Cache the custom emoji list (#1175)

* use emojiCache

* add emojiCacheTimestamp

* add function description

* better logging

controllers/emoji.go

@@ -4,9 +4,11 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"net/http"
+	"os"
 	"path"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"github.com/owncast/owncast/config"
 	"github.com/owncast/owncast/models"
@@ -17,28 +19,44 @@ import (
 // to need it to be.  The config is getting a bit bloated.
 const emojiDir = "/img/emoji" // Relative to webroot
 
-// GetCustomEmoji returns a list of custom emoji via the API.
+var emojiCache = make([]models.CustomEmoji, 0)
-func GetCustomEmoji(w http.ResponseWriter, r *http.Request) {
+var emojiCacheTimestamp time.Time
-	emojiList := make([]models.CustomEmoji, 0)
 
+// getCustomEmojiList returns a list of custom emoji either from the cache or from the emoji directory.
+func getCustomEmojiList() []models.CustomEmoji {
 	fullPath := filepath.Join(config.WebRoot, emojiDir)
-	files, err := ioutil.ReadDir(fullPath)
+	emojiDirInfo, err := os.Stat(fullPath)
 	if err != nil {
 		log.Errorln(err)
-		// Throw HTTP 500
+	}
-		return
+	if emojiDirInfo.ModTime() != emojiCacheTimestamp {
+		log.Traceln("Emoji cache invalid")
+		emojiCache = make([]models.CustomEmoji, 0)
 	}
 
-	// Memoize this result somewhere?  Right now it iterates through the
+	if len(emojiCache) == 0 {
-	// filesystem every time the API is hit.  Should you need to restart
+		files, err := ioutil.ReadDir(fullPath)
-	// the server to add emoji?
+		if err != nil {
+			log.Errorln(err)
+			return emojiCache
+		}
 		for _, f := range files {
 			name := strings.TrimSuffix(f.Name(), path.Ext(f.Name()))
 			emojiPath := filepath.Join(emojiDir, f.Name())
 			singleEmoji := models.CustomEmoji{Name: name, Emoji: emojiPath}
-		emojiList = append(emojiList, singleEmoji)
+			emojiCache = append(emojiCache, singleEmoji)
 		}
 
+		emojiCacheTimestamp = emojiDirInfo.ModTime()
+	}
+
+	return emojiCache
+}
+
+// GetCustomEmoji returns a list of custom emoji via the API.
+func GetCustomEmoji(w http.ResponseWriter, r *http.Request) {
+	emojiList := getCustomEmojiList()
+
 	if err := json.NewEncoder(w).Encode(emojiList); err != nil {
 		InternalErrorHandler(w, err)
 	}