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)
 }

album_cover_cache_test.go

@@ -11,7 +11,9 @@ import (
 	. "gopkg.in/check.v1"
 )
 
-type AlbumCoverCacheSuite struct{}
+type AlbumCoverCacheSuite struct {
+	cache *AlbumCoverCache
+}
 
 var _ = Suite(&AlbumCoverCacheSuite{})
 
@@ -22,14 +24,21 @@ func (g *errorGetter) Get(URL string) (*http.Response, error) {
 	return nil, fmt.Errorf("I will always have an error")
 }
 
+func (s *AlbumCoverCacheSuite) SetUpSuite(c *C) {
+	s.cache = NewAlbumCoverCache(c.MkDir(), 10, 10*time.Second)
+	s.cache.getter = testGetter
+
+	for _, a := range albumsDataTest {
+		s.cache.RegisterCover(a.ID, a.CoverURL)
+	}
+}
+
 func (s *AlbumCoverCacheSuite) TestCanFetchCache(c *C) {
-	cache := NewAlbumCoverCache(c.MkDir(), 10, 10*time.Second)
-	cache.getter = testGetter
 
 	var resData = []bytes.Buffer{}
 	start := time.Now()
 	for _, a := range albumsDataTest {
-		cover, err := cache.GetCover(&a)
+		cover, err := s.cache.GetCover(a.ID)
 		var buf bytes.Buffer
 		if c.Check(err, IsNil) == true {
 			_, err := io.Copy(&buf, cover)
@@ -39,12 +48,12 @@ func (s *AlbumCoverCacheSuite) TestCanFetchCache(c *C) {
 		resData = append(resData, buf)
 	}
 
-	cache.getter = &errorGetter{}
+	s.cache.getter = &errorGetter{}
 
 	// now we check that we get it again, but from the disk, not
 	// hitting the web
 	for i, a := range albumsDataTest {
-		cover, err := cache.GetCover(&a)
+		cover, err := s.cache.GetCover(a.ID)
 		var buf bytes.Buffer
 		if c.Check(err, IsNil) == true {
 			_, err := io.Copy(&buf, cover)
@@ -56,10 +65,10 @@ func (s *AlbumCoverCacheSuite) TestCanFetchCache(c *C) {
 	}
 
 	// now if we it the TTL, we will reftech and get error
-	cache.TTL = 0
+	s.cache.TTL = 0
 
 	for _, a := range albumsDataTest {
-		cover, err := cache.GetCover(&a)
+		cover, err := s.cache.GetCover(a.ID)
 		c.Check(cover, IsNil)
 		c.Check(err, ErrorMatches, "I will always have an error")
 	}