create isLineageROMZip function

main.go

@@ -81,13 +81,8 @@ func updateROMCache(romDirectory string) {
 
 	for i, v := range files {
 
-		// skip directories
-		if v.Type().IsDir() {
-			continue
-		}
-
-		// skip non .zip files
-		if !strings.HasSuffix(v.Name(), ".zip") {
+		isLineageROM, splitName := isLineageROMZip(v)
+		if !isLineageROM {
 			continue
 		}
 
@@ -99,11 +94,6 @@ func updateROMCache(romDirectory string) {
 		}
 		romCache.Unlock()
 
-		// Parse filename and skip files that can't be parsed
-		splitName := strings.Split(v.Name(), "-")
-		if len(splitName) != 5 {
-			continue
-		}
 		go func(v fs.DirEntry) {
 			fInfo, err := v.Info()
 			if err != nil {
@@ -157,19 +147,10 @@ func moveBuildArtifacts(outDirectory, romDirectory string) bool {
 	var newROMs bool
 
 	for _, v := range files {
-		// skip directories
-		if v.Type().IsDir() {
-			continue
-		}
-		// skip non .zip files
-		if !strings.HasSuffix(v.Name(), ".zip") {
-			continue
-		}
-		// Parse filename and skip files that can't be parsed
-		splitName := strings.Split(v.Name(), "-")
-		if len(splitName) != 5 {
+		if isLineageROM, _ := isLineageROMZip(v); !isLineageROM { // skip files that aren't LineageOS ROMs
 			continue
 		}
+
 		newROMs = true
 		log.Printf("new build found - moving file %s", v.Name())
 		err := moveBuildFile(fmt.Sprintf("%s/%s", outDirectory, v.Name()), fmt.Sprintf("%s/%s", romDirectory, v.Name()))
@@ -182,6 +163,22 @@ func moveBuildArtifacts(outDirectory, romDirectory string) bool {
 	return newROMs
 }
 
+// false if a file is not a LineageOS ROM .zip file
+// no formal validation is performed - only file naming convention is checked
+// also returns a lineage ROM's filename sliced and delimited by -'s
+// Example filename: lineage-20.0-20230604-UNOFFICIAL-sunfish.zip
+func isLineageROMZip(v fs.DirEntry) (bool, []string) {
+
+	// skip directories, non .zip files and files that don't begin with lineage-
+	if v.Type().IsDir() || !strings.HasSuffix(v.Name(), ".zip") || !strings.HasPrefix(v.Name(), "lineage-") {
+		return false, nil
+	}
+
+	splitName := strings.Split(v.Name(), "-")
+	// expect 5 dashes
+	return len(splitName) == 5, splitName
+}
+
 // http - GET /
 // Writes JSON response for the updater app to know what versions are available to download
 func lineageOSROMListHandler(w http.ResponseWriter, r *http.Request) {
@@ -208,6 +205,7 @@ func lineageOSROMListHandler(w http.ResponseWriter, r *http.Request) {
 	}()
 }
 
+// Returns a sha256 hash of a file located at the path provided
 func hashFile(filename string) (string, error) {
 	f, err := os.Open(filename)
 	if err != nil {