From ae98a18b5295fb3c7608c09111a73bf3376158e9 Mon Sep 17 00:00:00 2001
From: Duncan Overbruck <mail@duncano.de>
Date: Fri, 24 Jul 2020 16:47:15 +0200
Subject: [PATCH] add album cover scaling and caching

---
 go.mod                              |  1 +
 go.sum                              |  3 ++
 server/ctrlsubsonic/handlers_raw.go | 68 +++++++++++++++++++++--------
 3 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/go.mod b/go.mod
index f364b7b..21cc728 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@ require (
 	github.com/Masterminds/semver v1.5.0 // indirect
 	github.com/Masterminds/sprig v2.22.0+incompatible
 	github.com/cespare/xxhash v1.1.0
+	github.com/disintegration/imaging v1.6.2
 	github.com/dustin/go-humanize v1.0.0
 	github.com/faiface/beep v1.0.2
 	github.com/google/uuid v1.1.1 // indirect
diff --git a/go.sum b/go.sum
index 5e28c02..5341869 100644
--- a/go.sum
+++ b/go.sum
@@ -20,6 +20,8 @@ github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/denisenkom/go-mssqldb v0.0.0-20181014144952-4e0d7dc8888f/go.mod h1:xN/JuLBIz4bjkxNmByTiV1IbhfnYb6oo99phBn4Eqhc=
 github.com/denisenkom/go-mssqldb v0.0.0-20191124224453-732737034ffd h1:83Wprp6ROGeiHFAP8WJdI2RoxALQYgdllERc3N5N2DM=
 github.com/denisenkom/go-mssqldb v0.0.0-20191124224453-732737034ffd/go.mod h1:xbL0rPBG9cCiLr28tMa8zpbdarY27NDyej4t/EjAShU=
+github.com/disintegration/imaging v1.6.2 h1:w1LecBlG2Lnp8B3jk5zSuNqd7b4DXhcjwek1ei82L+c=
+github.com/disintegration/imaging v1.6.2/go.mod h1:44/5580QXChDfwIclfc/PCwrr44amcmDAg8hxG0Ewe4=
 github.com/dustin/go-humanize v1.0.0 h1:VSnTsYCnlFHaM2/igO1h6X3HA71jcobQuxemgkq4zYo=
 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/erikstmartin/go-testdb v0.0.0-20160219214506-8d10e4a1bae5 h1:Yzb9+7DPaBjB8zlTR87/ElzFsnQfuHnVUVqpZZIcV5Y=
@@ -169,6 +171,7 @@ golang.org/x/image v0.0.0-20190220214146-31aff87c08e9/go.mod h1:kZ7UVZpmo3dzQBMx
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067 h1:KYGJGHOQy8oSi1fDlSpcZF0+juKwk/hEMv5SiwHogR0=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
+golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.0.0-20200430140353-33d19683fad8 h1:6WW6V3x1P/jokJBpRQYUJnMHRP6isStQwCozxnU7XQw=
 golang.org/x/image v0.0.0-20200430140353-33d19683fad8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/mobile v0.0.0-20180806140643-507816974b79 h1:t2JRgCWkY7Qaa1J2jal+wqC9OjbyHCHwIA9rVlRUSMo=
diff --git a/server/ctrlsubsonic/handlers_raw.go b/server/ctrlsubsonic/handlers_raw.go
index 461a9bb..46e16a9 100644
--- a/server/ctrlsubsonic/handlers_raw.go
+++ b/server/ctrlsubsonic/handlers_raw.go
@@ -1,12 +1,15 @@
 package ctrlsubsonic
 
 import (
+	"fmt"
 	"io"
 	"log"
 	"net/http"
+	"os"
 	"path"
 	"time"
 
+	"github.com/disintegration/imaging"
 	"github.com/jinzhu/gorm"
 
 	"go.senan.xyz/gonic/server/ctrlsubsonic/params"
@@ -53,30 +56,61 @@ func streamUpdateStats(dbc *db.DB, userID, albumID int) {
 	dbc.Save(&play)
 }
 
+const (
+	coverDefaultSize = 600
+	coverCacheFormat = "png"
+)
+
 func (c *Controller) ServeGetCoverArt(w http.ResponseWriter, r *http.Request) *spec.Response {
 	params := r.Context().Value(CtxParams).(params.Params)
 	id, err := params.GetID("id")
 	if err != nil {
 		return spec.NewError(10, "please provide an `id` parameter")
 	}
-	folder := &db.Album{}
-	err = c.DB.
-		Select("id, left_path, right_path, cover").
-		First(folder, id.Value).
-		Error
-	if gorm.IsRecordNotFoundError(err) {
-		return spec.NewError(10, "could not find a cover with that id")
+	size := params.GetOrInt("size", coverDefaultSize)
+	cacheFile := fmt.Sprintf("%s/%s-%d.%s", c.CachePath, id.String(), size,
+		coverCacheFormat)
+	_, err = os.Stat(cacheFile)
+	if os.IsNotExist(err) {
+		log.Printf("serving cover `%s`: cache [%s/%d] miss!\n",
+			cacheFile, coverCacheFormat, size)
+		folder := &db.Album{}
+		err = c.DB.
+			Select("id, left_path, right_path, cover").
+			First(folder, id.Value).
+			Error
+		if gorm.IsRecordNotFoundError(err) {
+			return spec.NewError(10, "could not find a cover with that id")
+		}
+		if folder.Cover == "" {
+			return spec.NewError(10, "no cover found for that folder")
+		}
+		absPath := path.Join(
+			c.MusicPath,
+			folder.LeftPath,
+			folder.RightPath,
+			folder.Cover,
+		)
+		src, err := imaging.Open(absPath)
+		if err != nil {
+			log.Printf("resizing cover `%s`: error: %v\n", absPath, err)
+			return nil
+		}
+		width := size
+		if width > src.Bounds().Dx() {
+			// don't upscale images
+			width = src.Bounds().Dx()
+		}
+		err = imaging.Save(imaging.Resize(src, width, 0, imaging.Lanczos), cacheFile)
+		if err != nil {
+			log.Printf("caching cover `%s`: error: %v\n", cacheFile, err)
+			return nil
+		}
+	} else {
+		log.Printf("serving cover `%s`: cache [%s/%d] hit!\n",
+			cacheFile, coverCacheFormat, size)
 	}
-	if folder.Cover == "" {
-		return spec.NewError(10, "no cover found for that folder")
-	}
-	absPath := path.Join(
-		c.MusicPath,
-		folder.LeftPath,
-		folder.RightPath,
-		folder.Cover,
-	)
-	http.ServeFile(w, r, absPath)
+	http.ServeFile(w, r, cacheFile)
 	return nil
 }