feat: RatingCalculator

Signed-off-by: Dup4 <lyuzhi.pan@gmail.com>

packages/libs/core/src/index.ts

@@ -1,4 +1,5 @@
 export * from "./export";
+export * from "./rating";
 export * from "./utils";
 
 export * from "./award";

packages/libs/core/src/rating/index.ts

@@ -0,0 +1,2 @@
+export * from "./rating-calculator";
+export * from "./rating-user";

packages/libs/core/src/rating/rating-calculator.ts

@@ -0,0 +1,94 @@
+import type { RatingUsers } from "./rating-user";
+import { RatingUser } from "./rating-user";
+
+// https://www.wikiwand.com/en/Elo_rating_system
+export class RatingCalculator {
+  users: RatingUsers;
+
+  constructor() {
+    this.users = [];
+  }
+
+  calcP(userA: RatingUser, userB: RatingUser) {
+    return 1.0 / (1.0 + 10 ** ((userB.oldRating - userA.oldRating) / 400.0));
+  }
+
+  getExSeed(users: RatingUsers, rating: number, ownUser: RatingUser) {
+    const exUser = new RatingUser();
+    let res = 0;
+
+    users.forEach((user) => {
+      if (user.id !== ownUser.id) {
+        res += this.calcP(user, exUser);
+      }
+    });
+
+    return res;
+  }
+
+  calcRating(users: RatingUsers, rank: number, user: RatingUser) {
+    let left = 1;
+    let right = 8000;
+
+    while (right - left > 1) {
+      const mid = Math.floor((left + right) / 2);
+      if (this.getExSeed(users, mid, user) < rank) {
+        right = mid;
+      } else {
+        left = mid;
+      }
+    }
+
+    return left;
+  }
+
+  calculate() {
+    // Calculate seed
+    for (let i = 0; i < this.users.length; i++) {
+      const u = this.users[i];
+      u.seed = 1.0;
+      for (let j = 0; j < this.users.length; j++) {
+        if (i !== j) {
+          const otherUser = this.users[j];
+          u.seed += this.calcP(otherUser, u);
+        }
+      }
+    }
+
+    // Calculate initial delta and sumDelta
+    let sumDelta = 0;
+    for (let i = 0; i < this.users.length; i++) {
+      const u = this.users[i];
+      u.delta = Math.floor(
+        (this.calcRating(this.users, Math.sqrt(u.rank * u.seed), u)
+          - u.oldRating)
+          / 2,
+      );
+      sumDelta += u.delta;
+    }
+
+    // Calculate first inc
+    let inc = Math.floor(-sumDelta / this.users.length) - 1;
+    for (let i = 0; i < this.users.length; i++) {
+      const u = this.users[i];
+      u.delta += inc;
+    }
+
+    // Calculate second inc
+    this.users = this.users.sort((a, b) => b.oldRating - a.oldRating);
+    const s = Math.min(this.users.length, Math.floor(4 * Math.round(Math.sqrt(this.users.length))));
+    let sumS = 0;
+    for (let i = 0; i < s; i++) {
+      sumS += this.users[i].delta;
+    }
+    inc = Math.min(Math.max(Math.floor(-sumS / s), -10), 0);
+
+    // Calculate new rating
+    this.users.forEach((u) => {
+      u.delta += inc;
+      u.newRating = u.oldRating + u.delta;
+    });
+
+    this.users = this.users.sort((a, b) => a.rank - b.rank);
+  }
+}

packages/libs/core/src/rating/rating-user.ts

@@ -0,0 +1,21 @@
+export class RatingUser {
+  id: string;
+
+  rank: number;
+  seed: number;
+  delta: number;
+  oldRating: number;
+  newRating: number;
+
+  constructor() {
+    this.id = "";
+
+    this.rank = 0;
+    this.seed = 1;
+    this.delta = 0;
+    this.oldRating = 0;
+    this.newRating = 0;
+  }
+}
+
+export type RatingUsers = Array<RatingUser>;