = &perPage
return h
}
func MakePagingHeaders(r *http.Request, hints ...*PagingHints) ([]string, error) {
// Parse hints
hint := new(PagingHints)
for _, h := range hints {
if h == nil {
continue
}
if h.HasNext != nil {
hint.HasNext = h.HasNext
}
if h.TotalCount != nil {
hint.TotalCount = h.TotalCount
}
if h.Page != nil {
hint.Page = h.Page
}
if h.PerPage != nil {
hint.PerPage = h.PerPage
}
}
if hint.Page == nil || hint.PerPage == nil {
page, perPage, err := ParsePagingParameters(r)
if err != nil {
return nil, err
}
hint.Page, hint.PerPage = &page, &perPage
}
locationURL := url.URL{
Path: r.URL.Path,
RawQuery: r.URL.RawQuery,
Fragment: r.URL.Fragment,
}
q := locationURL.Query()
// Ensure per_page is set
q.Set(perPageQueryParam, strconv.FormatInt(*hint.PerPage, 10))
links := make([]string, 0, 4)
q.Set(pageQueryParam, "1")
locationURL.RawQuery = q.Encode()
links = append(links, fmt.Sprintf(
"<%s>; rel=\"first\"", locationURL.String(),
))
if (*hint.Page) > 1 {
q.Set(pageQueryParam, strconv.FormatInt(*hint.Page-1, 10))
locationURL.RawQuery = q.Encode()
links = append(links, fmt.Sprintf(
"<%s>; rel=\"prev\"", locationURL.String(),
))
}
// TotalCount takes precedence over HasNext
if hint.TotalCount != nil && *hint.TotalCount > 0 {
lastPage := (*hint.TotalCount-1) / *hint.PerPage + 1
if *hint.Page < lastPage {
// Add "next" link
q.Set(pageQueryParam, strconv.FormatUint(uint64(*hint.Page)+1, 10))
locationURL.RawQuery = q.Encode()
links = append(links, fmt.Sprintf(
"<%s>; rel=\"next\"", locationURL.String(),
))
}
// Add "last" link
q.Set(pageQueryParam, strconv.FormatInt(lastPage, 10))
locationURL.RawQuery = q.Encode()
links = append(links, fmt.Sprintf(
"<%s>; rel=\"last\"", locationURL.String(),
))
} else if hint.HasNext != nil && *hint.HasNext {
q.Set(pageQueryParam, strconv.FormatUint(uint64(*hint.Page)+1, 10))
locationURL.RawQuery = q.Encode()
links = append(links, fmt.Sprintf(
"<%s>; rel=\"next\"", locationURL.String(),
))
}
return links, nil
}
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