feat: cache resized images

diskcache/file_cache.go

@@ -0,0 +1,110 @@
+package diskcache
+
+import (
+	"context"
+	"crypto/sha1" //nolint:gosec
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/spf13/afero"
+)
+
+type FileCache struct {
+	fs afero.Fs
+
+	// granular locks
+	scopedLocks struct {
+		sync.Mutex
+		sync.Once
+		locks map[string]sync.Locker
+	}
+}
+
+func New(fs afero.Fs, root string) *FileCache {
+	return &FileCache{
+		fs: afero.NewBasePathFs(fs, root),
+	}
+}
+
+func (f *FileCache) Store(ctx context.Context, key string, value []byte) error {
+	mu := f.getScopedLocks(key)
+	mu.Lock()
+	defer mu.Unlock()
+
+	fileName := f.getFileName(key)
+	if err := f.fs.MkdirAll(filepath.Dir(fileName), 0700); err != nil {
+		return err
+	}
+
+	if err := afero.WriteFile(f.fs, fileName, value, 0700); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (f *FileCache) Load(ctx context.Context, key string) (value []byte, exist bool, err error) {
+	r, ok, err := f.open(key)
+	if err != nil || !ok {
+		return nil, ok, err
+	}
+	defer r.Close()
+
+	value, err = ioutil.ReadAll(r)
+	if err != nil {
+		return nil, false, err
+	}
+	return value, true, nil
+}
+
+func (f *FileCache) Delete(ctx context.Context, key string) error {
+	mu := f.getScopedLocks(key)
+	mu.Lock()
+	defer mu.Unlock()
+
+	fileName := f.getFileName(key)
+	if err := f.fs.Remove(fileName); err != nil && err != os.ErrNotExist {
+		return err
+	}
+	return nil
+}
+
+func (f *FileCache) open(key string) (afero.File, bool, error) {
+	fileName := f.getFileName(key)
+	file, err := f.fs.Open(fileName)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, false, nil
+		}
+		return nil, false, err
+	}
+
+	return file, true, nil
+}
+
+// getScopedLocks pull lock from the map if found or create a new one
+func (f *FileCache) getScopedLocks(key string) (lock sync.Locker) {
+	f.scopedLocks.Do(func() { f.scopedLocks.locks = map[string]sync.Locker{} })
+
+	f.scopedLocks.Lock()
+	lock, ok := f.scopedLocks.locks[key]
+	if !ok {
+		lock = &sync.Mutex{}
+		f.scopedLocks.locks[key] = lock
+	}
+	f.scopedLocks.Unlock()
+
+	return lock
+}
+
+func (f *FileCache) getFileName(key string) string {
+	hasher := sha1.New() //nolint:gosec
+	_, _ = hasher.Write([]byte(key))
+	hash := hex.EncodeToString(hasher.Sum(nil))
+	return fmt.Sprintf("%s/%s/%s", hash[:1], hash[1:3], hash)
+}