Add mirgrate for code formatting

README.en.md

@@ -45,4 +45,6 @@ Who upgraded from a commit BEFORE [d8be150fc6b8c43af61c5e4aca4fc0fe0445aef3](htt
 ALTER TABLE `user` ADD `prefer_formatted_code` TINYINT(1) NOT NULL DEFAULT 1 AFTER `public_email`;
 ```
 
+To make code formatting work, `clang-format` needs to be installed. [migrates/format-old-codes.js](migrates/format-old-codes.js) may help formating old submissions' codes.
+
 Who upgraded from a commit BEFORE [c192e8001ac81cab132ae033b39f09a094587633](https://github.com/syzoj/syzoj/commit/c192e8001ac81cab132ae033b39f09a094587633) (Mar 23, 2019) **MUST** install `redis-server` and [pygments](http://pygments.org/) on the web server. Markdown contents may be broken by switching to new renderer, [migrates/html-table-merge-cell-to-md.js](migrates/html-table-merge-cell-to-md.js) may help the migration。

README.md

@@ -45,4 +45,6 @@ ALTER TABLE `problem` ADD `publicize_time` DATETIME NOT NULL DEFAULT CURRENT_TIM
 ALTER TABLE `user` ADD `prefer_formatted_code` TINYINT(1) NOT NULL DEFAULT 1 AFTER `public_email`;
 ```
 
+为使代码格式化功能正常工作，`clang-format` 需要被安装。[migrates/format-old-codes.js](migrates/format-old-codes.js) 可能对格式化旧提交记录的代码有帮助。
+
 从该 commit [c192e8001ac81cab132ae033b39f09a094587633](https://github.com/syzoj/syzoj/commit/c192e8001ac81cab132ae033b39f09a094587633)（2019 年 3 月 23 日）前更新的用户**必须**在网站服务器上安装 `redis-server` 与 [pygments](http://pygments.org/)。旧的 Markdown 内容可能因切换到新渲染器被破坏，[migrates/html-table-merge-cell-to-md.js](migrates/html-table-merge-cell-to-md.js) 可能对迁移有所帮助。

migrates/format-old-codes.js

@@ -0,0 +1,47 @@
+/*
+ * This script will help format all submissions' codes whose id in a interval.
+ * 
+ * Useful when upgrading from a version that doesn't support code formatting.
+ */
+
+const JudgeState = syzoj.model('judge_state');
+const FormattedCode = syzoj.model('formatted_code');
+const CodeFormatter = syzoj.lib('code_formatter');
+require('.');
+
+const fn = async (begin, end) => {
+  for (let i = begin; i < end; i++) {
+    const judge_state = await JudgeState.fromID(i);
+    if (!judge_state) continue;
+
+    if (!judge_state.language) continue;
+
+    const key = syzoj.utils.getFormattedCodeKey(judge_state.code, judge_state.language);
+    if (!key) continue;
+
+    let formatted_code = await FormattedCode.findOne({ where: { key: key } });
+
+    const code = await CodeFormatter(judge_state.code, syzoj.languages[judge_state.language].format);
+    if (code === null) {
+      console.error(`Format ${i} failed.`);
+      continue;
+    }
+
+    if (!formatted_code) {
+      formatted_code = await FormattedCode.create({
+        key: key,
+        code: code
+      });
+    } else continue; // formatted_code.code = code;
+
+    try {
+      await formatted_code.save();
+      console.error(`Format and save ${i} success.`);
+    } catch (e) {
+      console.error(`Save ${i} failed:`, e);
+    }
+  }
+};
+
+// NOTE: Uncomment and fill arguments to run.
+// fn(begin, end) // [begin, end)