forked from baron/baron-sso
104 lines
2.3 KiB
Go
104 lines
2.3 KiB
Go
package pagination
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import (
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"encoding/base64"
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"encoding/json"
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"errors"
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"sort"
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"strings"
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"time"
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"gorm.io/gorm"
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)
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type Cursor struct {
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Timestamp time.Time `json:"timestamp"`
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ID string `json:"id"`
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}
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func Encode(timestamp time.Time, id string) string {
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if timestamp.IsZero() || strings.TrimSpace(id) == "" {
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return ""
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}
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payload, err := json.Marshal(Cursor{
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Timestamp: timestamp.UTC(),
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ID: id,
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})
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if err != nil {
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return ""
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}
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return base64.RawURLEncoding.EncodeToString(payload)
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}
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func Decode(raw string) (*Cursor, error) {
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raw = strings.TrimSpace(raw)
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if raw == "" {
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return nil, nil
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}
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decoded, err := base64.RawURLEncoding.DecodeString(raw)
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if err != nil {
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return nil, err
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}
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var cursor Cursor
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if err := json.Unmarshal(decoded, &cursor); err != nil {
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return nil, err
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}
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if cursor.Timestamp.IsZero() || strings.TrimSpace(cursor.ID) == "" {
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return nil, errors.New("invalid cursor")
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}
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return &cursor, nil
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}
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func ComesAfter(timestamp time.Time, id string, cursor *Cursor) bool {
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if cursor == nil {
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return true
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}
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if timestamp.Before(cursor.Timestamp) {
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return true
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}
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return timestamp.Equal(cursor.Timestamp) && id < cursor.ID
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}
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func SortByKeyDesc[T any](items []T, key func(T) (time.Time, string)) {
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sort.SliceStable(items, func(i, j int) bool {
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leftTime, leftID := key(items[i])
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rightTime, rightID := key(items[j])
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if !leftTime.Equal(rightTime) {
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return leftTime.After(rightTime)
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}
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return leftID > rightID
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})
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}
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func PageByCursor[T any](items []T, limit int, cursorRaw string, key func(T) (time.Time, string)) ([]T, string, error) {
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cursor, err := Decode(cursorRaw)
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if err != nil {
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return nil, "", err
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}
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filtered := make([]T, 0, len(items))
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for _, item := range items {
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timestamp, id := key(item)
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if ComesAfter(timestamp, id, cursor) {
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filtered = append(filtered, item)
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}
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}
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if len(filtered) <= limit {
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return filtered, "", nil
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}
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page := filtered[:limit]
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lastTimestamp, lastID := key(page[len(page)-1])
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return page, Encode(lastTimestamp, lastID), nil
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}
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func ApplyCreatedAtIDCursor(db *gorm.DB, cursor *Cursor, createdAtColumn string, idColumn string) *gorm.DB {
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if cursor == nil {
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return db
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}
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return db.Where(
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createdAtColumn+" < ? OR ("+createdAtColumn+" = ? AND "+idColumn+" < ?)",
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cursor.Timestamp,
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cursor.Timestamp,
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cursor.ID,
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)
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}
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