添加功能：pretest discuss user dashboard statistics

hydro/model/system.js

@@ -11,41 +11,20 @@ async function update(_id, operation, config) {
     await coll.findOneAndUpdate({ _id }, operation, config);
     return get(_id);
 }
+async function set(_id, value) {
+    await coll.findOneAndUpdate({ _id }, { value }, { upsert: true });
+    return get(_id);
+}
 /**
- * Increments the user counter.
+ * Increments the counter.
  * @returns {number} Integer value after increment.
  */
-function incUserCounter() {
-    return update('userCounter', { $inc: { value: 1 } }, { upsert: true });
-}
-/**
- * Increments the problem ID counter.
- * @returns {number} Integer value before increment.
- */
-function incPidCounter() {
-    return update('userCounter', { $inc: { value: 1 } }, { upsert: true });
-}
-async function acquireLock(name) {
-    const value = Math.floor(Math.random() * 0xFFFFFFFF);
-    try {
-        await coll.updateOne({ _id: `lock_${name}`, value: 0 }, { $set: { value } }, { upsert: true });
-    } catch (e) { return null; }
-    return value;
-}
-async function releaseLock(name, value) {
-    const result = await coll.updateOne({ _id: `lock_${name}`, value }, { $set: { value: 0 } });
-    return !!result.matchedCount;
-}
-async function releaseLockAnyway(name) {
-    await coll.updateOne({ _id: `lock_${name}` }, { $set: { value: 0 } });
-    return true;
+function inc(field) {
+    return update(field, { $inc: { value: 1 } }, { upsert: true });
 }
 module.exports = {
     get,
     update,
-    incPidCounter,
-    incUserCounter,
-    acquireLock,
-    releaseLock,
-    releaseLockAnyway,
+    inc,
+    set,
 };