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pager.go
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pager.go
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package client
import (
"errors"
"github.com/cloudfoundry/go-cfclient/v3/internal/path"
"github.com/cloudfoundry/go-cfclient/v3/resource"
)
var ErrNoResultsReturned = errors.New("expected 1 or more results, but got 0")
var ErrExactlyOneResultNotReturned = errors.New("expected exactly 1 result, but got less or more than 1")
type Pager struct {
NextPageReader *path.QuerystringReader
PreviousPageReader *path.QuerystringReader
TotalResults int
TotalPages int
}
func NewPager(pagination resource.Pagination) *Pager {
nextPageReader, _ := path.NewQuerystringReader(pagination.Next.Href)
previousPageReader, _ := path.NewQuerystringReader(pagination.Previous.Href)
return &Pager{
NextPageReader: nextPageReader,
PreviousPageReader: previousPageReader,
TotalResults: pagination.TotalResults,
TotalPages: pagination.TotalPages,
}
}
func (p *Pager) HasNextPage() bool {
return p.NextPageReader != nil
}
func (p *Pager) NextPage(opts ListOptioner) {
if p.HasNextPage() {
page := p.NextPageReader.Int(PageField)
perPage := p.NextPageReader.Int(PerPageField)
opts.CurrentPage(page, perPage)
}
}
func (p *Pager) HasPreviousPage() bool {
return p.PreviousPageReader != nil
}
func (p *Pager) PreviousPage(opts ListOptioner) {
if p.HasPreviousPage() {
page := p.PreviousPageReader.Int(PageField)
perPage := p.PreviousPageReader.Int(PerPageField)
opts.CurrentPage(page, perPage)
}
}
type ListFunc[T ListOptioner, R any] func(opts T) ([]R, *Pager, error)
func AutoPage[T ListOptioner, R any](opts T, list ListFunc[T, R]) ([]R, error) {
var all []R
for {
page, pager, err := list(opts)
if err != nil {
return nil, err
}
all = append(all, page...)
if !pager.HasNextPage() {
break
}
pager.NextPage(opts)
}
return all, nil
}
// Single returns a single object from the call to list or an error if matches > 1 or matches < 1
func Single[T ListOptioner, R any](opts T, list ListFunc[T, R]) (R, error) {
matches, _, err := list(opts)
if err != nil {
return *new(R), err
}
if len(matches) != 1 {
return *new(R), ErrExactlyOneResultNotReturned
}
return matches[0], nil
}
// First returns the first object from the call to list or an error if matches < 1
func First[T ListOptioner, R any](opts T, list ListFunc[T, R]) (R, error) {
matches, _, err := list(opts)
if err != nil {
return *new(R), err
}
if len(matches) < 1 {
return *new(R), ErrNoResultsReturned
}
return matches[0], nil
}