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153 lines
3.1 KiB
153 lines
3.1 KiB
package post
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import (
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"bytes"
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"database/sql"
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"errors"
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"fmt"
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"io"
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"sync"
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)
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var (
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// ErrAssetNotFound is used to indicate an Asset could not be found in the
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// AssetStore.
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ErrAssetNotFound = errors.New("asset not found")
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)
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// AssetStore implements the storage and retrieval of binary assets, which are
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// intended to be used by posts (e.g. images).
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type AssetStore interface {
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// Set sets the id to the contents of the given io.Reader.
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Set(id string, from io.Reader) error
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// Get writes the id's body to the given io.Writer, or returns
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// ErrAssetNotFound.
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Get(id string, into io.Writer) error
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// Delete's the body stored for the id, if any.
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Delete(id string) error
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}
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type assetStore struct {
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db *sql.DB
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}
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// NewAssetStore initializes a new AssetStore using an existing SQLDB.
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func NewAssetStore(db *SQLDB) AssetStore {
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return &assetStore{
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db: db.db,
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}
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}
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func (s *assetStore) Set(id string, from io.Reader) error {
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body, err := io.ReadAll(from)
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if err != nil {
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return fmt.Errorf("reading body fully into memory: %w", err)
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}
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_, err = s.db.Exec(
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`INSERT INTO assets (id, body)
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VALUES (?, ?)
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ON CONFLICT (id) DO UPDATE SET body=excluded.body`,
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id, body,
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)
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if err != nil {
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return fmt.Errorf("inserting into assets: %w", err)
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}
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return nil
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}
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func (s *assetStore) Get(id string, into io.Writer) error {
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var body []byte
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err := s.db.QueryRow(`SELECT body FROM assets WHERE id = ?`, id).Scan(&body)
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if errors.Is(err, sql.ErrNoRows) {
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return ErrAssetNotFound
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} else if err != nil {
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return fmt.Errorf("selecting from assets: %w", err)
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}
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if _, err := io.Copy(into, bytes.NewReader(body)); err != nil {
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return fmt.Errorf("writing body to io.Writer: %w", err)
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}
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return nil
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}
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func (s *assetStore) Delete(id string) error {
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_, err := s.db.Exec(`DELETE FROM assets WHERE id = ?`, id)
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return err
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}
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////////////////////////////////////////////////////////////////////////////////
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type cachedAssetStore struct {
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inner AssetStore
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m sync.Map
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}
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// NewCachedAssetStore wraps an AssetStore in an in-memory cache.
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func NewCachedAssetStore(assetStore AssetStore) AssetStore {
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return &cachedAssetStore{
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inner: assetStore,
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}
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}
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func (s *cachedAssetStore) Set(id string, from io.Reader) error {
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buf := new(bytes.Buffer)
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from = io.TeeReader(from, buf)
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if err := s.inner.Set(id, from); err != nil {
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return err
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}
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s.m.Store(id, buf.Bytes())
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return nil
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}
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func (s *cachedAssetStore) Get(id string, into io.Writer) error {
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if bodyI, ok := s.m.Load(id); ok {
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if err, ok := bodyI.(error); ok {
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return err
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}
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if _, err := io.Copy(into, bytes.NewReader(bodyI.([]byte))); err != nil {
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return fmt.Errorf("writing body to io.Writer: %w", err)
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}
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return nil
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}
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buf := new(bytes.Buffer)
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into = io.MultiWriter(into, buf)
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if err := s.inner.Get(id, into); errors.Is(err, ErrAssetNotFound) {
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s.m.Store(id, err)
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return err
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} else if err != nil {
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return err
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}
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s.m.Store(id, buf.Bytes())
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return nil
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}
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func (s *cachedAssetStore) Delete(id string) error {
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if err := s.inner.Delete(id); err != nil {
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return err
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}
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s.m.Delete(id)
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return nil
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}
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