Cursor Type for Pagination. Implements Text, JSON and GQL Marshalers.

cursor.go

package types

import (
	"context"
	"fmt"
	"io"
	"time"

	"github.com/btcsuite/btcutil/base58"
	"github.com/vmihailenco/msgpack/v5"
)

type Cursor struct {
	ID        string    `msgpack:"i"`
	CreatedAt time.Time `msgpack:"v"`
}

func (c *Cursor) UnmarshalText(text []byte) error {
	b := base58.Decode(string(text))

	if err := msgpack.Unmarshal(b, &c); err != nil {
		return fmt.Errorf("msgpack unmarshal cursor: %w", err)
	}

	return nil
}

func (c Cursor) MarshalText() ([]byte, error) {
	b, err := msgpack.Marshal(c)
	if err != nil {
		return nil, fmt.Errorf("msgpack marshal cursor: %w", err)
	}

	return []byte(base58.Encode(b)), nil
}

func (c *Cursor) UnmarshalJSON(text []byte) error {
	return c.UnmarshalText(text)
}

func (c Cursor) MarshalJSON() ([]byte, error) {
	return c.MarshalText()
}

func (c *Cursor) UnmarshalGQL(v any) error {
	switch v := v.(type) {
	case string:
		return c.UnmarshalText([]byte(v))
	case []byte:
		return c.UnmarshalText(v)
	default:
		return fmt.Errorf("gql unmarshal cursor: invalid type %T", v)
	}
}

func (c Cursor) MarshalGQLContext(_ context.Context, w io.Writer) error {
	b, err := c.MarshalText()
	if err != nil {
		return fmt.Errorf("gql marshal cursor: %w", err)
	}

	_, err = w.Write(b)
	if err != nil {
		return fmt.Errorf("gql marshal cursor: write: %w", err)
	}

	return nil
}

func (c Cursor) String() string {
	b, err := c.MarshalText()
	if err != nil {
		return fmt.Sprintf("<cursor_error=%q>", err)
	}
	return string(b)
}