Changes AlbumCacheCover interface

album_cover_cache.go

@@ -2,7 +2,9 @@ package main
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
+	"sync"
 	"time"
 
 	"github.com/peterbourgon/diskv"
@@ -12,6 +14,8 @@ import (
 type AlbumCoverCache struct {
 	dv     *diskv.Diskv
 	getter HTTPGetter
+	URLs   map[AlbumID]string
+	lock   sync.RWMutex
 	// time to live of the cache, data which is older than this TTL will be automatically removed
 	TTL time.Duration
 }
@@ -23,70 +27,85 @@ func NewAlbumCoverCache(basepath string, maxRequest uint, window time.Duration)
 			BasePath:     basepath,
 			CacheSizeMax: 100 * 1024 * 1024, // 100 Mb
 		}),
+		URLs:   make(map[AlbumID]string),
 		getter: NewRateLimitedGetter(maxRequest, window),
 		TTL:    3 * 31 * 24 * time.Hour, // 3 Months
 	}
 	return res
 }
 
-func (c *AlbumCoverCache) fetch(a *Album) (io.ReadCloser, error) {
-	resp, err := c.getter.Get(a.CoverURL)
-	if err != nil {
-		return nil, err
+func (c *AlbumCoverCache) fetch(ID AlbumID) (io.ReadCloser, error) {
+	URL, ok := c.URLs[ID]
+	if ok == false {
+		return nil, fmt.Errorf("Cover URL for Album %d is not registered", ID)
 	}
-	defer closeOrPanic(resp.Body, "GET "+a.CoverURL)
 
-	err = c.dv.WriteStream(c.dataKey(a), resp.Body, false)
+	resp, err := c.getter.Get(URL)
 	if err != nil {
 		return nil, err
 	}
+	defer closeOrPanic(resp.Body, "GET "+URL)
+
+	err = c.dv.WriteStream(c.dataKey(ID), resp.Body, false)
+	if err != nil {
+		return nil, err
+	}
+
 	md := coverMetadata{
 		Age: time.Now(),
 	}
 	mdbyte, err := json.Marshal(&md)
 	if err == nil {
-		err = c.dv.Write(c.metadataKey(a), mdbyte)
+		err = c.dv.Write(c.metadataKey(ID), mdbyte)
 		if err != nil {
 			return nil, err
 		}
 	}
 
-	return c.dv.ReadStream(c.dataKey(a), false)
+	return c.dv.ReadStream(c.dataKey(ID), false)
 }
 
 type coverMetadata struct {
 	Age time.Time
 }
 
-func (c *AlbumCoverCache) metadataKey(a *Album) string {
-	return AlbumIDString(a.ID) + ".metadata"
+func (c *AlbumCoverCache) metadataKey(ID AlbumID) string {
+	return AlbumIDString(ID) + ".metadata"
 }
 
-func (c *AlbumCoverCache) dataKey(a *Album) string {
-	return AlbumIDString(a.ID) + ".data"
+func (c *AlbumCoverCache) dataKey(ID AlbumID) string {
+	return AlbumIDString(ID) + ".data"
+}
+
+func (c *AlbumCoverCache) RegisterCover(ID AlbumID, URL string) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.URLs[ID] = URL
 }
 
 // GetCover retrieves from the cache or either from www.bedetheque.com the Cover of an album
-func (c *AlbumCoverCache) GetCover(a *Album) (io.ReadCloser, error) {
-	//
-	if c.dv.Has(c.metadataKey(a)) == false {
-		return c.fetch(a)
+func (c *AlbumCoverCache) GetCover(ID AlbumID) (io.ReadCloser, error) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+
+	if c.dv.Has(c.metadataKey(ID)) == false {
+		return c.fetch(ID)
 	}
 
-	mdbytes, err := c.dv.Read(c.metadataKey(a))
+	mdbytes, err := c.dv.Read(c.metadataKey(ID))
 	if err != nil {
-		return c.fetch(a)
+		return c.fetch(ID)
 	}
 	var md coverMetadata
 	err = json.Unmarshal(mdbytes, &md)
 	if err != nil {
-		return c.fetch(a)
+		return c.fetch(ID)
 	}
 
 	// check TTL
 	if time.Now().Add(-c.TTL).After(md.Age) == true {
-		return c.fetch(a)
+		return c.fetch(ID)
 	}
 
-	return c.dv.ReadStream(c.dataKey(a), false)
+	return c.dv.ReadStream(c.dataKey(ID), false)
 }