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paging.go
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paging.go
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package main
// this file contains some paging related utility functions
import (
"fmt"
"strconv"
"strings"
"github.com/almighty/almighty-core/app"
"github.com/almighty/almighty-core/rest"
"github.com/goadesign/goa"
errs "github.com/pkg/errors"
)
const (
pageSizeDefault = 20
pageSizeMax = 100
)
func computePagingLimts(offsetParam *string, limitParam *int) (offset int, limit int) {
if offsetParam == nil {
offset = 0
} else {
offsetValue, err := strconv.Atoi(*offsetParam)
if err != nil {
offset = 0
} else {
offset = offsetValue
}
}
if offset < 0 {
offset = 0
}
if limitParam == nil {
limit = pageSizeDefault
} else {
limit = *limitParam
}
if limit <= 0 {
limit = pageSizeDefault
} else if limit > pageSizeMax {
limit = pageSizeMax
}
return offset, limit
}
func setPagingLinks(links *app.PagingLinks, path string, resultLen, offset, limit, count int, additionalQuery ...string) {
format := func(additional []string) string {
if len(additional) > 0 {
return "&" + strings.Join(additional, "&")
}
return ""
}
// prev link
if offset > 0 && count > 0 {
var prevStart int
// we do have a prev link
if offset <= count {
prevStart = offset - limit
} else {
// the first range that intersects the end of the useful range
prevStart = offset - (((offset-count)/limit)+1)*limit
}
realLimit := limit
if prevStart < 0 {
// need to cut the range to start at 0
realLimit = limit + prevStart
prevStart = 0
}
prev := fmt.Sprintf("%s?page[offset]=%d&page[limit]=%d%s", path, prevStart, realLimit, format(additionalQuery))
links.Prev = &prev
}
// next link
nextStart := offset + resultLen
if nextStart < count {
// we have a next link
next := fmt.Sprintf("%s?page[offset]=%d&page[limit]=%d%s", path, nextStart, limit, format(additionalQuery))
links.Next = &next
}
// first link
var firstEnd int
if offset > 0 {
firstEnd = offset % limit // this is where the second page starts
} else {
// offset == 0, first == current
firstEnd = limit
}
first := fmt.Sprintf("%s?page[offset]=%d&page[limit]=%d%s", path, 0, firstEnd, format(additionalQuery))
links.First = &first
// last link
var lastStart int
if offset < count {
// advance some pages until touching the end of the range
lastStart = offset + (((count - offset - 1) / limit) * limit)
} else {
// retreat at least one page until covering the range
lastStart = offset - ((((offset - count) / limit) + 1) * limit)
}
realLimit := limit
if lastStart < 0 {
// need to cut the range to start at 0
realLimit = limit + lastStart
lastStart = 0
}
last := fmt.Sprintf("%s?page[offset]=%d&page[limit]=%d%s", path, lastStart, realLimit, format(additionalQuery))
links.Last = &last
}
func buildAbsoluteURL(req *goa.RequestData) string {
return rest.AbsoluteURL(req, req.URL.Path)
}
func parseInts(s *string) ([]int, error) {
if s == nil || len(*s) == 0 {
return []int{}, nil
}
split := strings.Split(*s, ",")
result := make([]int, len(split))
for index, value := range split {
converted, err := strconv.Atoi(value)
if err != nil {
return nil, errs.WithStack(err)
}
result[index] = converted
}
return result, nil
}
func parseLimit(pageParameter *string) (s *int, l int, e error) {
params, err := parseInts(pageParameter)
if err != nil {
return nil, 0, errs.WithStack(err)
}
if len(params) > 1 {
return ¶ms[0], params[1], nil
}
if len(params) > 0 {
return nil, params[0], nil
}
return nil, 100, nil
}