From e5ac43a59e3702d01879b563a550e062bf34f142 Mon Sep 17 00:00:00 2001
From: Sergey Stepanov <sergystepanov@gmail.com>
Date: Thu, 1 Jun 2023 16:16:10 +0300
Subject: [PATCH] Use faster lib scan

---
 pkg/games/library.go      | 44 +++++++++++++--------------------------
 pkg/games/library_test.go | 20 +++++++++++++-----
 2 files changed, 29 insertions(+), 35 deletions(-)

diff --git a/pkg/games/library.go b/pkg/games/library.go
index c8a84148..fec3cc47 100644
--- a/pkg/games/library.go
+++ b/pkg/games/library.go
@@ -1,10 +1,7 @@
 package games
 
 import (
-	"crypto/md5"
-	"fmt"
-	"io"
-	"os"
+	"io/fs"
 	"path/filepath"
 	"strings"
 	"sync"
@@ -18,8 +15,8 @@ import (
 // libConf is an optimized internal library configuration
 type libConf struct {
 	path      string
-	supported map[string]bool
-	ignored   map[string]bool
+	supported map[string]struct{}
+	ignored   map[string]struct{}
 	verbose   bool
 	watchMode bool
 }
@@ -37,9 +34,8 @@ type library struct {
 	games map[string]GameMetadata
 	log   *logger.Logger
 
-	// to restrict parallel execution
-	// or throttling
-	// !CAS would be better
+	// to restrict parallel execution or throttling
+	// for file watch mode
 	mu                sync.Mutex
 	isScanning        bool
 	isScanningDelayed bool
@@ -56,7 +52,6 @@ type FileExtensionWhitelist interface {
 }
 
 type GameMetadata struct {
-	uid string
 	// the display name of the game
 	Name string
 	// the game file extension (e.g. nes, n64)
@@ -150,16 +145,14 @@ func (lib *library) Scan() {
 	start := time.Now()
 	var games []GameMetadata
 	dir := lib.config.path
-	err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	err := filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
 
-		if info != nil && !info.IsDir() && lib.isFileExtensionSupported(path) {
+		if info != nil && !info.IsDir() && lib.isExtAllowed(path) {
 			meta := getMetadata(path, dir)
-			meta.uid = hash(path)
-
-			if !lib.config.ignored[meta.Name] {
+			if _, ok := lib.config.ignored[meta.Name]; !ok {
 				games = append(games, meta)
 			}
 		}
@@ -239,12 +232,13 @@ func (lib *library) set(games []GameMetadata) {
 	lib.games = res
 }
 
-func (lib *library) isFileExtensionSupported(path string) bool {
+func (lib *library) isExtAllowed(path string) bool {
 	ext := filepath.Ext(path)
 	if ext == "" {
 		return false
 	}
-	return lib.config.supported[ext[1:]]
+	_, ok := lib.config.supported[ext[1:]]
+	return ok
 }
 
 // getMetadata returns game info from a path
@@ -278,20 +272,10 @@ func (lib *library) dumpLibrary() {
 		gameList.String(), len(lib.games), lib.lastScanDuration)
 }
 
-// hash makes an MD5 hash of the string
-func hash(str string) string {
-	h := md5.New()
-	_, err := io.WriteString(h, str)
-	if err != nil {
-		return ""
-	}
-	return fmt.Sprintf("%x", h.Sum(nil))
-}
-
-func toMap(list []string) map[string]bool {
-	res := make(map[string]bool)
+func toMap(list []string) map[string]struct{} {
+	res := make(map[string]struct{}, len(list))
 	for _, s := range list {
-		res[s] = true
+		res[s] = struct{}{}
 	}
 	return res
 }
diff --git a/pkg/games/library_test.go b/pkg/games/library_test.go
index 759389e8..f42890a8 100644
--- a/pkg/games/library_test.go
+++ b/pkg/games/library_test.go
@@ -25,16 +25,12 @@ func TestLibraryScan(t *testing.T) {
 		library := NewLib(config.Library{
 			BasePath:  test.directory,
 			Supported: []string{"gba", "zip", "nes"},
-			Ignored:   []string{"neogeo", "pgm"},
 		}, l)
 		library.Scan()
 		games := library.GetAll()
 
-		list := _map(games, func(meta GameMetadata) string {
-			return meta.Name
-		})
+		list := _map(games, func(g GameMetadata) string { return g.Name })
 
-		// ^2 complexity (;
 		all := true
 		for _, expect := range test.expected {
 			found := false
@@ -52,6 +48,20 @@ func TestLibraryScan(t *testing.T) {
 	}
 }
 
+func Benchmark(b *testing.B) {
+	log := logger.Default()
+	logger.SetGlobalLevel(logger.Disabled)
+	library := NewLib(config.Library{
+		BasePath:  "../../assets/games",
+		Supported: []string{"gba", "zip", "nes"},
+	}, log)
+
+	for i := 0; i < b.N; i++ {
+		library.Scan()
+		_ = library.GetAll()
+	}
+}
+
 func _map(vs []GameMetadata, f func(info GameMetadata) string) []string {
 	vsm := make([]string, len(vs))
 	for i, v := range vs {