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package asset
import (
"bytes"
"database/sql"
"errors"
"fmt"
"io"
"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
)
var (
// ErrNotFound is used to indicate an Asset could not be found in the
// Store.
ErrNotFound = errors.New("asset not found")
)
// Store implements the storage and retrieval of binary assets, which are
// intended to be used by posts (e.g. images).
type Store interface {
// Set sets the id to the contents of the given io.Reader.
Set(id string, from io.Reader) error
// Get writes the id's body to the given io.Writer, or returns
// ErrNotFound.
Get(id string, into io.Writer) error
// Delete's the body stored for the id, if any.
Delete(id string) error
// List returns all ids which are currently stored.
List() ([]string, error)
}
type store struct {
db *post.SQLDB
}
// NewStore initializes a new Store using an existing SQLDB.
func NewStore(db *post.SQLDB) Store {
return &store{
db: db,
}
}
func (s *store) Set(id string, from io.Reader) error {
body, err := io.ReadAll(from)
if err != nil {
return fmt.Errorf("reading body fully into memory: %w", err)
}
_, err = s.db.Exec(
`INSERT INTO assets (id, body)
VALUES (?, ?)
ON CONFLICT (id) DO UPDATE SET body=excluded.body`,
id, body,
)
if err != nil {
return fmt.Errorf("inserting into assets: %w", err)
}
return nil
}
func (s *store) Get(id string, into io.Writer) error {
var body []byte
err := s.db.QueryRow(`SELECT body FROM assets WHERE id = ?`, id).Scan(&body)
if errors.Is(err, sql.ErrNoRows) {
return ErrNotFound
} else if err != nil {
return fmt.Errorf("selecting from assets: %w", err)
}
if _, err := io.Copy(into, bytes.NewReader(body)); err != nil {
return fmt.Errorf("writing body to io.Writer: %w", err)
}
return nil
}
func (s *store) Delete(id string) error {
_, err := s.db.Exec(`DELETE FROM assets WHERE id = ?`, id)
return err
}
func (s *store) List() ([]string, error) {
rows, err := s.db.Query(`SELECT id FROM assets ORDER BY id ASC`)
if err != nil {
return nil, fmt.Errorf("querying: %w", err)
}
defer rows.Close()
var ids []string
for rows.Next() {
var id string
if err := rows.Scan(&id); err != nil {
return nil, fmt.Errorf("scanning row: %w", err)
}
ids = append(ids, id)
}
return ids, nil
}
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