add ${page} to download subpath

assets/tr.json

@@ -128,7 +128,8 @@
         "Delete all": "删除全部",
         "Related": "相关",
         "Related artworks": "相关作品",
-        "Related users": "相关用户"
+        "Related users": "相关用户",
+        "Replace with '-p${index}' if the work have more than one images, otherwise replace with blank.": "替换为'-p${index}'如果作品有多张图片, 否则替换为空白"
     },
     "zh_TW": {
         "Search": "搜索",
@@ -259,6 +260,7 @@
         "Delete all": "刪除全部",
         "Related": "相關",
         "Related artworks": "相關作品",
-        "Related users": "相關用戶"
+        "Related users": "相關用戶",
+        "Replace with '-p${index}' if the work have more than one images, otherwise replace with blank.": "替換為'-p${index}'如果作品有多張圖片, 否則替換為空白"
     }
 }

lib/network/download.dart

@@ -131,6 +131,8 @@ class DownloadingTask {
     subPathPatten = subPathPatten.replaceAll(r"${title}", illust.title);
     subPathPatten = subPathPatten.replaceAll(r"${author}", illust.author.name);
     subPathPatten = subPathPatten.replaceAll(r"${index}", index.toString());
+    subPathPatten = subPathPatten.replaceAll(r"${page}",
+        illust.images.length == 1 ? "" : "-p$index");
     subPathPatten = subPathPatten.replaceAll(r"${ext}", ext);
     subPathPatten = subPathPatten.replaceAll(r"${AI}", illust.isAi ? "AI" : "");
     List<String> extractTags(String input) {

lib/pages/settings_page.dart

@@ -408,6 +408,7 @@ ${"Some keywords will be replaced by the following rule:".tl}
   \${author} -> ${"Name of the author".tl}
   \${id} -> ${"Artwork ID".tl}
   \${index} -> ${"Index of the image in the artwork".tl}
+  \${page} -> ${"Replace with '-p\${index}' if the work have more than one images, otherwise replace with blank.".tl}
   \${ext} -> ${"File extension".tl}
   \${AI} -> ${"Replace with 'AI' if the work was generated by AI, otherwise replace with blank".tl}
   \${tag(*)} -> ${"Replace with * if the work have tag *, otherwise replace with blank.".tl}