First Commit

src/database/lock.ts

@@ -0,0 +1,43 @@
+export type Release = { release: () => void };
+
+export default class PathLock {
+   locks: {
+      path: string[],
+      next: (() => void)[]
+   }[] = [];
+
+   constructor() { }
+
+   async lock(path: string[]) {
+      let locks = this.locks.filter(lock => {
+         let idxs = Math.min(lock.path.length, path.length);
+         if (idxs === 0) return true;
+         for (let i = 0; i < idxs; i++) {
+            if (lock.path[i] !== path[i])
+               return false;
+         }
+         return true;
+      })
+
+      if (locks.length > 0) { // await till release
+         await Promise.all(locks.map(l => new Promise(res => l.next.push(res))))
+      } else {
+         let lock = {
+            path: path,
+            next: []
+         }
+         this.locks.push(lock);
+         locks = [lock];
+      }
+
+      return () => {
+         locks.forEach(lock => {
+            if (lock.next.length > 0) {
+               setImmediate(() => lock.next.shift()());
+            } else {
+               this.locks.splice(this.locks.indexOf(lock), 1);
+            }
+         })
+      }
+   }
+}