adjust client difficulty

src/models/StratumV1ClientStatistics.ts

@@ -1,25 +1,77 @@
 import { ClientStatisticsService } from '../ORM/client-statistics/client-statistics.service';
 import { ClientEntity } from '../ORM/client/client.entity';
 
+const CACHE_SIZE = 30;
+const TARGET_SUBMISSION_PER_SECOND = 30;
 export class StratumV1ClientStatistics {
 
+    private submissionCacheStart: Date;
+    private submissionCache = [];
 
     constructor(private readonly clientStatisticsService: ClientStatisticsService) {
-
+        this.submissionCacheStart = new Date();
     }
 
     public async addSubmission(client: ClientEntity, targetDifficulty: number) {
 
+        if (this.submissionCache.length > CACHE_SIZE) {
+            this.submissionCache.shift();
+        }
+
+        this.submissionCache.push({
+            time: new Date(),
+            difficulty: targetDifficulty,
+        });
+
         await this.clientStatisticsService.save({
             time: new Date(),
             difficulty: targetDifficulty,
             address: client.address,
             clientName: client.clientName,
             sessionId: client.sessionId,
-
         });
 
     }
 
+    public getSuggestedDifficulty(clientDifficulty: number) {
+
+        // miner hasn't submitted shares in one minute
+        if (this.submissionCache.length == 0 && (new Date().getTime() - this.submissionCacheStart.getTime()) / 1000 > 60) {
+            return this.blpo2(clientDifficulty >> 1);
+        }
+
+        if (this.submissionCache.length < CACHE_SIZE) {
+            return null;
+        }
+
+        const sum = this.submissionCache.reduce((pre, cur) => {
+            pre += cur.difficulty;
+            return pre;
+        }, 0);
+        const diffSeconds = (this.submissionCache[this.submissionCache.length - 1].time.getTime() - this.submissionCache[0].time.getTime()) / 1000;
+
+        const difficultyPerSecond = sum / diffSeconds;
+
+        const targetDifficulty = difficultyPerSecond * TARGET_SUBMISSION_PER_SECOND;
+
+        if (clientDifficulty << 1 < targetDifficulty || clientDifficulty >> 1 > targetDifficulty) {
+            return this.blpo2(targetDifficulty)
+        }
+
+        return null;
+
+
+    }
+
+    private blpo2(x) {
+        x = x | (x >> 1);
+        x = x | (x >> 2);
+        x = x | (x >> 4);
+        x = x | (x >> 8);
+        x = x | (x >> 16);
+        x = x | (x >> 32);
+        return x - (x >> 1);
+    }
+
 
 }