Initial commit

Proof-of-concept implementation. Bugs will occur.

internal/domains/cacher/files.go

@@ -0,0 +1,98 @@
+package cacher
+
+import (
+	"crypto/md5"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"source.hodakov.me/hdkv/faketunes/internal/domains/cacher/dto"
+	"source.hodakov.me/hdkv/faketunes/internal/domains/cacher/models"
+)
+
+// GetFileDTO gets the ALAC file from cache or transcodes one with transcoder if needed.
+func (c *Cacher) GetFileDTO(sourcePath string) (*dto.CacheItem, error) {
+	item, err := c.getFile(sourcePath)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w (%w)", ErrCacher, ErrFailedToGetSourceFile, err)
+	}
+
+	return models.CacheItemModelToDTO(item), nil
+}
+
+func (c *Cacher) getFile(sourcePath string) (*models.CacheItem, error) {
+	sourceFileInfo, err := os.Stat(sourcePath)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w (%w)", ErrCacher, ErrFailedToGetSourceFile, err)
+	}
+
+	keyData := fmt.Sprintf("%s:%d", sourcePath, sourceFileInfo.ModTime().UnixNano())
+	hash := md5.Sum([]byte(keyData))
+	cacheKey := fmt.Sprintf("%x", hash)
+	cacheFilePath := filepath.Join(c.cacheDir, cacheKey+".m4a")
+
+	c.cacheMutex.Lock()
+	defer c.cacheMutex.Unlock()
+
+	// Check if file information exists in cache
+	if item, ok := c.items[cacheKey]; ok {
+		if _, err := os.Stat(item.Path); err != nil {
+			// File exists in cache and on disk
+			item.Updated = time.Now().UTC()
+
+			c.updateCachedStat(sourcePath, item.Size)
+
+			return item, nil
+		}
+	}
+
+	// Check if file exists on disk but information about it doesn't exist in
+	// the memory (for example, after application restart).
+	if cachedFileInfo, err := os.Stat(cacheFilePath); err == nil {
+		// Verify that the file on disk is newer than the source file and has content.
+		// If that's the case, return the item information and store it in memory.
+		if cachedFileInfo.ModTime().After(sourceFileInfo.ModTime()) &&
+			cachedFileInfo.Size() > 1024 {
+			item := &models.CacheItem{
+				Path:    cacheFilePath,
+				Size:    cachedFileInfo.Size(),
+				Updated: time.Now().UTC(),
+			}
+			c.items[cacheKey] = item
+			c.currentSize += cachedFileInfo.Size()
+
+			c.updateCachedStat(sourcePath, item.Size)
+
+			return item, nil
+		}
+	}
+
+	// File does not exist on disk, need to transcode.
+	// Register in the queue
+	c.transcoder.QueueChannel() <- struct{}{}
+	defer func() {
+		<-c.transcoder.QueueChannel()
+	}()
+
+	// Convert file
+	size, err := c.transcoder.Convert(sourcePath, cacheFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w (%w)", ErrCacher, ErrFailedToTranscodeFile, err)
+	}
+
+	// Add converted file information to cache
+	item := &models.CacheItem{
+		Path:    cacheFilePath,
+		Size:    size,
+		Updated: time.Now(),
+	}
+	c.items[cacheKey] = item
+	c.currentSize += size
+
+	c.updateCachedStat(sourcePath, size)
+	// TODO: run cleanup on inotify events.
+	c.cleanup()
+
+	return item, nil
+}