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paginator.go
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paginator.go
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// Copyright © 2022 Ory Corp
// SPDX-License-Identifier: Apache-2.0
package keysetpagination
import (
"fmt"
"strings"
"github.com/gobuffalo/pop/v6"
)
type (
Item interface{ PageToken() string }
columnOrdering struct {
name string
order string
}
Paginator struct {
token, defaultToken string
size, defaultSize, maxSize int
isLast bool
additionalColumn columnOrdering
}
Option func(*Paginator) *Paginator
)
func (p *Paginator) Token() string {
if p.token == "" {
return p.defaultToken
}
return p.token
}
func (p *Paginator) Size() int {
size := p.size
if size == 0 {
size = p.defaultSize
if size == 0 {
size = 100
}
}
if p.maxSize > 0 && size > p.maxSize {
size = p.maxSize
}
return size
}
func parseToken(idField string, s string) map[string]string {
tokens := strings.Split(s, "/")
if len(tokens) != 2 {
return map[string]string{idField: s}
}
r := map[string]string{}
for _, p := range tokens {
parts := strings.Split(p, "=")
if len(parts) != 2 {
continue
}
r[parts[0]] = parts[1]
}
return r
}
func (p *Paginator) IsLast() bool {
return p.isLast
}
func (p *Paginator) ToOptions() []Option {
return []Option{
WithToken(p.token),
WithSize(p.size),
WithDefaultToken(p.defaultToken),
WithDefaultSize(p.defaultSize),
WithMaxSize(p.maxSize),
withIsLast(p.isLast),
}
}
// Paginate returns a function that paginates a pop.Query.
// Usage:
//
// q := c.Where("foo = ?", foo).Scope(keysetpagination.Paginate[Item](paginator))
func Paginate[I Item](p *Paginator) pop.ScopeFunc {
var item I
model := &pop.Model{Value: item}
id := model.IDField()
return func(q *pop.Query) *pop.Query {
eid := q.Connection.Dialect.Quote(id)
tokenParts := parseToken(id, p.Token())
idValue := tokenParts[id]
if column, ok := model.Columns().Cols[p.additionalColumn.name]; ok {
quoteName := q.Connection.Dialect.Quote(column.Name)
value := tokenParts[column.Name]
q = q.
Where(fmt.Sprintf("%s > ? OR (%s = ? AND %s > ?)", quoteName, quoteName, eid), value, value, idValue).
Order(fmt.Sprintf("%s %s", quoteName, p.additionalColumn.order))
} else {
q = q.
Where(fmt.Sprintf(`%s > ?`, eid), idValue)
}
return q.
Limit(p.Size() + 1).
// we always need to order by the id field last
Order(fmt.Sprintf(`%s ASC`, eid))
}
}
// Result removes the last item (if applicable) and returns the paginator for the next page.
func Result[I Item](items []I, p *Paginator) ([]I, *Paginator) {
if len(items) > p.Size() {
items = items[:p.Size()]
return items, &Paginator{
token: items[len(items)-1].PageToken(),
defaultToken: p.defaultToken,
size: p.size,
defaultSize: p.defaultSize,
maxSize: p.maxSize,
}
}
return items, &Paginator{
defaultToken: p.defaultToken,
size: p.size,
defaultSize: p.defaultSize,
maxSize: p.maxSize,
isLast: true,
}
}
func WithDefaultToken(t string) Option {
return func(opts *Paginator) *Paginator {
opts.defaultToken = t
return opts
}
}
func WithDefaultSize(size int) Option {
return func(opts *Paginator) *Paginator {
opts.defaultSize = size
return opts
}
}
func WithMaxSize(size int) Option {
return func(opts *Paginator) *Paginator {
opts.maxSize = size
return opts
}
}
func WithToken(t string) Option {
return func(opts *Paginator) *Paginator {
opts.token = t
return opts
}
}
func WithSize(size int) Option {
return func(opts *Paginator) *Paginator {
opts.size = size
return opts
}
}
func WithColumn(name string, order string) Option {
return func(opts *Paginator) *Paginator {
opts.additionalColumn = columnOrdering{
name: name,
order: order,
}
return opts
}
}
func withIsLast(isLast bool) Option {
return func(opts *Paginator) *Paginator {
opts.isLast = isLast
return opts
}
}
func GetPaginator(modifiers ...Option) *Paginator {
opts := &Paginator{}
for _, f := range modifiers {
opts = f(opts)
}
return opts
}