feat: impl fs backed blob store

apps/backend/internal/blob/err.go

@@ -0,0 +1,8 @@
+package blob
+
+import "errors"
+
+var (
+	ErrConflict = errors.New("key already used for a different blob")
+	ErrNotFound = errors.New("key not found")
+)

apps/backend/internal/blob/fs_store.go

@@ -0,0 +1,95 @@
+package blob
+
+import (
+	"context"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+var _ Store = &FSStore{}
+
+type FSStore struct {
+	config FSStoreConfig
+}
+
+type FSStoreConfig struct {
+	Root string
+}
+
+func NewFSStore(config FSStoreConfig) *FSStore {
+	return &FSStore{config: config}
+}
+
+func (s *FSStore) Put(ctx context.Context, key Key, reader io.Reader) error {
+	path := filepath.Join(s.config.Root, string(key))
+
+	err := os.MkdirAll(filepath.Dir(path), 0755)
+	if err != nil {
+		return err
+	}
+
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_EXCL, 0644)
+	if err != nil {
+		if os.IsExist(err) {
+			return ErrConflict
+		}
+		return err
+	}
+
+	defer f.Close()
+	_, err = io.Copy(f, reader)
+	if err != nil {
+		_ = os.Remove(path)
+		return err
+	}
+
+	return nil
+}
+
+func (s *FSStore) Retrieve(ctx context.Context, key Key) (io.ReadCloser, error) {
+	path := filepath.Join(s.config.Root, string(key))
+	f, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	return f, nil
+}
+
+func (s *FSStore) Delete(ctx context.Context, key Key) error {
+	err := os.Remove(filepath.Join(s.config.Root, string(key)))
+	// no op if file does not exist
+	// swallow error if file does not exist
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+func (s *FSStore) Move(ctx context.Context, srcKey, dstKey Key) error {
+	oldPath := filepath.Join(s.config.Root, string(srcKey))
+	newPath := filepath.Join(s.config.Root, string(dstKey))
+
+	_, err := os.Stat(newPath)
+	if err == nil {
+		return ErrConflict
+	}
+
+	err = os.MkdirAll(filepath.Dir(newPath), 0755)
+	if err != nil {
+		return err
+	}
+
+	err = os.Rename(oldPath, newPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return ErrNotFound
+		}
+		return err
+	}
+
+	return nil
+}

apps/backend/internal/blob/key.go

@@ -0,0 +1,3 @@
+package blob
+
+type Key string

apps/backend/internal/blob/store.go

@@ -0,0 +1,13 @@
+package blob
+
+import (
+	"context"
+	"io"
+)
+
+type Store interface {
+	Put(ctx context.Context, key Key, reader io.Reader) error
+	Retrieve(ctx context.Context, key Key) (io.ReadCloser, error)
+	Delete(ctx context.Context, key Key) error
+	Move(ctx context.Context, srcKey, dstKey Key) error
+}