first commit

cache.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+// NoLyricsCache tracks songs that previously had no results.
+type NoLyricsCache struct {
+	Tracks map[string]time.Time
+	mutex  sync.RWMutex
+}
+
+func loadCache(cacheFile string) (*NoLyricsCache, error) {
+	cache := &NoLyricsCache{Tracks: make(map[string]time.Time)}
+
+	if _, err := os.Stat(cacheFile); os.IsNotExist(err) {
+		return cache, nil
+	}
+
+	data, err := os.ReadFile(cacheFile)
+	if err != nil {
+		return cache, err
+	}
+
+	if len(data) == 0 {
+		return cache, nil
+	}
+
+	err = json.Unmarshal(data, &cache.Tracks)
+	if cache.Tracks == nil {
+		cache.Tracks = make(map[string]time.Time)
+	}
+
+	return cache, err
+}
+
+func (c *NoLyricsCache) SaveCache(cacheFile string, ttl time.Duration) error {
+	cacheSnapshot := c.prunedCopy(ttl)
+
+	data, err := json.MarshalIndent(cacheSnapshot, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return writeFileAtomically(cacheFile, data, 0644)
+}
+
+func (c *NoLyricsCache) IsTrackedAsNoLyrics(trackID string, ttl time.Duration) bool {
+	c.mutex.RLock()
+	timestamp, exists := c.Tracks[trackID]
+	c.mutex.RUnlock()
+
+	if !exists {
+		return false
+	}
+
+	if isCacheEntryExpired(timestamp, ttl) {
+		c.mutex.Lock()
+		if ts, ok := c.Tracks[trackID]; ok && isCacheEntryExpired(ts, ttl) {
+			delete(c.Tracks, trackID)
+		}
+		c.mutex.Unlock()
+		return false
+	}
+
+	return true
+}
+
+func (c *NoLyricsCache) AddNoLyrics(trackID string) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	c.Tracks[trackID] = time.Now()
+}
+
+func (c *NoLyricsCache) prunedCopy(ttl time.Duration) map[string]time.Time {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	for trackID, timestamp := range c.Tracks {
+		if isCacheEntryExpired(timestamp, ttl) {
+			delete(c.Tracks, trackID)
+		}
+	}
+
+	cacheSnapshot := make(map[string]time.Time, len(c.Tracks))
+	for trackID, timestamp := range c.Tracks {
+		cacheSnapshot[trackID] = timestamp
+	}
+
+	return cacheSnapshot
+}
+
+func createTrackIdentifier(metadata Metadata) string {
+	return fmt.Sprintf("%s-%s-%s",
+		strings.ToLower(strings.TrimSpace(metadata.ArtistName)),
+		strings.ToLower(strings.TrimSpace(metadata.AlbumName)),
+		strings.ToLower(strings.TrimSpace(metadata.TrackName)))
+}
+
+func isCacheEntryExpired(timestamp time.Time, ttl time.Duration) bool {
+	if ttl <= 0 {
+		return false
+	}
+
+	return time.Since(timestamp) > ttl
+}
+
+func writeFileAtomically(path string, data []byte, perm os.FileMode) error {
+	dir := filepath.Dir(path)
+	base := filepath.Base(path)
+
+	tempFile, err := os.CreateTemp(dir, base+".tmp-*")
+	if err != nil {
+		return err
+	}
+
+	tempPath := tempFile.Name()
+	cleanup := func() {
+		tempFile.Close()
+		os.Remove(tempPath)
+	}
+
+	if _, err := tempFile.Write(data); err != nil {
+		cleanup()
+		return err
+	}
+
+	if err := tempFile.Chmod(perm); err != nil {
+		cleanup()
+		return err
+	}
+
+	if err := tempFile.Close(); err != nil {
+		os.Remove(tempPath)
+		return err
+	}
+
+	if err := os.Rename(tempPath, path); err != nil {
+		os.Remove(tempPath)
+		return err
+	}
+
+	return nil
+}